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The esterase status of blood plasma can claim to be one of the universal markers of various diseases; therefore, it deserves attention when searching for markers of the severity of COVID-19 and other infectious and non-infectious pathologies. When analyzing the esterase status of blood plasma, the esterase activity of serum albumin, which is the major protein in the blood of mammals, should not be ignored. The purpose of this study is to expand understanding of the esterase status of blood plasma and to evaluate the relationship of the esterase status, which includes information on the amount and enzymatic activity of human serum albumin (HSA), with other biochemical parameters of human blood, using the example of surviving and deceased patients with confirmed COVID-19. In experiments in vitro and in silico, the activity of human plasma and pure HSA towards various substrates was studied, and the effect of various inhibitors on this activity was tested. Then, a comparative analysis of the esterase status and a number of basic biochemical parameters of the blood plasma of healthy subjects and patients with confirmed COVID-19 was performed. Statistically significant differences have been found in esterase status and biochemical indices (including albumin levels) between healthy subjects and patients with COVID-19, as well as between surviving and deceased patients. Additional evidence has been obtained for the importance of albumin as a diagnostic marker. Of particular interest is a new index, [Urea] × [MDA] × 1000/(BChEb × [ALB]), which in the group of deceased patients was 10 times higher than in the group of survivors and 26 times higher than the value in the group of apparently healthy elderly subjects.

Molecular design by means of quantum-chemistry to improve an acid catalysed acyl-migration reaction through protonated amide nitrogen atom in carboxamides.

Dendrimers are regular hyperbranched macromolecules. The complex structure of the relaxation spectrum is one of the many features of dendrimers that does not fit into the classical concepts of poly...

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 generation of N-acyl pyrazole from acyl hydrazide and acetyl acetone typically at 50 °C for 3.5–6 h with up to 99% isolated yields. 1H NMR titration data and DFT calculations indicate that the catalytic activity of the iodine(III) is caused by the binding with a ketone.

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 spe...

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, g...

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 been characterized by means of nuclear magnetic resonance. The measured spectra reveal that, despite being dried under vacuum, all the studied mixtures contained variable amounts of water, but, while in those with the salt cations of lower ionic potentials (Li+, Ca2+) only bulk free water that can be almost completely removed from the mixture is found, mixtures with the cations of higher ionic potentials (Mg2+, Al3+) contain only hydration water structurally anchored in the primary solvation shells of the metal cations forming coordination complexes inside the polar nanoregions of the densely ionic solvent and, thus, non-removable under vacuum. This hydration water is not properly detected by common Karl Fisher methods and these solutions are sometimes mistakenly considered anhydrous. Moreover, our NMR measurements confirm the nanostructured solvation paradigm, since they show that the influence of the addition of salt on the chemical shifts of the signals associated to hydrogen atoms in the apolar regions of the protic ionic liquid is negligible. Single-particle dynamics of cations of low and high ionic potentials was also studied, and our observations for the diffusion coefficients of lithium and aluminium cations support the conclusion that Li+ diffusion takes place inside anhydrous [Li(NO3)4]3− complexes, while kinetic complexes with Al3+ gather around [Al(H2O)6]3+) aqua ions.

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 be favorable for the enhancement in transfection efficiency of lysine based dendrimers. In this work, we have synthesized a new second-generation poly-L-lysine dendrimer with repeating units containing two linear Arg residues between neighboring lysine branching points (Lys-2Arg dendrimer) and studied its physicochemical properties. We confirmed the structure of Lys-2Arg dendrimer using various one- and two-dimensional 1H and 13C NMR spectroscopy methods. Comparison of T1H relaxation data for Lys-2Arg and Lys-2Lys dendrimers showed that the replacement of double Lys residues with double Arg residues resulted in a sharp decrease in the mobility of methylene groups in side segments and in the main chain of e-Lys inner segments. We suggest that this unexpected effect is caused by a guanidine–guanidine pairing effect in water, which leads to entanglements between dendrimer branches.

open access article 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 enzymatic and non‐enzymatic activities of albumin that determine its participation in redox modulation of plasma and intercellular fluid. For the first time, the results of numerous clinical, biochemical, spectroscopic and computational experiments devoted to the study of allosteric modulation of the functional properties of the protein associated with its participation in antioxidant defence are analysed. It has been concluded that it is fundamentally possible to regulate the antioxidant properties of albumin with various ligands, and the binding and/or enzymatic features of the protein by changing its redox status. The perspectives for using the antioxidant properties of albumin in practice are discussed.

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 amide nitrogen in hydrogen bonding (which can be regarded as the incipient state of a proton transfer process) is less well-studied. Thus, it would be a worthy goal to investigate the enthalpy of this interaction. We prepared and investigated a set of peri-substituted naphthalenes containing the protonated dimethylamino group next to the amide nitrogen atom ("amide proton sponges"), which could serve as models for the study of an intramolecular hydrogen bond with the amide nitrogen atom. X-Ray analysis, NMR spectra, basicity values as well as quantum chemical calculations revealed the existence of a hydrogen bond with the amide nitrogen, that should be attributed to the borderline between moderate and weak intramolecular hydrogen bonds (2-7 kcal ⋅ mol-1 ).

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 substrates. Seventeen new 3-NR2-1,2,4-triazoles were characterized by HRESI+-MS and IR, 1H, and 13C{1H} NMR spectroscopies and five species additionally by single-crystal X-ray diffraction (XRD). The ZnII-catalyzed reaction proceeds via initial generation of the [Zn{RC(=O)NHNH2}3](ZnCl4) complexes (exemplified by isolation of the complex with R = Ph, 76%; characterized by HRESI+-MS, IR, CP-MAS TOSS 13C{1H} NMR, and XRD). Electronic effects of substituents at the acyl hydrazide moiety do not significantly affect the reaction rate and the yield of the target triazoles, whereas the steric hindrances reduce the reaction rate without affecting the yield of the heterocycles.

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 derivatives of DMAN has been prepared in a good to reasonable yield after quenching the reaction mass with different electrophiles. A possibility of further functionalization of thus introduced meta-substituents to synthesize more complex 3-substituted derivatives of DMAN is also demonstrated.

The Publisher's final version can be found by following the DOI link. Open access article. 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 albumin, using the example of bovine serum albumin (BSA) and p-nitrophenyl acetate (NPA). The site of BSA esterase activity was then determined using molecular modelling methods. According to the data obtained, the accumulation of acetate in the presence of BSA in the reaction mixture is much more intense as compared with the spontaneous hydrolysis of NPA, which indicates true esterase activity of albumin towards NPA. Similar results were obtained for p-nitophenyl propionate (NPP) as substrate. The rate of acetate and propionate release confirms the assumption that there is a site of true esterase activity in the albumin molecule, which is different from the site of the pseudo-esterase activity Sudlow II. The results of molecular modelling of BSA and NPA interaction make it possible to postulate that Sudlow site I is the site of true esterase activity of albumin.

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 subsequent aggregation of helices. Upon increase of the κ-carrageenan/gelatin (w/w) ratio Z the rate of the fast process slows down by a factor of 1.6–2.4. Further analysis was done by studying the dependence of spin-spin relaxation times of protons of gelatin on Z in the aqueous phase. A qualitative scheme describing hydrogel formation in the complex solution is given. It is hypothesized that at higher concentration of PECs the hydrogel structure network is stabilized by three types of nodes: triple helices of gelatin and intra-/inter-molecular double helices of κ-carrageenan.

For the search of effective microemulsion systems with the properties demanded for various applications the knowledge of structural properties of the reverse microemulsions for various compositions and temperatures is of high value. In the present study, the microstructure and diffusion of the components of water-in-n-decane Winsor IV microemulsions stabilized by a mixture of nonionic surfactants Span 80 (sorbitane monooleate, HLB 4.9) and Tween 80 (polyoxyethylene sorbitan monooleate, HLB 15.0) at the weight ratios 49:51 (i.e. at the maximal ability to solubilize water) were investigated by viscosimetry, PGSTE NMR and DLS. The system phase diagram obtained at 298.2 K includes the intermediate heterogeneous region between the reverse micelles region and the microemulsions. The water-to-surfactant molar ratio was changed up to 15.5 (13 wt.% of water) at the weight ratios n-decane: surfactants 65:35 and 85:15. The microemulsion droplets are spherical (that is corresponded also to the cryo-TEM data) and grow with the increase of water content. The temperature effect on the aggregates diffusion (and on the aggregates size) in the range 298.2–318.2 K is not pronounced. The bimodal distributions of the diffusion coefficients determined using both DLS and PGSTE NMR methods are specific for the system. The slower diffusion mode relates to the diffusion of mixed microemulsion droplets with the radii Rh ∼10–20 nm. The second stable form of nanoaggregates are “dry” micelles with Rh ∼ 1–2 nm. The data on the diffusion coefficients are of special interest in particular for the molecular dynamic simulation of the reverse micelles or of the microemulsion droplets.

The intermolecular interactions between an anionic polysaccharide from the red algae κ-carrageenan and a gelatin polypeptide, forming stoichiometric polysaccharide–polypeptide (bio)polyelectrolyte complexes in the aqueous phase, were examined. The major method of investigation was high-resolution 1 H NMR spectroscopy. Additional data were obtained by UV absorption spectroscopy, light scattering dispersion and capillary viscometry. Experimental data were interpreted in terms of the changing roles of electrostatic interactions, hydrophobic interactions and hydrogen bonds when κ-carrageenan–gelatin complexes are formed. At high temperatures, when biopolymer macromolecules in solution are in the state of random coil, hydrophobic interactions make a major contribution to complex stabilization. At the temperature of gelatin’s coil → helix conformational transition and at lower temperatures, electrostatic interactions and hydrogen bonds play a defining role in complex formation. A proposed model of the κ-carrageenan–gelatin complex is discussed.

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 focus on the validation of two theoretical assumptions for dendrimers: (i) independence of NMR relaxations on excluded volume effects and (ii) similarity of mobilities of side and terminal segments of dendrimers. For this purpose we study 1H NMR spin-lattice relaxation time, T1H, of two similar peptide dendrimers of the second generation, with and without side fragments in their inner segments. Temperature dependences of 1/T1H in the temperature range from 283 to 343 K were measured for inner and terminal groups of the dendrimers dissolved in deuterated water. We have shown that the 1/T1H temperature dependences of inner groups for both dendrimers (with and without side fragments) practically coincide despite different densities of atoms inside these dendrimers. This result confirms the first theoretical assumption. The second assumption is confirmed by the 1/T1H temperature dependences of terminal groups which are similar for both dendrimers.

CF3-Substituted ketimines synthesized from trifluoroacetone, hexafluoroacetone, and trifluoroacetophenones were studied in aza-Henry reactions with nitroalkanes. We found that nitromethane and nitropropane react with CF3-substituted ketimines to form the target β-nitroamines in high yield. The aza-Henry reaction proceeded under mild conditions in the presence of an appropriate base. A new simple method for the synthesis of β-nitroamines bearing CF3 group was developed. α-CF3-β-nitroamines can easily be converted into trifluoromethylated 1,2-diamines, α-aminooximes, and imidazolidinones.

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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 detection of the labeled nanocarriers. In this work, we have synthesized new histidine-rich lysine-based dendrimers (Lys-2His dendrimer) with two linear histidine (His) residues in every inner segment. The presence of His residues has enabled us to perform controlled deuteration of Lys-2His dendrimers. The high deuteration degree (around 70%) does not practically change after redissolving the samples in H2O and heating them at 40 &deg, C, which indicates the isotopic label stability.

CF3-Substituted ketimines synthesized from trifluoroacetone, hexafluoroacetone, and trifluoroacetophenones were studied in aza-Henry reactions with nitroalkanes. We found that nitromethane and nitropropane react with CF3-substituted ketimines to form the target β-nitroamines in high yield. The aza-Henry reaction proceeded under mild conditions in the presence of an appropriate base. A new simple method for the synthesis of β-nitroamines bearing CF3 group was developed. α-CF3-β-nitroamines can easily be converted into trifluoromethylated 1,2-diamines, α-aminooximes, and imidazolidinones.

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 relaxation.

Oxidative Nef reaction of 2-nitroalkanamines or N -(2-nitroalkyl)carboxamides bearing trifluoromethyl group affords amino acids, amino ketones or hydroxyhydantoins depending on structure of the starting compounds.

The reaction of 2-(dialkylamino)-1,3-thiazol-4-amines and 1,2-dimethyl-1 H-imidazol-5-amine with aryl isocyanates, α-chloroalkyl isocyanates, N-(alkoxycarbonyl)imidoyl chlorides and 2,4,6-tris(trifluoromethyl)-1,3,5-triazine leads to thiapurines and purines containing trifluoromethyl groups in the 2- and 6-positions of the pyrimidine ring.

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 obtained in good yields. The formation of 3-Li-DMAN is especially desired since no method of direct meta-functionalization of DMAN is known to date. The relative stability and structure of DMAN lithium derivatives have been examined with the help of X-ray and multinuclear NMR measurements as well as DFT calculations.

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) bulk water. Up to now, the values of hydration parameters suggested for the description of various solutions of organic compounds were not thoroughly analyzed in the aspect of the consideration of the total molecular composition. The temperature and concentration dependences of relaxation rates of water deuterons were studied in a wide range of concentration and temperature in aqueous (D2O) solutions of a set of ω-amino acids. Assuming the coordination number of the CH2 group equal to 7, which was determined from quantum-chemical calculations, it was found that the rotational correlation times of water molecules near the methylene group is 1.5-2 times greater than one for pure water. The average rotational mobility of water molecules in the hydration shells of hydrophilic groups of ω-amino acids is a bit slower than that in pure solvent at temperatures higher that 60 °C, but at lower temperatures, it is 0.8-1.0 of values of correlation times for bulk water. The technique suggested provides the basis for the characterization of different hydrophobic and hydrophilic species in the convenient terms of the rotational correlation times for the nearest water molecules.

Three β-hydroxynaphthylamides (morpholine, pyrrolidine and dimethylamine derivatives) have been synthesized and their conformational state was analyzed by NMR, X-ray and DFT calculations. In aprotic solution the molecules contain intramolecular OHO hydrogen bonds, which change into intermolecular ones in solid state. The energy barriers for the amide group rotation around the CN bond were estimated from the line shape analysis of 1H and 13C NMR signals. A tentative correlation between the barrier height and the strength of OHO bond was proposed. Calculations of the potential energy profiles for the rotations around CC and CN bonds were done. In case of morpholine derivative experimental indications of additional dynamics: chair–chair ‘ring flip’ in combination with the twisting around CC bond were obtained and confirmed by quantum chemistry calculations.

The interaction of α-chloro-β,β,β-trifluoroethylisocyanates with 'push-pull' enamines having a methyl group at the α-position was investigated. As a result, a set of 4-dialkylamino-6-trifluoromethyl-5,6-dihydro-2-pyridinones was obtained. Structural sensitivity of the reaction was found and discussed.

N-(Methoxycarbonyl)trihaloacetimidoylchlorides react with 5-aminopyrazoles under mild conditions to give N-methoxycarbonyl-N'-(5-pyrazolyl)trihaloacetamidines, which furnish 6-trihalomethyl-4H-pyrazolo[3,4-d]pyrimidin-4-ones by thermal intramolecular cyclocondensation.

A systematic review is presented on the synthesis and the physical and chemical properties of N-acyl-, N-sulphonyl-, N-phosphoryl- and N-alkenyl-carbodiimides. The bibliography includes 90 references.

The reaction of 2-(dialkylamino)-1,3-thiazol-4-amines and 1,2-dimethyl-1 H-imidazol-5-amine with aryl isocyanates, α-chloroalkyl isocyanates, N-(alkoxycarbonyl)imidoyl chlorides and 2,4,6-tris(trifluoromethyl)-1,3,5-triazine leads to thiapurines and purines containing trifluoromethyl groups in the 2- and 6-positions of the pyrimidine ring.

The interaction of α-chloro-β,β,β-trifluoroethylisocyanates with 'push-pull' enamines having a methyl group at the α-position was investigated. As a result, a set of 4-dialkylamino-6-trifluoromethyl-5,6-dihydro-2-pyridinones was obtained. Structural sensitivity of the reaction was found and discussed.

N-(Methoxycarbonyl)trihaloacetimidoylchlorides react with 5-aminopyrazoles under mild conditions to give N-methoxycarbonyl-N'-(5-pyrazolyl)trihaloacetamidines, which furnish 6-trihalomethyl-4H-pyrazolo[3,4-d]pyrimidin-4-ones by thermal intramolecular cyclocondensation.