[The possible role of the elements of protein secondary structure in adaptation to the action of ionizing radiation]. / O vozmozhnoi roli élementov vtorichnoi struktury belkov v adaptatsii k deistviiu ioniziruiushchei radiatsii.

Changes in the secondary structure of enzymes induced by gamma-rays 60Co at doses not exceeding one ionization per macromolecule were studied to elucidate a possible role of radiation-chemical processes in the evolution of proteins. The data on the comparative radioresistance of various types of secondary protein structures, alpha-helix, parallel and anti-parallel beta-structures, and beta-turn, were obtained by the method of circular dichroism. It was shown that beta-turns were resistant against radiation, alpha-helix was relatively stable, and beta-layer underwent significant changes. The importance of these structural types in the evolution of proteins is discussed. A special role of beta-turn as structural elements fixing the confirmation of macromolecules and therefore responsible for adaptation of the protein structure against a constant radiation background is proposed.

[Radiation-protective effect of S-methylmethionine (vitamin U)]. / Protivoluchevoe deistvie S-metilmetionina (vitamina U).

S-Methylmethionine had moderate radioprotective activity, the efficiency of radioprotection was 15-30%, the value of dose decrease coefficient-1.2. Biological effect of S-methylmethionine was probably provided by its ability to decrease the level of lipid peroxidation and inhibit monoamine oxidase activity.

[The characteristics of the action of gamma irradiation on the secondary structure of ribonuclease in vitro and the effect of oxygen on this process]. / Osobennosti deistviia gamma-oblucheniia na vtorichnuiu strukturu ribonukleazy in vitro i vliianie kisloroda na étot protsess.

The change in the secondary structure of ribonuclease after 60Co gamma irradiation with a dose of 1,000 Gy in 0.2% aqueous solution was estimated using the circular dichroism method. The beta structures were significantly changed, while other types of the secondary structure (alpha-helix and beta-turns) changed insignificantly. The secondary structure injury was also affected by oxygen. The data are attributed to characteristics of the secondary structure of this enzyme.

[The simultaneous synthesis of peptides and oligonucleotides on kaolinite with the participation of aminoacyladenylates]. / Odnovremennyi sintez peptidov i oligonukleotidov na kaolinite s uchastiem aminoatsiladenilatov.

A simultaneous synthesis of peptides (2-5 residues) and oligonucleotides (3-9 residues) has been carried out on caolinite matrix using amino acids and aminoacyladenylates as substrates. The rate of oligomer synthesis on mineral surface is higher than that in solution. The mechanism of synthesis has been described. The data has been discussed in connection with abiogenesis of two major types of biopolymers, proteins and nucleic acids.

[Structural and functional properties of irradiated nuclear membranes at the air-water phase interface]. / Strukturno-funktsional'nye svoistva obluchennykh iadernykh membran na granitse razdela faz vozdukh-voda.

The monolayer technique, the methods of electron microscopy and IR-spectroscopy were used to study isolated nuclear membranes of calf thymus cells. The data obtained permitted to study the relationship between structural disorders induced by irradiation of membranes, the changes in their functional status, and the role played by a lipid component of membranes in these processes.

[Radiation sensitivity of membrane-bound glucose-6-phosphatase]. / Radiatsionnaia chuvstvitel'nost' membranosviazannoi gliukozo-6-fosfatazy.

A comparative study was made of the effect of X-radiation on the membrane-bound glucoso-6-phosphatase of the nuclear membrane and microsomal fraction of calf thymus cells. Dose- and concentration-dependencies of inactivation of glucoso-6-phosphatase are indicative of a higher radiosensitivity of glucoso-6-phosphatase of nuclear membranes than that of microsomes. This difference in radiosensitivity is associated with the peculiarities of the composition and structural organization of these two membrane systems of a cell.

[Study of radiation damage to nuclear membranes by IR spectroscopy and monolayer technics]. / Issledovanie radiatsionnykh narushenii iadernykh membran metodom IK-spektroskopii i monosloinoi tekhniki.

A study was made of the effect of X-radiation on nuclear membranes. Good resolution spectra of nuclear membrane of equal effective thickness were obtained by the method of internal reflection spectroscopy in the infrared region. The experiment indicated the presence of major characteristic bands of protein and phospholipid molecular groups of non-irradiated nuclear membranes. Conformational changes in the samples of the exposed (100 and 1000 Gy) lipoprotein complex resulted in some quantitative changes in the absorption intensities of the molecular groups of membranes. These data are consistent with the behaviour of nuclear membranes on the interphase, studied by the Langmur monolayer technique, and with the changes in the membrane morphology observed with the electron microscope.

[The effect of oxygen on denaturation and aggregation of enzyme macromolecules during gamma-irradiation]. / Vliianie kisloroda na denaturatsiiu i agregatsiiu makromolekul fermenta v protsesse gamma-oblucheniia.

The ribonuclease molecules irradiated in a solution in the presence of 18O2 were separated, by the method of gel-chromatography, into fractions of aggregated macromolecules, denatured monomers and the molecules which retained the original sizes. Oxygen was bound by the molecules of all fractions. The oxygen binding prevented the aggregation of macromolecules. The fractions of molecules of monomer forms, obtained after irradiation in the presence of oxygen, were more inactive than those obtained after irradiation in vacuum.

[Kinetics of abiogenic peptide bond synthesis with aminoacyladenylate participation as condensing agents]. / Issledovanie kinetiki abiogennogo sinteza peptidnoi sviazi pri uchastii aminoatsiladenilatov v kachestve kondensiruiuschchikh agentov.

Kinetics of the process has been investigated employing differential spectroscopy technique. Possibility of synthesis of peptide bonds in aqueous solutions using aminoacyladenylates as condensing agents was shown. Analysis of the data obtained shows that the synthesis of peptide bond under the conditions investigated with the excess amounts of the second substrate follow the first order equation for irreversible reactions, the rate of the reaction decreasing with the increase in substrate concentrations. Velocity constants are determined for the first order reaction at different substrate concentrations. The data obtained are discussed in relation to the problem of abiogenic synthesis of biologically important macromolecules.

[Photochemical formation of pyruvic acid in a solution of acetaldehyde and ammonium nitrate]. / Fotokhimicheskoe obrazovanie pirovinogradnoi kisloty v rastvore atsetal'degida i nitrata ammoniia.

It has been demonstrated that UV irradiation of acetaldehyde (2.5%) and ammonium nitrate (1.5%) solutions results in the synthesis of the pyruvic acid (PA). With the increase in the duration of irradiation, the yield of the produced PA decreases which is associated both with its photolysis and with its further transformations, for instance, into amino acids. The results obtained are discussed in relation to abiogenic synthesis of biologically important compounds in prebiological evolution and to possible development of metabolic pathways which are found in contemporary organisms.