Solute Molecules In Water Research Articles

Molecular insights into the interactions between PEG carriers and drug molecules from Celastrus hindsii: a multi-scale simulation study

Efficient drug delivery is crucial for the creation of effective pharmaceutical treatments, and polyethylene glycol (PEG) carriers have been emerged as promising candidates for this purpose due to their bio-compatibility, enhancement of drug solubility, and stability. In this study, we utilized molecular simulations to examine the interactions between PEG carriers and selected drug molecules extracted from Celastrus hindsii: Hindsiilactone A, Hindsiiquinoflavan B, Maytenfolone A, and Celasdin B. The simulations provided detailed insights into the binding affinity, stability, and structural properties of these drug molecules when complexed with PEG carriers. A multi-scale approach combining density functional theory (DFT), extended tight-binding (xTB), and molecular dynamics (MD) simulations was conducted to investigate both unbound and bound states of PEG/drug systems. The results from DFT and xTB calculations revealed that the unbound complex has an unfavorable binding free energy, primarily due to negative contributions of delta solvation free energy and entropy. The MD simulations provided more detailed insights into the interactions between PEG and drug molecules in water solutions. By integrating the findings from the multi-scale simulations, a comprehensive picture of the unbound and bound states of PEG and drug systems were obtained. This information is valuable for understanding the molecular mechanisms governing the binding of drugs in PEG-based delivery platforms, and it contributes to the rational design and optimization of these systems.

The p-n heterojunction of BiVO4/Cu2O was decorated by plasma Ag NPs for efficient photoelectrochemical degradation of Rhodamine B

The photoelectrochemical (PEC) properties of BiVO4 are limited by the poor separation and transfer of photogenerated electron-hole pairs and easy recombination. Hence, we designed the ternary composite photoelectrode through the embedding of Ag in BiVO4/Cu2O p-n heterojunction and evaluated its PEC performance by degrading Rhodamine B (RhB) for the first time. As expected, the BiVO4/Ag/Cu2O photoelectrode among four of the BiVO4-based photoelectrodes achieved the highest photocurrent density (3.36 mA/cm2), which is about 8.6 times than pure BiVO4 photoelectrode (0.39 mA/cm2). Additionally, the resulting fabricated BiVO4/Ag/Cu2O composite as the working photoelectrode performs a highly efficient degradation of RhB molecules in water solution through PEC process (86% within 120 min), which is 2.8 times than pure BiVO4. It is noteworthy that the generation of built-in potential at the interface of BiVO4/Cu2O p-n heterojunction plays a crucial role in the carriers' separation efficiency. Meanwhile, the surface plasmon resonance (SPR) of Ag nanoparticles (NPs) displays a magnificent role in improving the PEC performance by hot-electrons injection (HET) and plasma resonance energy transfer (PRET) to metal semiconductors. This research may inspire a new design for the synergistic effect of p-n heterojunction and plasmon to enhance PEC properties of pollution degradation.

Experimental and computational analysis of N-methylcytisine alkaloid in solution and prediction of biological activity by docking calculations

N-methylcytisine alkaloid was fully characterised by FTIR and ultraviolet spectroscopies. Two structures of this alkaloid that change the position of carbonyl groups, called C1 and C2, were theoretically analysed in both the gas phase and water solution at the B3LYP/6-311++G** level of theory. The dipole moment values of this molecule increase in the solution. The structural properties of N-methylcytisine were analysed to investigate its conformational preference given in natural sources. Then, Mulliken, MK and NPA charges with bond orders, natural bond orbital, molecular electrostatic potentials and topological properties expose a higher stability of this molecule in water solution. The frontier orbital analysis justifies the blue and red colourations observed in the mapped surfaces corresponding to electron density. Very good agreements with experimental data are observed for C2 in both 1H- and 13C-NMR spectra and their presence was supported by the ultraviolet spectra. For the first time, a complete assignment of infrared bands and force constants of N-methylcytisine in both media are reported as the scaled frequencies are in agreement with those experimentals. Molecular docking studies were used to predict the biological activity, which evidenced that N-methylcytisine alkaloid can act as partial agonist of nicotinic acetylcholine receptors.

Microwave dielectrometer application to antibiotic concentration control in water solution

Subject and Purpose. This study focuses on the original waveguide-differential dielectrometer designed for complex permittivity measurements of high-loss liquids in the microwave range towards the determination of pharmaceutical ingredient concentrations in water solutions at room temperature. The suitability of the device and effectiveness of the dielectrometry method are tested on such pharmaceutical ingredients as lincomycin and levofloxacin over a wide range of concentrations. Methods and Methodology. The main idea of the method consists in that the complex propagation coefficients of the HE11 wave are obtained from the amplitude and phase shift differences acquired by the wave after it has passed through the two measuring cells of the waveguide-differential dielectrometer. Results. We have shown that the proposed dielectometry method allows a real-time determination of pharmaceutical ingredient concentrations in water solution by measuring the wave attenuation and phase shift differences. We have found that unless concentrations of pharmaceutical ingredients are low, few free water molecules in water solution are bound to the pharmaceutical ingredients. The number of free water molecules in solution decreases as the concentration of pharmaceutical ingredients rises. Conclusion. The current study confirms that the dielectometry method and the device developed provide effective determination of pharmaceutical ingredient concentrations in water solutions.

Antimicrobial Effects of Ozonated Water Against

The objective of this study was to evaluate the efficacy of ozonated water for antimicrobial. For evaluated the antibacterial activity, the ozonated water used to investigate against generic E. coli. The ozone generator used in this study was containing electric discharge units, a circulating fan and a cylinder of pure oxygen that was calibrated to release oxygen at 0.5 mg/L per min. after that, the ozonated water produce by bubbled through ozone gas into the distilled water. The concentration of ozonated water measure with the fluorescence light intensity generated by HTA molecules in water solutions. Another that, the antibacterial activity against, the results showed that the antimicrobial activities against of ozonated water high antimicrobial power and a potential for acute generic E. coli

Building Conjugated Donor-Acceptor Cross-Links into Metal-Organic Frameworks for Photo- and Electroactivity.

We convert a coordination network into a covalent solid, while maintaining the crystallinity and greatly enhancing the framework rigidity and redox-active and photochemical properties. Specifically, intensely light-absorbing push-pull functions are postsynthetically installed by reacting the electrophilic TCNE (tetracyanoethylene) guests and the electron-rich alkyne side arms on a microporous Zr-organic framework, generating black microporous crystallites with a band gap smaller than 1.0 eV. The reaction proceeds in the known [2 + 2] cycloaddition-retroelectrocyclization mechanism and extensively establishes conjugated (polyene) bridges across the linker molecules. The donor (4-methoxyphenyl) and acceptor (dicyanovinyl) couples of the polyene bridges also act as an efficient fluorescent quencher and can be selectively installed in a thin outer layer of the host crystallite to form a core-shell assembly for turn-on fluorescent sensing of small amine molecules in water solutions.

Site-Selective Photoinduced Electron Transfer of Excited-State Intermolecular Hydrogen-Bonded Cluster in Solution

In this work, the electronic excited states of hypoxanthine in solution such as water and acetonitrile are investigated by the time-dependent density functional theory (TDDFT) method. We demonstrated for the first time that the intermolecular excited-state electron transfer (ESET) from solvents to the hypoxanthine through excited-state intermolecular hydrogen-bonds cluster exhibits obvious site-selectivity. Excited-state electron transfer could only occur at the N7 site of hypoxanthine molecule in water solution, while that is the N9 site in acetonitrile. Potential energy surfaces for different electronic states of hypoxanthine with and without the influence of the excited-state hydrogen bonding cluster are also discussed. Site-selective ESET is proposed to induce the internal conversion of hypoxanthine from S2 state to S1 at a conical intersection, which is responsible for the ultrashort lifetime of hypoxanthine in excited state in solution. These results pave a novel way to understand the photophysical and photochemical behaviors of DNA bases and their derivatives in solution phase.

Semi-permeable membrane fabricated from organoclay/PS/EVA irradiated by ɣ-rays for water purification from dyes

This article summarizes the modification of bentonite to organoclay consisting of aniline monomer incorporated into the bentonite matrices. The organoclay (OC) hybrid has been exposed to gamma rays at dose of 50 kGy resulting the aniline polymerization. Organoclay's color is dark red. The blend polymer (PS/PEVA) was mixed with 33 wt% organoclay in Toluene solvent and then irradiated to 50 kGy. Many characterization techniques have been used to identify changes in clay in organoclay (OC) have relatively high surface area, strong dye adsorption and highly variable surface area. XRD analysis shows increased of interplanar distance (d) of bentonite after aniline modification that confirmed by FTIR analysis and also when composite with blend polymer (PS/PEVA). SEM reveals the irregular pores structure of semi-permeable membrane ranged from 35 to 3 μm. In this article, novel membrane's ability to purify water polluted with three different dyes: Toluidine Blue (TB), Amido Black (AB) and Remazol Red (RR). It is inferred from results that the aniline treatment enhances dye adsorption by bentonite and increases dye adsorption when composite with blend polymer. This future is give effective water purification membrane. It was found that over 99% TB molecules in water solution were adsorbed by OC/PS/PEVA in fifteen second.

BiVO4/BiO0.67F1.66 heterojunction enhanced charge carrier separation to boost photocatalytic activity

BiVO4/BiO0.67F1.66 heterojunction composites with cake-like morphology have been successfully synthesized by a two-step hydrothermal route for the first time. As-prepared BiVO4/BiO0.67F1.66 microstructures were characterized with X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible (UV-vis) diffuse absorption spectroscope, and Brunauer-Emmett-Teller (BET) surface area measurements. The photocatalytic performance of the BiVO4/BiO0.67F1.66 composites was evaluated by studying the visible-light decomposition of rhodamine B (RhB) and phenol molecules in water solution. The BiVO4/BiO0.67F1.66 composites exhibit an obviously improved photocatalytic activity in comparison with the pure BiVO4, as a result of the increased surface area and the unique p–n heterojunction between BiO0.67F1.66 and BiVO4.

Zwitterionization of glycine in water environment: Stabilization mechanism and NMR spectral signatures.

At physiological conditions, myriads of biomolecules (e.g., amino acids, peptides, and proteins) exist predominantly in the zwitterionic structural form and their biological functions will result in these conditions. However these geometrical structures are inaccessible energetically in the gas phase, and at this point, stabilization of amino-acids in physiological conditions is still under debate. In this paper, the electronic properties of a glycine molecule in the liquid environment were studied by performing a relaxation of the glycine geometry in liquid water using the free energy gradient method combined with a sequential quantum mechanics/molecular mechanics approach. A series of Monte Carlo Metropolis simulations of the glycine molecule embedded in liquid water, followed by only a quantum mechanical calculation in each of them were carried out. Both the local and global liquid environments were emphasized to obtain nuclear magnetic resonance (NMR) parameters for the glycine molecule in liquid water. The results of the equilibrium structure in solution and the systematic study of the hydrogen bonds were used to discard the direct proton transfer from the carboxyl group to the ammonium group of the glycine molecule in water solution. The calculations of the Density Functional Theory (DFT) were performed to study the polarization of the solvent in the parameters of nuclear magnetic resonance of the glycine molecule in liquid water. DFT calculations predicted isotropic chemical changes on the H, C, N, and O atoms of glycine in liquid water solution which agree with the available experimental data.

Application of reference-modified density functional theory: Temperature and pressure dependences of solvation free energy.

Recently, we proposed a reference-modified density functional theory (RMDFT) to calculate solvation free energy (SFE), in which a hard-sphere fluid was introduced as the reference system instead of an ideal molecular gas. Through the RMDFT, using an optimal diameter for the hard-sphere reference system, the values of the SFE calculated at room temperature and normal pressure were in good agreement with those for more than 500 small organic molecules in water as determined by experiments. In this study, we present an application of the RMDFT for calculating the temperature and pressure dependences of the SFE for solute molecules in water. We demonstrate that the RMDFT has high predictive ability for the temperature and pressure dependences of the SFE for small solute molecules in water when the optimal reference hard-sphere diameter determined for each thermodynamic condition is used. We also apply the RMDFT to investigate the temperature and pressure dependences of the thermodynamic stability of an artificial small protein, chignolin, and discuss the mechanism of high-temperature and high-pressure unfolding of the protein. © 2017 Wiley Periodicals, Inc.

Thermodynamics of hydration of fullerols [C60(OH)n] and hydrogen bond dynamics in their hydration shells.

Molecular dynamics simulations of fullerene and fullerols [C60(OH)n, where n = 2-30] in aqueous solutions have been performed for the purpose of obtaining a detailed understanding of the structural and dynamic properties of these nanoparticles in water. The structures, dynamics and hydration free energies of the solute molecules in water have been analysed. Radial distribution functions, spatial density distribution functions and hydrogen bond analyses are employed to characterize the solvation shells of water around the central solute molecules. We have found that water molecules form two solvation shells around the central solute molecule. Hydrogen bonding in the bulk solvent is unaffected by increasing n. The large decrease in solvation enthalpies of these solute molecules for n > 14 enhances solubilisation. The diffusion constants of solute molecules decrease with increasing n. The solvation free energy of C60 in water is positive (52.8 kJ/mol), whereas its value for C60(OH)30 is highly negative (-427.1 kJ/mol). The effects of surface hydroxylation become more dominant once the fullerols become soluble.

Decoration of gold nanoparticles with cysteine in solution: reactive molecular dynamics simulations.

The dynamics of gold nanoparticle functionalization by means of adsorption of cysteine molecules in water solution is simulated through classical reactive molecular dynamics simulations based on an accurately parametrized force field. The adsorption modes of the molecules are characterized in detail disclosing the nature of the cysteine-gold interactions and the stability of the final material. The simulation results agree satisfactorily with recent experimental and theoretical data and confirm previous findings for a similar system. The covalent attachments of the molecules to the gold support are all slow physisorptions followed by fast chemisorptions. However, a great variety of binding arrangements can be observed. Interactions with the adsorbate caused surface modulations in terms of adatoms and dislocations which contributed to strengthen the cysteine adsorption.

Experimental and Quantum Chemical Evaluations of Pyridine Oxidation Under Drug Development Stress Test Conditions

The oxidation reaction of pyridine by hydrogen peroxides in water media was investigated by combining quantum chemical calculations and laboratory experiments. Pyridine was selected as a model system for aromatic amines that frequently occurs in drug molecules. Several different reaction conditions, commonly used in stress testing of drug molecules during drug development, were investigated to increase mechanistic insight to this class of oxidation reactions. Of special interest is to note that small amounts of acetonitrile, a regularly used cosolvent to keep poorly soluble drug molecules in water solution, could catalyze the oxidation reaction in the presence of hydrogen peroxide. Consequently, attention needs to be taken when comparing data from different stress test studies of amine oxidation by hydrogen peroxides at different pH, and with and without acetonitrile. In particular, they need to be controlled when identifying the proper intrinsic stability of the drug molecule.

Interaction of Spin-Labeled Lipid Membranes with Transition Metal Ions.

The large values of spin relaxation enhancement (RE) for PC spin-labels in the phospholipid membrane induced by paramagnetic metal salts dissolved in the aqueous phase can be explained by Heisenberg spin exchange due to conformational fluctuations of the nitroxide group as a result of membrane fluidity, flexibility of lipid chains, and, possibly, amphiphilic nature of the nitroxide label. Whether the magnetic interaction occurs predominantly via Heisenberg spin exchange (Ni) or by the dipole–dipole (Gd) mechanism, it is essential for the paramagnetic ion to get into close proximity to the nitroxide moiety for efficient RE. For different salts of Ni the RE in phosphatidylcholine membranes follows the anionic Hofmeister series and reflects anion adsorption followed by anion-driven attraction of paramagnetic cations on the choline groups. This adsorption is higher for chaotropic ions, e.g., perchlorate. (A chaotropic agent is a molecule in water solution that can disrupt the hydrogen bonding network between water molecules.) However, there is no anionic dependence of RE for model membranes made from negatively charged lipids devoid of choline groups. We used Ni-induced RE to study the thermodynamics and electrostatics of ion/membrane interactions. We also studied the effect of membrane composition and the phase state on the RE values. In membranes with cholesterol a significant difference is observed between PC labels with nitroxide tethers long enough vs not long enough to reach deep into the membrane hydrophobic core behind the area of fused cholesterol rings. This study indicates one must be cautious in interpreting data obtained by PC labels in fluid membranes in terms of probing membrane properties at different immersion depths when it can be affected by paramagnetic species at the membrane surface.

Fluorescence detection of hydroxyl radicals in water produced by atmospheric pulsed discharges

It has been proven that hydroxyl (OH) radicals can be generated by streamer discharges across water surfaces under ambient atmospheric conditions. Hydroxyl radicals have the highest oxidation capability amongst all oxygen-based reactive species, thus OH play an important role in oxidation of organic molecules and the bactericidal effects of plasma discharges. In this study, generation of hydroxyl radicals in water by pulsed streamer discharges was investigated. Terephthalic acid was used as a chemical probe as this acid is converted into 2-hydroxyterephthalic acid (HTA) by chemical reaction with OH radicals. The concentration of OH radicals was quantified by measuring the fluorescence light intensity generated by HTA molecules in water solutions. Both positive and negative pulsed discharges with different voltage levels were tested. Two different types of sample holder – non-conductive plastic dishes, and dishes lined with conductive aluminum foil – were used in order to investigate the effect of the discharge propagation path on the efficiency of OH production. The efficiency of OH production was measured as a function of: the distance between the needle electrode and the water surface; the magnitude and polarity of HV energization; and the total delivered charge. The obtained results will help in optimization of non-thermal plasma systems for chemical and biological decontamination.

A solvation-free-energy functional: a reference-modified density functional formulation.

The three-dimensional reference interaction site model (3D-RISM) theory, which is one of the most applicable integral equation theories for molecular liquids, overestimates the absolute values of solvation-free-energy (SFE) for large solute molecules in water. To improve the free-energy density functional for the SFE of solute molecules, we propose a reference-modified density functional theory (RMDFT) that is a general theoretical approach to construct the free-energy density functional systematically. In the RMDFT formulation, hard-sphere (HS) fluids are introduced as the reference system instead of an ideal polyatomic molecular gas, which has been regarded as the appropriate reference system of the interaction-site-model density functional theory for polyatomic molecular fluids. We show that using RMDFT with a reference HS system can significantly improve the absolute values of the SFE for a set of neutral amino acid side-chain analogues as well as for 504 small organic molecules.

Aggregation-Induced Emission Mechanism of Dimethoxy-Tetraphenylethylene in Water Solution: Molecular Dynamics and QM/MM Investigations.

Molecular dynamics simulations and combined quantum mechanics and molecular mechanics calculations are employed to investigate dimethoxy-tetraphenylethylene (DMO-TPE) molecules in water solution for their detailed aggregation process and the mechanism of aggregation-induced emission. The molecular dynamics simulations show that the aggregates start to appear in the nanosecond time scale, and small molecular aggregates appear at low concentration; whereas the large aggregates with a chain-type structure appear at high concentration, and the intramolecular rotation is largely restricted by a molecular aggregated environment. The average radical distribution demonstrates that the waters join the aggregation process and that two types of hydrogen bonds between DMO-TPE and water molecules are built with the peaks at about 0.5 and 0.7 nm, respectively. The spectral features further reveal that the aggregates dominantly present J-type aggregation although they fluctuate between J-type and H-type at a given temperature. The statistical absorption, emission spectra, and the aggregation-induced emission enhancement with respect to the solution concentration agree well with the experimental measurements, indicating the significant effect of molecular environments on the molecular properties.

Photo-degradation of carbamazepine using TiO2 suspended photocatalysts

Carbamazepine (CBZ), a persistent pharmaceutical compound, cannot be effectively removed (<10%) by conventional wastewater treatment plants. This study investigates the removal of this molecule in water solution using a photocatalytic process at 365 nm. Five commercial TiO2-based photocatalysts (P90, P25, UV100, PC500, and ST01) were tested over a range of operating parameters (type and concentration of photocatalysts, pH, treatment time, and light intensity). The best operating conditions for CBZ degradation in solution (99% CBZ removal) were obtained using P90 as photocatalyst at a concentration of 1.5 g/L for 90 min of treatment with a pH of 5.0 and a light intensity of 18.9 W/m2. Under these conditions, removal of 74% of total organic carbon was recorded. This optimized photocatalytic process can treat either relatively high concentrations of CBZ (5 mg/L to 20 mg/L) or low concentrations of CBZ (37 µg/L) in water. The initial rate of photocatalytic degradation of CBZ using P90 as photocatalyst can be described by the Langmuir–Hinshelwood (L–H) kinetic model with a reaction rate constant of 2.22 ± 0.003 mg/L/min at ca. 20 °C.

Why is Benzene Soluble in Water? Role of OH/π Interaction in Solvation.

The XH/π interaction (X = C, N, or O) plays an essential role in a variety of fundamental processes in condensed phase, and it attracts broad interests in the fields of chemistry and biochemistry in recent years. This issue has a direct relevance to an intriguing phenomenon that a benzene molecule exhibits a negative solvation free energy of -0.87 kcal/mol in ambient water though it is a typical nonpolar organic solute. In this work, we developed a novel method to analyze the free energy δμ due to the electron density fluctuation of a solute in solution to clarify the mechanism responsible for the affinity of benzene to bulk water. Explicitly, the free energy δμ is decomposed into contributions from σ and π electrons in π-conjugated systems on the basis of the QM/MM method combined with a theory of solutions. With our analyses, the free energy δμ(π) arising from the fluctuation of π electrons in benzene was obtained as -0.94 kcal/mol and found to be the major source of the affinity of benzene to water. Thus, the role of π electrons in hydration is quantified for the first time with our analyses. Our method was applied to phenyl methyl ether (PME) in water solution to examine the substituent effects of the electron donating group (EDG) on the hydration of a π-conjugated system. The delocalization effect of the π electrons on hydration was also investigated performing the decomposition analyses for ethene and 1,3-butadiene molecules in water solutions. It was revealed that the stabilization due to δμ(π) for butadiene (-0.76 kcal/mol) is about three times as large as that for ethene (-0.26 kcal/mol), which suggests the importance of the delocalization effect of the π electrons in mediating the affinity to polar solvent.