Spectroscopic study of low temperature interactions in metal-organic co-condensates.

The results on spectroscopic study of low temperature interactions of metal atoms, small clusters and nanoparticles with different organic and inorganic substances in the temperature range 12-300 K are presented. Complexation and reactions of atoms and clusters of magnesium, samarium and silver with carbon dioxide, ethylene and some mesogenic cyanophenyls were studied by the technique of matrix isolation and low temperature co-condensation of metal and ligand vapors, low temperature UV-Vis, IR- and ESR-spectroscopy in combination with quantum chemistry calculations. It was shown that cryochemical reactions of metal particles of different sizes reflected the system's redundant energy.

Spectroscopic study of low temperature interactions in Sm-mesogenic cyanophenyl co-condensates.

The IR- and UV-Vis spectroscopic study of samarium-mesogenic 4-pentyl-4'-cyanobiphenyl low temperatures co-condensates was made in temperature range 90-300 K. Two labile complexes with different metal/ligand ratio of 1:2 and 1:1 were found. They were characterized by methods of IR- and UV-spectroscopy. The solid state transformation of complex Sm(5CB)2 to Sm(5CB) was shown to take place at 170-210 K. The kinetics of the process revealed a wide distribution of complex reactivity and of reaction activation energy.

[Effect of temperature and composition of frozen solutions on the rate of peroxidase oxidation of 2,3-dimethyl-1,4-naphthoquinol-1-dimethylphosphate]. / Vliianie temperatury i sostava zamorozhennogo rastvora na skorost' kataliziruemogo peroksidazoi okisleniia 2,3-dimetil-1,4-naftokhinol-1-dimetilfosfata.

The horseradish peroxidase-catalyzed oxidation of 2.3-dimethyl-1.4-naphthoquinol-1-dimethylphosphate by hydrogen peroxide was investigated within the temperature range of +20 divided by -35 degrees. The increase in the concentration of the buffer solution accelerated the reaction in liquid solutions at 0 degrees and 20 degrees. The unusual shapes of the curves of temperature dependences of the reaction rate in frozen solutions of different composition can probably be due to temperature variations in some physico-chemical parameters of the system under study.

[Effect of horse radish peroxidase immobilization on the kinetics of enzymatic oxidation of guaiacol in frozen solutions]. / Vliianie immobilizatsii peroksidazy na kinetiku fermentativnogo okisleniia gvaiakola v zamorozhennykh rastvorakh.

The kinetics of horse radish peroxidase (EC 1.11.1.7) catalyzed oxidation of guaiacol by hydrogen peroxide has been studied within the temperature region of +20--35 degrees C. The covalent attachment of the enzyme to polyacrylamide gel had no significant influence on the activation energy of the reaction in liquid solutions. For frozen solutions it was demonstrated that the temperature dependencies of the reaction rate differ greatly for the soluble and bound forms of the enzyme. The observed phenomenon is probably due to the differences in the molecular mobility, distribution and arrangement of reactants in frozen state.

[The secondary structure of amides of adenylic acid containing D- and L-aromatic amino acids]. / Osebennosti vtorichnoi struktury amidov adenilovoi kisloty, soderzhashchikh D- i L-aromaticheskie aminokislety

Adenylyl-(5'leads to N)-amino acids containing as amino components, methyl esters of D-, L- and DL-phenylalanine, D-, L- and DL-tyrosine, and D-, L- and DL-tryptophan have been investigated by proton magnetic resonance (PMR) spectroscopy and circular dichroism (CD). The temperature and pD dependences of proton chemical shifts of these compounds have been studied. These data, together with the magnitudes of the upfield chemical shifts of the PMR signals of adenine and aromatic amino acids residues in adenylyl-(5'leads to N)-amino acids, have enabled us to construct conformational models of these compounds. The proposed conformation has been substantiated by the CD results. It is shown that in adenylyl-(5'leads to N)-amino acids the planes of adenine and amino acid aromatic moieties are roughly parallel. The aromatic rings of phenylalanine and tyrosine are localized approximately above the centre of adenine. In adenylyl-(5'leads to N)-D, -(L)-tryptophan, the six-membered rings of the indole overlaps the five-membraned ring of adenine indole partially overlaps the six-membered ring of adenine. A difference in the non-covalent interactions of D- and L-amino acids with nucleotides has been revealed. The mutual localization of the aromatic systems of AMP and the amino acids and also the positions of -OCH3 group with respect to the centre of the amino acid aromatic moiety differs in the series of the studied nucleotide derivatives of D- and L-amino acids.

[The secondary structure of nucleotidyl-(5' bound to N)-amino acids containing different heterocyclic bases and amino acids]. / Issledovanie vtorichnoi struktury nukleotidil-(5' leads to N)-aminokislot s razlichnoi prirodoi osnovaniia i aminokisloty

Nucleotidyl-(5' leads to N)-amino acids containing different heterocycle bases: adenine, guanine, hypoxanthine, cytosine, uracyl, and aromatic amino acids: phenylalanine, tyrosine and tryptophan, have been investigated by proton magnetic resonance and circular dichroism. For all the compounds studied folded conformation have been shown stabilized by hydrophobic interaction in aqueous solution. The comparison of the results of the studied nucleotidyl-(5' leads to N)-amino acids unable us to build four secondary structure types in these very compounds. Phenylalanine and tyrosine derivatives of purine nucleotides can be regarded as the first type, tryptophan derivatives of purine nucleotides as the second type, phenylalanine and tyrosine derivatives of pyrimidine nucleotides as the third type and tryptophan derivatives of pyrimidine nucleotides as the fourth type. For each group of these compounds conformational models have been built. In all these compounds the anti-conformation has been proved to exist.

Dependence of noncovalent interactions of benzene and adenine rings on distance between them in adenylyl-(5' yields N)-omega-arylalkylamines.

A series of adenylyl-(5' yields N)-omega-arylalkylamines, containing from one to six methylene groups in the amino component, was studied by methods of nuclear magnetic resonance and circular dichroism. It was shown that independently of the length of the aliphatic chain of the amine convergence of the adenine and benzene rings and a hydrophobic interaction between them occur. The plane of the benzene ring is inclined toward the adenine ring, which has an anticonformation relative to the ribose. The structure of the intramolecular complex and the energy of the interaction of the aromatic systems of the amine and nucleotide depend on the number of methylene groups in the amino component. Maximum interaction occurs in the presence of two methylene groups; weakening of the interaction occurs with an increase in the chain to four links, which does not change upon further lengthening of the chain. The conformation of adenylyl-(5' yields N)-benzylamine differs from the structure of the other compounds of the series investigated.