Application of deuterium–hydrogen exchange to study the secondary structure of oligonucleotide ions in a gas phase

At present, the secondary structure of oligonucleotide ions in a gas phase is almost not understood. One of the main points is the retention of a hairpin secondary structure during ionization. In this work, we used a deuterium–hydrogen exchange reaction in a gas phase at atmospheric pressure for studying the conformational dynamics of oligonucleotide ions formed as a result of electrospray ionization. The exchange reactions of two oligonucleotides, which consisted of the identical sets of nucleotides but differed in their sequence, have been studied. One of these oligonucleotides formed a hairpin secondary structure, but the other did not. It has been found that both of the oligonucleotides demonstrate similar reaction dynamics of deuterium/hydrogen exchange in the gas phase; thereby indicating that the secondary structure has been completely destroyed during ionization.     

Hydrogenolysis of the C-O bond of hydroxylactams as a convenient method for the synthesis of substituted isoindolin-1-ones

A simple and efficient method for the synthesis of isoindolin-1-ones containing alkyl or aryl substituents at positions 2 and (or) 3 was suggested. The method is based on the earlier unknown Pd⁰-catalyzed hydrogenolysis of hydroxylactams.     

Direct and inverse boundary value problems for models of stationary reaction–convection–diffusion

Direct and inverse boundary value problems for models of stationary reaction–convection–diffusion are investigated. The direct problem consists in finding a solution of the corresponding boundary value problem for given data on the boundary of the domain of the independent variable. The peculiarity of the direct problem consists in the inhomogeneity and irregularity of mixed boundary data. Solvability and stability conditions are specified for the direct problem. The inverse boundary value problem consists in finding some traces of the solution of the corresponding boundary value problem for given standard and additional data on a certain part of the boundary of the domain of the independent variable. The peculiarity of the inverse problem consists in its ill-posedness. Regularizing methods and solution algorithms are developed for the inverse problem.     

Synthesis of 3-aminomethyl-substituted pyrazoles and isoxazoles

A series of new 3-(aminomethyl)pyrazoles and 3-(aminomethyl)isoxazoles was synthesized along a route involving the formation as key intermediates of esters of 5-substituted 1H-pyrazole-3-carboxylic and 1H-isoxazole-3-carboxylic acids. All compounds obtained were characterized by physicochemical constants, IR, ¹H, ¹³C NMR, and mass spectra.     

Synthesis of stereoarray isotope labeled (SAIL) lysine via the "head-to-tail" conversion of SAIL glutamic acid

A stereoarray isotope labeled (SAIL) lysine, (2S,3R,4R,5S,6R)-[3,4,5,6-(2)H(4);1,2,3,4,5,6-(13)C(6);2,6-(15)N(2)]lysine, was synthesized by the "head-to-tail" conversion of SAIL-Glu, (2S,3S,4R)-[3,4-(2)H(2);1,2,3,4,5-(13)C(5);2-(15)N]glutamic acid, with high stereospecificities for all five chiral centers. With the SAIL-Lys in hand, the unambiguous simultaneous stereospecific assignments were able to be established for each of the prochiral protons within the four methylene groups of the Lys side chains in proteins.     

A Comparison of Tissue Spray and Lipid Extract Direct Injection Electrospray Ionization Mass Spectrometry for the Differentiation of Eutopic and Ectopic Endometrial Tissues

Recent research revealed that tissue spray mass spectrometry enables rapid molecular profiling of biological tissues, which is of great importance for the search of disease biomarkers as well as for online surgery control. However, the payback for the high speed of analysis in tissue spray analysis is the generally lower chemical sensitivity compared with the traditional approach based on the offline chemical extraction and electrospray ionization mass spectrometry detection. In this study, high resolution mass spectrometry analysis of endometrium tissues of different localizations obtained using direct tissue spray mass spectrometry in positive ion mode is compared with the results of electrospray ionization analysis of lipid extracts. Identified features in both cases belong to three lipid classes: phosphatidylcholines, phosphoethanolamines, and sphingomyelins. Lipids coverage is validated by hydrophilic interaction liquid chromatography with mass spectrometry of lipid extracts. Multivariate analysis of data from both methods reveals satisfactory differentiation of eutopic and ectopic endometrium tissues. Overall, our results indicate that the chemical information provided by tissue spray ionization is sufficient to allow differentiation of endometrial tissues by localization with similar reliability but higher speed than in the traditional approach relying on offline extraction.

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Structural and functional changes in the membrane and membrane skeleton of red blood cells induced by peroxynitrite

The changes in passive ion permeability of the red blood cell membrane after peroxynitrite action (3 microM-3 mM) have been studied by biophysical (using radioisotopes of rubidium, sodium and sulphur (sulphate)) and electrophysiological methods. The enhancement of passive membrane permeability to cations (potassium and sodium ions) and the inhibition of anion flux through the anion exchanger in peroxynitrite-treated red blood cells were revealed. In patch-clamp experiments the whole-cell conductance after peroxynitrite (80 muM) treatment of red blood cells increased 3-3.5-fold with a shift in the reversal potential from -7.0+/-1.5 mV to -4.3+/-0.9 mV (n=7, p=0.005). The addition of cobalt and nickel ions to red blood cell suspensions before peroxynitrite treatment had no effect on the peroxynitrite-induced cation flux but zinc ions in the same condition decreased cation flux about 2-fold. Using atomic force microscopy methods we revealed an increase in red blood cell membrane stiffness and the membrane skeleton complexity after peroxynitrite action. We conclude that the peroxynitrite-induced water and ion imbalance and reorganization in membrane structure lead to crenation of red blood cells.