Search Results (90)

This study presents the synthesis and physicochemical characterization of coordination compounds formed between chrysin, a natural flavonoid, and transition metal ions: Mn(II), Co(II), and Zn(II). The complexes were obtained under mildly basic conditions and analyzed using elemental analysis, thermogravimetric analysis (TGA), silver-assisted laser desorption/ionization mass spectrometry (SALDI-MS), FT-IR spectroscopy, and ¹H NMR. The spectroscopic data confirm that chrysin coordinates as a bidentate ligand through the 5-hydroxyl and 4-carbonyl groups, with structural differences depending on the metal ion involved. The mass spectrometry results revealed distinct stoichiometries: 1:2 metal-to-ligand ratios for Mn(II) and Co(II), and 1:1 for Zn(II), with additional hydroxide coordination. Biological assays demonstrated that Co(II) and Mn(II) complexes exhibit enhanced antibacterial and anti-biofilm activity compared to free chrysin, particularly against drug-resistant Staphylococcus epidermidis, whereas the Zn(II) complex showed negligible biological activity. Full article

Coumarins are known for interacting with proteins and exhibiting diverse biological activities. This study investigates the interaction between coumarin-343 (C343) and human (HSA) and bovine (BSA) serum albumins. Fluorescence spectroscopy and theoretical simulations, including density functional theory (DFT) and molecular docking, were used to analyze the ligand–protein complex formation. The fluorescence quenching data revealed that C343 binds to both proteins, with binding constants of 2.1 × 10⁵ mol·L⁻¹ (HSA) and 6.5 × 10⁵ mol·L⁻¹ (BSA), following a 1:1 stoichiometry. Binding site markers identified drug site I (DS1), located in subdomain IIA, as the preferential binding region for both proteins. Computational results supported these findings, showing high affinity for DS1, with binding energies of −69.02 kcal·mol⁻¹ (HSA) and −67.22 kcal·mol⁻¹ (BSA). While complex formation was confirmed for both proteins, differences emerged in the induced circular dichroism (ICD) signals. HSA displayed a distinct ICD profile compared to BSA in both intensity and absorption maximum. Molecular Docking revealed that the C343 conformation differed between HSA and BSA, explaining the variation in ICD signals. These results highlight the importance of protein structure in modulating ligand interactions and spectral responses. Full article

Plant invasions play a significant role in global environmental change. Traditionally, it was believed that invasive plants absorb and utilize nitrogen (N) more efficiently than native plants by adjusting their preferred N forms in accordance with the dominant N forms present in the soil. More recently, invasive plants are now understood to optimize their N acquisition by directly mediating soil N transformations. This review highlights how exotic species optimize their nitrogen acquisition by influencing soil nitrogen dynamics based on their preferred nitrogen forms, and the various mechanisms, including biological nitrification inhibitor (BNI) release, pH alterations, and changes in nutrient stoichiometry (carbon to nitrogen ratio), that regulate the soil nitrogen dynamics of exotic plants. Generally, invasive plants accelerate soil gross nitrogen transformations to maintain a high supply of NH₄⁺ and NO₃⁻ in nitrogen-rich ecosystems irrespective of their preference. However, they tend to minimize nitrogen losses to enhance nitrogen availability in nitrogen-poor ecosystems, where, in such situations, plants with different nitrogen preferences usually affect different nitrogen transformation processes. Therefore, a comprehensive understanding requires more situ data on the interactions between invasive plant species’ preferential N form uptake and the characteristics of soil N transformations. Understanding the combination of these processes is essential to elucidate how exotic plants optimize nitrogen use efficiency (NUE) and minimize nitrogen losses through denitrification, leaching, or runoff, which are considered critical for the success of invasive plant species. This review also highlights some of the most recent discoveries in the responses of invasive plants to the different forms and amounts of N and how plants affect soil N transformations to optimize their N acquisition, emphasizing the significance of how plant–soil interactions potentially influence soil N dynamics. Full article

The benefits of partially substituting inorganic fertilizers with organic fertilizers have been extensively acknowledged. However, the key mechanisms behind nutrient transformation and supply for stable crop yields are still not fully understood. Based on an 11-year field experiment with a wheat–maize rotation system, this study explored the advantages of combined straw and manure substitution under various organic substitution regimes. These regimes included an unfertilized control (CK), inorganic nitrogen, phosphorus, and potassium fertilizers (NPK), NPK substituted with straw (NPKS), NPK substituted with manure (NPKM), and NPK substituted with both straw and manure (NPKSM). Compared to NPK and NPKS, NPKM and NPKSM significantly improved wheat yield by 12.8% and 13.8%, respectively. Bulk soil organic carbon (SOC), total nitrogen (TN), available superphosphate (AP), β-glucosidase (βG), urease (URE), and alkaline phosphatase (ALP) were all higher in the NPKM treatment than in the NPKSM treatment. However, compared to NPKM, NPKSM significantly decreased the potential nitrification rate by 31.0% and increased the soil NH₄⁺-N content. Correspondingly, the functional genes of nitrification were also found to be decreased in the NPKSM treatment. In the rhizosphere, most soil factors increased compared to bulk soil, but treatment differences were smaller. However, the differences among treatments were reduced in the rhizosphere. The high amount of manure applied in the NPKM treatment caused excessive soil phosphorus accumulation, reaching over 46.7 mg/kg, resulting in lower N/P and C/P ratios. The soil quality index (SQI), based on soil nutrients, enzymes, functional genes, and C:N:P stoichiometry, was 9.9% higher in NPKSM than in NPKM. Bulk soil SQIs showed stronger correlations with wheat yields than rhizosphere SQIs, highlighting that bulk soil was superior to rhizosphere in predicting crop yield. Partial least squares path modeling showed that C/N, N/P, and C/P ratios strongly influenced SQIs. The NPKSM treatment, which improved soil nutrients, biological factors, and balanced C:N:P stoichiometry, is an effective strategy for sustainable agriculture. Future practices should focus on maintaining stoichiometric balance to sustain soil quality and crop yields. Full article

This study investigates the long-term seasonal shifts in nutrient dynamics and eutrophication processes in the Romanian Black Sea coastal waters using multi-decadal data (1960/1976/1980–2023). The findings highlight significant seasonal and interannual changes, revealing a progressive rise in seawater temperature, declining oxygen concentrations, and notable shifts in nutrient stoichiometry, particularly an increasing nitrogen–phosphorus (N:P) ratio. These changes are closely associated with increased occurrences of harmful algal blooms (Noctiluca scintillans), emphasizing the complex relationship between warming, nutrient and dissolved oxygen cycles, and biological activity. Seasonal patterns show that prolonged warmer periods, especially during autumn, exacerbate oxygen depletion and nutrient imbalances, with implications for marine life and food webs. The study underscores the importance of targeted nitrogen reduction strategies, including optimized fertilizer use, improved wastewater treatment, and the establishment of buffer zones to minimize land-based nutrient inputs. Regional cooperation and integrated coastal management aligned with the Marine Strategy Framework Directive are essential for mitigating eutrophication. The results provide critical insights into the impacts of climate change on the Black Sea ecosystems. This research contributes to global efforts under SDG 13 (Climate Action), SDG 14 (Life Below Water), and SDG 3 (Good Health and Well-being), addressing the key challenges to marine biodiversity, water quality, and ecosystem sustainability. Full article

Isothermal titration calorimetry (ITC) is a widely used and valuable technique for studying the binding interactions and the formation and dissociation of molecular complexes. ITC directly measures the energetics associated with the interactions and allows for a precise and complete thermodynamic description of association and binding processes, thereby providing an understanding of the interaction mechanisms. In this review, the role, practical aspects related to the experimental design and setup, advantages, and challenges of using ITC to evaluate polyphenol–macromolecule binding are discussed in detail. The focus is on the possibilities offered by ITC, but at the same time, its limitations are taken into account, especially in the study of complex biological processes and in the subsequent reliable determination of thermodynamic parameters. Polyphenols and proteins typically exhibit exothermic interactions, producing strong signals and distinctive titration curves that can be fitted by one- or two-site binding models; of course, there are exceptions to this. Tannins and tannin fractions usually have a high binding stoichiometry and stronger interactions with proteins than the smaller polyphenols. The driving forces behind these interactions vary, but in many cases, both hydrogen bonding and hydrophobic interactions have been reported. The interactions between polyphenols and polysaccharides or lipid bilayers have been far less studied by ITC in comparison to polyphenol–protein interactions. ITC could be utilized more extensively to study polyphenol–macromolecule interactions, as it is an excellent tool for evaluating the thermodynamic parameters of these interactions, and when used together with other techniques, ITC can also help understand how these interactions affect bioavailability, food applications, and other uses of polyphenols. Full article

Extracellular vesicles (EVs) are promising biomarkers for diagnosing complex diseases such as cancer and neurodegenerative disorders. Yet, their clinical application is hindered by challenges in isolating cancer-derived EVs efficiently due to their broad size distribution in biological samples. This study introduces a microfluidic device fabricated using off-stoichiometry thiol-ene and cyclic olefin copolymer, addressing the absorption limitations of polydimethylsiloxane (PDMS). The device streamlines a standard laboratory assay into a semi-automated microfluidic chip, integrating sample mixing and magnetic particle separation. Using the microfluidic device, the binding kinetics between EVs and anti-CD9 nanobodies were measured for the first time. Based on the binding kinetics, already after 10 min the EV capture was saturated and comparable to standard laboratory assays, offering a faster alternative to antibody-based immunomagnetic protocols. Furthermore, this study reveals the binding kinetics of EVs to anti-CD9 nanobodies for the first time. Our findings demonstrate the potential of the microfluidic device to enhance clinical diagnostics by offering speed and reducing manual labor without compromising accuracy. Full article

The phosphorylation state of 20 types of intracellular proteins in the presence of the protein phosphatase 1 (PP1)- and PP2A-specific Ser/Thr phosphatase inhibitor calyculin A or the Tyr phosphatase inhibitor pervanadate was visualized by Phos-tag SDS-PAGE followed by immunoblotting. All blots showed a Phos-tag pattern indicating increased phosphorylation in the presence of one or both phosphatase inhibitors. The increase in phosphorylation stoichiometry per protein tends to be greater for Ser/Thr phosphatase inhibition than for Tyr phosphatase inhibition. This is consistent with the fact that the number of Ser/Thr kinase genes in the human genome is greater than that of Tyr kinases and with the fact that the phospho-Ser/phospho-Thr ratio in the actual human phosphoproteome is far greater than that of phospho-Tyr ratio. This suggests that cellular proteins are routinely and randomly phosphorylated by different kinases with no biological significance, simply depending on the frequency of substrate encounters. Phosphatase is responsible for routinely removing these unwanted phosphate groups systematically and maintaining the dynamic equilibrium of physiological protein phosphorylation. Phos-tag SDS-PAGE visualized that the kinase reaction involves many incidental phosphorylation and that phosphatases play broader roles besides being strict counterparts to kinases. Full article

Co-composting efficiently reclaims dredged sediments (S) and green waste (GW), creating stable products for agricultural applications. However, the use of S-GW co-composts can be limited by legislative thresholds, especially for co-composts with a high S percentage. The evaluation of S-GW co-compost stability by biological assessment can allow for a better understanding of S and GW recycling, as well as the S-GW co-compost application. For this purpose, the microbial biomass, composition, respiration, and eco-enzyme stoichiometry (EST) were assessed, coupled with chemical analysis, in the co-composting of S and GW in different ratios. The Photinia x fraseri and Viburnum tinus L. growth was monitored in a plant trial, comparing the studied co-composts with a control substrate. The EST approach was applied as an indicator of the co-composting stability during the process and after the plant cultivation. The chemical and biological parameters confirmed the suitability of co-composting in the GW and S recovery and the EST approach highlighted a better stability for the 3S:1GW co-compost at the end of the process and after plant cultivation. Viburnum tinus showed a similar growth to the control, while Photinia x fraseri resulted in being more sensitive to the co-compost. The biological assessments were good indicators of the S-GW compost stability for their application in crop cultivation. Full article

Indo-Pacific tropical island streams are home to freshwater pipefish (Microphis spp., Syngnathidae). Otoliths were used to uncover life history traits in four species, including a New Caledonian endemic. All four species present the same methodological challenge: their otoliths are small, fragile and mute for growth marks using basic observation tools. Strontium (Sr) is calcium substituent in the mineral lattice, driven by salinity conditions, and thus useful to study diadromous migrations. Synchrotron-based scanning X-ray fluorescence 2D high-resolution mapping allowed us to tackle the global and hyperfine strontium (Sr) distribution. We developed analytical imaging processes to retrieve biological information from otoliths from the data generated via synchrotron analysis. We uncovered plasticity in the life cycle: all species were amphidromous, apart from some freshwater residents from New Caledonia. Understanding life cycle modalities is crucial to categorize species distribution limits and to implement adapted conservation measures, especially when endemic species are at stake. 2D fine-scale images outlined the heterogeneity of Sr distribution: in addition to the trivial Sr incorporation driven by environmental ionic conditions, there is an unusual mosaic arrangement of Sr distribution and we hypothesize that biological control, especially growth during the early life stages, may sometimes overrule stoichiometry. This shows that it is worth studying otolith formation and element integration at imbricated scales, and our methods and results provide a strong basis for future works and prospects in otolith science. Full article

Galectin-3 is a protein involved in many intra- and extra-cellular processes. It has been identified as a diagnostic or prognostic biomarker for certain types of heart disease, kidney disease and cancer. Galectin-3 comprises a carbohydrate recognition domain (CRD) and an N-terminal domain (NTD), which is unstructured and contains eight collagen-like Pro-Gly-rich tandem repeats. While the structure of the CRD has been solved using protein crystallography, current knowledge about conformations of full-length galectin-3 is limited. To fill in this knowledge gap, we performed molecular dynamics (MD) simulations of full-length galectin-3. We systematically re-scaled the solute–solvent interactions in the Martini 3 force field to obtain the best possible agreement between available data from SAXS experiments and the ensemble of conformations generated in the MD simulations. The simulation conformations were found to be very diverse, as reflected, e.g., by (i) large fluctuations in the radius of gyration, ranging from about 2 to 5 nm, and (ii) multiple transient contacts made by amino acid residues in the NTD. Consistent with evidence from NMR experiments, contacts between the CRD and NTD were observed to not involve the carbohydrate-binding site on the CRD surface. Contacts within the NTD were found to be made most frequently by aromatic residues. Formation of fuzzy complexes with unspecific stoichiometry was observed to be mediated mostly by the NTD. Taken together, we offer a detailed picture of the conformational ensemble of full-length galectin-3, which will be important for explaining the biological functions of this protein at the molecular level. Full article

The influences of legume diversification on soil carbon (C) pools and sequestration, particularly in Himalayan pastureland, remain poorly understood. Moreover, the impact of legume diversification activities and the stoichiometry of soil enzymes in C biogeochemistry at the ecosystem level remains largely overlooked. The purpose of this study is to investigate the influences of legume diversification on activities and the stoichiometry of soil enzymes and their control of C sequestration in pasturelands. Four experimental fertilized species combinations, namely, SG (50% Festuca arundinacea + 50% Dactylis glomerata), SGL1 (25% Festuca arundinacea + 25% Dactylis glomerata + 50% Onobrychis viciifolia), SGL2 (25% Festuca arundinacea + 25% Dactylis glomerata + 50% Trifolium pratense), SGL12 (25% Festuca arundinacea + 25% Dactylis glomerata + 25% Onobrychis viciifolia + 25% Trifolium pratense), and natural pasture (NG) were compared. Soils under SGL1, SGL2, and SG12 had ~18, 36, and 22% greater soil C than SG, respectively. Among the pastures with fertilization, the C mineralization was suppressed by legume diversification. C sequestration under SGL1, SGL2, and SG12 was ~27, 22, and 38% higher than SG, respectively, at the 0–30 cm soil layer. The ratios of DHA are as follows: for PhOX and DHA, PerOX significantly decreased with an increasing grass–legume mixture, suggesting greater C sequestration. PCA analysis revealed that C sequestration under legume diversification and enzymatic stoichiometry had an indirect but substantial impact on C sequestration. The increasing C sequestration under SGL12 was complemented by higher productivity. Data suggested that increasing legumes in pastureland might greatly enhance ecosystem functions such as soil C storage, productivity, ecorestoration efficiency, and biological activity in Indian Himalayan pastureland. Full article

The nutrient availability of carbon (C), nitrogen (N), and phosphorus (P) has been decreasing due to a decline in the biological function of yellow soil, limiting potato yield (PY). Increasing biochar or organic fertilizer input is an effective way to improve soil microbiological fertility. However, indexes to regulate soil microbiological fertility using biochar and organic fertilizer individually or in combination and these indexes’ associations with PY remain unclear. In this study, four fertilization strategies were developed using the nutrient balance method: CK (recommended NPK fertilization), BC (NPK + biochar), OF (NPK + organic fertilizer), and BF (NPK + 1/2 biochar + 1/2 organic fertilizer). Using different fertilization strategies, the eco-stoichiometry characteristics of the soil microbial biomass and enzyme activity; the bioavailability of C, N, and P; and the differences in PY were investigated, and the direct and indirect effects of these factors on PY were determined over a two-year period. The results showed that exogenous organic matter input could considerably affect the stoichiometric ratios of soil microbial biomass; C; N; P; the stoichiometric ratios of C-converting, N-converting, and P-converting enzyme activities (expressed as BG+CBH, NAG+LAP, and AP, respectively); and the integrated enzyme index (IEI). The IEI was the highest in BF, followed by OF, BC, and CK. A significant positive correlation was found between the microbial biomass C, N, and P and their corresponding converting enzyme activities (p < 0.05). The ln(BG+CBH):ln(NAG+LAP), ln(BG+CBH):lnAP, and ln(NAG+LAP):lnAP ratios were all higher than 1:1, but they approached 1:1 in the order of CK-BC-OF-BF. Compared to soil C and N, P-converting enzyme activity was the primary limiting factor for soil nutrient conversion in the study area. BF was less restricted by P and more balanced in its nutrient ratio. The microbial biomass C:N:P could affect PY in eight ways. (1) Microbial biomass C:N directly decreased PY, and microbial biomass C:P indirectly increased PY. (2) It could decrease C-converting enzyme activity, (3) decrease N availability to increase C-converting enzyme activity, (4) decrease P availability, or (5) decrease P availability to decrease the soil C:P-converting enzyme activity ratio. Microbial biomass N:P indirectly increased PY (6) by increasing the soil C:P-converting enzyme activity ratio, (7) by increasing C-converting enzyme activity, or (8) by increasing N availability to increase C-converting enzyme activity. Thus, BF is an effective strategy for regulating the soil microbiological fertility index; enhancing C, N, and P nutrient conversion; and increasing PY. The input of exogenous organic matter can alter the stoichiometric ratios of soil microbial biomass C, N, and P; the stoichiometric ratios of C-converting, N-converting, and P-converting enzyme activities; and nutrient availability, thus regulating PY. Microbial biomass N:P and soil C:P-converting enzyme activity ratios influence PY the most. Full article

The photophysical and sensory properties of the donor–acceptor pyrazoloquinoline derivative (PQPc) were investigated using absorption, steady-state, and time-resolved fluorescence measurements. The compound synthesized from commercial, readily available substrates exhibited absorptions in the UV–Vis range, with a maximum of the longwave band around 390 nm. The maximum fluorescence was around 460–480 nm, depending on the solvent. The quantum yield was between 12.87% (for n-hexane) and 0.75% (for acetonitrile) and decreased with increasing solvent polarity. The PET mechanism was implicated as the cause of fluorescence quenching. Divalent ions such as Zn²⁺, Pb²⁺, Cd²⁺, Ca²⁺, Mg²⁺, Co²⁺, Ni²⁺, and Cu²⁺ were introduced to study the fluorescent response of PQPc. A 13-times increase in fluorescence quantum yield was observed after the addition of Zn²⁺ ions. Detailed research was carried out for the PQPc-Zn²⁺ system in order to check the possibility of analytical applications of PQPc as a fluorescent sensor. A detection limit of Zn²⁺ was set at the value level 1.93 × 10⁻⁷ M. PQPc-Zn²⁺ complexes had a stoichiometry of 1:1 with a binding constant of 859 M⁻¹. Biological studies showed that the sensor was localized in cells near the membrane and cytoplasm and may be used to detect zinc ions in eukaryotic cells. Full article

This study provides a comprehensive investigation into the formation, characteristics, and biological activity of a chromium complex with the organic reagent NTADBrP. The article presents detailed insights into the H1-NMR spectrum of the organic reagent and examines the optimal conditions for chromium complex formation, considering the effects of time, pH, and temperature. The stoichiometry and stability constant of the complex are determined using specific methods, leading to the calculation of a significant stability constant. Additionally, a calibration curve for the chromium ion is derived, and the complex’s biological activity against Escherichia coli and Staphylococcus bacteria is studied. These findings contribute to the understanding of chromium complex behavior and open new avenues for applications in analytical chemistry and pharmaceutical research. Full article