[A new N-acyl derivative of (S)-cysteine for quantitative determination of enantiomers of amino compounds by HPLC method with a precolumn modification with o-phthalaldehyde]. / Novoe N-atsil'noe proizvodnoe (S)-tsisteina dlia kolichestvennogo opredeleniia énantiomerov aminosoedineniii metodom VEZhKh s predkolonochnoi modifikatsiei opto-ftalevym al'degidom.

N-Phenylacetyl-(R)-phenylglycyl-(S)-cysteine (NPPC) was used for the determination of enantiomers of primary amines by rpHPLC with a precolumn modification with o-phthalaldehyde. NPPC was compared with the classic SH reagent N-acetyl-(S)-cysteine (NAC) in the analysis of stereomers of nonfunctionalized amines and amino alcohols. After the NAC modification, the resulting diastereomeric isoindoles were difficult to separate by HPLC, and satisfactory resolution was achieved only for some aliphatic amino alcohols. The use of NPPC improved the chromatographic analysis of stereomeric amino alcohols and, in addition, allowed the enantiomeric analysis of the nonfunctionalized amines. Similarity between the side radicals of the amino component and the thiol reagent favored the diastereomer separation. This method was used for determination of the absolute concentration of individual enantiomers of amines in the course of stereoselective enzymatic reactions. The optically active NPPC was prepared with a high yield by a chemoenzymatic synthesis based on a regioselective acylation of the (S)-cysteine amino group in aqueous medium by the action of penicillin acylase. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 5; see also http: // www.maik.ru.

Construction of a Full-Atomic Mechanistic Model of Human Apurinic/Apyrimidinic Endonuclease APE1 for Virtual Screening of Novel Inhibitors.

A full-atomic molecular model of human apurinic/apyrimidinic endonuclease APE1, an important enzyme in the DNA repair system, has been constructed. The research consisted of hybrid quantum mechanics/molecular mechanics modeling of the enzyme-substrate interactions, as well as calculations of the ionization states of the amino acid residues of the active site of the enzyme. The choice of the APE1 mechanism with an Asp210 residue as a proton acceptor was validated by means of a generalization of modeling and experimental data. Interactions were revealed in the active site that are of greatest significance for binding the substrate and potential APE1 inhibitors (potential co-drugs of interest in the chemo- and radiotherapy of oncological diseases).

Mutation of Residue ßF71 of Escherichia coli Penicillin Acylase Results in Enhanced Enantioselectivity and Improved Catalytic Properties.

Residue phenylalanine 71 of the ß-chain of penicillin acylase from E. coli is involved in substrate binding and chiral discrimination of its enantiomers. Different amino acid residues have been introduced at position ßF71, and the mutants were studied with respect to their enantioselectivity and substrate specificity. Some mutants demonstrated remarkably improved catalytic activity. Moreover, mutation of ßF71 residue allowed to enhance penicillin acylase enantioselectivity. The catalytic activity to the specific substrates was improved up to 36 times, most notably for K, R, and L mutants. Increased activity to a D-phenylglycine derivative - a valuable specificity improvement for biocatalytic synthesis of new penicillins and cephalosporins - was shown for ßF71R and ßF71L mutants. The synthetic capacity of penicillin acylase with 6-aminopenicillanic acid as an external nucleophile was especially sensitive to mutation of the ß71 residue in contrast to the synthesis with 7-aminodeacetoxycephalosporanic acid.

[The nature of the thermomechanical reactions of the vascular wall]. / O prirode termomekhanicheskikh reaktsii sosudistoi stenki.

Thermosensitivity of the guinea pig aorta wall stretched to 1.05-1.40 of its initial length, was shown to completely depend on the connective tissue: the thermomechanical responses of the stretched aorta entailed changes in its stiffness typical for an agonist-induced vessel tissue contraction. The connective tissue component of the mechanical response of the vascular wall seems to have a universal character.