Mikhail A. Vovk's research while affiliated with Saint Petersburg State University and other places

Publications (24)

Article
Full-text available
In this paper we study two lysine-based peptide dendrimers with Lys-His-Arg and Lys-Arg-His repeating units and terminal lysine groups. Combination of His and Arg properties in a dendrimer could be important for biomedical applications, especially for prevention of dendrimer aggregation and for penetration of dendrimers through various cell membran...
Article
Acid catalysis of weakly distorted or undistorted carboxamides in acyl-migration reactions proceeding through N-protonation is the process with low probability in contrast to O-protonation. This circumstance made the experimental study...
Article
Full-text available
Serum albumin possesses esterase and pseudo-esterase activities towards a number of endogenous and exogenous substrates, but the mechanism of interaction of various esters and other compounds with albumin is still unclear. In the present study, proton nuclear magnetic resonance (1H NMR) has been applied to the study of true esterase activity of alb...
Article
Hypervalent iodine(III)-derivatives display higher catalytic activity than other aliphatic and aromatic iodine(I)– or bromine(I)-containing substrates for a Knorr-type reaction of N-acetyl hydrazides with acetyl acetone to give N-acyl pyrazoles. The highest activity was observed for dibenziodolium triflate, for which 10 mol% resulted in the generat...
Article
Tetrabromomethane functions as an organic catalyst for non‐redox reactions of carbonyl species and, in particular, it enhances the aldehyde–acyl hydrazide condensation to give N‐acyl hydrazones. This simple, inexpensive, and commercially available halomethane provides up to 14‐fold acceleration of the Schiff reaction; the kinetic data indicate that...
Article
Full-text available
As a carrier of many biologically active compounds, blood is exposed to oxidants to a greater extent than the intracellular environment. Serum albumin plays a key role in antioxidant defence under both normal and oxidative stress conditions. This review evaluates data published in the literature and from our own research on the mechanisms of the en...
Article
The aggregation of a series of mono- and dilithionaphthalenes in THF solutions in the presence of tetramethylethylenediamine (TMEDA) and pentamethyldiethylenetriamine (PMDTA) was studied by NMR spectroscopy and quantum chemical calculations. The stability of dimeric species in diluted solutions as well as reasons of their disaggregation in some cas...
Article
The protonation of the carboxamide nitrogen atom is an essential part of in vivo and in vitro processes (cis‐trans isomerization, amides hydrolysis etc). This phenomenon is well studied in geometrically strongly distorted amides, although there is little data concerning the protonation of undistorted amides. In the latter case, the participation of...
Article
Full-text available
A brief overview is given of the papers published over the last two decades on the subject of solid-state ¹³C NMR spectra of such carbon nanostructures as milled graphite and its oxide, graphene, graphene oxide, carbon nanotubes, nanodiamonds, fullerenes and their derivatives. The main focus is put on the characteristic values of experimental isotr...
Article
The main purpose of this study was to investigate the local structure and dynamics in ‘water-in-salt’ solutions, namely the ternary concentrated LiCl–CsCl–D2O electrolytes. Water based electrolyte solutions are components of natural waters, they are very widespread and possess many practical abilities. NMR was applied as the main technique to study...
Article
Full-text available
Due to their well-defined structure, multivalency, biocompatibility, and low toxicity, lysine dendrimers can be used as safe and efficient nanocarriers for drug and gene delivery. One useful strategy for improving the gene delivery properties of dendrimers is modification with arginine amino acid (Arg) residues. Incorporation of Arg residues could...
Article
Full-text available
Peptide dendrimers, due to their biocompatibility and low toxicity, are highly promising candidates as nanocarriers for drugs and genes. The development of this kind of delivery system requires reliable monitoring of their metabolic and biological pathways. In this respect, hydrogen isotope labeling has tremendous importance, being a safe tool for...
Article
With the aim to analyze the microstructure of the polar nanoregions of mixtures of ionic liquids and inorganic salts and the single particle dynamics of metal cations in these densely ionic environments, solutions of inorganic nitrate salts (lithium, magnesium, calcium and aluminium nitrates) in the protic ionic liquid ethylammonium nitrate have be...
Article
Zinc(II)-catalyzed (10 mol % ZnCl2) coupling of acyl hydrazides and dialkylcyanamides in ethanol leads to 3-dialkylamino-1,2,4-triazoles (76–99%; 17 examples). This reaction represents a novel, straightforward, and high-yielding approach to practically important 3-NR2-1,2,4-triazoles, which utilizes commercially available and/or easily generated su...
Article
Full-text available
Peptide dendrimers are good candidates for diverse biomedical applications due to their biocompatibility and low toxicity. The local orientational mobility of groups with different radial localization inside dendrimers is important characteristic for drug and gene delivery, synthesis of nanoparticles, and other specific purposes. In this paper we f...
Article
Lithiation of 1,8-bis(dimethylamino)naphthalene (DMAN) with Schlosser's superbase (n-BuLi–t-BuOK) in the presence of TMEDA in hexane was examined. It has been shown that, compared with previously studied n-BuLi–TMEDA or t-BuLi–TMEDA mixtures, this reagent provides much more selective meta-lithiation. A variety of 3-substituted and 3,6-disubstituted...
Article
The ¹H NMR spectroscopy is used to study the kinetics of gelation in the aqueous mixtures of κ-carrageenan with gelatin. The time dependence of NMR signals intensities shows that the kinetics of gel formation consists of classical ‘fast’ (rate constant k ≈ 6 h⁻¹) and ‘slow’ (k ≈ 1 h⁻¹) periods, corresponding to a coil → helix transition and subsequ...
Article
It has been found that 1,8-bis(dimethylamino)naphthalene (DMAN), unlike N,N-dimethylaniline, undergoes ring metallation in the n-BuLi-TMEDA-Et2O system with a low selectivity and in poor total yields. The situation is significantly improved in the t-BuLi-TMEDA-n-hexane system when 3- and 4-lithium derivatives become the only reaction products obtai...
Article
Hydration phenomena play a very important role in various processes, in particular in biological systems. Water molecules in aqueous solutions of organic compounds can be distributed among the following substructures: (i) hydration shells of hydrophilic functional groups of molecules, (ii) water in the environment of nonpolar moieties and (iii) bul...
Article
Different ion-water clusters for the CH3COO− ion that simulate the structure of its hydrate shells in solution are considered on the basis of the quantum mechanical approach. The possible coordination of water molecules around the ion is studied and the calculation results are compared with the experimental data obtained by nuclear magnetic relaxat...

Citations

... Another important effect is the change of the global conformation of histidine-containing dendrimer with the changing of the pH level. We have found that the Lys-2His dendrimer undergoes a conformational transition from a swollen conformation at low pH to a collapsed conformation at normal pH [48]. This circumstance can play an important role for using the histidine-containing dendrimer as a nanocontainer. ...
... Ultimately, this study highlighted four of the most promising azolium halogen bond donors, which are expected to exhibit high catalytic activity. Finally, in [7], hypervalent iodine(III) derivatives were found to have higher catalytic activity than other aliphatic and aromatic iodine(I)-or bromine(I)-containing substrates for a Knorrtype reaction of N-acetyl hydrazides with acetylacetone to yield N-acyl pyrazoles. The highest activity was observed for dibenziodolium triflate, for which 10 mol% resulted in the generation of N-acyl pyrazole from acyl hydrazide and acetylacetone typically at 50 • C for 3.5-6 h with up to 99% isolated yields. ...
... Enzymes ampersand non-enzymatic substances in the body assume the role of scavenging excess reactive oxygen species in the antioxidant defense system. SOD, CAT, and GSH-Px in the enzymatic antioxidant system are essential to maintaining oxidative homeostasis in the body (26). Superoxide anion radicals are turned into hydrogen peroxide by SOD during disproportionation, and then GSH-Px and CAT combine to break down the hydrogen peroxide into non-toxic substances (27). ...
... Many of these techniques are easy to implement as well. When done correctly, NMR can provide truly unique information [2][3][4][5]. The same is with solid state NMR. ...
... The amide I vibration has been found to be heavily dependent on the formation of intramolecular hydrogen bonds in proteins, and hydrogen bonds, in turn, are integral in the stabilization of various protein secondary structures [1][2][3][4][5][6][7][8][9]. As a result, vibrational spectroscopy combined with density functional theory (DFT) computations is commonly employed to investigate the molecular geometries, dynamics, and secondary structures of short peptide chains . ...
... However, microscopes can only analyze the small region at the atomic scale and the determination of the bonding states is another challenge [53,56]. In contrast, some evaluation methods such as infrared-ray (IR) [21,45,[57][58][59][60][61][62][63], Raman [21,22,45,[63][64][65][66][67], nuclear magnetic resonance [45,[68][69][70][71][72], and X-ray photoelectron spectroscopy (XPS) [22,23,[71][72][73][74][75] have been studied to analyze carbon materials precisely by combining especially with calculation because these methods can analyze the large region and the averaged information of edge structures can be readily obtained. ...
... Indeed, such behavior has been recently reported in ternary water-in-salt solutions of LiClÀ CsClÀ D 2 O, where most of the molecules and ions seem to move as dynamic clusters named "cybotactic groups". [20] Contrary to this expectation, our NMR diffusion data provides distinct diffusion coefficients for water molecules, the Cl À anion and corresponding cations, indicating their independent translational dynamics in saturated salt solutions. ...
... However, dendrimers of high generations are toxic due to many of their positively charged terminal groups. To avoid the problem, it is possible to use dendrimers of lower generations [78][79][80][81], or modify the terminal groups of dendrimers by noncharged or negatively charged groups, for example, hydroxyl or carboxyl [82]; or by functional groups [83]; or link terminal groups to drug molecules [84]; or move at least parts of the charges from terminal groups to internal spacers of the dendrimer [85][86][87]; or link terminal groups to linear hydrophilic tails, for example polyethylene glycol (PEG) [88,89]. It is also possible to design hybrid amphiphilic molecules consisting of one dendron with one or more linear hydrophobic tails attached to its root ( Figure 13) [9,[90][91][92]. ...
... However, dendrimers of high generations are toxic due to many of their positively charged terminal groups. To avoid the problem, it is possible to use dendrimers of lower generations [78][79][80][81], or modify the terminal groups of dendrimers by noncharged or negatively charged groups, for example, hydroxyl or carboxyl [82]; or by functional groups [83]; or link terminal groups to drug molecules [84]; or move at least parts of the charges from terminal groups to internal spacers of the dendrimer [85][86][87]; or link terminal groups to linear hydrophilic tails, for example polyethylene glycol (PEG) [88,89]. It is also possible to design hybrid amphiphilic molecules consisting of one dendron with one or more linear hydrophobic tails attached to its root ( Figure 13) [9,[90][91][92]. ...
... In this field, ionic liquids (ILs) exhibit a unique combination of physicochemical properties, such as high electrochemical stability, broad liquid range, high conductivity, compatible with electrode materials and neither flammable nor volatile that make them ideal candidates for electrolyte and energy storage applications and amazing results have been shown in applications such as super-capacitors, Li-ion batteries, dye sensitized solar cells, sensor materials and metal plating processes, offering the possibility of enhanced safety and stability [1]. ILs and inorganic salts mixtures are behind a new generation of active media for, as, for example, electrolytes in lithium batteries [2][3][4]. ...