Search Results (125)

Narcotics trafficking is a fundamental part of organized crime, posing significant and evolving challenges for forensic investigations. Addressing these challenges requires rapid, precise, and scientifically validated analytical methods for reliable identification of illicit substances. Over the past five years, forensic drug testing has advanced considerably, improving detection of traditional drugs—such as tetrahydrocannabinol, cocaine, heroin, amphetamine-type stimulants, and lysergic acid diethylamide—as well as emerging new psychoactive substances (NPS), including synthetic cannabinoids (e.g., 5F-MDMB-PICA), cathinones (e.g., α-PVP), potent opioids (e.g., carfentanil), designer psychedelics (e.g., 25I-NBOMe), benzodiazepines (e.g., flualprazolam), and dissociatives (e.g., 3-HO-PCP). Current technologies include colorimetric assays, ambient ionization mass spectrometry, and chromatographic methods coupled with various detectors, all enhancing accuracy and precision. Vibrational spectroscopy techniques, like Raman and Fourier transform infrared spectroscopy, have become essential for non-destructive identification. Additionally, new sensors with disposable electrodes and miniaturized transducers allow ultrasensitive on-site detection of drugs and metabolites. Advanced chemometric algorithms extract maximum information from complex data, enabling faster and more reliable identifications. An important emerging trend is the adoption of green analytical methods—including direct analysis, solvent-free extraction, miniaturized instruments, and eco-friendly chromatographic processes—that reduce environmental impact without sacrificing performance. This review provides a comprehensive overview of innovations over the last five years in forensic drug analysis based on the ScienceDirect database and highlights technological trends shaping the future of forensic toxicology. Full article

Vanillin photoinduced deprotonation was evaluated and analyzed. Vibronic states and transitions were computationally investigated. Optimizations and vertical electron transitions in the gas phase and with the continuum solvation model were computed using the time-dependent density functional theory. Static absorption and emission (photostatic optical) spectra were statistically averaged over the excited instantaneous molecular conformers fluctuating on quantum–classical molecular dynamic trajectories. Photostatic optical spectra were generated using the hybrid quantum–classical molecular dynamics for explicit solvent models. Conical intersection searching and nonadiabatic molecular dynamics simulations defined potential energy surface propagations, intersections, dissipations, and dissociations. The procedure included mixed-reference spin–flip excitations for both procedures and trajectory surface hopping for photodynamics. Insignificant structural deformations vs. hydroxyl bond cleavage followed by deprotonation were demonstrated starting from different initial structural conditions, which included optimized, transition state, and several other important fluctuating configurations in various environments. Vanillin electronic structure changes were illustrated and analyzed at the key points on conical intersection and nonadiabatic molecular dynamics trajectories by investigating molecular orbital symmetry and electron density difference. The hydroxyl group decomposed on transition to a σ-molecular orbital localized on the elongated O–H bond. Full article

The tetrameric protein transthyretin (TTR) transports the hormone thyroxine in plasma and cerebrospinal fluid. Certain point mutations of TTR, including the Val122Ile mutation investigated here, destabilize the tetramer leading to its dissociation, misfolding, aggregation, and the eventual buildup of amyloid fibrils in the myocardium. Cioffi et al. reported the design and synthesis of a novel TTR kinetic stabilizing ligand, referred to here as TKS14, that inhibited TTR dissociation and amyloid fibril formation. In this study, molecular dynamics simulations were used to investigate the binding of TKS14 and eight TSK14 derivatives to the Val122Ile TTR mutant. For each complex, the ligand’s solvent accessible surface area (SASA), ligand–receptor hydrogen-bonding interactions, and the free energy of ligand-binding to TTR were investigated. The goal of this study was to identify the TSK14 functional groups that contributed to TTR stabilization. TKS14 was found to form a stable, two-point interaction with TTR by hydrogen bonding to Ser-117 residues in the inner receptor binding pocket and interacting through hydrogen bonds and electrostatically with Lys-15 residues near the receptor’s surface. The free energy of TKS14-TTR binding was −18.0 kcal mol⁻¹ and the ligand’s average SASA value decreased by over 80% upon binding to the receptor. The thermodynamic favorability of TTR binding decreased when TKS14 derivatives contained either methyl ester, amide, tetrazole, or N-methyl functional groups that disrupted the above two-point interaction. One derivative in which a tetrazole ring was added to TKS14 was found to form hydrogen bonds with Thr-106, Thr-119, Ser-117, and Lys-15 residues. This derivative had a free energy of TTR binding of −21.4 kcal mol⁻¹. Overall, the molecular dynamics simulations showed that the functional groups within the TKS14 structural template can be tuned to optimize the thermodynamic favorability of ligand binding. Full article

We study the structures of 24-crown-8/H⁺/diaminopropanol (CR/DAPH⁺) and 24-crown-8/CsF/H⁺/diaminopropanol (CR/CsF/DAPH⁺) non-covalent host–guest complexes in both the gas phase and aqueous solution using the density functional theory (DFT) method. We examine the environment (complexation with CR vs. solvation) around the guest functional groups (ammoium, hydroxyl, and amino) in the CR/DAPH⁺ and CR/CsF/DAPH⁺ complexes. We find that the gas-phase configurations with the ‘naked’ hydroxyl/amino devoid of H-bonding with CR or CR/CsF are structurally correlated with the lowest Gibbs free energy conformers in aqueous solution in which the functional groups are solvated off the CR or CR/CsF host. We predict that the latter thermodynamically disadvantageous host–guest configurations would be identified in the gas phase by infrared multiphoton dissociation (IRMPD) spectroscopy, originating from the complexes in aqueous solution. This predicted ‘thermodynamic reversal’ and ‘structural correlation’ of the host–guest configurations in the gas phase vs. in solution are discussed in relation to the possibility of obtaining information on host–guest–solvent interactions in the solution phase from the gas-phase host–guest configurations. Full article

Affinity gel electrophoresis was introduced about 50 years ago. Proteins interact with a ligand immobilized in the support. Specific interactions cause a decrease in electrophoretic mobility. The presence of a free ligand, competing with an immobilized ligand, restores electrophoretic mobility. In affinity capillary electrophoresis, the ligand is mobile, and its interaction with a specific protein changes the mobility of the protein–ligand complex. This review mostly focuses on gel affinity electrophoresis. The theoretical basis of this technique, ligand immobilization strategies, and principles for determination of ligand affinity are addressed. Factors affecting specificity and strength of interactions are discussed, in particular, the structure of the affinity matrix, pH, temperature, hydrostatic pressure, solvent, co-solvents, electric field, and other physico-chemical conditions. Capillary affinity electrophoresis principles and uses are also briefly introduced. Affinity gel electrophoresis can be used for qualitative and quantitative purposes. This includes detection of specific proteins in complex media, investigation of specific interactions, protein heterogeneity, molecular and genetic polymorphism, estimation of dissociation constants of protein–ligand complexes, and conformational stability of binding sites. Future prospects, in particular for screening of engineered mutants and potential new drugs, coupling to other analytical methods, and ultra-microtechnological developments, are addressed in light of trends and renewal of this old technique. Full article

Background: Luteolin, a flavonoid with well-documented antioxidant properties, has garnered significant attention for its potential therapeutic effects. Objectives: This study aims to investigate the antioxidant properties of luteolin under the influence of solvents, utilizing computational techniques to elucidate its interactions and its potential role as a modulator of enzymatic activities, particularly with Cytochrome 17A1. Methods: Density Functional Theory (DFT) calculations were employed to determine luteolin’s electronic and structural characteristics. Key aspects analyzed included electron density distribution and the energies of the frontier molecular orbitals (HOMO and LUMO). Free radical scavenging mechanisms were explored by comparing the dissociation enthalpy of the O–H bond in the absence and presence of water molecules. Additionally, molecular docking simulations were performed to assess the interactions of luteolin with Cytochrome 17A1, identifying preferred binding sites and interaction energies. Results: The findings indicate that luteolin possesses distinct structural and electronic features that contribute to its effectiveness in protecting against oxidative stress. However, hydrogen bonding interactions with water molecules were found to influence the dissociation enthalpy of the O–H bond. Docking simulations revealed significant interaction profiles between luteolin and Cytochrome 17A1, suggesting its potential role as a modulator of this protein. Conclusions: This study underscores the therapeutic potential of luteolin and highlights the importance of computational techniques in predicting and understanding the molecular interactions of bioactive compounds with biological targets. The results provide valuable insights that may aid in developing new therapeutic strategies for diseases associated with oxidative stress. Full article

The incorporation of transition metal atoms into [Ge₉] clusters is a widely studied area of Zintl-cluster chemistry. Recently, it was shown that clusters comprising single transition metal atoms in the cluster surface show catalytic properties. Here, we present a synthetic approach to four new compounds comprising silylated Ge₉ clusters with organometallic ruthenium complexes. [η⁵-Ge₉Hyp₃]RuCp* (1), [η¹-Ge₉(Si^tBu₂H)₃]RuCp(PPh₃)₂ (2), and [Hyp₃Ge₉][RuCp(PPh₃)₂(MeCN)] (3b) (Cp = cyclopentadienyl, Cp* = pentamethylcyclopentadienyl, Hyp = Si(SiMe₃)₃, Ph = C₆H₅, ^tBu = tert-butyl) were characterized by means of NMR spectroscopy and single-crystal structure determination. In the case of 2, a new isomer with an approximated C_4v symmetric monocapped square antiprism of nine Ge atoms with an unexpected ligand arrangement comprising three ditertbutylsilane ligands attached to the open square was obtained. [Hyp₃Ge₉][RuCp(PPh₃)₂] (3a) was characterized via NMR spectroscopy and LIFDI mass spectrometry. Overall, we were able to show that the steric demand of the ligands Cp vs. Cp* and hypersilylchloride vs. ditertbutylsilane strongly influence the arrangement of the atoms and ligands on the cluster. In addition, the solvent also affects the cluster, as it appears that the ruthenium atom in 3a dissociates from the cluster surface upon acetonitrile coordination to form 3b. These results show that choosing the right synthetic tools and ligands makes a big difference in the outcome of the metalation reaction. Full article

Ethylene carbonate is, among other applications, used in Li-ion batteries as an electrolyte solvent to dissociate Li-salt. Supercritical CO₂ extraction is a promising method for the recycling of electrolyte solvents from spent batteries. To design an extraction process, knowledge of the solute solubility is essential. In this work, the solubility of ethylene carbonate at different pressure (80–160 bar) and temperature (40 °C, and 60 °C) conditions is studied. It is shown that the solubility of ethylene carbonate increased with pressure at both temperatures, ranging from 0.24 to 8.35 g/kg CO₂. The retrieved solubility data were fitted using the Chrastil model, and the average equilibrium association number was determined to be 4.46 and 4.02 at 40 °C and 60 °C, respectively. Scanning electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction analysis of the collected ethylene carbonate indicated that the crystal morphology and structure remained unchanged. A proof-of-principle experiment showed that EC can be successfully extracted from Li-ion battery waste at 140 bar and 40 °C. Full article

Planar heterojunction (PHJ) is employed to obtain proper vertical phase separation for highly efficient polymer solar cells (PSCs). However, it heavily relies on the choice of orthogonal solvent in the production process. Here, we fabricated a pseudo-bilayer bulk heterojunction (PBHJ) PSC with cross-distribution in the vertical direction by preparing two layers of PM6 and BTP-eC9 blends in an o-XY solution with different dilution ratios to study the morphological evolution of PBHJ film. We found that the PBHJ film exhibits more uniform and suitable continuous interpenetrating network morphology and proper phase separation in the vertical direction for the formation of p-i-n structure. This provides an effective channel for exciton dissociation and charge transport, which is confirmed by both exciton generation simulations and charge dynamics measurements. The PBHJ devices can effectively inhibit trap recombination and accelerate charge separation and transfer. Based on good active layer morphology and balanced charge mobility, all-green solvent-processed PSCs with champion power conversion efficiencies (PCEs) of 18.48% and 16.83% are obtained in PM6:BTP-eC9 and PTQ10:BTP-eC9 systems, respectively. This work reveals the potential mechanism of morphological evolution induced by the PBHJ structure and provides an alternative approach for developing solution processing PSCs. Full article

Organic solar cells (OSCs) are made from carbon-rich organic compounds with low environmental impacts, unlike the silicon in traditional solar panels. Some of these organic materials can be broken down and reprocessed, enabling the recovery of valuable components. Specifically, the active-layer materials that make up OSCs can be designed with sustainability in mind. However, it is important to note that practical active materials that can be used for the commercialization of OSCs are still an area of research and development due to their low efficiency/stability and processability. Herein, we designed and synthesized three A-D-A’-D-A-type long-conjugated non-fullerene acceptors (NFAs) by incorporating various electron-withdrawing groups into the benzothiadiazole-diindacenodithiophene core. These NFAs, by changing their end-capping groups, exhibit not only distinct physical, optical, and electrochemical properties, but also differences in crystallinity and exciton dissociation. As a result, they exhibited significant differences in photovoltaic performance in PM6 donor-based binary devices. The introduction of small amounts of NFAs as a third component in the PM6:BTP-eC9 blend significantly enhanced its photon harvesting capabilities and influenced its charge transfer dynamics. Finally, we achieved a remarkable power conversion efficiency of nearly 17% by utilizing an eco-friendly solvent. This study provides valuable insights for the development of NFAs in efficient and eco-friendly OSCs. Full article

Using the self-consistent field approach, we studied the salt-controlled vertical segregation of mixed polymer brushes immersed into a selective solvent. We considered brushes containing two types of chains: polyelectrolyte (charged) chains and neutral chains. The hydrophobicity of both types of chains is characterized by the Flory–Huggins parameters ${\chi }_C$ and ${\chi }_N$, respectively. It was assumed that the hydrophobicity is varied only for the polyelectrolyte chains (${\chi }_C$), while other polymer chains in the brush remain hydrophilic (${\chi }_N=0$) and neutral. Thus, in our model, the solvent selectivity ($\chi ={\chi }_C-{\chi }_N$) was varied, which can be controlled in a real experiment, for example, by changing the temperature. At low salt concentrations, the polyelectrolyte chains swell and occupy the surface of the mixed brush. At high salt concentrations, the hydrophobic polyelectrolyte chains collapse and give place to neutral chains on the surface. By changing the selectivity of the solvent and the ionic strength of the solution, the surface properties of such mixed brushes can be controlled. Based on the numerical simulations results, it is shown how the critical selectivity corresponding to the segregation transition in polyelectrolyte/neutral brushes depends on the ionic strength of the solution. It is shown that at the same ionic strength, the critical selectivity increases with an increasing degree of dissociation of charged groups, as well as with an increasing fraction of polyelectrolyte chains in the mixed brush. It has also been shown that at low ionic strengths, the critical selectivity of the solvent decreases with increasing grafting density, while at high ionic strengths, on the contrary, it increases. Within the framework of the mean field theory, a two-parameter model has been constructed that quantitatively describes these dependencies. Full article

Linear relationships, expressing the electrochemical properties of molecules as functions of structure, give insight into the associated electrochemical process and are a tool for prediction. Many biological activities rely on water-based dissociation, making electrochemical properties a bridge between structure and activity. Motivated by a previous study, a replica is made here on a different dataset in order to validate/invalidate the previously reported results. There are several methods for obtaining structure-based descriptors. Some of the methods have been devised to account for molecular topology, some to account for molecular geometry, and others to account for both. Two methods are involved here to derive structure-based descriptors and further obtain structure–property relationships (FMPI and ChPE). In order to express structure descriptors, both FMPI and ChPE express first the topology of the molecule, using the heavy atoms identity matrix and the heavy atoms adjacency matrix, both square symmetric matrices in the belief that symmetry is one major factor of molecular stability. A set of 2,6-dimethyl-1,4-dihydropyridine derivatives with oxidation peak potentials and coulometrically determined number of electrons experimental data is subjected to the search for structure–activity relationships. Even if the 2,6-dimethyl-1,4-dihydropyridine is a symmetric compound (of C_s point group), their derivatives are generally not symmetric (9 out of 24 are asymmetric). The dataset is subjected to descriptive and inferential statistics in order to filter out the most relevant structure–activity relationship. The geometry is built using three levels of theory (one from molecular mechanics and two others from density functionals, of which one accounts for the interaction with water as solvent). One challenge of picking one out of two reported measured values is dealt with by calculating the likelihood associated with the two choices. Relevant structure–activity models are extracted and discussed. The use of in vivo (in water, SM8 model) models in geometry optimization (from MMFF94 and B3LYP and to M06 + Water SM8) results in a precision gain, but this is, in most of the cases, not statistically significant, and this can be considered a negative result. Full article

Aminoacetaldehyde (glycinal, NH₂CH₂CHO) is a first-generation oxidation product of monoethanolamine (MEA, NH₂CH₂CH₂OH), a solvent widely used for CO₂ gas separation, which is proposed as the basis for a range of carbon capture technologies. A complete oxidation mechanism for MEA is required to understand the atmospheric transformation of carbon capture plant emissions, as well as the degradation of this solvent during its use and the oxidative destruction of waste solvent. In this study, we have investigated the ^•OH radical-initiated oxidation chemistry of aminoacetaldehyde using quantum chemical calculations and RRKM theory/master equation kinetic modeling. This work predicts that aminoacetaldehyde has a tropospheric lifetime of around 6 h and that the reaction predominantly produces the NH₂CH₂C^•O radical intermediate at room temperature, along with minor contributions from NH₂^•CHCHO and ^•NHCH₂CHO. The dominant radical intermediate NH₂CH₂C^•O is predicted to promptly dissociate to NH₂^•CH₂ and CO, where NH₂^•CH₂ is known to react with O₂ under tropospheric conditions to form the imine NH = CH₂ + HO₂. The NH₂^•CHCHO radical experiences captodative stabilization and is found to form a weakly bound peroxyl radical upon reaction with O₂. Instead, the major oxidation product of NH₂^•CHCHO and the aminyl radical ^•NHCH₂CHO is the imine NH = CHCHO (+HO₂). In the atmosphere, the dominant fate of imine compounds is thought to be hydrolysis, where NH = CH₂ will form ammonia and formaldehyde, and NH = CHCHO will produce ammonia and glyoxal. Efficient conversion of the dominant first-generation oxidation products of MEA to ammonia is consistent with field observations and supports the important role of imine intermediates in MEA oxidation. Full article

The synergistic interactions between nitrogen doses and microbial inoculation in crops indicate the potential for integrated nutrient management strategies in plant cultivation. Therefore, this study investigated the interactive effects of nitrogen doses and Azospirillum brasilense inoculation on wheat flour characteristics in terms of the falling number and color parameters and yields of reducing sugars obtained by subcritical water hydrolysis (SWH) from wheat bran. The strip-plot experimental design, bifactorial with three replications, was applied. Factor A was three wheat cultivars: ORS Agile (AGI), ORS Feroz (FER), and TSZ Dominadore (DOM). Factor D was five nitrogen doses in the topdressing: 0, 20, 40, 60, and 80 kg ha⁻¹. The lowest value of falling number of 332 s was achieved with flour from FER cultivar using a nitrogen dose of 80 kg ha⁻¹ with A. brasilense inoculation. The SWH produced yields of reducing sugars (Y_RS) from wheat bran of up to 6.74 ± 0.18 g (100 g of wheat bran)⁻¹ for the cultivar DOM when using a nitrogen dose of 60 kg ha⁻¹ associated with A. brasilense inoculation. In this cultivation condition, the falling number was 408 s and the color parameters were L* of 92.49, a* of −0.26, and b* of 11.91. In the other conditions, the Y_RS ranged from 2.93 ± 0.63 to 6.52 ± 0.04 g (100 g of wheat bran)⁻¹. Both flour and bran are nutritional products with high application potential, and this study indicated SWH as a promising technique to dissociate the lignocellulosic complex of wheat bran without using hazardous solvents. Full article

The amount of free ions, ion pairs, and higher aggregate of the possible species present in a solution during the gold(I)-catalyzed alkoxylation of unsaturated hydrocarbon, i.e., ISIP (inner sphere ion pair) [(NHC)AuX] and OSIP (outer sphere ion pairs) [(NHC)Au(TME)X] [NHC 1,3-bis(2,6-di-isopropylphenyl)-imidazol-2-ylidene; TME = tetramethylethylene (2,3-bis methyl-butene); X⁻ = Cl⁻, BF₄⁻, OTf⁻; and OTs⁻ BArF₄⁻ (ArF = 3,5-(CF₃)₂C₆H₃)], has been determined. The ¹H and ¹⁹F DOSY NMR measurements conducted in catalytic conditions indicate that the dissociation degree (α) of the equilibrium ion pair/free ions {[(NHC)Au(TME)X] [(NHC)Au(TME)]⁺ + X⁻} depends on the nature of the counterion (X⁻) when chloroform is the catalytic solvent: while the compounds containing OTs⁻ and OTf⁻ as the counterion gave a low α (which means a high number of ion pairs) of 0.13 and 0.24, respectively, the compounds containing BF₄⁻ and BArF₄⁻ showed higher α values of 0.36 and 0.32, respectively. These results experimentally confirm previous deductions based on catalytic and theoretical data: the lower the α value, the greater the catalytic activity because the anion that can activate methanol during a nucleophilic attack, although the lower propensity to activate methanol of BF₄⁻ and BArF₄⁻, as suggested by the DFT calculations, cannot be completely overlooked. As for the effect of the solvent, α increases as the dielectric constant increases, as expected, and in particular, green solvents with high dielectric constants show a very high α (0.90, 0.84, 0.80, and 0.70 for propylene carbonate, γ-valerolactone, acetone, and methanol, respectively), thus confirming that the moderately high activity of NHC-Au-OTf in these solvents is due to the specific effect of polar functionalities (O-H, C=O, O-R) in activating methanol. Finally, the DOSY measurements conducted in p-Cymene show the formation of quadrupole species: under these conditions, the anion can better exercise its ‘template’ and ‘activating’ roles, giving the highest TOF. Full article