The role of Tyr102 residue in the functioning of bacterial NAD+-dependent formate dehydrogenase of Pseudomonas sp. 101.

Once you have missed the first button …, you'll never manage to button up Johann Wolfgang von Goethe Formate oxidation is a final step of methanol oxidation in methylotrophic prokaryotes and is important for detoxification of formate in other organisms. The structural mechanism of the formate dehydrogenase (FDH) of Pseudomonas sp. 101 has been studied for about 30 years. In the active center of FDH, the oxidation of formic acid into carbon dioxide in a NAD+-dependent way takes place. Residues that form the active center of that enzyme, as well as those that form the so-called substrate channel, are engaged in the catalytic cycle. Our study allowed to characterize a new residue, Tyr102, involved in the work of the enzyme. This residue is located in the outer neck of the substrate channel (at the beginning of the path of the substrate to the active center) and acts as a "button" which connects two enzyme domains into an active, "buttoned up" conformation. Our study of the kinetic parameters of mutant enzymes has shown that Tyr102Phe substitution leads to an approximately 80-fold increase of the Michaelis constant relative to the native enzyme, unlike Phe311Trp and Phe311Tyr substitution of neighboring residue Phe311. Our analysis of the Tyr102Phe mutant in the open conformation by X-ray crystallography has shown that its overall fold remains almost the same as that of the native enzyme. Molecular dynamics simulations of the ternary complexes of the native FDH enzyme and its Tyr102Phe mutant showed that Tyr102Phe substitution results in the loss of an interdomain hydrogen bond between the Tyr102 and Gln313 residues, which, in turn, destabilizes the closed conformation and affects the isolation of the FDH active site from water molecules. Our structural investigations have shown that Tyr102Phe replacement also leads to the destruction of interdomain contacts of Phe102 with Phe311, Pro312 residues, and decreases the stability of the Leu103-Val127 beta bridge. Phylogenetic analysis also confirmed the importance of the Tyr102 residue for enzymes from the FDH family, in which it is absolutely conserved.

[The use of Dnipro activated charcoal filamentous material in performing extracorporeal sorption detoxification]. / Zastosuvannia aktyvovanoho vuhletsevoho voloknystoho materialu "Dnipro" pry provedenii ekstrakorporal'noï sorbtsiinoï detoksykatsiï.

Experimental estimation of properties of an activated carbonic fibrillar material "Dnipro" was conducted. Its application perspectivity while conduction of plasmo-, lympho- and hemosorption was proved.

[The prospects for the use of computers in dentistry]. / Perspektivy primeneniia EVM v stomatologii.

A universal soft-art complex tentatively named Arm-Stomatolog, covering all sections of dentistry, has been developed. It is based on individual programs in dentistry, making use of high-level algorithmic languages fitted to modern operation systems and permitting block-to-block fitting of individual programs to unite them in a complex.

[Study of the epidemic significance of noncultivated forms of Vibrio cholerae by the polymerase chain reaction]. / Issledovanie épidemicheskoi znacheimost nekul'tiviruemykh form kholernykh vibrionov metodom polimeraznoi tsepnoi reaktsii.

A specific method of the isolation of the cholera toxin gene by the directional amplification of DNA in the polymerase chain reaction (PCR) has been developed. The product of this reaction has a molecular weight of 440 sequence pairs and is a DNA fragment located on the A-subunit of V. cholerae gene vct. The sensitivity of the method permits the detection of one bacterial cell in the reaction mixture. The method is effective when V. cholerae purified DNA, cell lysates and the DNA of total microflora isolated from the water of natural springs are used. The study of water samples from natural water bodies by the method of PRC has revealed cholera toxin genes of V. cholerae noncultivated forms ni 5 out of 7 water samples taken from natural water bodies at the regions of Azerbaijan endemic for cholera and made it possible to evaluate the number of V. cholerae. The prospects of using PCR for the control of the epidemiological situation in regions endemic for cholera are discussed.

[Use of a dual-frequency spectrophotometric method for determining the DNA content in the male sex cells of bulls, rams and boars]. / Izopolzvane na dvuvulnoviia spektrofotometrichen metod za opredeliane sudurzhanieto na DNK v muzhki polovi kletki na bik, koch i nerez.

Investigated were the absorption spectral curves of alkaline protein hydrolysates and DNA-extracts from bull, ram and boar spermatozoa employing the method of Schmidt-Tannhauser. It was established that the double-wave method could be used to determine the content of DNA in the investigated ejaculated at the following values of the two waves and coefficients: 268 nm and 280 nm; K = 1350 for ram spermatozoa, and 268 nm and 281 nm; K = 1175 for bull and boar spermatozoa. The evaluation of the quantitative content of DNA per spermatozoid of bull, ram and boar was also carried out, establishing that the figures obtained are approximately equal.