[Luminescence of stable stacking aggregates of adenine and uracil in water].

Luminescence and excitation spectra of the highly luminescent stacking dimers of adenine and uracil in water solutions are studied. By the luminescence excitation spectra method it is shown that the stacking aggregates of adenine and uracil are formed with participation of rare forms of monomer molecules: N7H tautomers of adenine and the uracil molecules in rare forms of hydratation, for example molecules without H-bonds with water. The study of temperature dependence of luminescence intensity of monomers and stacking dimers of uracil has shown that stacking dimers do not dissociate even at 85 degrees C similarly as described earlier for adenine and adenosine. Stable stacking aggregates of nucleic bases are most likely to be the precursors of RNA molecules in chemical evolution. This hypothesis is supported by new data on their stability.

[Study of spectral and luminescent manifestations of the aggregation of thymine chromophores in aqueous solutions of polythymidylic acid at room temperature in connection with the task of photochemical record of information on thymine].

Luminescence and excitation luminescence spectra of water solutions of polythymidylic acid at room temperature were studied. Three luminescence bands at different excitation wavelengths were observed: at 338 nm, which was known earlier, and two new bands, at 320 and 350 nm. The study of excitation luminescence spectra that have not been studied earlier led us to interpret the band at 320 nm as a band of chromophores that do not interact, the band at 338 nm as a band of photochemically most active densely packed stacking dimers (absorption band exciton splitting approximately 4000 cm(-1)), and the band at 350 nm as a band of photochemically inactive big stacking aggregates (n > or = 10, exciton splitting approximately 8000 cm(-1)). Changes in optical density at 270 nm of poly-T water solutions after consecutive irradiations with UV light at 297+302 and 248 nm were studied. The causes of incomplete reversibility are discussed.

[Influence of UV irradiation on microbiological degradation of petroleum products].

Changes in the rates of microbiological degradation of kerosene, diesel fuel, and fuel oil under the effect of UV irradiation were estimated by testing the respiratory activity of microbial communities. The strongest inhibitory effect was observed upon simultaneous UV irradiation of both natural water and petroleum products. Concentrations of CO2 in the microbial communities (microcosms) decreased from 6.7 to 3.6 vol. % upon oxidation of kerosene, from 5.9 to 0.8 vol. % upon oxidation of diesel fuel, and from 5.7 to 0.05 vol. % upon oxidation of fuel oil.

[Photochemical revelation of the stacking aggregation of thymine chromophores in water solutions of polythymidylic acid].

The structure heterogeneity of water solutions of polyribothymidylic acid at T(room) was studied from changes caused in their absorption spectra by the photodimerization reaction. Three fractions of thymine chromophores were revealed from the differential absorption spectra: (a) the main fraction consisting of weakly interacting (isolated chromophores) chromophores with the absorption spectrum maximum at approximately 270 nm; (b) pair chromophores of the first type with the absorption spectrum maxima at 260 and 290 nm (exciton splitting 4000 cm(-1)); and (c) pair chromophores of the second type with the absorption spectrum maxima at 250 and 280 nm (exciton splitting 4300 cm(-1)). The revealed aggregates have a relatively high photochemical activity in the photodimerization reaction in comparison with the isolated chromophores. They contribute little to the total absorption spectrum of solutions but make a great contribution to its changes at the initial stages of the UV irradiation of solutions.

[Seasonal change in the hygienic indices of the quality of fishes from the Amur River].

The paper is the first to present the results of a comprehensive assessment of the seasonal changes in the hygienic indices of the quality of newly caught fishes from the Amur River. Microbiological analysis of their flesh tissues and gills and physicochemical studies has been used as basic techniques for the determination of some classes of volatile substances (nitrocompounds, histamine, trimethylamine, aldehydes, alcohols, ketones, etc.). The consequences of the entry of saprophytic bacteria into the fish contaminated with many pollutants and the specific features of production of volatile products involved in the formation of "chemical" odors are discussed.

[Luminescence of thymine aqueous solutions at the room temperature]. / Liuminestsentsiia vodnykh rastvorov timina pri komnatnoi temperature.

The distinguishing features of luminescence of aqueous thymine solutions at room temperature (a broadening of luminescence spectra as compared with low-temperature spectra and differences between excitation and absorption spectra) are discussed. It is shown that these features are due to bimolecular photochemical reactions that lead to the formation of photoproducts (at the first stages, photoadducts) with a comparatively high luminescence ability.

[Non-flame atomic absorption method of the analysis of mercury-containing biological materials]. / Neplamennyi atomno-absorbtsionnyi metod v analize rtut'soderzhashchikh biomaterialov.

Julia-2 mercury analyzer is modified. Gasodynamic scheme of the device is altered: water vapors can no longer enter the cuvette, the circulation mode is realized. Equilibrium concentration of mercury vapors is thus attained. The analytical signal is well reproduced. Alteration of the reactor volume improves the sensitivity of testing larger samples.

[Spectral manifestations of conformation heterogeneity of a cytidine dinucleotide. A fraction with strong exciton base-base interaction]. / Spektral'nye proiavleniia konformatsionnoi geterogennosti v tsitidinovom dinukleotide. Obnaruzhenie fraktsii s sil'nym éksitonnym vzaimodeistviem mezhdu osnovaniiami.

The absorption, emission and excitation luminescence spectra of CpCp have been studied in comparison with the same of Cp at 77K in the glass mixture (ethyleneglycol: water, 1:1, v/v). It is shown, that the CpCp fluorescence is of dual nature: eximer and exciton. The exciton absorption spectrum with split band (3000 cm-1) has been calculated by means of the fluorescence exciton spectrum. It corresponds to the "conservative" part of the CD spectrum.

[Charge transfer complexes of nucleic acid purine bases with benzoquinone. Evidence that nucleic acid components are pi-donors]. / Kompleksy s perenosom zariada azotistykh osnovanii nukleinovykh kislot i ikh analogov s benzokhinonom. Dokazatel'stvo pi-donornogo kharaktera.

The absorption bands of the charge transfer complexes between nucleic acid, purine components and some of their derivatives (9CH3--Ade, Ado, dAdo, pA, App, Guo, Gpp, Gppp, Cof, Hyp) as electron donors and p-benzoquinone as the acceptor were obtained by the differential method in water solution at 293 K. These bands lie in the range 330--430 nm and have all characteristic properties of the charge transfer bands. All points of the relationships between the energy corresponding to the charge transfer band maximum (hvct) and the donor ionization potential (Id) for the nucleic acid components and their derivatives fall on the same straight line for the pi-donors (the aromatic molecules), known from literature data, which differ markedly from the same straight line for n-donors (the alifatic amines), obtained in this work. It shows that the investigated nucleic acid components and their derivatives are the pi-donors in the charge transfer complexes with p-benzoquinone.

[Spectral manifestations of different types of acriflavine binding to DNA in ultraviolet and visible region]. / Spektral'nye proiavleniia raznykh tipov sviazi akriflavina s DNK v ul'trafioletrovoi i vidimoi oblastiakh

Difference absorption spectra (complex-sum of the initial reagents) are obtained in the visible and longwave UV region for the system of actiflavine and DNA in a number of cases differing in initial and final degrees of DNA filling by the dye, in particular separately for two types of dye binding to DNA. For these binding types conventional absorption spectra are calculated. In the visible region for the first binding type ("strong" binding) red shift of the absorption band is observed; for the second type ("weak" binding) we observed splitting of the band, short wavelength component being highly prevailing, and hypochromism. In the UV region for both binding types the spectra changed in approximately similar way; a slight blue shift and a rather remarkable hypochromism are observed. It is shown that the dye brings the main contribution into the spectral changes in the UV region. If to take into account the spectral properties of molecular aggregates the data obtained are compatible with the intercalation model for "strong" binding and dye stacking on DNA for "weak" binding.