Features of changes of higher nervous performance indicators on stress influence in preliminary gamma- radiation-exposed of rats

Studies of active avoidance behavioral reactions (shuttle box) changes under exposure of stress (foot-shock) in the rats preliminary exposed to single total γ-radiation at doses of 0.5 and 1.0 Gy gave the following results. Reactions of conditioned behavior indices to stress are individual, but in general they are characterized by signif-icant direct effect of activation, which could be followed by depression during time period after stress applica-tion. Effects of stress in the rats previously exposed at the dose of 1.0 Gy exceed those in the animals both direct-ly after stress application and during the time periods without stress. Interaction between factors of ionizing radi-ation and stress were found for the tested indices at the dose of 1.0 Gy. Rats exposed at the dose of 0.5 Gy in-crease of direct response to stressing was not found, but it was evident in delayed responses

Temperature dependences of ion currents of alcohol clusters under low-temperature secondary ion mass spectrometric conditions

The dependences of ion currents on temperature (ion thermograms) obtained by monitoring the abundance of different types of ions during the thawing of frozen samples of methanol and ethanol in low-temperature secondary ion mass spectrometry revealed special features in the temperature behaviour of the samples. Correlations between the changes in ion production and phase transitions (melting, boiling, evaporation) in the sample with temperature increase were revealed

Modeling of recognition sites of nucleic acid bases and amide side chains of amino acids. Combination of experimental and theoretical approaches

A combined experimental-theoretical approach to modeling of building blocks of recognition complexes formed by nucleic acid bases and the amino-acids side-chain amino group is reviewed. The approach includes the temperature dependent field-ionization mass spectrometry and ab initio quantum chemical calculations. The mass spectrometric technique allows determination of interaction enthalpies of biomolecules in the gas phase, and the results it produces are directly comparable to the results obtained through theoretical modeling. In our works we have analyzed both thermodynamic and structural aspects of the recognition complexes of four canonical nucleic acid bases and acrylamide, which models the side chain of asparagine and glutamine. It has been shown that all bases can interact with amide group of the amino acids via their Watson-Crick sites when being incorporated into a single strand DNA or RNA. Stability of the complexes studied, expressed as $-\Delta H$ (kJ mole-1) decreases as: m9Gua $(-59.5) > m^1$Cyt $(-57.0) > m^9$Ade $(-52.0) \gg m^1$Ura $(-40.6)$. We have determined that in the double stranded DNA only purine bases can be recognized

Observation of crystallization of amorphous solid water under the conditions of secondary emission mass spectrometric experiments

A phenomenon of termination of sputtering of protonated water clusters (H2O)nH⁺ in low-temperature secondary emission mass spectrometric studies of solid water was observed in the temperature range of crystallization of amorphous solid water (ASW). In this range the mass spectra contained only H₃O⁺, H₂O⁺•, and OH⁺ ions. The following explanation of the revealed phenomenon is suggested: the heat supplied to the ASW sample by the bombarding particles is spent on initiation of an amorphous–crystalline transition within the condensed sample but not for the transfer of the sample matter to the gas phase. At the same time heat released on crystallization causes a local rise in temperature of the crystallizing sample surface, which enhances the rate of sublimation of ice. The resulting increased concentration of subliming water molecules over the sample surface is reflected in the growth of abundance of H₂O⁺• molecular ion-radical, produced by gas-phase ionization mechanism. The appearance of a set of low-mass peaks in the course of crystallization observed for some types of ASW samples is explained by the release of gases trapped in the ASW film during its growth

Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization

Noncovalent interaction of methylene blue dye cation (MB⁺) with single walled carbon nanotubes (CNT) is characterized by molecular dynamics (MD) simulation, quantum chemical calculations, and laser desorption/ionization (LDI) mass spectrometry. The MD simulation of the (MB⁺)_<i>n</i>–CNT (<i>n</i> = 1–10) complexes in water demonstrates that the MB⁺ cations are adsorbed on the nanotube surface in the monomeric form. MD reveals both parallel and perpendicular orientations of the MB⁺ tricyclic plane in relation to the long axis of CNT when placed in the water environment. The interaction energy between the components of the complex in the perpendicular conformation, as determined by quantum chemical calculations at the DFT/M05-2X/6-31++G­(d,p) level of theory, explains why the bending of the MB⁺ cation at the sulfur atom weakens the π-system of bonds and allows for the perpendicular orientation to occur. It is also found that the adsorbed MB⁺ induces positive electrostatic potential around the adjacent semicylindrical segment of the nanotube. The mainly monomolecular adsorption of the MB⁺ cations at the CNT surface leads to the absence in the LDI mass spectra of (MB⁺)_<i>n</i>–CNT of features corresponding to products of the reduction of MB⁺ commonly observed in the LDI mass spectra of crystalline dyes

Noncovalent Interaction of Methylene Blue with Carbon Nanotubes: Theoretical and Mass Spectrometry Characterization

Noncovalent interaction of methylene blue dye cation (MB⁺) with single walled carbon nanotubes (CNT) is characterized by molecular dynamics (MD) simulation, quantum chemical calculations, and laser desorption/ionization (LDI) mass spectrometry. The MD simulation of the (MB⁺)_<i>n</i>–CNT (<i>n</i> = 1–10) complexes in water demonstrates that the MB⁺ cations are adsorbed on the nanotube surface in the monomeric form. MD reveals both parallel and perpendicular orientations of the MB⁺ tricyclic plane in relation to the long axis of CNT when placed in the water environment. The interaction energy between the components of the complex in the perpendicular conformation, as determined by quantum chemical calculations at the DFT/M05-2X/6-31++G­(d,p) level of theory, explains why the bending of the MB⁺ cation at the sulfur atom weakens the π-system of bonds and allows for the perpendicular orientation to occur. It is also found that the adsorbed MB⁺ induces positive electrostatic potential around the adjacent semicylindrical segment of the nanotube. The mainly monomolecular adsorption of the MB⁺ cations at the CNT surface leads to the absence in the LDI mass spectra of (MB⁺)_<i>n</i>–CNT of features corresponding to products of the reduction of MB⁺ commonly observed in the LDI mass spectra of crystalline dyes