A comparative analysis was conducted on DNA interaction with two new manganese complexes (mononuclear complex with one 1,10-phenanthroline, binuclear complex with six 1,10-phenanthroline ligands), as well as with free 1,10-phenanthroline and Mn2+ ions in solutions with different NaCl concentrations. The results showed that manganese in the mononuclear complex coordinates to N7 of guanine in the major groove of DNA. This binding facilitates the penetration of 1,10-phenanthroline into the same groove, where it subsequently intercalates between DNA bases. In contrast, the binuclear manganese complex binds externally through electrostatic interactions at the periphery of the double helix. Such binding screens the negative charges of DNA and promotes intra- and intermolecular DNA - DNA contacts through the association of hydrophobic phenanthroline ligands. Intercalation of 1,10-phenanthroline is unfavourable for the binuclear manganese complex. DNA conformational changes upon its binding with Mn2+ ions and free 1,10-phenanthroline show both similarities and significant differences compared with those caused by the manganese complexes. Computer modelling revealed that free 1,10-phenanthroline preferentially binds within the minor groove of DNA, exhibiting specificity for A-T base pairs. However, it can also localize near the major groove, particularly adjacent to G-C base pairs.

The modes of interaction of monofunctional Zn( ii ) complexes with bispyrazolate ligands with DNA and BSA biomolecules were investigated, alongside comparative cytotoxicity studies.

The diffusion properties and, as a consequence, the hydrodynamic radius, R h, of dendrimers are of great importance for both theoretical studies and practical applications. In addition, the comparison of R h values from simulations and experiments serves to verify the accuracy of the simulations. In this work, the translational mobility of polyamidoamine (PAMAM) dendrimers in methanol solution is investigated using molecular dynamics simulations. It is shown that the classical correction method related to the simulation cell sizes for R h obtained from translational mobility gives underestimated values for different dendrimer generations. The approximation of the hydrodynamic radius using a linear fit to an infinitely diluted solution gives R h close to experimental data for PAMAM dendrimers in methanol but requires simulation for multiple cell sizes. In contrast to this approach, the calculation from rotational diffusion allows R h to be estimated using a single cell and yields values close to the experimental ones without any correction.

The pervaporation process is an energy efficient and more environmentally friendly way of separating low molecular liquid components compared to traditional methods. In this work microsecond trajectories of molecular dynamics simulations with full-atomistic resolution model are used to study the behavior of benzene/methanol and cyclohexane/methanol mixtures in homopolymer (poly-m-phenylene isophthalamide) and its composite with MOF UiO-66 (NH2) for pervaporation separation. The equilibrium and dynamic properties of liquids molecules in polymer and composite systems are analyzed. We establish that the mobility of benzene and cyclohexane is significantly lower than that of methanol. However, these effects are caused by different reasons, namely, lyophilic and lyophobic interactions of benzene and cyclohexane with the polymer, respectively. According to our data, the inclusion of MOF in the polymer leads to an improvement of the pervaporation characteristics.

Molecular dynamics computer simulation of three substances ethylbenzene (EB), pentastyrene (PS-5), and polystyrene-25 (PS-25) was performed to investigate the local order of the phenyl rings in monomers and side-chain polymers. Monomer molecules (EB) tend to be in T-configuration, which corresponds to isotropic local structure. Phenyl rings in chained molecules PS-5 and PS-25 partly cooperate in both parallel-displaced and “sandwich” configuration with π–π stacking. These configurations are locally anisotropic and lead to the increasing of Kerr constant K. Analysis of the local structure was performed by calculating the cylindrical distribution function.

Thin-film composite (TFC) membranes obtained by forming a selective polyamide (PA) layer on a surface of a porous membrane-substrate via interfacial polymerization (IP) technique are the most effective membranes for nanofiltration (NF). The idea of this study is that addition of polyethylene glycol-polypropylene glycol-polyethylene glycol (PEG-PPG-PEG) block copolymers to the polyphenylsulfone (PPSU) casting solution tunes the pore structure (pore size and porosity), water contact angle and topology of the selective layer of ultrafiltration (UF) membranes. This influences the formation of PA layer via IP since membrane-substrate significantly effects the first stage of IP reaction. For the first time the effect of PEG-PPG-PEG copolymer molecular weight, content of PEG blocks and copolymer concentration in the PPSU casting solution on the structure, hydrophilicity and performance of ultrafiltration and TFC NF membranes was revealed. It was found that increase in PEG block content and PEG-PPG-PEG molecular weight led to the increase in pore size, porosity and hydrophilicity of selective layer of ultrafiltration membranes which results in the formation of thinner and more uniform PA layer with higher cross-linking degree of NF membranes via IP. It was revealed that NF membrane flux increased with the rise in the content of PEG units from 10 to 80 wt.% and increase in molecular weight of PEG-PPG-PEG block copolymer. Modification of PPSU membrane-substrate yielded the increase in selectivity of the corresponding TFC NF membranes due to the formation of more uniform and denser defect-free PA layer attributed to the rise in hydrophilicity of membrane substrate. It was found that membrane substrate modification by PEG-PPG-PEG results in the enhancement of antifouling performance toward bovine serum albumin (flux recovery ratio is 99-100%) and long-term stability during 48 h operation compared to the reference membrane. Modification of PPSU membrane substrate by F38 PEG-PPG-PEG block copolymer (Mn= 5 000 g·mol-1, PEG block content of 80 wt.%) was found to yield the TFC NF membranes with the best combination of permeation, separation and antifouling performance and long-term stability.

In the present study the behavior of Cu(II) and Zn(II) complexes with ethylenediamine and 2,2 ':6 ',2 '' terpyridine in an aqueous environment was studied by classical MD simulations. Special attention was paid to the effect of Cu2+ for Zn2+ substitution on complex water surroundings and mobility. The replacement of a metal ion affects the structure of the complex water environment only in the vicinity of its location. However, it changes such a characteristic as the lifetime of a water molecule in the first coordination shell of a metal which can significantly affect the mobility of the complex. Moreover, the degree of influence on translational and rotational mobility can be different. [GRAPHICS]

We report on shear-stress relaxation of melts of poly(propyleneimine) (PPI) dendrimers of different generations (G2–G5). The aim of this study was to confirm our previous conclusion in Sheveleva et al. [Phys. Chem. Chem. Phys. 24, 13049–13056 (2022)] for carbosilane dendrimers that an impenetrable inner region leads to the manifestation of the crowded environment effect. The systems of PPI dendrimer melts are studied using atomistic molecular dynamics simulations. The time and frequency dependencies of the dynamic shear-stress modulus are investigated. The results are in good agreement with the available rheological experimental data for G2–G4 PPI. We have found that the crowded environment effect does not manifest itself in the mechanical relaxation of G4 PPI dendrimers in contrast to G4 carbosilane dendrimers. Despite their similar topology and close sizes, G4 PPI does not form an impenetrable core. The G5 PPI dendrimer has an impenetrable inner region, and the crowded environment effect is observed. As in carbosilane dendrimers, the maximal time of mechanical relaxation is increased due to the crowded environment effect. However, the opposite situation is for the rotational diffusion of the G5 PPI dendrimers. In contrast to carbosilane dendrimers, the rotational mobility of G5 PPI significantly slows down even taking into account the increase in the dendrimer size. The hydrogen bonding between PPI dendrimers affects the mechanical relaxation at high frequencies (short times) and enhances with growing G.

The experimental study of the DNA interaction with three cadmium coordination compounds [Cd(phen)3](CH3CO2)2, [Cd(phen)2(H2O)2](CH3CO2)2, and [Cd2(phen)4(H2O)2](CH3CO2)4 was carried out using spectrophotometry, viscosity, and dynamic light scattering methods. The role of the solution ionic strength (concentration of NaCl) was analyzed. All compounds can penetrate (fully or partly) to the major or minor DNA grooves. It was shown that, in addition to the important role of electrostatic interactions in the formation of the complex, intercalation of the 1,10-phenanthroline ligand occurs for compounds [Cd(phen)2(H2O)2](CH3CO2)2 and [Cd2(phen)4(H2O)2](CH3CO2)4. Compound [Cd(phen)3](CH3CO2)2 binds to DNA externally. The coordination bond between cadmium and DNA was formed in DNA complexes with [Cd2(phen)4(H2O)2](CH3CO2)4. Preliminary computer modeling of the DNA interaction with the compounds used was performed.

This paper deals with the results of simulation of extractive purification process of model diesel fuel (the mixture of n-hexane with thiophene and m-xylene) by molecular dynamics simulation using N-methylpyrrolidinium acetate ionic liquid as an extractant. The extractive purification process was simulated for several model fuel systems with different concentrations of sulfur and aromatic containing components. The ionic liquid exhibits high extractive ability, the degrees of desulfurization and dearomatization reach 85–90 and 60[Formula: see text]wt.%, respectively. The results were proved by experimental studies of a mixture by the ionic liquid. After 1[Formula: see text]h of contact of the ionic liquid and the model mixture, the degree of purification against thiophene was 94.2[Formula: see text]wt.%.

Membrane technology is an actively developing area of modern societies; with the help of high-performance membranes, it is possible to separate various mixtures for many industrial tasks. The objective of this study was to develop novel effective membranes based on poly(vinylidene fluoride) (PVDF) by its modification with various nanoparticles (TiO2, Ag-TiO2, GO-TiO2, and MWCNT/TiO2). Two types of membranes have been developed: dense membranes for pervaporation and porous membranes for ultrafiltration. The optimal content of nanoparticles in the PVDF matrix was selected: 0.3 wt% for porous membranes and 0.5 wt% for dense ones. The structural and physicochemical properties of the developed membranes were studied using FTIR spectroscopy, thermogravimetric analysis, scanning electron and atomic force microscopies, and measuring of contact angles. In addition, the molecular dynamics simulation of PVDF and the TiO2 system was applied. The transport properties and cleaning ability under ultraviolet irradiation of porous membranes were studied by ultrafiltration of a bovine serum albumin solution. The transport properties of dense membranes were tested in pervaporation separation of a water/isopropanol mixture. It was found that membranes with the optimal transport properties are as follows: the dense membrane modified with 0.5 wt% GO-TiO2 and the porous membrane modified with 0.3 wt% MWCNT/TiO2 and Ag-TiO2.

The rheological properties of macromolecules represent one of the fundamental features of polymer systems which expand the possibilities of using and developing new materials based on them. In this work, we studied the shear-stress relaxation of the second generation PAMAM and PPI dendrimer melts by atomistic molecular dynamics simulation. The time dependences of relaxation modulus G(t) and the frequency dependences of the storage G′(ω) and loss G″(ω) moduli were obtained. The results were compared with the similar dependences for the polycarbosilane (PCS) dendrimer of the same generation. The chemical structure of the dendrimer segments has been found to strongly influence their mechanical relaxation. In particular, it has been shown that hydrogen bonding in PAMAM dendrimers leads to an entanglement of macromolecules and the region is observed where G′(ω) > G″(ω). This slows down the mechanical relaxation and rotational diffusion of macromolecules. We believe that our comprehensive research contributes to the systematization of knowledge about the rheological properties of dendrimers.

Pervaporation is the purification technology which utilizes the transport properties of polymer membranes and has several important properties: energy efficiency, environmental friendliness, and a high degree of purification. To improve the transport properties, polymer membranes are modified with special nanoparticles. In this work we study the translational mobility of methanol and toluene molecules inside a poly-m-phenylene isophthalamide membrane with and without the nanoparticle of UiO-66 (NH2) metal-organic framework (UiO-66 (NH2) MOF) using full atomistic molecular dynamics simulation with microsecond trajectories. It was found that methanol has a high translational mobility inside the polymer matrix. Moreover, this mobility is significantly increased by addition of UiO-66 (NH2) MOF. Toluene molecules are practically immobile inside the polymer matrix and tend to form clusters with each other. Due to the inclusion of a nanoparticle, toluene molecules “get stuck” inside UiO-66 (NH2) MOF and its surface. We believe that the obtained results will contribute to the purposeful development and study of polymer matrices for the pervaporation process.

Alizarin is a natural anthraquinone molecule with moderate antioxidative capacity. Some earlier investigations indicated that it can inhibit osteosarcoma and breast carcinoma cell proliferation by inhibiting of phosphorylation process of ERK protein (extracellular signal-regulated kinases). Several mechanisms of deactivation of one of the most reactive oxygen species, hydroperoxyl radical, by alizarin are estimated: hydrogen atom abstraction (HAA), radical adduct formation (RAF), and single electron transfer (SET). The plausibility of those mechanisms is estimated using density functional theory. The obtained results indicated HAA as the only thermodynamically plausible mechanism. For that purpose, two possible mechanistic pathways for hydrogen atom abstraction are studied in detail: hydrogen atom transfer (HAT) and proton-coupled electron transfer (PCET). Water and benzene are used as models of solvents with opposite polarity. To examine the difference between HAT and PCET is used kinetical approach based on the Transition state theory (TST) and determined rate constants (k). Important data used for a distinction between HAT and PCET mechanisms are obtained by applying the Quantum Theory of Atoms in Molecules (QTAIM), and by the analysis of single occupied molecular orbitals (SOMOs) in transition states for two examined mechanisms. The molecular docking analysis and molecular dynamic are used to predict the most probable positions of binding of alizarin to the sequence of ApoB-100 protein, a protein component of plasma low-density lipoproteins (LDL). It is found that alizarin links the nitrated polypeptide forming the π-π interactions with the amino acids Phenylalanine and Nitrotyrosine. The ability of alizarin to scavenge hydroperoxyl radical when it is in a sandwich structure between the polypeptide and radical species, as the operative reaction mechanism, is not significantly changed concerning its antioxidant capacity in the absence of polypeptide. Therefore, alizarin can protect the polypeptide from harmful hydroperoxyl radical attack, positioning itself between the polypeptide chain and the reactive oxygen species.

The effect of the presence of divalent and trivalent metal ions in solutions upon DNA packaging induced by the photosensitive azobenzene-containing surfactant is considered. It has been shown that the addition of divalent and trivalent metal ions does not affect the DNA- surfactant interaction for both the cis-and the trans-isomers of the surfactant. At the same time, the ionic strength of the solution, which is provided by a certain concentration of the salt, has a huge impact. It affects the association of surfactant molecules with each other and their binding to DNA. It has been shown by computer simulation that cobalt hexamine is attracted to the N7 atom of guanine in the major groove of DNA and does not penetrate into grooves near the AT base pairs.

The active application of ultrafiltration in various industries requires the development of novel membranes with tailored properties and good fouling resistance. This work is devoted to the improvement of ultrafiltration properties of polyacrylonitrile (PAN) membranes by various TiO2 modification approaches: (1) ex situ method -the introduction of pre-formed micro-or nanoparticles; (2) in situ method -the formation of TiO2 particles in the casting solution; and (3) surface modification method-dynamic deposition of TiO2 on the membrane surface. The effect of the various TiO2 immobilization techniques on the structure of PAN membranes was studied by scanning electron and atomic force microscopies, and the contact angle measurements. The introduction of TiO2 particles improved membrane performance and antifouling stability under UV irradiation in ultrafiltration of industrially important feeds -bovine serum albumin solution (BSA) and coolant lubricant emulsion. The affinity to water of TiO2-modified PAN membrane was confirmed by atomistic molecular dynamics simulations, swelling experiments, and calorimetric study of wetting. PAN membrane with 0.5 wt% TiO2 nanoparticles had the optimal transport characteristics and improved surface self-cleaning ability after UV irradiation: pure water, coolant lubricant, and BSA fluxes (849, 38, and 68 L/(m(2)h), respectively), and flux recovery ratio after UV-illumination (95%).

The melts of four fractions of polystyrene are investigated by the method of electric birefringence. It is found that the electro-optical properties of the melt greatly depend on the length of the polymer chain. The fractions with the highest molecular weight showed an increase in the Kerr constant K at temperatures above 120°C. The anomalous nature of the temperature dependence of the form K ∝ T is explained by the fact that at high temperatures the flexibility of the polymer chain begins to grow rapidly. This process is called the liquid-liquid transition. As a result, the short-range orientational order increases, which is associated with a change in the mutual orientation of phenyl rings.

As a rule, the polymeric membranes have low permeability in separation of low molecular weight components. In spite of this fact, the membrane processes have significant advantages compare with conventional technologies, in particular, low energy consumption and environmental friendliness. To improve transport properties of the polymer membrane their modification should be carried out. In the present work, the development of highly methanol-permeable pervaporation membranes based on poly-m-phenylene isophthalamide (PA) is achieved by two strategies: (i) modification of PA by novel synthesized and characterized highly stable metal-organic framework UiO-66(NH2)-EDTA particles and (ii) development of supported membranes with thin selective layer on the regenerated cellulose substrate. First time the composite structure has been simulated: atomistic molecular dynamics simulations demonstrate the partial penetration of polymer inside the modifier and confirms the nature of the interaction between polymer and modifier assessed by spectroscopic methods. The optimal characteristics in respect of industrial use are obtained for supported PA/UiO-66(NH2)-EDTA (15%) membrane: 1.55 kg/(m(2)h) permeation flux and 93.1 wt% methanol in the permeate for the separation of azeotropic methanol/toluene mixture.

The DNA interaction with cis-isomers of photosensitive azobenzene-containing surfactants was studied by both experimental methods and computer simulation. It was shown that before the organization of micelles, such surfactants in the cis-conformation form associates of only a single type with a disordered orientation of molecules. In contrast, for trans-isomers, there exist two types of associates with head-to-head or head-to-tail orientations of molecules in dependence on salt concentration in a solution. The comparison of cis- and trans-isomer binding to DNA and the influence of salt concentration on the formation of their complexes with DNA were studied. It was shown that cis-isomers interact with phosphate groups of DNA and that their molecules were also located along the minor groove of DNA.