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Feature Papers in Molecular Biophysics

A topical collection in International Journal of Molecular Sciences (ISSN 1422-0067). This collection belongs to the section "Molecular Biophysics".

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Editors


grade E-Mail Website
Collection Editor
Department of Molecular Medicine, USF Health Byrd Alzheimer’s Research Institute, Morsani College of Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, MDC07, Tampa, FL 33612, USA
Interests: intrinsically disordered proteins; protein folding; protein misfolding; partially folded proteins; protein aggregation; protein structure; protein function; protein stability; protein biophysics; protein bioinformatics; conformational diseases; protein–ligand interactions; protein–protein interactions; liquid-liquid phase transitions
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

As follows from the title, this Topical Collection “Feature Papers in Molecular Biophysics” aims to collect high quality research articles, short communications, and review articles in all the fields of molecular biophysics. Since the aim of this Topical Collection is to illustrate, through selected works, frontier research in molecular biophysics, we encourage Editorial Board Members of the Molecular Biophysics Section of the International Journal of Molecular Sciences to contribute papers reflecting the latest progress in their research field, or to invite relevant experts and colleagues to do so.

Topics include, but are not limited to:

  • molecular structure and dynamics
  • nucleic acid structure and dynamics
  • protein structure and dynamics
  • membrane structure and dynamics
  • biomimetic material structure and dynamics
  • molecular simulations
  • molecular modeling
  • single molecule biophysics
  • biophysical techniques in the study of biomacromolecular and biomimetic systems
  • biomolecular interactions
  • biomimetic material interactions
  • macromolecular structure determination or prediction
  • characterization of disordered proteins and their interactions
  • computational biophysics
  • bioinformatics
  • biophysical and computational approaches to drug design and development
  • advances in molecular biophysical methodologies as well as imaging techniques and data analysis
  • application of biophysical methods

Prof. Dr. Ian A. Nicholls
Prof. Dr. Vladimir N. Uversky
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. International Journal of Molecular Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. There is an Article Processing Charge (APC) for publication in this open access journal. For details about the APC please see here. Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • biophysics
  • molecular imprinting
  • molecular simulations
  • molecular structure
  • molecular dynamics
  • molecular mechanics
  • thermodynamics
  • biomolecular interactions
  • protein structure and folding
  • intrinsically disordered proteins
  • structure prediction
  • nucleic acid–protein interactions
  • protein–membrane interactions
  • protein–DNA interactions
  • posttranslational modifications
  • drug–receptor interactions
  • protein design
  • protein engineering
  • protein–ligand binding
  • transmembrane proteins
  • chaperones
  • enzymology
  • molecular recognition
  • molecular modeling
  • membrane dynamics
  • macromolecular structure and dynamics
  • DNA structure and dynamics
  • RNA structure
  • genome structure
  • structure–function relationships
  • ion channels
  • spectroscopic techniques
  • biomolecular NMR
  • inter-molecular interactions
  • X-ray crystallography
  • macromolecular crystallography
  • crystal thermodynamics
  • microcalorimetry
  • transient kinetic techniques
  • fluorescence imaging
  • single-molecule microscopy
  • statistical mechanics
  • computer simulations
  • computational modeling
  • molecular modeling

Published Papers (148 papers)

2025

Jump to: 2024, 2023, 2022, 2021, 2020, 2019

30 pages, 4516 KiB  
Article
Mutational Scanning and Binding Free Energy Computations of the SARS-CoV-2 Spike Complexes with Distinct Groups of Neutralizing Antibodies: Energetic Drivers of Convergent Evolution of Binding Affinity and Immune Escape Hotspots
by Mohammed Alshahrani, Vedant Parikh, Brandon Foley, Nishank Raisinghani and Gennady Verkhivker
Int. J. Mol. Sci. 2025, 26(4), 1507; https://doi.org/10.3390/ijms26041507 - 11 Feb 2025
Abstract
The rapid evolution of SARS-CoV-2 has led to the emergence of variants with increased immune evasion capabilities, posing significant challenges to antibody-based therapeutics and vaccines. In this study, we conducted a comprehensive structural and energetic analysis of SARS-CoV-2 spike receptor-binding domain (RBD) complexes [...] Read more.
The rapid evolution of SARS-CoV-2 has led to the emergence of variants with increased immune evasion capabilities, posing significant challenges to antibody-based therapeutics and vaccines. In this study, we conducted a comprehensive structural and energetic analysis of SARS-CoV-2 spike receptor-binding domain (RBD) complexes with neutralizing antibodies from four distinct groups (A–D), including group A LY-CoV016, group B AZD8895 and REGN10933, group C LY-CoV555, and group D antibodies AZD1061, REGN10987, and LY-CoV1404. Using coarse-grained simplified simulation models, rapid energy-based mutational scanning, and rigorous MM-GBSA binding free energy calculations, we elucidated the molecular mechanisms of antibody binding and escape mechanisms, identified key binding hotspots, and explored the evolutionary strategies employed by the virus to evade neutralization. The residue-based decomposition analysis revealed energetic mechanisms and thermodynamic factors underlying the effect of mutations on antibody binding. The results demonstrate excellent qualitative agreement between the predicted binding hotspots and the latest experiments on antibody escape. These findings provide valuable insights into the molecular determinants of antibody binding and viral escape, highlighting the importance of targeting conserved epitopes and leveraging combination therapies to mitigate the risk of immune evasion. Full article
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22 pages, 5762 KiB  
Article
Transcriptomics Unveil Canonical and Non-Canonical Heat Shock-Induced Pathways in Human Cell Lines
by Andrew Reinschmidt, Luis Solano, Yonny Chavez, William Drew Hulsy and Nikolas Nikolaidis
Int. J. Mol. Sci. 2025, 26(3), 1057; https://doi.org/10.3390/ijms26031057 - 26 Jan 2025
Abstract
The cellular stress response (CSR) is a conserved mechanism that protects cells from -environmental and physiological stressors. The heat shock response (HSR), a critical component of the CSR, utilizes molecular chaperones to mitigate proteotoxic stress caused by elevated temperatures. We hypothesized that while [...] Read more.
The cellular stress response (CSR) is a conserved mechanism that protects cells from -environmental and physiological stressors. The heat shock response (HSR), a critical component of the CSR, utilizes molecular chaperones to mitigate proteotoxic stress caused by elevated temperatures. We hypothesized that while the canonical HSR pathways are conserved across cell types, specific cell lines may exhibit unique transcriptional responses to heat shock. To test this, we compared the transcriptomic responses of HEK293, HepG2, and HeLa cells under control conditions immediately following heat shock and after an 8-h recovery period. RNA sequencing revealed the conserved activation of canonical HSR pathways, including the unfolded protein response, alongside the -enrichment of the non-canonical “Receptor Ligand Activity” pathway across all cell lines. Cell-line-specific variations were observed, with HepG2 cells exhibiting significantly higher ex-pression levels of certain genes compared to other cell lines under stress conditions, as well as greater fold changes in gene expression relative to its control conditions. Validation by qPCR confirmed the activation of key genes within the “Receptor Ligand Activity” pathway across time points. These findings provide insights into conserved and context-specific aspects of the HSR, contributing to a more comprehensive understanding of stress response mechanisms across mammalian cells. Full article
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20 pages, 3149 KiB  
Article
Look Beyond Plasma Membrane Biophysics: Revealing Considerable Variability of the Dipole Potential Between Plasma and Organelle Membranes of Living Cells
by Mate Szabo, Bence Cs. Szabo, Kitti Kurtan, Zoltan Varga, Gyorgy Panyi, Peter Nagy, Florina Zakany and Tamas Kovacs
Int. J. Mol. Sci. 2025, 26(3), 889; https://doi.org/10.3390/ijms26030889 - 22 Jan 2025
Viewed by 597
Abstract
Due to the lack of measurement techniques suitable for examining compartments of intact, living cells, membrane biophysics is almost exclusively investigated in the plasma membrane despite the fact that its alterations in intracellular organelles may also contribute to disease pathogenesis. Here, we employ [...] Read more.
Due to the lack of measurement techniques suitable for examining compartments of intact, living cells, membrane biophysics is almost exclusively investigated in the plasma membrane despite the fact that its alterations in intracellular organelles may also contribute to disease pathogenesis. Here, we employ a novel, easy-to-use, confocal microscopy-based approach utilizing F66, an environment-sensitive fluorophore in combination with fluorescent organelle markers and quantitative image analysis to determine the magnitude of the molecular order-related dipole potential in the plasma membrane and intracellular organelles of various tumor and neural cell lines. Our comparative analysis demonstrates considerable intracellular variations of the dipole potential that may be large enough to modulate protein functions, with an inward decreasing gradient on the route of the secretory/endocytic pathway (plasma membrane >> lysosome > Golgi > endoplasmic reticulum), whereas mitochondrial membranes are characterized by a dipole potential slightly larger than that of lysosomes. Our approach is suitable and sensitive enough to quantify membrane biophysical properties selectively in intracellular compartments and their comparative analysis in intact, living cells, and, therefore, to identify the affected organelles and potential therapeutic targets in diseases associated with alterations in membrane lipid composition and thus biophysics such as tumors, metabolic, neurodegenerative, or lysosomal storage disorders. Full article
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21 pages, 2794 KiB  
Review
The Ferroxidase–Permease System for Transport of Iron Across Membranes: From Yeast to Humans
by Matteo Amadei, Fabio Polticelli, Giovanni Musci and Maria Carmela Bonaccorsi di Patti
Int. J. Mol. Sci. 2025, 26(3), 875; https://doi.org/10.3390/ijms26030875 - 21 Jan 2025
Viewed by 351
Abstract
Transport of iron across the cell membrane is a tightly controlled process carried out by specific proteins in all living cells. In yeast and in mammals, a system formed by an enzyme with ferroxidase activity coupled to a membrane transporter supports iron uptake [...] Read more.
Transport of iron across the cell membrane is a tightly controlled process carried out by specific proteins in all living cells. In yeast and in mammals, a system formed by an enzyme with ferroxidase activity coupled to a membrane transporter supports iron uptake or iron efflux, respectively. Ferroxidase belongs to the family of blue multicopper oxidases, enzymes able to couple the one-electron oxidation of substrate(s) to full reduction of molecular oxygen to water. On the other hand, the permeases are widely different and are specific to Fe3+ and Fe2+ in yeast and multicellular organisms, respectively. This review will describe the yeast and human ferroxidase–permease systems, highlighting similarities and differences in structure, function and regulation of the respective protein components. Full article
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2024

Jump to: 2025, 2023, 2022, 2021, 2020, 2019

20 pages, 5179 KiB  
Article
AlphaFold2-Based Characterization of Apo and Holo Protein Structures and Conformational Ensembles Using Randomized Alanine Sequence Scanning Adaptation: Capturing Shared Signature Dynamics and Ligand-Induced Conformational Changes
by Nishank Raisinghani, Vedant Parikh, Brandon Foley and Gennady Verkhivker
Int. J. Mol. Sci. 2024, 25(23), 12968; https://doi.org/10.3390/ijms252312968 - 2 Dec 2024
Viewed by 936
Abstract
Proteins often exist in multiple conformational states, influenced by the binding of ligands or substrates. The study of these states, particularly the apo (unbound) and holo (ligand-bound) forms, is crucial for understanding protein function, dynamics, and interactions. In the current study, we use [...] Read more.
Proteins often exist in multiple conformational states, influenced by the binding of ligands or substrates. The study of these states, particularly the apo (unbound) and holo (ligand-bound) forms, is crucial for understanding protein function, dynamics, and interactions. In the current study, we use AlphaFold2, which combines randomized alanine sequence masking with shallow multiple sequence alignment subsampling to expand the conformational diversity of the predicted structural ensembles and capture conformational changes between apo and holo protein forms. Using several well-established datasets of structurally diverse apo-holo protein pairs, the proposed approach enables robust predictions of apo and holo structures and conformational ensembles, while also displaying notably similar dynamics distributions. These observations are consistent with the view that the intrinsic dynamics of allosteric proteins are defined by the structural topology of the fold and favor conserved conformational motions driven by soft modes. Our findings provide evidence that AlphaFold2 combined with randomized alanine sequence masking can yield accurate and consistent results in predicting moderate conformational adjustments between apo and holo states, especially for proteins with localized changes upon ligand binding. For large hinge-like domain movements, the proposed approach can predict functional conformations characteristic of both apo and ligand-bound holo ensembles in the absence of ligand information. These results are relevant for using this AlphaFold adaptation for probing conformational selection mechanisms according to which proteins can adopt multiple conformations, including those that are competent for ligand binding. The results of this study indicate that robust modeling of functional protein states may require more accurate characterization of flexible regions in functional conformations and the detection of high-energy conformations. By incorporating a wider variety of protein structures in training datasets, including both apo and holo forms, the model can learn to recognize and predict the structural changes that occur upon ligand binding. Full article
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16 pages, 2725 KiB  
Article
5-PC as a Lipid Probe Molecule and as a Second Phospholipid in Binary Phospholipid Mixtures: Saturation Recovery EPR Studies
by Witold K. Subczynski and Justyna Widomska
Int. J. Mol. Sci. 2024, 25(23), 12913; https://doi.org/10.3390/ijms252312913 - 30 Nov 2024
Viewed by 569
Abstract
Mixtures of two phospholipids (PLs) with different main phase transition temperatures were investigated. Host PLs (HPLs) were represented by DMPC, DPPC, DSPC, and DMPE. The admixed PL was the spin-labeled phosphatidylcholine 5-PC(1-palmitoyl-2-(5-doxylstearoyl)phosphatidylcholine), with a unique opportunity to monitor the properties and the local [...] Read more.
Mixtures of two phospholipids (PLs) with different main phase transition temperatures were investigated. Host PLs (HPLs) were represented by DMPC, DPPC, DSPC, and DMPE. The admixed PL was the spin-labeled phosphatidylcholine 5-PC(1-palmitoyl-2-(5-doxylstearoyl)phosphatidylcholine), with a unique opportunity to monitor the properties and the local environments of all admixed PL molecules using saturation recovery EPR methods. Below the HPL phase transition temperatures, 5-PC mixes with HPL to form two distinct pools with different rotational diffusion rates. The fluidity of the local environment in these two pools is very different, being more fluid for molecules with greater rotational diffusion rates. Above the HPL phase transition temperature, 5-PC mixes with HPL uniformly. This is independent of the HPL, observed for 5-PC concentrations from 0.25 mol% up to 20 mol% and for the wide temperature range. Assuminga very low concentration of 5-PC is an ideal probe molecule, we can conclude that small fluid phase domains made of HPL molecules are formed below the phase transition temperature of the HPL bilayers. In binary mixtures of HPLs with 5-PC, below the phase transition of HPL bilayers, fluid phase domains are created within the bulk gel phase of HPL lipids by the admixed second PL, namely 5-PC. Full article
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20 pages, 8833 KiB  
Article
Calcium Indicators with Fluorescence Lifetime-Based Signal Readout: A Structure–Function Study
by Tatiana R. Simonyan, Larisa A. Varfolomeeva, Anastasia V. Mamontova, Alexey A. Kotlobay, Andrey Y. Gorokhovatsky, Alexey M. Bogdanov and Konstantin M. Boyko
Int. J. Mol. Sci. 2024, 25(23), 12493; https://doi.org/10.3390/ijms252312493 - 21 Nov 2024
Viewed by 1177
Abstract
The calcium cation is a crucial signaling molecule involved in numerous cellular pathways. Beyond its role as a messenger or modulator in intracellular cascades, calcium’s function in excitable cells, including nerve impulse transmission, is remarkable. The central role of calcium in nervous activity [...] Read more.
The calcium cation is a crucial signaling molecule involved in numerous cellular pathways. Beyond its role as a messenger or modulator in intracellular cascades, calcium’s function in excitable cells, including nerve impulse transmission, is remarkable. The central role of calcium in nervous activity has driven the rapid development of fluorescent techniques for monitoring this cation in living cells. Specifically, genetically encoded calcium indicators (GECIs) are the most in-demand molecular tools in their class. In this work, we address two issues of calcium imaging by designing indicators based on the successful GCaMP6 backbone and the fluorescent protein BrUSLEE. The first indicator variant (GCaMP6s-BrUS), with a reduced, calcium-insensitive fluorescence lifetime, has potential in monitoring calcium dynamics with a high temporal resolution in combination with advanced microscopy techniques, such as light beads microscopy, where the fluorescence lifetime limits acquisition speed. Conversely, the second variant (GCaMP6s-BrUS-145), with a flexible, calcium-sensitive fluorescence lifetime, is relevant for static measurements, particularly for determining absolute calcium concentration values using fluorescence lifetime imaging microscopy (FLIM). To identify the structural determinants of calcium sensitivity in these indicator variants, we determine their spatial structures. A comparative structural analysis allowed the optimization of the GCaMP6s-BrUS construct, resulting in an indicator variant combining calcium-sensitive behavior in the time domain and enhanced molecular brightness. Our data may serve as a starting point for further engineering efforts towards improved GECI variants with fine-tuned fluorescence lifetimes. Full article
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13 pages, 1545 KiB  
Article
Phase-Sensitive Fluorescence Image Correlation Spectroscopy
by Andrew H. A. Clayton
Int. J. Mol. Sci. 2024, 25(20), 11165; https://doi.org/10.3390/ijms252011165 - 17 Oct 2024
Viewed by 688
Abstract
Fluorescence lifetime imaging microscopy is sensitive to molecular interactions and environments. In homo-dyne frequency-domain fluorescence lifetime imaging microscopy, images of fluorescence objects are acquired at different phase settings of the detector. The detected intensity as a function of detector phase is a sinusoidal [...] Read more.
Fluorescence lifetime imaging microscopy is sensitive to molecular interactions and environments. In homo-dyne frequency-domain fluorescence lifetime imaging microscopy, images of fluorescence objects are acquired at different phase settings of the detector. The detected intensity as a function of detector phase is a sinusoidal function that is sensitive to the lifetime of the fluorescent species. In this paper, the theory of phase-sensitive fluorescence image correlation spectroscopy is described. In this version of lifetime imaging, image correlation spectroscopy analysis (i.e., spatial autocorrelation) is applied to successive fluorescence images acquired at different phase settings of the detector. Simulations of different types of lifetime distributions reveal that the phase-dependent density of fluorescent objects is dependent on the heterogeneity of lifetimes present in the objects. We provide an example of this analysis workflow to a cervical cancer cell stained with a fluorescent membrane probe. Full article
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24 pages, 5207 KiB  
Article
Predicting Mutation-Induced Allosteric Changes in Structures and Conformational Ensembles of the ABL Kinase Using AlphaFold2 Adaptations with Alanine Sequence Scanning
by Nishank Raisinghani, Mohammed Alshahrani, Grace Gupta and Gennady Verkhivker
Int. J. Mol. Sci. 2024, 25(18), 10082; https://doi.org/10.3390/ijms251810082 - 19 Sep 2024
Cited by 2 | Viewed by 1812
Abstract
Despite the success of AlphaFold2 approaches in predicting single protein structures, these methods showed intrinsic limitations in predicting multiple functional conformations of allosteric proteins and have been challenged to accurately capture the effects of single point mutations that induced significant structural changes. We [...] Read more.
Despite the success of AlphaFold2 approaches in predicting single protein structures, these methods showed intrinsic limitations in predicting multiple functional conformations of allosteric proteins and have been challenged to accurately capture the effects of single point mutations that induced significant structural changes. We examined several implementations of AlphaFold2 methods to predict conformational ensembles for state-switching mutants of the ABL kinase. The results revealed that a combination of randomized alanine sequence masking with shallow multiple sequence alignment subsampling can significantly expand the conformational diversity of the predicted structural ensembles and capture shifts in populations of the active and inactive ABL states. Consistent with the NMR experiments, the predicted conformational ensembles for M309L/L320I and M309L/H415P ABL mutants that perturb the regulatory spine networks featured the increased population of the fully closed inactive state. The proposed adaptation of AlphaFold can reproduce the experimentally observed mutation-induced redistributions in the relative populations of the active and inactive ABL states and capture the effects of regulatory mutations on allosteric structural rearrangements of the kinase domain. The ensemble-based network analysis complemented AlphaFold predictions by revealing allosteric hotspots that correspond to state-switching mutational sites which may explain the global effect of regulatory mutations on structural changes between the ABL states. This study suggested that attention-based learning of long-range dependencies between sequence positions in homologous folds and deciphering patterns of allosteric interactions may further augment the predictive abilities of AlphaFold methods for modeling of alternative protein sates, conformational ensembles and mutation-induced structural transformations. Full article
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16 pages, 3438 KiB  
Article
Measurement and Characterization of the Electrical Properties of Actin Filaments
by Serena Paladini, Barbara Truglia, Karthik Shankar and Jack Adam Tuszynski
Int. J. Mol. Sci. 2024, 25(10), 5485; https://doi.org/10.3390/ijms25105485 - 17 May 2024
Cited by 1 | Viewed by 887
Abstract
Actin filaments, as key components of the cytoskeleton, have aroused great interest due to their numerous functional roles in eukaryotic cells, including intracellular electrical signaling. The aim of this research is to characterize the alternating current (AC) conduction characteristics of both globular and [...] Read more.
Actin filaments, as key components of the cytoskeleton, have aroused great interest due to their numerous functional roles in eukaryotic cells, including intracellular electrical signaling. The aim of this research is to characterize the alternating current (AC) conduction characteristics of both globular and polymerized actin and quantitatively compare their values to those theoretically predicted earlier. Actin filaments have been demonstrated to act as conducting bionanowires, forming a signaling network capable of transmitting ionic waves in cells. We performed conductivity measurements for different concentrations of actin, considering both unpolymerized and polymerized actin to identify potential differences in their electrical properties. These measurements revealed two relevant characteristics: first, the polymerized actin, arranged in filaments, has a lower impedance than its globular counterpart; second, an increase in the actin concentration leads to higher conductivities. Furthermore, from the data collected, we developed a quantitative model to represent the electrical properties of actin in a buffer solution. We hypothesize that actin filaments can be modeled as electrical resistor–inductor–capacitor (RLC) circuits, where the resistive contribution is due to the viscous ion flows along the filaments; the inductive contribution is due to the solenoidal flows along and around the helix-shaped filament and the capacitive contribution is due to the counterion layer formed around each negatively charged filament. Full article
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19 pages, 1766 KiB  
Article
RadPhysBio: A Radiobiological Database for the Prediction of Cell Survival upon Exposure to Ionizing Radiation
by Vassiliki Zanni, Dimitris Papakonstantinou, Spyridon A. Kalospyros, Dimitris Karaoulanis, Gökay Mehmet Biz, Lorenzo Manti, Adam Adamopoulos, Athanasia Pavlopoulou and Alexandros G. Georgakilas
Int. J. Mol. Sci. 2024, 25(9), 4729; https://doi.org/10.3390/ijms25094729 - 26 Apr 2024
Viewed by 1774
Abstract
Based on the need for radiobiological databases, in this work, we mined experimental ionizing radiation data of human cells treated with X-rays, γ-rays, carbon ions, protons and α-particles, by manually searching the relevant literature in PubMed from 1980 until 2024. In order to [...] Read more.
Based on the need for radiobiological databases, in this work, we mined experimental ionizing radiation data of human cells treated with X-rays, γ-rays, carbon ions, protons and α-particles, by manually searching the relevant literature in PubMed from 1980 until 2024. In order to calculate normal and tumor cell survival α and β coefficients of the linear quadratic (LQ) established model, as well as the initial values of the double-strand breaks (DSBs) in DNA, we used WebPlotDigitizer and Python programming language. We also produced complex DNA damage results through the fast Monte Carlo code MCDS in order to complete any missing data. The calculated α/β values are in good agreement with those valued reported in the literature, where α shows a relatively good association with linear energy transfer (LET), but not β. In general, a positive correlation between DSBs and LET was observed as far as the experimental values are concerned. Furthermore, we developed a biophysical prediction model by using machine learning, which showed a good performance for α, while it underscored LET as the most important feature for its prediction. In this study, we designed and developed the novel radiobiological ‘RadPhysBio’ database for the prediction of irradiated cell survival (α and β coefficients of the LQ model). The incorporation of machine learning and repair models increases the applicability of our results and the spectrum of potential users. Full article
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24 pages, 703 KiB  
Review
Transmission-Blocking Vaccines against Schistosomiasis Japonica
by Chika P. Zumuk, Malcolm K. Jones, Severine Navarro, Darren J. Gray and Hong You
Int. J. Mol. Sci. 2024, 25(3), 1707; https://doi.org/10.3390/ijms25031707 - 30 Jan 2024
Cited by 2 | Viewed by 2649
Abstract
Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can [...] Read more.
Control of schistosomiasis japonica, endemic in Asia, including the Philippines, China, and Indonesia, is extremely challenging. Schistosoma japonicum is a highly pathogenic helminth parasite, with disease arising predominantly from an immune reaction to entrapped parasite eggs in tissues. Females of this species can generate 1000–2200 eggs per day, which is about 3- to 15-fold greater than the egg output of other schistosome species. Bovines (water buffalo and cattle) are the predominant definitive hosts and are estimated to generate up to 90% of parasite eggs released into the environment in rural endemic areas where these hosts and humans are present. Here, we highlight the necessity of developing veterinary transmission-blocking vaccines for bovines to better control the disease and review potential vaccine candidates. We also point out that the approach to producing efficacious transmission-blocking animal-based vaccines before moving on to human vaccines is crucial. This will result in effective and feasible public health outcomes in agreement with the One Health concept to achieve optimum health for people, animals, and the environment. Indeed, incorporating a veterinary-based transmission vaccine, coupled with interventions such as human mass drug administration, improved sanitation and hygiene, health education, and snail control, would be invaluable to eliminating zoonotic schistosomiasis. Full article
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2023

Jump to: 2025, 2024, 2022, 2021, 2020, 2019

13 pages, 2946 KiB  
Article
Simultaneous Improvement in the Thermostability and Catalytic Activity of Epoxidase Lsd18 for the Synthesis of Lasalocid A
by Ning Liu, Hongli Xiao, Yongjian Zang, Longji Zhou, Jun Mencius, Zhiwei Yang, Shu Quan and Xi Chen
Int. J. Mol. Sci. 2023, 24(23), 16795; https://doi.org/10.3390/ijms242316795 - 27 Nov 2023
Viewed by 1452
Abstract
Enzymes used in the synthesis of natural products are potent catalysts, capable of efficient and stereoselective chemical transformations. Lsd18 catalyzes two sequential epoxidations during the biosynthesis of lasalocid A, a polyether polyketide natural product. We performed protein engineering on Lsd18 to improve its [...] Read more.
Enzymes used in the synthesis of natural products are potent catalysts, capable of efficient and stereoselective chemical transformations. Lsd18 catalyzes two sequential epoxidations during the biosynthesis of lasalocid A, a polyether polyketide natural product. We performed protein engineering on Lsd18 to improve its thermostability and catalytic activity. Utilizing structure-guided methods of FoldX and Rosetta-ddG, we designed 15 mutants of Lsd18. Screening of these mutants using thermal shift assay identified stabilized variants Lsd18-T189M, Lsd18-S195M, and the double mutant Lsd18-T189M-S195M. Trypsin digestion, molecular dynamic simulation, circular dichroism (CD) spectroscopy, and X-ray crystallography provided insights into the molecular basis for the improved enzyme properties. Notably, enhanced hydrophobic interaction within the enzyme core and interaction of the protein with the FAD cofactor appear to be responsible for its better thermostability. Full article
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17 pages, 1929 KiB  
Article
Biophysical Insights into the Antitumoral Activity of Crotalicidin against Breast Cancer Model Membranes
by Maria C. Klaiss-Luna, Juan M. Giraldo-Lorza, Małgorzata Jemioła-Rzemińska, Kazimierz Strzałka and Marcela Manrique-Moreno
Int. J. Mol. Sci. 2023, 24(22), 16226; https://doi.org/10.3390/ijms242216226 - 12 Nov 2023
Cited by 3 | Viewed by 1508
Abstract
Bioactive peptides have emerged as promising therapeutic agents with antimicrobial, antifungal, antiparasitic, and, recently, antitumoral properties with a mechanism of action based on membrane destabilization and cell death, often involving a conformational change in the peptide. This biophysical study aims to provide preliminary [...] Read more.
Bioactive peptides have emerged as promising therapeutic agents with antimicrobial, antifungal, antiparasitic, and, recently, antitumoral properties with a mechanism of action based on membrane destabilization and cell death, often involving a conformational change in the peptide. This biophysical study aims to provide preliminary insights into the membrane-level antitumoral mode of action of crotalicidin, a cationic host defense peptide from rattlesnake venom, toward breast cancer cell lines. The lipid composition of breast cancer cell lines was obtained after lipid extraction and quantification to prepare representative cell membrane models. Membrane–peptide interaction studies were performed using differential scanning calorimetry and Fourier-transform infrared spectroscopy. The outcome evidences the potential antitumoral activity and selectivity of crotalicidin toward breast cancer cell lines and suggests a mechanism initiated by the electrostatic interaction of the peptide with the lipid bilayer surface and posterior conformation change with membrane intercalation between the acyl chains in negatively charged lipid systems. This research provides valuable information that clears up the antitumoral mode of action of crotalicidin. Full article
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17 pages, 2475 KiB  
Article
K+-Dependent Photocycle and Photocurrent Reveal the Uptake of K+ in Light-Driven Sodium Pump
by Jikang Xu, Qifan Yang, Baofu Ma, Longjie Li, Fei Kong, Lan Xiao and Deliang Chen
Int. J. Mol. Sci. 2023, 24(19), 14414; https://doi.org/10.3390/ijms241914414 - 22 Sep 2023
Cited by 2 | Viewed by 1483
Abstract
Engineering light-controlled K+ pumps from Na+-pumping rhodopsins (NaR) greatly expands the scope of optogenetic applications. However, the limited knowledge regarding the kinetic and selective mechanism of K+ uptake has significantly impeded the modification and design of light-controlled K+ [...] Read more.
Engineering light-controlled K+ pumps from Na+-pumping rhodopsins (NaR) greatly expands the scope of optogenetic applications. However, the limited knowledge regarding the kinetic and selective mechanism of K+ uptake has significantly impeded the modification and design of light-controlled K+ pumps, as well as their practical applications in various fields, including neuroscience. In this study, we presented K+-dependent photocycle kinetics and photocurrent of a light-driven Na+ pump called Nonlabens dokdonensis rhodopsin 2 (NdR2). As the concentration of K+ increased, we observed the accelerated decay of M intermediate in the wild type (WT) through flash photolysis. In 100 mM KCl, the lifetime of the M decay was approximately 1.0 s, which shortened to around 0.6 s in 1 M KCl. Additionally, the K+-dependent M decay kinetics were also observed in the G263W/N61P mutant, which transports K+. In 100 mM KCl, the lifetime of the M decay was approximately 2.5 s, which shortened to around 0.2 s in 1 M KCl. According to the competitive model, in high KCl, K+ may be taken up from the cytoplasmic surface, competing with Na+ or H+ during M decay. This was further confirmed by the K+-dependent photocurrent of WT liposome. As the concentration of K+ increased to 500 mM, the amplitude of peak current significantly dropped to approximately ~60%. Titration experiments revealed that the ratio of the rate constant of H+ uptake (kH) to that of K+ uptake (kK) is >108. Compared to the WT, the G263W/N61P mutant exhibited a decrease of approximately 40-fold in kH/kK. Previous studies focused on transforming NaR into K+ pumps have primarily targeted the intracellular ion uptake region of Krokinobacter eikastus rhodopsin 2 (KR2) to enhance K+ uptake. However, our results demonstrate that the naturally occurring WT NdR2 is capable of intracellular K+ uptake without requiring structural modifications on the intracellular region. This discovery provides diverse options for future K+ pump designs. Furthermore, we propose a novel photocurrent-based approach to evaluate K+ uptake, which can serve as a reference for similar studies on other ion pumps. In conclusion, our research not only provides new insights into the mechanism of K+ uptake but also offers a valuable point of reference for the development of optogenetic tools and other applications in this field. Full article
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14 pages, 2778 KiB  
Article
A High-Throughput Small-Angle X-ray Scattering Assay to Determine the Conformational Change of Plasminogen
by Adam J. Quek, Nathan P. Cowieson, Tom T. Caradoc-Davies, Paul J. Conroy, James C. Whisstock and Ruby H. P. Law
Int. J. Mol. Sci. 2023, 24(18), 14258; https://doi.org/10.3390/ijms241814258 - 19 Sep 2023
Cited by 2 | Viewed by 1359
Abstract
Plasminogen (Plg) is the inactive form of plasmin (Plm) that exists in two major glycoforms, referred to as glycoforms I and II (GI and GII). In the circulation, Plg assumes an activation-resistant “closed” conformation via interdomain interactions and is mediated by the lysine [...] Read more.
Plasminogen (Plg) is the inactive form of plasmin (Plm) that exists in two major glycoforms, referred to as glycoforms I and II (GI and GII). In the circulation, Plg assumes an activation-resistant “closed” conformation via interdomain interactions and is mediated by the lysine binding site (LBS) on the kringle (KR) domains. These inter-domain interactions can be readily disrupted when Plg binds to lysine/arginine residues on protein targets or free L-lysine and analogues. This causes Plg to convert into an “open” form, which is crucial for activation by host activators. In this study, we investigated how various ligands affect the kinetics of Plg conformational change using small-angle X-ray scattering (SAXS). We began by examining the open and closed conformations of Plg using size-exclusion chromatography (SEC) coupled with SAXS. Next, we developed a high-throughput (HTP) 96-well SAXS assay to study the conformational change of Plg. This method enables us to determine the Kopen value, which is used to directly compare the effect of different ligands on Plg conformation. Based on our analysis using Plg GII, we have found that the Kopen of ε-aminocaproic acid (EACA) is approximately three times greater than that of tranexamic acid (TXA), which is widely recognized as a highly effective ligand. We demonstrated further that Plg undergoes a conformational change when it binds to the C-terminal peptides of the inhibitor α2-antiplasmin (α2AP) and receptor Plg–RKT. Our findings suggest that in addition to the C-terminal lysine, internal lysine(s) are also necessary for the formation of open Plg. Finally, we compared the conformational changes of Plg GI and GII directly and found that the closed form of GI, which has an N-linked glycosylation, is less stable. To summarize, we have successfully determined the response of Plg to various ligand/receptor peptides by directly measuring the kinetics of its conformational changes. Full article
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17 pages, 2938 KiB  
Article
Evaluating the Cysteine-Rich and Catalytic Subdomains of Human Tyrosinase and OCA1-Related Mutants Using 1 μs Molecular Dynamics Simulation
by Taariq Woods and Yuri V. Sergeev
Int. J. Mol. Sci. 2023, 24(17), 13032; https://doi.org/10.3390/ijms241713032 - 22 Aug 2023
Cited by 2 | Viewed by 1422
Abstract
The inherited disorder oculocutaneous albinism type 1 (OCA1) is caused by mutations in the TYR gene encoding tyrosinase (Tyr), an enzyme essential to producing pigments throughout the human body. The intramelanosomal domain of Tyr consists of the cysteine-rich and tyrosinase catalytic subdomains, which [...] Read more.
The inherited disorder oculocutaneous albinism type 1 (OCA1) is caused by mutations in the TYR gene encoding tyrosinase (Tyr), an enzyme essential to producing pigments throughout the human body. The intramelanosomal domain of Tyr consists of the cysteine-rich and tyrosinase catalytic subdomains, which are essential for enzymatic activity. In protein unfolding, the roles of these subdomains are not well established. Here, we performed six molecular dynamics simulations at room temperature for Tyr and OCA1-related mutant variants P406L and R402Q intramelanosomal domains. The proteins were simulated for 1 μs in water and urea to induce unfolding. In urea, we observed increases in surface area, decreases in intramolecular hydrogen bonding, and decreases in hydrophobic interactions, suggesting a ‘molten globule’ state for each protein. Between all conditions, the cysteine-rich subdomain remains stable, whereas the catalytic subdomain shows increased flexibility. This flexibility is intensified by the P406L mutation, while R402Q increases the catalytic domain’s rigidity. The cysteine-rich subdomain is rigid, preventing the protein from unfolding, whereas the flexibility of the catalytic subdomain accommodates mutational changes that could inhibit activity. These findings match the conclusions from our experimental work suggesting the function alteration by the P406L mutation, and the potential role of R402Q as a polymorphism. Full article
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19 pages, 11780 KiB  
Article
Elucidating the Racemization Mechanism of Aliphatic and Aromatic Amino Acids by In Silico Tools
by Mateo S. Andino, José R. Mora, José L. Paz, Edgar A. Márquez, Yunierkis Perez-Castillo and Guillermin Agüero-Chapin
Int. J. Mol. Sci. 2023, 24(15), 11877; https://doi.org/10.3390/ijms241511877 - 25 Jul 2023
Cited by 1 | Viewed by 1825
Abstract
The racemization of biomolecules in the active site can reduce the biological activity of drugs, and the mechanism involved in this process is still not fully comprehended. The present study investigates the impact of aromaticity on racemization using advanced theoretical techniques based on [...] Read more.
The racemization of biomolecules in the active site can reduce the biological activity of drugs, and the mechanism involved in this process is still not fully comprehended. The present study investigates the impact of aromaticity on racemization using advanced theoretical techniques based on density functional theory. Calculations were performed at the ωb97xd/6-311++g(d,p) level of theory. A compelling explanation for the observed aromatic stabilization via resonance is put forward, involving a carbanion intermediate. The analysis, employing Hammett’s parameters, convincingly supports the presence of a negative charge within the transition state of aromatic compounds. Moreover, the combined utilization of natural bond orbital (NBO) analysis and intrinsic reaction coordinate (IRC) calculations confirms the pronounced stabilization of electron distribution within the carbanion intermediate. To enhance our understanding of the racemization process, a thorough examination of the evolution of NBO charges and Wiberg bond indices (WBIs) at all points along the IRC profile is performed. This approach offers valuable insights into the synchronicity parameters governing the racemization reactions. Full article
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16 pages, 2722 KiB  
Article
I-Shaped Dimers of a Plant Chloroplast FOF1-ATP Synthase in Response to Changes in Ionic Strength
by Stepan D. Osipov, Yury L. Ryzhykau, Egor V. Zinovev, Andronika V. Minaeva, Sergey D. Ivashchenko, Dmitry P. Verteletskiy, Vsevolod V. Sudarev, Daria D. Kuklina, Mikhail Yu. Nikolaev, Yury S. Semenov, Yuliya A. Zagryadskaya, Ivan S. Okhrimenko, Margarita S. Gette, Elizaveta A. Dronova, Aleksei Yu. Shishkin, Norbert A. Dencher, Alexander I. Kuklin, Valentin Ivanovich, Vladimir N. Uversky and Alexey V. Vlasov
Int. J. Mol. Sci. 2023, 24(13), 10720; https://doi.org/10.3390/ijms241310720 - 27 Jun 2023
Cited by 3 | Viewed by 1994
Abstract
F-type ATP synthases play a key role in oxidative and photophosphorylation processes generating adenosine triphosphate (ATP) for most biochemical reactions in living organisms. In contrast to the mitochondrial FOF1-ATP synthases, those of chloroplasts are known to be mostly monomers [...] Read more.
F-type ATP synthases play a key role in oxidative and photophosphorylation processes generating adenosine triphosphate (ATP) for most biochemical reactions in living organisms. In contrast to the mitochondrial FOF1-ATP synthases, those of chloroplasts are known to be mostly monomers with approx. 15% fraction of oligomers interacting presumably non-specifically in a thylakoid membrane. To shed light on the nature of this difference we studied interactions of the chloroplast ATP synthases using small-angle X-ray scattering (SAXS) method. Here, we report evidence of I-shaped dimerization of solubilized FOF1-ATP synthases from spinach chloroplasts at different ionic strengths. The structural data were obtained by SAXS and demonstrated dimerization in response to ionic strength. The best model describing SAXS data was two ATP-synthases connected through F1/F1′ parts, presumably via their δ-subunits, forming “I” shape dimers. Such I-shaped dimers might possibly connect the neighboring lamellae in thylakoid stacks assuming that the FOF1 monomers comprising such dimers are embedded in parallel opposing stacked thylakoid membrane areas. If this type of dimerization exists in nature, it might be one of the pathways of inhibition of chloroplast FOF1-ATP synthase for preventing ATP hydrolysis in the dark, when ionic strength in plant chloroplasts is rising. Together with a redox switch inserted into a γ-subunit of chloroplast FOF1 and lateral oligomerization, an I-shaped dimerization might comprise a subtle regulatory process of ATP synthesis and stabilize the structure of thylakoid stacks in chloroplasts. Full article
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14 pages, 5035 KiB  
Review
On the Roles of the Nuclear Non-Coding RNA-Dependent Membrane-Less Organelles in the Cellular Stress Response
by Anastasia A. Gavrilova, Anna S. Fefilova, Innokentii E. Vishnyakov, Irina M. Kuznetsova, Konstantin K. Turoverov, Vladimir N. Uversky and Alexander V. Fonin
Int. J. Mol. Sci. 2023, 24(9), 8108; https://doi.org/10.3390/ijms24098108 - 30 Apr 2023
Cited by 3 | Viewed by 2266
Abstract
At the beginning of the 21st century, it became obvious that radical changes had taken place in the concept of living matter and, in particular, in the concept of the organization of intracellular space. The accumulated data testify to the essential importance of [...] Read more.
At the beginning of the 21st century, it became obvious that radical changes had taken place in the concept of living matter and, in particular, in the concept of the organization of intracellular space. The accumulated data testify to the essential importance of phase transitions of biopolymers (first of all, intrinsically disordered proteins and RNA) in the spatiotemporal organization of the intracellular space. Of particular interest is the stress-induced reorganization of the intracellular space. Examples of organelles formed in response to stress are nuclear A-bodies and nuclear stress bodies. The formation of these organelles is based on liquid–liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs) and non-coding RNA. Despite their overlapping composition and similar mechanism of formation, these organelles have different functional activities and physical properties. In this review, we will focus our attention on these membrane-less organelles (MLOs) and describe their functions, structure, and mechanism of formation. Full article
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15 pages, 2205 KiB  
Article
Oligomeric State and Holding Activity of Hsp60
by Celeste Caruso Bavisotto, Alessia Provenzano, Rosa Passantino, Antonella Marino Gammazza, Francesco Cappello, Pier Luigi San Biagio and Donatella Bulone
Int. J. Mol. Sci. 2023, 24(9), 7847; https://doi.org/10.3390/ijms24097847 - 25 Apr 2023
Cited by 5 | Viewed by 1923
Abstract
Similar to its bacterial homolog GroEL, Hsp60 in oligomeric conformation is known to work as a folding machine, with the assistance of co-chaperonin Hsp10 and ATP. However, recent results have evidenced that Hsp60 can stabilize aggregation-prone molecules in the absence of Hsp10 and [...] Read more.
Similar to its bacterial homolog GroEL, Hsp60 in oligomeric conformation is known to work as a folding machine, with the assistance of co-chaperonin Hsp10 and ATP. However, recent results have evidenced that Hsp60 can stabilize aggregation-prone molecules in the absence of Hsp10 and ATP by a different, “holding-like” mechanism. Here, we investigated the relationship between the oligomeric conformation of Hsp60 and its ability to inhibit fibrillization of the Ab40 peptide. The monomeric or tetradecameric form of the protein was isolated, and its effect on beta-amyloid aggregation was separately tested. The structural stability of the two forms of Hsp60 was also investigated using differential scanning calorimetry (DSC), light scattering, and circular dichroism. The results showed that the protein in monomeric form is less stable, but more effective against amyloid fibrillization. This greater functionality is attributed to the disordered nature of the domains involved in subunit contacts. Full article
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36 pages, 18751 KiB  
Review
FDA-Approved Fluorinated Heterocyclic Drugs from 2016 to 2022
by Carla Rizzo, Sara Amata, Ivana Pibiri, Andrea Pace, Silvestre Buscemi and Antonio Palumbo Piccionello
Int. J. Mol. Sci. 2023, 24(9), 7728; https://doi.org/10.3390/ijms24097728 - 23 Apr 2023
Cited by 47 | Viewed by 5800
Abstract
The inclusion of fluorine atoms or heterocyclic moiety into drug structures represents a recurrent motif in medicinal chemistry. The combination of these two features is constantly appearing in new molecular entities with various biological activities. This is demonstrated by the increasing number of [...] Read more.
The inclusion of fluorine atoms or heterocyclic moiety into drug structures represents a recurrent motif in medicinal chemistry. The combination of these two features is constantly appearing in new molecular entities with various biological activities. This is demonstrated by the increasing number of newly synthesized fluorinated heterocyclic compounds among the Food and Drug Administration FDA-approved drugs. In this review, the biological activity, as well as the synthetic aspects, of 33 recently FDA-approved fluorinated heterocyclic drugs from 2016 to 2022 are highlighted. Full article
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23 pages, 6113 KiB  
Article
A Novel Ambroxol-Derived Tetrahydroquinazoline with a Potency against SARS-CoV-2 Proteins
by Alena I. Krysantieva, Julia K. Voronina and Damir A. Safin
Int. J. Mol. Sci. 2023, 24(5), 4660; https://doi.org/10.3390/ijms24054660 - 28 Feb 2023
Cited by 12 | Viewed by 2766
Abstract
We report synthesis of a novel 1,2,3,4-tetrahydroquinazoline derivative, named 2-(6,8-dibromo-3-(4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazolin-2-yl)phenol (1), which was obtained from the hydrochloride of 4-((2-amino-3,5-dibromobenzyl)amino)cyclohexan-1-ol (ambroxol hydrochloride) and salicylaldehyde in EtOH. The resulting compound was produced in the form of colorless crystals of the composition 1∙0.5EtOH. [...] Read more.
We report synthesis of a novel 1,2,3,4-tetrahydroquinazoline derivative, named 2-(6,8-dibromo-3-(4-hydroxycyclohexyl)-1,2,3,4-tetrahydroquinazolin-2-yl)phenol (1), which was obtained from the hydrochloride of 4-((2-amino-3,5-dibromobenzyl)amino)cyclohexan-1-ol (ambroxol hydrochloride) and salicylaldehyde in EtOH. The resulting compound was produced in the form of colorless crystals of the composition 1∙0.5EtOH. The formation of the single product was confirmed by the IR and 1H spectroscopy, single-crystal and powder X-ray diffraction, and elemental analysis. The molecule of 1 contains a chiral tertiary carbon of the 1,2,3,4-tetrahydropyrimidine fragment and the crystal structure of 1∙0.5EtOH is a racemate. Optical properties of 1∙0.5EtOH were revealed by UV-vis spectroscopy in MeOH and it was established that the compound absorbs exclusively in the UV region up to about 350 nm. 1∙0.5EtOH in MeOH exhibits dual emission and the emission spectra contains bands at about 340 and 446 nm upon excitation at 300 and 360 nm, respectively. The DFT calculations were performed to verify the structure as well as electronic and optical properties of 1. ADMET properties of the R-isomer of 1 were evaluated using the SwissADME, BOILED-Egg, and ProTox-II tools. As evidenced from the blue dot position in the BOILED-Egg plot, both human blood–brain barrier penetration and gastrointestinal absorption properties are positive with the positive PGP effect on the molecule. Molecular docking was applied to examine the influence of the structures of both R-isomer and S-isomer of 1 on a series of the SARS-CoV-2 proteins. According to the docking analysis results, both isomers of 1 were found to be active against all the applied SARS-CoV-2 proteins with the best binding affinities with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207–379-AMP). Ligand efficiency scores for both isomers of 1 inside the binding sites of the applied proteins were also revealed and compared with the initial ligands. Molecular dynamics simulations were also applied to evaluate the stability of complexes of both isomers with Papain-like protease (PLpro) and nonstructural protein 3 (Nsp3_range 207–379-AMP). The complex of the S-isomer with Papain-like protease (PLpro) was found to be highly unstable, while the other complexes are stable. Full article
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19 pages, 4023 KiB  
Article
Structural Characteristics of High-Mobility Group Proteins HMGB1 and HMGB2 and Their Interaction with DNA
by Tatiana Y. Starkova, Alexander M. Polyanichko, Tatiana O. Artamonova, Anna S. Tsimokha, Alexey N. Tomilin and Elena V. Chikhirzhina
Int. J. Mol. Sci. 2023, 24(4), 3577; https://doi.org/10.3390/ijms24043577 - 10 Feb 2023
Cited by 13 | Viewed by 2849
Abstract
Non-histone nuclear proteins HMGB1 and HMGB2 (High Mobility Group) are involved in many biological processes, such as replication, transcription, and repair. The HMGB1 and HMGB2 proteins consist of a short N-terminal region, two DNA-binding domains, A and B, and a C-terminal sequence of [...] Read more.
Non-histone nuclear proteins HMGB1 and HMGB2 (High Mobility Group) are involved in many biological processes, such as replication, transcription, and repair. The HMGB1 and HMGB2 proteins consist of a short N-terminal region, two DNA-binding domains, A and B, and a C-terminal sequence of glutamic and aspartic acids. In this work, the structural organization of calf thymus HMGB1 and HMGB2 proteins and their complexes with DNA were studied using UV circular dichroism (CD) spectroscopy. Post-translational modifications (PTM) of HMGB1 and HMGB2 proteins were determined with MALDI mass spectrometry. We have shown that despite the similar primary structures of the HMGB1 and HMGB2 proteins, their post-translational modifications (PTMs) demonstrate quite different patterns. The HMGB1 PTMs are located predominantly in the DNA-binding A-domain and linker region connecting the A and B domains. On the contrary, HMGB2 PTMs are found mostly in the B-domain and within the linker region. It was also shown that, despite the high degree of homology between HMGB1 and HMGB2, the secondary structure of these proteins is also slightly different. We believe that the revealed structural properties might determine the difference in the functioning of the HMGB1 and HMGB2 as well as their protein partners. Full article
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19 pages, 5843 KiB  
Article
Investigation of Multi-Subunit Mycobacterium tuberculosis DNA-Directed RNA Polymerase and Its Rifampicin Resistant Mutants
by Mokgerwa Zacharia Monama, Fisayo Olotu and Özlem Tastan Bishop
Int. J. Mol. Sci. 2023, 24(4), 3313; https://doi.org/10.3390/ijms24043313 - 7 Feb 2023
Cited by 6 | Viewed by 2637
Abstract
Emerging Mycobacterium tuberculosis (Mtb) resistant strains have continued to limit the efficacies of existing antitubercular therapies. More specifically, mutations in the RNA replicative machinery of Mtb, RNA polymerase (RNAP), have been widely linked to rifampicin (RIF) resistance, which has led [...] Read more.
Emerging Mycobacterium tuberculosis (Mtb) resistant strains have continued to limit the efficacies of existing antitubercular therapies. More specifically, mutations in the RNA replicative machinery of Mtb, RNA polymerase (RNAP), have been widely linked to rifampicin (RIF) resistance, which has led to therapeutic failures in many clinical cases. Moreover, elusive details on the underlying mechanisms of RIF-resistance caused by Mtb-RNAP mutations have hampered the development of new and efficient drugs that are able to overcome this challenge. Therefore, in this study we attempt to resolve the molecular and structural events associated with RIF-resistance in nine clinically reported missense Mtb RNAP mutations. Our study, for the first time, investigated the multi-subunit Mtb RNAP complex and findings revealed that the mutations commonly disrupted structural–dynamical attributes that may be essential for the protein’s catalytic functions, particularly at the βfork loop 2, β’zinc-binding domain, the β’ trigger loop and β’jaw, which in line with previous experimental reports, are essential for RNAP processivity. Complementarily, the mutations considerably perturbed the RIF-BP, which led to alterations in the active orientation of RIF needed to obstruct RNA extension. Consequentially, essential interactions with RIF were lost due to the mutation-induced repositioning with corresponding reductions in the binding affinity of the drug observed in majority of the mutants. We believe these findings will significantly aid future efforts in the discovery of new treatment options with the potential to overcome antitubercular resistance. Full article
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21 pages, 5896 KiB  
Article
Trimeric Architecture Ensures the Stability and Biological Activity of the Calf Purine Nucleoside Phosphorylase: In Silico and In Vitro Studies of Monomeric and Trimeric Forms of the Enzyme
by Alicja Dyzma, Beata Wielgus-Kutrowska, Agnieszka Girstun, Zoe Jelić Matošević, Krzysztof Staroń, Branimir Bertoša, Joanna Trylska and Agnieszka Bzowska
Int. J. Mol. Sci. 2023, 24(3), 2157; https://doi.org/10.3390/ijms24032157 - 21 Jan 2023
Cited by 1 | Viewed by 1966
Abstract
Mammalian purine nucleoside phosphorylase (PNP) is biologically active as a homotrimer, in which each monomer catalyzes a reaction independently of the others. To answer the question of why the native PNP forms a trimeric structure, we constructed, in silico and in vitro, the [...] Read more.
Mammalian purine nucleoside phosphorylase (PNP) is biologically active as a homotrimer, in which each monomer catalyzes a reaction independently of the others. To answer the question of why the native PNP forms a trimeric structure, we constructed, in silico and in vitro, the monomeric form of the enzyme. Molecular dynamics simulations showed different geometries of the active site in the non-mutated trimeric and monomeric PNP forms, which suggested that the active site in the isolated monomer could be non-functional. To confirm this hypothesis, six amino acids located at the interface of the subunits were selected and mutated to alanines to disrupt the trimer and obtain a monomer (6Ala PNP). The effects of these mutations on the enzyme structure, stability, conformational dynamics, and activity were examined. The solution experiments confirmed that the 6Ala PNP mutant occurs mainly as a monomer, with a secondary structure almost identical to the wild type, WT PNP, and importantly, it shows no enzymatic activity. Simulations confirmed that, although the secondary structure of the 6Ala monomer is similar to the WT PNP, the positions of the amino acids building the 6Ala PNP active site significantly differ. These data suggest that a trimeric structure is necessary to stabilize the geometry of the active site of this enzyme. Full article
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18 pages, 10215 KiB  
Article
Triacylglycerol Composition and Chemical-Physical Properties of Cocoa Butter and Its Derivatives: NMR, DSC, X-ray, Rheological Investigation
by Maria Francesca Colella, Nadia Marino, Cesare Oliviero Rossi, Lucia Seta, Paolino Caputo and Giuseppina De Luca
Int. J. Mol. Sci. 2023, 24(3), 2090; https://doi.org/10.3390/ijms24032090 - 20 Jan 2023
Cited by 6 | Viewed by 3721
Abstract
In recent years, the food industry has become increasingly involved in researching vegetable fats and oils with appropriate mechanical properties (ease of transport, processing, and storage) and a specific lipidic composition to ensure healthy products for consumers. The chemical–physical behavior of these matrices [...] Read more.
In recent years, the food industry has become increasingly involved in researching vegetable fats and oils with appropriate mechanical properties (ease of transport, processing, and storage) and a specific lipidic composition to ensure healthy products for consumers. The chemical–physical behavior of these matrices depends on their composition in terms of single fatty acids (FA). However, as we demonstrate in this work, these properties, as well as the absorption, digestion and uptake in humans of specific FAs, are also largely determined by their regiosomerism within the TriAcylGlycerols (TAG) moieties (sn-1,2,3 positions). The goal of this work is to study for the first time vegetable fats obtained directly from a sample of natural cocoa butter (CB) through a process that manipulates the distribution of FAs but not their nature. Even if the initial percentage of each FA in the mixture remains the same, CB derivatives seem to show improved chemical–physical features. In order to understand which factors account for their physical and chemical characteristics, and to check whether or not the obtained new matrices could be considered as valid alternatives to other vegetable fats (e.g., palm oil (PO)), we carried out an experimental investigation at both the macroscopic and molecular level including: (i) Differential Scanning Calorimetry (DSC) analyses to examine thermal features; (ii) rheological testing to explore mechanical properties; (iii) powder X-ray diffraction (PXRD) to evaluate the solid-state phases of the obtained fats; and (iv) 1H and 13C Nuclear Magnetic Resonance (NMR, 1D and 2D) spectroscopy to rapidly analyze fatty acid composition including regioisomeric distribution on the glycerol backbone. These last results open up the possibility of using NMR spectroscopy as an alternative to the chromatographic techniques routinely employed for the investigation of similar matrices. Full article
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12 pages, 2851 KiB  
Article
Proof-of-Concept Method to Study Uncharacterized Methyltransferases Using PRDM15
by Li-Na Zhao, Ernesto Guccione and Philipp Kaldis
Int. J. Mol. Sci. 2023, 24(2), 1327; https://doi.org/10.3390/ijms24021327 - 10 Jan 2023
Viewed by 2143
Abstract
The PRDM family of methyltransferases has been implicated in cellular proliferation and differentiation and is deregulated in human diseases, most notably in cancer. PRDMs are related to the SET domain family of methyltransferases; however, from the 19 PRDMs only a few PRDMs with [...] Read more.
The PRDM family of methyltransferases has been implicated in cellular proliferation and differentiation and is deregulated in human diseases, most notably in cancer. PRDMs are related to the SET domain family of methyltransferases; however, from the 19 PRDMs only a few PRDMs with defined enzymatic activities are known. PRDM15 is an uncharacterized transcriptional regulator, with significant structural disorder and lack of defined small-molecule binding pockets. Many aspects of PRDM15 are yet unknown, including its structure, substrates, reaction mechanism, and its methylation profile. Here, we employ a series of computational approaches for an exploratory investigation of its potential substrates and reaction mechanism. Using the knowledge of PRDM9 and current knowledge of PRDM15 as basis, we tried to identify genuine substrates of PRDM15. We start from histone-based peptides and learn that the native substrates of PRDM15 may be non-histone proteins. In the future, a combination of sequence-based approaches and signature motif analysis may provide new leads. In summary, our results provide new information about the uncharacterized methyltransferase, PRDM15. Full article
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10 pages, 2618 KiB  
Article
Single–Molecule Study of DNAzyme Reveals Its Intrinsic Conformational Dynamics
by Yiming Zhang, Zongzhou Ji, Xin Wang, Yi Cao and Hai Pan
Int. J. Mol. Sci. 2023, 24(2), 1212; https://doi.org/10.3390/ijms24021212 - 7 Jan 2023
Cited by 1 | Viewed by 2345
Abstract
DNAzyme is a class of DNA molecules that can perform catalytic functions with high selectivity towards specific metal ions. Due to its potential applications for biosensors and medical therapeutics, DNAzyme has been extensively studied to characterize the relationships between its biochemical properties and [...] Read more.
DNAzyme is a class of DNA molecules that can perform catalytic functions with high selectivity towards specific metal ions. Due to its potential applications for biosensors and medical therapeutics, DNAzyme has been extensively studied to characterize the relationships between its biochemical properties and functions. Similar to protein enzymes and ribozymes, DNAzymes have been found to undergo conformational changes in a metal–ion–dependent manner for catalysis. Despite the important role the conformation plays in the catalysis process, such structural and dynamic information might not be revealed by conventional approaches. Here, by using the single–molecule fluorescence resonance energy transfer (smFRET) technique, we were able to investigate the detailed conformational dynamics of a uranyl–specific DNAzyme 39E. We observed conformation switches of 39E to a folded state with the addition of Mg2+ and to an extended state with the addition of UO22+. Furthermore, 39E can switch to a more compact configuration with or without divalent metal ions. Our findings reveal that 39E can undergo conformational changes spontaneously between different configurations. Full article
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11 pages, 21247 KiB  
Article
The Effect of Arginine on the Phase Stability of Aqueous Hen Egg-White Lysozyme Solutions
by Sandi Brudar and Barbara Hribar-Lee
Int. J. Mol. Sci. 2023, 24(2), 1197; https://doi.org/10.3390/ijms24021197 - 7 Jan 2023
Cited by 5 | Viewed by 1825
Abstract
The effect of arginine on the phase stability of the hen egg-white lysozyme (HEWL) has been studied via molecular dynamics computer simulations, as well as experimentally via cloud-point temperature determination. The experiments show that the addition of arginine increases the stability of the [...] Read more.
The effect of arginine on the phase stability of the hen egg-white lysozyme (HEWL) has been studied via molecular dynamics computer simulations, as well as experimentally via cloud-point temperature determination. The experiments show that the addition of arginine increases the stability of the HEWL solutions. The computer simulation results indicate that arginine molecules tend to self-associate. If arginine residues are located on the protein surface, the free arginine molecules stay in their vicinity and prevent the way protein molecules “connect” through them to form clusters. The results are not sensitive to a particular force field and suggest a possible microscopic mechanism of the stabilizing role of arginine as an excipient. Full article
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2022

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14 pages, 2671 KiB  
Article
An Overlooked Hepcidin–Cadmium Connection
by Dawid Płonka, Marta D. Wiśniewska, Manuel D. Peris-Díaz, Artur Krężel, Arkadiusz M. Bonna and Wojciech Bal
Int. J. Mol. Sci. 2022, 23(24), 15483; https://doi.org/10.3390/ijms232415483 - 7 Dec 2022
Cited by 1 | Viewed by 1739
Abstract
Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed [...] Read more.
Hepcidin (DTHFPICIFCCGCCHRSKCGMCCKT), an iron-regulatory hormone, is a 25-amino-acid peptide with four intramolecular disulfide bonds circulating in blood. Its hormonal activity is indirect and consists of marking ferroportin-1 (an iron exporter) for degradation. Hepcidin biosynthesis involves the N-terminally extended precursors prepro-hepcidin and pro-hepcidin, processed by peptidases to the final 25-peptide form. A sequence-specific formation of disulfide bonds and export of the oxidized peptide to the bloodstream follows. In this study we considered the fact that prior to export, reduced hepcidin may function as an octathiol ligand bearing some resemblance to the N-terminal part of the α-domain of metallothioneins. Consequently, we studied its ability to bind Zn(II) and Cd(II) ions using the original peptide and a model for prohepcidin extended N-terminally with a stretch of five arginine residues (5R-hepcidin). We found that both form equivalent mononuclear complexes with two Zn(II) or Cd(II) ions saturating all eight Cys residues. The average affinity at pH 7.4, determined from pH-metric spectroscopic titrations, is 1010.1 M−1 for Zn(II) ions; Cd(II) ions bind with affinities of 1015.2 M−1 and 1014.1 M−1. Using mass spectrometry and 5R-hepcidin we demonstrated that hepcidin can compete for Cd(II) ions with metallothionein-2, a cellular cadmium target. This study enabled us to conclude that hepcidin binds Zn(II) and Cd(II) sufficiently strongly to participate in zinc physiology and cadmium toxicity under intracellular conditions. Full article
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27 pages, 6065 KiB  
Article
Unveiling the Metal-Dependent Aggregation Properties of the C-terminal Region of Amyloidogenic Intrinsically Disordered Protein Isoforms DPF3b and DPF3a
by Tanguy Leyder, Julien Mignon, Denis Mottet and Catherine Michaux
Int. J. Mol. Sci. 2022, 23(23), 15291; https://doi.org/10.3390/ijms232315291 - 4 Dec 2022
Cited by 4 | Viewed by 2118
Abstract
Double-PHD fingers 3 (DPF3) is a BAF-associated human epigenetic regulator, which is increasingly recognised as a major contributor to various pathological contexts, such as cardiac defects, cancer, and neurodegenerative diseases. Recently, we unveiled that its two isoforms (DPF3b and DPF3a) are amyloidogenic intrinsically [...] Read more.
Double-PHD fingers 3 (DPF3) is a BAF-associated human epigenetic regulator, which is increasingly recognised as a major contributor to various pathological contexts, such as cardiac defects, cancer, and neurodegenerative diseases. Recently, we unveiled that its two isoforms (DPF3b and DPF3a) are amyloidogenic intrinsically disordered proteins. DPF3 isoforms differ from their C-terminal region (C-TERb and C-TERa), containing zinc fingers and disordered domains. Herein, we investigated the disorder aggregation properties of C-TER isoforms. In agreement with the predictions, spectroscopy highlighted a lack of a highly ordered structure, especially for C-TERa. Over a few days, both C-TERs were shown to spontaneously assemble into similar antiparallel and parallel β-sheet-rich fibrils. Altered metal homeostasis being a neurodegeneration hallmark, we also assessed the influence of divalent metal cations, namely Cu2+, Mg2+, Ni2+, and Zn2+, on the C-TER aggregation pathway. Circular dichroism revealed that metal binding does not impair the formation of β-sheets, though metal-specific tertiary structure modifications were observed. Through intrinsic and extrinsic fluorescence, we found that metal cations differently affect C-TERb and C-TERa. Cu2+ and Ni2+ have a strong inhibitory effect on the aggregation of both isoforms, whereas Mg2+ impedes C-TERb fibrillation and, on the contrary, enhances that of C-TERa. Upon Zn2+ binding, C-TERb aggregation is also hindered, and the amyloid autofluorescence of C-TERa is remarkably red-shifted. Using electron microscopy, we confirmed that the metal-induced spectral changes are related to the morphological diversity of the aggregates. While metal-treated C-TERb formed breakable and fragmented filaments, C-TERa fibrils retained their flexibility and packing properties in the presence of Mg2+ and Zn2+ cations. Full article
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22 pages, 2506 KiB  
Review
How Functional Lipids Affect the Structure and Gating of Mechanosensitive MscS-like Channels
by Vanessa Judith Flegler, Tim Rasmussen and Bettina Böttcher
Int. J. Mol. Sci. 2022, 23(23), 15071; https://doi.org/10.3390/ijms232315071 - 1 Dec 2022
Cited by 6 | Viewed by 2816
Abstract
The ability to cope with and adapt to changes in the environment is essential for all organisms. Osmotic pressure is a universal threat when environmental changes result in an imbalance of osmolytes inside and outside the cell which causes a deviation from the [...] Read more.
The ability to cope with and adapt to changes in the environment is essential for all organisms. Osmotic pressure is a universal threat when environmental changes result in an imbalance of osmolytes inside and outside the cell which causes a deviation from the normal turgor. Cells have developed a potent system to deal with this stress in the form of mechanosensitive ion channels. Channel opening releases solutes from the cell and relieves the stress immediately. In bacteria, these channels directly sense the increased membrane tension caused by the enhanced turgor levels upon hypoosmotic shock. The mechanosensitive channel of small conductance, MscS, from Escherichia coli is one of the most extensively studied examples of mechanically stimulated channels. Different conformational states of this channel were obtained in various detergents and membrane mimetics, highlighting an intimate connection between the channel and its lipidic environment. Associated lipids occupy distinct locations and determine the conformational states of MscS. Not all these features are preserved in the larger MscS-like homologues. Recent structures of homologues from bacteria and plants identify common features and differences. This review discusses the current structural and functional models for MscS opening, as well as the influence of certain membrane characteristics on gating. Full article
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15 pages, 3239 KiB  
Article
Pharmaceutical Functionalization of Monomeric Ionic Liquid for the Preparation of Ionic Graft Polymer Conjugates
by Aleksy Mazur, Katarzyna Niesyto and Dorota Neugebauer
Int. J. Mol. Sci. 2022, 23(23), 14731; https://doi.org/10.3390/ijms232314731 - 25 Nov 2022
Cited by 8 | Viewed by 1809
Abstract
Polymerizable choline-based ionic liquid (IL), i.e., [2-(methacryloyloxy)ethyl]-trimethylammonium (TMAMA/Cl¯), was functionalized by an ion exchange reaction with pharmaceutical anions, i.e., cloxacillin (CLX¯) and fusidate (FUS¯), as the antibacterial agents. The modified biocompatible IL monomers (TMAMA/CLX¯, TMAMA/FUS¯) were copolymerized with methyl methacrylate (MMA) to prepare [...] Read more.
Polymerizable choline-based ionic liquid (IL), i.e., [2-(methacryloyloxy)ethyl]-trimethylammonium (TMAMA/Cl¯), was functionalized by an ion exchange reaction with pharmaceutical anions, i.e., cloxacillin (CLX¯) and fusidate (FUS¯), as the antibacterial agents. The modified biocompatible IL monomers (TMAMA/CLX¯, TMAMA/FUS¯) were copolymerized with methyl methacrylate (MMA) to prepare the graft copolymers (19–50 mol% of TMAMA units) serving as the drug (co)delivery systems. The in vitro drug release, which was driven by the exchange reaction of the pharmaceutical anions to phosphate ones in PBS medium, was observed for 44% of CLX¯ (2.7 μg/mL) and 53% of FUS¯ (3.6 μg/mL) in the single systems. Similar amounts of released drugs were detected for the dual system, i.e., 41% of CLX¯ (2.2 μg/mL) and 33% of FUS¯ (2.0 μg/mL). The investigated drug ionic polymer conjugates were examined for their cytotoxicity by MTT test, showing a low toxic effect against human bronchial epithelial cells (BEAS-2B) and normal human dermal fibroblasts (NHDF) as the normal cell lines. The satisfactory drug contents and the release profiles attained for the well-defined graft polymers with ionically bonded pharmaceuticals in the side chains make them promising drug carriers in both separate and combined drug delivery systems. Full article
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19 pages, 1452 KiB  
Article
Study of Membrane-Immobilized Oxidoreductases in Wastewater Treatment for Micropollutants Removal
by Agata Zdarta and Jakub Zdarta
Int. J. Mol. Sci. 2022, 23(22), 14086; https://doi.org/10.3390/ijms232214086 - 15 Nov 2022
Cited by 5 | Viewed by 2296
Abstract
The development of efficient strategies for wastewater treatment to remove micropollutants is of the highest importance. Hence, in this study, we presented a rapid approach to the production of biocatalytic membranes based on commercially available cellulose membrane and oxidoreductase enzymes including laccase, tyrosinase, [...] Read more.
The development of efficient strategies for wastewater treatment to remove micropollutants is of the highest importance. Hence, in this study, we presented a rapid approach to the production of biocatalytic membranes based on commercially available cellulose membrane and oxidoreductase enzymes including laccase, tyrosinase, and horseradish peroxidase. Effective enzyme deposition was confirmed based on Fourier transform infrared spectra, whereas results of spectrophotometric measurements showed that immobilization yield for all proposed systems exceeded 80% followed by over 80% activity recovery, with the highest values (over 90%) noticed for the membrane-laccase system. Further, storage stability and reusability of the immobilized enzyme were improved, reaching over 75% after, respectively, 20 days of storage, and 10 repeated biocatalytic cycles. The key stage of the study concerned the use of produced membranes for the removal of hematoporphyrin, (2,4-dichlorophenoxy)acetic acid (2,4-D), 17α-ethynylestradiol, tetracycline, tert-amyl alcohol (anesthetic drug), and ketoprofen methyl ester from real wastewater sampling at various places in the wastewater treatment plant. Although produced membranes showed mixed removal rates, all of the analyzed compounds were at least partially removed from the wastewater. Obtained data clearly showed, however, that composition of the wastewater matrix, type of pollutants as well as type of enzyme strongly affect the efficiency of enzymatic treatment of wastewater. Full article
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15 pages, 2742 KiB  
Article
Metal Binding to Sodium Heparin Monitored by Quadrupolar NMR
by Daniel Sieme, Christian Griesinger and Nasrollah Rezaei-Ghaleh
Int. J. Mol. Sci. 2022, 23(21), 13185; https://doi.org/10.3390/ijms232113185 - 29 Oct 2022
Cited by 3 | Viewed by 2100
Abstract
Heparins and heparan sulfate polysaccharides are negatively charged glycosaminoglycans and play important roles in cell-to-matrix and cell-to-cell signaling processes. Metal ion binding to heparins alters the conformation of heparins and influences their function. Various experimental techniques have been used to investigate metal ion-heparin [...] Read more.
Heparins and heparan sulfate polysaccharides are negatively charged glycosaminoglycans and play important roles in cell-to-matrix and cell-to-cell signaling processes. Metal ion binding to heparins alters the conformation of heparins and influences their function. Various experimental techniques have been used to investigate metal ion-heparin interactions, frequently with inconsistent results. Exploiting the quadrupolar 23Na nucleus, we herein develop a 23Na NMR-based competition assay and monitor the binding of divalent Ca2+ and Mg2+ and trivalent Al3+ metal ions to sodium heparin and the consequent release of sodium ions from heparin. The 23Na spin relaxation rates and translational diffusion coefficients are utilized to quantify the metal ion-induced release of sodium ions from heparin. In the case of the Al3+ ion, the complementary approach of 27Al quadrupolar NMR is employed as a direct probe of ion binding to heparin. Our NMR results demonstrate at least two metal ion-binding sites with different affinities on heparin, potentially undergoing dynamic exchange. For the site with lower metal ion binding affinity, the order of Ca2+ > Mg2+ > Al3+ is obtained, in which even the weakly binding Al3+ ion is capable of displacing sodium ions from heparin. Overall, the multinuclear quadrupolar NMR approach employed here can monitor and quantify metal ion binding to heparin and capture different modes of metal ion-heparin binding. Full article
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17 pages, 965 KiB  
Review
Addressing Noise and Estimating Uncertainty in Biomedical Data through the Exploration of Chemical Space
by Enrique J. deAndrés-Galiana, Juan Luis Fernández-Martínez, Lucas Fernández-Brillet, Ana Cernea and Andrzej Kloczkowski
Int. J. Mol. Sci. 2022, 23(21), 12975; https://doi.org/10.3390/ijms232112975 - 26 Oct 2022
Cited by 1 | Viewed by 1802
Abstract
Noise is a basic ingredient in data, since observed data are always contaminated by unwanted deviations, i.e., noise, which, in the case of overdetermined systems (with more data than model parameters), cause the corresponding linear system of equations to have an imperfect solution. [...] Read more.
Noise is a basic ingredient in data, since observed data are always contaminated by unwanted deviations, i.e., noise, which, in the case of overdetermined systems (with more data than model parameters), cause the corresponding linear system of equations to have an imperfect solution. In addition, in the case of highly underdetermined parameterization, noise can be absorbed by the model, generating spurious solutions. This is a very undesirable situation that might lead to incorrect conclusions. We presented mathematical formalism based on the inverse problem theory combined with artificial intelligence methodologies to perform an enhanced sampling of noisy biomedical data to improve the finding of meaningful solutions. Random sampling methods fail for high-dimensional biomedical problems. Sampling methods such as smart model parameterizations, forward surrogates, and parallel computing are better suited for such problems. We applied these methods to several important biomedical problems, such as phenotype prediction and a problem related to predicting the effects of protein mutations, i.e., if a given single residue mutation is neutral or deleterious, causing a disease. We also applied these methods to de novo drug discovery and drug repositioning (repurposing) through the enhanced exploration of huge chemical space. The purpose of these novel methods that address the problem of noise and uncertainty in biomedical data is to find new therapeutic solutions, perform drug repurposing, and accelerate and optimize drug discovery, thus reestablishing homeostasis. Finding the right target, the right compound, and the right patient are the three bottlenecks to running successful clinical trials from the correct analysis of preclinical models. Artificial intelligence can provide a solution to these problems, considering that the character of the data restricts the quality of the prediction, as in any modeling procedure in data analysis. The use of simple and plain methodologies is crucial to tackling these important and challenging problems, particularly drug repositioning/repurposing in rare diseases. Full article
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12 pages, 2636 KiB  
Article
Discrimination of Brassica juncea Varieties Using Visible Near-Infrared (Vis-NIR) Spectroscopy and Chemometrics Methods
by Soo-In Sohn, Subramani Pandian, Young-Ju Oh, John-Lewis Zinia Zaukuu, Yong-Ho Lee and Eun-Kyoung Shin
Int. J. Mol. Sci. 2022, 23(21), 12809; https://doi.org/10.3390/ijms232112809 - 24 Oct 2022
Cited by 3 | Viewed by 2053
Abstract
Brown mustard (Brassica juncea (L.) is an important oilseed crop that is mostly used to produce edible oils, industrial oils, modified lipids and biofuels in subtropical nations. Due to its higher level of commercial use, the species has a huge array of [...] Read more.
Brown mustard (Brassica juncea (L.) is an important oilseed crop that is mostly used to produce edible oils, industrial oils, modified lipids and biofuels in subtropical nations. Due to its higher level of commercial use, the species has a huge array of varieties/cultivars. The purpose of this study is to evaluate the use of visible near-infrared (Vis-NIR) spectroscopy in combination with multiple chemometric approaches for distinguishing four B. juncea varieties in Korea. The spectra from the leaves of four different growth stages of four B. juncea varieties were measured in the Vis-NIR range of 325–1075 nm with a stepping of 1.5 nm in reflectance mode. For effective discrimination, the spectral data were preprocessed using three distinct approaches, and eight different chemometric analyses were utilized. After the detection of outliers, the samples were split into two groups, one serving as a calibration set and the other as a validation set. When numerous preprocessing and chemometric approaches were applied for discriminating, the combination of standard normal variate and deep learning had the highest classification accuracy in all the growth stages achieved up to 100%. Similarly, few other chemometrics also yielded 100% classification accuracy, namely, support vector machine, generalized linear model, and the random forest. Of all the chemometric preprocessing methods, Savitzky–Golay filter smoothing provided the best and most convincing discrimination. The findings imply that chemometric methods combined with handheld Vis-NIR spectroscopy can be utilized as an efficient tool for differentiating B. juncea varieties in the field in all the growth stages. Full article
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9 pages, 1132 KiB  
Article
Arrangement of Hydrogen Bonds in Aqueous Solutions of Different Globular Proteins
by Amber R. Titus, Pedro P. Madeira, Luisa A. Ferreira, Alexander I. Belgovskiy, Elizabeth K. Mann, Jay Adin Mann, Jr., William V. Meyer, Anthony E. Smart, Vladimir N. Uversky and Boris Y. Zaslavsky
Int. J. Mol. Sci. 2022, 23(19), 11381; https://doi.org/10.3390/ijms231911381 - 27 Sep 2022
Cited by 4 | Viewed by 2313
Abstract
This work presents the first evidence that dissolved globular proteins change the arrangement of hydrogen bonds in water, with different proteins showing quantitatively different effects. Using ATR-FTIR (attenuated total reflection—Fourier transform infrared) spectroscopic analysis of OH-stretch bands, we obtain quantitative estimates of the [...] Read more.
This work presents the first evidence that dissolved globular proteins change the arrangement of hydrogen bonds in water, with different proteins showing quantitatively different effects. Using ATR-FTIR (attenuated total reflection—Fourier transform infrared) spectroscopic analysis of OH-stretch bands, we obtain quantitative estimates of the relative amounts of the previously reported four subpopulations of water structures coexisting in a variety of aqueous solutions. Where solvatochromic dyes can measure the properties of solutions of non-ionic polymers, the results correlate well with ATR-FTIR measurements. In protein solutions to which solvatochromic dye probes cannot be applied, NMR (nuclear magnetic resonance) spectroscopy was used for the first time to estimate the hydrogen bond donor acidity of water. We found strong correlations between the solvent acidity and arrangement of hydrogen bonds in aqueous solutions for several globular proteins. Even quite similar proteins are found to change water properties in dramatically different ways. Full article
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12 pages, 4190 KiB  
Article
Clustering Analysis, Structure Fingerprint Analysis, and Quantum Chemical Calculations of Compounds from Essential Oils of Sunflower (Helianthus annuus L.) Receptacles
by Yi He, Kaifeng Liu, Lu Han and Weiwei Han
Int. J. Mol. Sci. 2022, 23(17), 10169; https://doi.org/10.3390/ijms231710169 - 5 Sep 2022
Cited by 7 | Viewed by 2122
Abstract
Sunflower (Helianthus annuus L.) is an appropriate crop for current new patterns of green agriculture, so it is important to change sunflower receptacles from waste to useful resource. However, there is limited knowledge on the functions of compounds from the essential oils [...] Read more.
Sunflower (Helianthus annuus L.) is an appropriate crop for current new patterns of green agriculture, so it is important to change sunflower receptacles from waste to useful resource. However, there is limited knowledge on the functions of compounds from the essential oils of sunflower receptacles. In this study, a new method was created for chemical space network analysis and classification of small samples, and applied to 104 compounds. Here, t-SNE (t-Distributed Stochastic Neighbor Embedding) dimensions were used to reduce coordinates as node locations and edge connections of chemical space networks, respectively, and molecules were grouped according to whether the edges were connected and the proximity of the node coordinates. Through detailed analysis of the structural characteristics and fingerprints of each classified group, our classification method attained good accuracy. Targets were then identified using reverse docking methods, and the active centers of the same types of compounds were determined by quantum chemical calculation. The results indicated that these compounds can be divided into nine groups, according to their mean within-group similarity (MWGS) values. The three families with the most members, i.e., the d-limonene group (18), α-pinene group (10), and γ-maaliene group (nine members) determined the protein targets, using PharmMapper. Structure fingerprint analysis was employed to predict the binding mode of the ligands of four families of the protein targets. Thence, quantum chemical calculations were applied to the active group of the representative compounds of the four families. This study provides further scientific information to support the use of sunflower receptacles. Full article
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17 pages, 3047 KiB  
Article
Albumin/Thiacalix[4]arene Nanoparticles as Potential Therapeutic Systems: Role of the Macrocycle for Stabilization of Monomeric Protein and Self-Assembly with Ciprofloxacin
by Luidmila Yakimova, Aisylu Kunafina, Olga Mostovaya, Pavel Padnya, Timur Mukhametzyanov, Alexandra Voloshina, Konstantin Petrov, Artur Boldyrev and Ivan Stoikov
Int. J. Mol. Sci. 2022, 23(17), 10040; https://doi.org/10.3390/ijms231710040 - 2 Sep 2022
Cited by 3 | Viewed by 2387
Abstract
The therapeutic application of serum albumin is determined by the relative content of the monomeric form compared to dimers, tetramers, hexamers, etc. In this paper, we propose and develop an approach to synthesize the cone stereoisomer of p-tert-butylthiacalix[4]arene with sulfobetaine fragments stabilization [...] Read more.
The therapeutic application of serum albumin is determined by the relative content of the monomeric form compared to dimers, tetramers, hexamers, etc. In this paper, we propose and develop an approach to synthesize the cone stereoisomer of p-tert-butylthiacalix[4]arene with sulfobetaine fragments stabilization of monomeric bovine serum albumin and preventing aggregation. Spectral methods (UV-vis, CD, fluorescent spectroscopy, and dynamic light scattering) established the influence of the synthesized compounds on the content of monomeric and aggregated forms of BSA even without the formation of stable thiacalixarene/protein associates. The effect of thiacalixarenes on the efficiency of protein binding with the antibiotic ciprofloxacin was shown by fluorescence spectroscopy. The binding constant increases in the presence of the macrocycles, likely due to the stabilization of monomeric forms of BSA. Our study clearly shows the potential of this macrocycle design as a platform for the development of the fundamentally new approaches for preventing aggregation. Full article
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9 pages, 3686 KiB  
Article
A TD-DFT-Based Study on the Attack of the OH· Radical on a Guanine Nucleotide
by João Santiago, Jhaison C. de Faria, Miguel San-Miguel and Mario A. Bernal
Int. J. Mol. Sci. 2022, 23(17), 10007; https://doi.org/10.3390/ijms231710007 - 2 Sep 2022
Cited by 3 | Viewed by 2519
Abstract
Heavy charged particles induce severe damage in DNA, which is a radiobiological advantage when treating radioresistant tumors. However, these particles can also induce cancer in humans exposed to them, such as astronauts in space missions. This damage can be directly induced by the [...] Read more.
Heavy charged particles induce severe damage in DNA, which is a radiobiological advantage when treating radioresistant tumors. However, these particles can also induce cancer in humans exposed to them, such as astronauts in space missions. This damage can be directly induced by the radiation or indirectly by the attack of free radicals mainly produced by water radiolysis. We previously studied the impact of a proton on a DNA base pair, using the Time Dependent-Density Functional Theory (TD-DFT). In this work, we go a step further and study the attack of the OH· radical on the Guanine nucleotide to unveil how this molecule subsequently dissociates. The OH· attack on the H1′, H2′, H3′, and H5′ atoms in the guanine was investigated using the Ehrenfest dynamics within the TD-DFT framework. In all cases, the hydrogen abstraction succeeded, and the subsequent base pair dissociation was observed. The DNA dissociates in three major fragments: the phosphate group, the deoxyribose sugar, and the nitrogenous base, with slight differences, no matter which hydrogen atom was attacked. Hydrogen abstraction occurs at about 6 fs, and the nucleotide dissociation at about 100 fs, which agrees with our previous result for the direct proton impact on the DNA. These calculations may be a reference for adjusting reactive force fields so that more complex DNA structures can be studied using classical molecular dynamics, including both direct and indirect DNA damage. Full article
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17 pages, 4896 KiB  
Article
Impact of Growth Conditions on Pseudomonas fluorescens Morphology Characterized by Atomic Force Microscopy
by Houssem Kahli, Laure Béven, Christine Grauby-Heywang, Nesrine Debez, Ibtissem Gammoudi, Fabien Moroté, Hana Sbartai and Touria Cohen-Bouhacina
Int. J. Mol. Sci. 2022, 23(17), 9579; https://doi.org/10.3390/ijms23179579 - 24 Aug 2022
Cited by 8 | Viewed by 7031
Abstract
This work is dedicated to the characterization by Atomic Force Microscopy (AFM) of Pseudomonas fluorescens, bacteria having high potential in biotechnology. They were first studied first in optimal conditions in terms of culture medium and temperature. AFM revealed a more-or-less elongated morphology [...] Read more.
This work is dedicated to the characterization by Atomic Force Microscopy (AFM) of Pseudomonas fluorescens, bacteria having high potential in biotechnology. They were first studied first in optimal conditions in terms of culture medium and temperature. AFM revealed a more-or-less elongated morphology with typical dimensions in the micrometer range, and an organization of the outer membrane characterized by the presence of long and randomly distributed ripples, which are likely related to the organization of lipopolysaccharides (LPS). The outer membrane also presents invaginations, some of them showing a reorganization of ripples, which could be the first sign of a bacterial stress response. In a second step, bacteria grown under unfavorable conditions were characterized. The choice of the medium appeared to be more critical in the case of the second generation of cells, the less adapted medium inducing not only changes in the membrane organization but also larger damages in bacteria. An increased growth temperature affected both the usual “swollen” morphology and the organization of the outer membrane. Here also, LPS likely contribute to membrane remodelling, which makes them potential markers to track cell state changes. Full article
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19 pages, 42214 KiB  
Article
RNA-As-Graphs Motif Atlas—Dual Graph Library of RNA Modules and Viral Frameshifting-Element Applications
by Qiyao Zhu, Louis Petingi and Tamar Schlick
Int. J. Mol. Sci. 2022, 23(16), 9249; https://doi.org/10.3390/ijms23169249 - 17 Aug 2022
Cited by 4 | Viewed by 2318
Abstract
RNA motif classification is important for understanding structure/function connections and building phylogenetic relationships. Using our coarse-grained RNA-As-Graphs (RAG) representations, we identify recurrent dual graph motifs in experimentally solved RNA structures based on an improved search algorithm that finds and ranks independent RNA substructures. [...] Read more.
RNA motif classification is important for understanding structure/function connections and building phylogenetic relationships. Using our coarse-grained RNA-As-Graphs (RAG) representations, we identify recurrent dual graph motifs in experimentally solved RNA structures based on an improved search algorithm that finds and ranks independent RNA substructures. Our expanded list of 183 existing dual graph motifs reveals five common motifs found in transfer RNA, riboswitch, and ribosomal 5S RNA components. Moreover, we identify three motifs for available viral frameshifting RNA elements, suggesting a correlation between viral structural complexity and frameshifting efficiency. We further partition the RNA substructures into 1844 distinct submotifs, with pseudoknots and junctions retained intact. Common modules are internal loops and three-way junctions, and three submotifs are associated with riboswitches that bind nucleotides, ions, and signaling molecules. Together, our library of existing RNA motifs and submotifs adds to the growing universe of RNA modules, and provides a resource of structures and substructures for novel RNA design. Full article
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14 pages, 3373 KiB  
Article
Time-Dependent DNA Origami Denaturation by Guanidinium Chloride, Guanidinium Sulfate, and Guanidinium Thiocyanate
by Marcel Hanke, Niklas Hansen, Emilia Tomm, Guido Grundmeier and Adrian Keller
Int. J. Mol. Sci. 2022, 23(15), 8547; https://doi.org/10.3390/ijms23158547 - 1 Aug 2022
Cited by 7 | Viewed by 3439
Abstract
Guanidinium (Gdm) undergoes interactions with both hydrophilic and hydrophobic groups and, thus, is a highly potent denaturant of biomolecular structure. However, our molecular understanding of the interaction of Gdm with proteins and DNA is still rather limited. Here, we investigated the denaturation of [...] Read more.
Guanidinium (Gdm) undergoes interactions with both hydrophilic and hydrophobic groups and, thus, is a highly potent denaturant of biomolecular structure. However, our molecular understanding of the interaction of Gdm with proteins and DNA is still rather limited. Here, we investigated the denaturation of DNA origami nanostructures by three Gdm salts, i.e., guanidinium chloride (GdmCl), guanidinium sulfate (Gdm2SO4), and guanidinium thiocyanate (GdmSCN), at different temperatures and in dependence of incubation time. Using DNA origami nanostructures as sensors that translate small molecular transitions into nanostructural changes, the denaturing effects of the Gdm salts were directly visualized by atomic force microscopy. GdmSCN was the most potent DNA denaturant, which caused complete DNA origami denaturation at 50 °C already at a concentration of 2 M. Under such harsh conditions, denaturation occurred within the first 15 min of Gdm exposure, whereas much slower kinetics were observed for the more weakly denaturing salt Gdm2SO4 at 25 °C. Lastly, we observed a novel non-monotonous temperature dependence of DNA origami denaturation in Gdm2SO4 with the fraction of intact nanostructures having an intermediate minimum at about 40 °C. Our results, thus, provide further insights into the highly complex Gdm–DNA interaction and underscore the importance of the counteranion species. Full article
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17 pages, 28348 KiB  
Article
Unravelling the Adaptation Mechanisms to High Pressure in Proteins
by Antonino Caliò, Cécile Dubois, Stéphane Fontanay, Michael Marek Koza, François Hoh, Christian Roumestand, Philippe Oger and Judith Peters
Int. J. Mol. Sci. 2022, 23(15), 8469; https://doi.org/10.3390/ijms23158469 - 30 Jul 2022
Cited by 7 | Viewed by 3236
Abstract
Life is thought to have appeared in the depth of the sea under high hydrostatic pressure. Nowadays, it is known that the deep biosphere hosts a myriad of life forms thriving under high-pressure conditions. However, the evolutionary mechanisms leading to their adaptation are [...] Read more.
Life is thought to have appeared in the depth of the sea under high hydrostatic pressure. Nowadays, it is known that the deep biosphere hosts a myriad of life forms thriving under high-pressure conditions. However, the evolutionary mechanisms leading to their adaptation are still not known. Here, we show the molecular bases of these mechanisms through a joint structural and dynamical study of two orthologous proteins. We observed that pressure adaptation involves the decoupling of protein–water dynamics and the elimination of cavities in the protein core. This is achieved by rearranging the charged residues on the protein surface and using bulkier hydrophobic residues in the core. These findings will be the starting point in the search for a complete genomic model explaining high-pressure adaptation. Full article
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24 pages, 3610 KiB  
Article
Synthesis, Physicochemical Characterization, and Antibacterial Performance of Silver—Lactoferrin Complexes
by Oleksandra Pryshchepa, Paweł Pomastowski, Katarzyna Rafińska, Adrian Gołębiowski, Agnieszka Rogowska, Maciej Monedeiro-Milanowski, Gulyaim Sagandykova, Bernhard Michalke, Philippe Schmitt-Kopplin, Michał Gloc, Renata Dobrucka, Krzysztof Kurzydłowski and Bogusław Buszewski
Int. J. Mol. Sci. 2022, 23(13), 7112; https://doi.org/10.3390/ijms23137112 - 26 Jun 2022
Cited by 10 | Viewed by 2782
Abstract
Antibiotic-resistant bacteria pose one of the major threats to human health worldwide. The issue is fundamental in the case of chronic wound treatment. One of the latest trends to overcome the problem is the search for new antibacterial agents based on silver. Thus, [...] Read more.
Antibiotic-resistant bacteria pose one of the major threats to human health worldwide. The issue is fundamental in the case of chronic wound treatment. One of the latest trends to overcome the problem is the search for new antibacterial agents based on silver. Thus, the aim of this research was to synthesize the silver-lactoferrin complex as a new generation of substances for the treatment of infected wounds. Moreover, one of the tasks was to investigate the formation mechanisms of the respective complexes and the influence of different synthesis conditions on the features of final product. The batch-sorption study was performed by applying the Langmuir and Freundlich isotherm models for the process description. Characterization of the complexes was carried out by spectroscopy, spectrometry, and separation techniques, as well as with electron microscopy. Additionally, the biological properties of the complex were evaluated, i.e., the antibacterial activity against selected bacteria and the impact on L929 cell-line viability. The results indicate the formation of a heterogeneous silver–lactoferrin complex that comprises silver nanoparticles. The complex has higher antibacterial strength than both native bovine lactoferrin and Ag+, while being comparable to silver toxicity. Full article
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17 pages, 3372 KiB  
Article
Exploration of Somatostatin Binding Mechanism to Somatostatin Receptor Subtype 4
by Rita Börzsei, Balázs Zoltán Zsidó, Mónika Bálint, Zsuzsanna Helyes, Erika Pintér and Csaba Hetényi
Int. J. Mol. Sci. 2022, 23(13), 6878; https://doi.org/10.3390/ijms23136878 - 21 Jun 2022
Cited by 4 | Viewed by 3150
Abstract
Somatostatin (also named as growth hormone-inhibiting hormone or somatotropin release-inhibiting factor) is a regulatory peptide important for the proper functioning of the endocrine system, local inflammatory reactions, mood and motor coordination, and behavioral responses to stress. Somatostatin exerts its effects via binding to [...] Read more.
Somatostatin (also named as growth hormone-inhibiting hormone or somatotropin release-inhibiting factor) is a regulatory peptide important for the proper functioning of the endocrine system, local inflammatory reactions, mood and motor coordination, and behavioral responses to stress. Somatostatin exerts its effects via binding to G-protein-coupled somatostatin receptors of which the fourth subtype (SSTR4) is a particularly important receptor mediating analgesic, anti-inflammatory, and anti-depressant effects without endocrine actions. Thus, SSTR4 agonists are promising drug candidates. Although the knowledge of the atomic resolution-binding modes of SST would be essential for drug development, experimental elucidation of the structures of SSTR4 and its complexes is still awaiting. In the present study, structures of the somatostatin–SSTR4 complex were produced using an unbiased, blind docking approach. Beyond the static structures, the binding mechanism of SST was also elucidated in the explicit water molecular dynamics (MD) calculations, and key binding modes (external, intermediate, and internal) were distinguished. The most important residues on both receptor and SST sides were identified. An energetic comparison of SST binding to SSTR4 and 2 offere