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
A.S. Konevaa, E. Ritter, Y.A. Anufrikova, A.A. Lezova, A.O. Klestovaa, N.A. Smirnova, E.A. Safonova, I. Smirnova
“Mixed aqueous solutions of nonionic surfactants Brij 35/Triton X-100: Micellar properties, solutes’ partitioning from micellar liquid chromatography and modelling with COSMOmic”
Colloids and Surfaces A, 2018, 538, 45–55.
Aqueous solutions of nonionic surfactants are of interest for bioprocesses, particularly as solubilizing agents for hydrophobic substances. To design such processes, the data on partition coefficients of solutes between micelles and their aqueous surrounding (Pmw) are of high value. An extended understanding of the partition behavior can be achieved from the structural information such as the micelle size and micelles composition.
In this work, mixtures of nonionic surfactants Triton X-100 and Brij 35 were under study. The data on critical micelle concentrations showed partly non-ideal behavior of the solutions. The compositions of mixed micelles at different molar Brij 35/Triton X-100 ratios in the surfactant mixture were estimated from the data on selfdiffusion coefficients (NMR diffusometry) and were calculated within the regular solution approach and predicted by Motomura’s model. The change of the mixed micelle composition in dependence on the total surfactant concentration was observed. It has been found, that the average value of the mixed micelles radii is∼4 nm. Whereas, the polydispersity indexes and the aggregation numbers increased with Triton X-100 fraction. Moreover, the Pmw values of different non-dissociated solutes (phenyl derivatives with various functional groups) were determined by means of micellar liquid chromatography (MLC) and were predicted using the thermodynamic model COSMOmic, an extension of COSMO-RS. In general, it has been proved that COSMOmic is able to predict Pmw in the mixed micellar system formed by nonionic surfactants. The obtained data show the possibility of modulating the partition behavior of solutes using the mixtures of nonionic surfactants. Apart from the hydrophobicity, the «surfactants – solute» specific interactions play an important role in the partition behavior of the investigated systems.
Комментарии к записи Colloids and Surfaces A, 2018, 538, 45–55 отключены
P.A. Sakharov, N.V. Rostovskii, A.F. Khlebnikov, M.S. Novikov
“Annulation of five-membered cyclic enols with 3-aryl-2H-azirines: Catalytic versus non-catalytic cycloaddition”
Tetrahedron, 2017, 73(31), 4663-4670.
A copper(I)-NHC-catalyzed annulation of 5-membered cyclic enols of furan, thiophene and indene family with 3-aryl-2H-azirines has been developed to provide a rapid access to furo[3,4-b]pyrrole, thieno[3,4-b]pyrrole, indeno[1,2-b]pyrrole derivatives. The reaction proceeds via a copper-initiated N-C2 azirine bond cleavage with the retention of the C=N double bond in the annulation product. The reaction of tetronic acids with 3-aryl-2H-azirines can also proceed under catalyst-free conditions, through a double addition of the enol to the azirine, but this route provides poor yields of the annulation products. This is the first example of the N-C2 bond cleavage in 2-unsubstituted 2H-azirines in the absence of a transition metal catalyst.
Комментарии к записи Tetrahedron, 2017, 73(31), 4663-4670 отключены
E. Abakumov, E. Maksimova, A. Tsibart
“Assessment of postfire soils degradation dynamics: Stability and molecular composition of humic acids with use of spectroscopy methods”
Land Degrad Dev., 2017, 1–10.
The effect of wildfires on the soils of the south taiga and forest-steppe environments of Central Russia (Histic Spodosols and Eutric Fluvic Arenosols) was investigated in terms of the content and quality of humic acids (HAs) using instrumental spectroscopic methods (solid-state carbon-13 nuclear magnetic resonance and electron spin resonance). The bulk elemental composition of HAs was not essentially altered in postfire soils; however, the organic matter of fire-affected superficial soil layers was characterized by changes in the structural composition and biochemical activity levels. Solid-state carbon-13 nuclear magnetic resonance spectroscopy showed that there is an intensive increase in aromatic compounds in HA molecules in soil from both the south taiga and forest-steppe environments. There is a pronounced and statistically significant decline of aliphatic chain content in response to exposure to fire. The free radicals content and the degree of molecular stabilization assessed with electron spin resonance showed an essential alteration of the HAs, expressed in the increase in the radical’s portion, in postfire soils compared with that found in soils not exposed to fire. It was also shown that the accumulation of aromatic compounds indicates only apparent stabilization of HAs due to the loss of periphery alkylic carbon species, which was confirmed by destabilization of the molecules as illustrated by the increase of free radicals.
Комментарии к записи Land Degrad Dev., 2017, 1–10 отключены