A.A. Vereschagin, V.V. Sizov, P.S. Vlasov, E.V. Alekseeva, A.S. Konev, O.V. Levin
“Water-stable [Ni(salen)]-type electrode material based on phenylazosubstituted salicylic aldehyde imine ligand”
New Journal of Chemistry, 2017, 41, 13918-13928
A novel electrode material was prepared by electrochemical oxidation of [4,4′-phenylazo-2,2′-(ethylenediimino-κ2N-methyl)diphenolate-κ2O]nickel, a [Ni(II)(salen)]-type complex, in chlorinated solvent. The chemical structure of the material was explored by FTIR, NMR and XPS techniques to determine the main components of the material and the nature of the linkage between them. The morphology of the material films was explored by SEM analysis. The electrochemical properties of the new material were studied by a set of voltammetric methods and an unusual stability of the material in aqueous medium was observed.
Комментарии к записи New Journal of Chemistry, 2017, 41, 13918-13928 отключены
M.M. Efremova, R.R. Kostikov, A.V. Stepakov, T.L. Panikorovsky, V.S. Shcherbakova, A.V. Ivanov, A.P. Molchanov
“Unusual Lewis-acid catalyzed formal (3+3)-cycloaddition of azomethine imines and nitrones to N-vinylpyrroles”
Tetrahedron, 2017, 73, 671-680
The addition of Lewis acids change the reaction mechanism of the cycloaddition of N-vinylpyrroles with azomethine imine and C,N-diarylnitrones. The formal (3+3)-cycloaddition is observed instead of (3+2)-dipolar cycloaddition, which take place in the absence of catalysts. This unusual (3+3)-cycloaddition leads to heterocyclic compounds with pyrazolo[1,2-a]pyrrolo[1,2-d][1,2,4]triazine- and pyrrolo[2,1-d][1,2,5]oxadiazine cores, which are difficultly achievable by other methods.
Комментарии к записи Tetrahedron, 2017, 73, 671-680 отключены
G. P. Kantin, M. Yu. Krasavin
“Microwave-promoted reaction of N-alk-1-enyl chloroacetamides with sodium azide unexpectedly yields 1H-imidazol-5(4H)-ones”
Mendeleev Commun., 2017, 27, 95-96
A novel method to prepare biologically relevant 1H-imidazol-5(4H)-ones from aliphatic amines, isobutyraldehyde, chloroacetyl chloride and sodium azide under microwave irradiation has been developed.
Комментарии к записи Mendeleev Commun., 2017, 27, 95-96 отключены
M. Chizhova, D. Dar’in, M. Krasavin
“Complications in the Castagnoli-Cushman reaction: An unusual course of reaction between cyclic anhydrides and sterically hindered indolenines”
Tetrahedron Letters, 2017, 58(35), 3470-3473
Attempted reaction of indolenines (which represent rather sterically hindered cyclic imines) with a series of dicarboxylic acid anhydrides yielded no expected product, the Castagnoli-Cushman lactam. Instead, products presumably formed via N-acyliminium species trapping by a carboxylate anion. Among them, hydrolytically labile 2:2 adducts of an indolenine and a cyclic anhydride, containing a 16-membered cyclic core, are particularly intriguing. This result contradicts the recently reported successful Castagnoli-Cushman reaction of indolenines with homophthalic anhydride suggesting a mechanistic switch in the course of the reaction.
Комментарии к записи Tetrahedron Letters, 2017, 3470-3473 отключены
S. O. Rabdano, S. A. Izmailov, D. A. Luzik, A. Groves, I. S. Podkorytov, N. R. Skrynnikov
“Onsеt of Disоrdеr and Protein Aggregation Due to Oxidation-Induced Intermolecular Disulfide ”
Scientific Reports, 2017, 7, 11161
We have investigated the behavior of second RNA-recognition motif (RRM2) of neuropathological protein TDP43 under the effect of oxidative stress as modeled in vitro. Toward this end we have used the specially adapted version of H/D exchange experiment, NMR relaxation and diffusion measurements, dynamic light scattering, controlled proteolysis, gel electrophoresis, site-directed mutagenesis and microsecond MD simulations. Under oxidizing conditions RRM2 forms disulfide-bonded dimers that experience unfolding and then assemble into aggregate particles (APs). These particles are strongly disordered, highly inhomogeneous and susceptible to proteolysis; some of them withstand the dithiothreitol treatment. They can recruit/release monomeric RRM2 through thiol-disulfide exchange reactions. By using a combination of dynamic light scattering and NMR diffusion data we were able to approximate the size distribution function for the APs. The key to the observed aggregation behavior is the diminished ability of disulfide-bonded RRM2 dimers to refold and their increased propensity to misfold, which makes them vulnerable to large thermal fluctuations. The emerging picture provides detailed insight on how oxidative stress can contribute to neurodegenerative disease, with unfolding, aggregation, and proteolytic cleavage as different facets of the process.
Комментарии к записи Scientific Reports, 2017, 7, 11161 отключены
S. Kalinin, S. Kopylov, T. Tuccinardi, A. Sapegin, D. Dar’in, A. Angeli, C.T. Supuran, M. Krasavin
“Lucky Switcheroo: Dramatic Potency and sеlеctivity Improvement of Imidazoline Inhibitors of Human Carbonic Anhydrase VII”
ACS Med. Chem. Lett, 2017, 8 (10), 1105–1109.
A substantial improvement of potency and selectivity of imidazoline-based inhibitors of hCA VII (a promising target for the treatment of seizures and neuropathic pain) was achieved by simply switching the position of the benzenesulfonamide moiety from N1 (as in the earlier reported series) to C2. Selectivity indices vs the off-target isoforms (hCA I, I, I and IV) greater than 100 were reached, which is exceedingly rare for hCA VII inhibitors. The drastic profile improvement of the new series has been rationalized by an additional hydrogen bonding with the nonconserved Q69 residue in the active site of hCA VII (absent in the other three isoforms studied), which also results in a favorable accommodation of the inhibitor’s lipophilic periphery in the nearby hydrophobic pocket. The robustness of the docking simulations was tested and confirmed by molecular dynamics simulations
Комментарии к записи ACS Med. Chem. Lett, 2017, 1105–1109 отключены
V.A. Rozentsvet, O.A. Stotskaya, V.P. Ivanova, M.G. Kuznetsova, P.M. Tolstoy, S.V. Kostjuk
“Structural characterization of polybutadiene synthesized via cationic mechanism”
J. Polym. Sci., Part A: Polym. Chem., 2018, 56, 387–398.
The microstructure of polybutadiene synthesized via cationic polymerization using TiCl4-based initiating systems has been investigated using 1D (1Н, 2Н, and 13С) and 2D (HSQC and HMBC) NMR spectroscopy. It was found that trans-1,4-unit is predominant structure of unsaturated part of polymer chain. Besides, the small amount of 1,2-structures was also detected, while cis-1,4-units were totally absent. The signals of carbon atoms of three types of head groups (trans-1,4-, 1,2-, and tert-butyl) and two types of end groups (trans-1,4-Cl and 1,2-Cl) were identified for the first time in macromolecules of cationic polybutadiene. It was showed that tert-butyl head groups were formed due to the presence in monomer of admixtures of isobutylene. The new methodology for calculation of the content of different structural units in polybutadiene chain as well as the head and end groups was proposed. It was established that main part of 1,2-units distributed randomly along the polybutadiene chain as separate units between trans-1,4-structures.
Комментарии к записи J. Polym. Sci., Part A: Polym. Chem., 2018, 56, 387–398 отключены
| Tags: Толстой
A.V. Artem’ev, I.Yu. Bagryanskaya, E.P. Doronina, P.M. Tolstoy, A.L. Gushchin, M.I. Rakhmanova, A.Yu. Ivanove, A.O. Suturina
“A new family of clusters containing a silver-centered tetracapped [Ag@Ag4(μ3-P)4] tetrahedron, inscribed within a N12 icosahedron”
Dalton Transactions, 2017, 46, 12425-12429.
An unprecedented silver-centered P-tetracapped [Ag@Ag4(μ3-P)4] tetrahedron inscribed within a N12 icosahedral cage has been discovered in the novel family of luminescent clusters. The latter are easily self-assembled by reacting AgI salts with tris(2-pyridyl)phosphine (Py3P).
Комментарии к записи Dalton Transactions, 2017, 46, 12425-12429 отключены
| Tags: Толстой
E.V. Abakumov, O.A. Rodina, A.K. Eskov
“Humification and Humic Acid Composition of Suspended
Soil in Oligotrophous Environments in South Vietnam”
Applied and Environmental Soil Science, 2018, Article ID 1026237.
Humification is considered to be a global process that is implemented in soils and organic sediments and also in natural water and air. The term “suspended soils” has become increasingly common in recent years. Suspended soils are defined as the part of the organic matter that has not undergone the full decomposition process and has not turned into the humus of terrestrial soils. Suspended soils were shown to contain higher total nitrogen, phosphorus, and potassium contents than the forest soil, but the moisture content in suspended soils was significantly lower. Our study of the structural composition of humic substances in suspended soils was conducted with an aim of evaluating the humification rates and structural composition of humic acids in the suspended soil in tropical forests of South Vietnam. Soil samples from three selected areas were investigated: the soil under phorophytes (mineral soil presented by samples of topsoil of the typical dry savanna landscape) and two soils from epiphytous formations. Samples were collected from savanna-type sparse communities, located on oligotrophous plains in Phú Quốc Island (South Vietnam) in 2015. General properties of the soil and the elemental composition of suspended soils were determined, and the humic substance chemical composition was evaluated using solid state 13C-NMR. Data obtained showed that the pH of the soils under phorophytes was higher than in the suspended soils; basal respiration did not tend to change indices between soils under phorophytes and suspended soils, but the suspended soil was less enriched by nitrogen than the soil under phorophytes. This can be related to the total amount of organic matter exposed to humification in various soils and to the presence of an essential portion of mineral particles in the soil under phorophytes. Data on elemental composition of the humic acids (HAs) indicated that one method of humification is implemented in all three soils that were investigated. The humic acids of the phorophyte soil showed the same content of aromatic fraction as the suspended soil. The most comparable soil type in terms of humic substance composition is Cambisols from humid forests of subboreal and subtropical zones. The humification process implemented in suspended soils showed the absence of mineral compounds or mineral fine earth, which indicated that humification in conditions of pure organic substrates can result in formation of deep humified organic matter, as shown by humic acids with an essential aromatic fraction content.
Комментарии к записи Applied and Environmental Soil Science, 2018, 1026237 отключены
A. I. Solomatina, P.S. Chelushkin, D.V. Krupenya, I.S. Podkorytov∥, T.O. Artamonova, V.V. Sizov, A.S. Melnikov, V.V. Gurzhiy, E.I. Koshel, V.I. Shcheslavskiy, S.P. Tunik
“Coordination to Imidazole Ring Switches on Phosphorescence of Platinum Cyclometalated Complexes: The Route to Selective Labeling of Peptides and Proteins via Histidine Residues”
Bioconjugate Chem., 2017, 28 (2), 426–437.
In this study, we have shown that substitution of chloride ligand for imidazole (Im) ring in the cyclometalated platinum complex Pt(phpy)(PPh3)Cl (1; phpy, 2-phenylpyridine; PPh3, triphenylphosphine), which is nonemissive in solution, switches on phosphorescence of the resulting compound. Crystallographic and nuclear magnetic resonance (NMR) spectroscopic studies of the substitution product showed that the luminescence ignition is a result of Im coordination to give the [Pt(phpy)(Im)(PPh3)]Cl complex. The other imidazole-containing biomolecules, such as histidine and histidine-containing peptides and proteins, also trigger luminescence of the substitution products. The complex 1 proved to be highly selective toward the imidazole ring coordination that allows site-specific labeling of peptides and proteins with 1 using the route, which is orthogonal to the common bioconjugation schemes via lysine, aspartic and glutamic acids, or cysteine and does not require any preliminary modification of a biomolecule. The utility of this approach was demonstrated on (i) site-specific modification of the ubiquitin, a small protein that contains only one His residue in its sequence, and (ii) preparation of nonaggregated HSA-based Pt phosphorescent probe. The latter particles easily internalize into the live HeLa cells and display a high potential for live-cell phosphorescence lifetime imaging (PLIM) as well as for advanced correlation PLIM and FLIM experiments.
Комментарии к записи Bioconjugate Chem., 2017, 28, 426–437 отключены