Biomedical subjects
Publications and source records attributed to M A Chepyzheva.
A method for detection of 14C and 125I radioactivity in labeled samples with variable quenching using only liquid scintillation counter is described. Precision, sensitivity and reproduction of this method are comparable with those of the previously used ones, but this method is more suitable and adequate for computerisation.
Characteristics of dioxan-based scintillation system have been studied. A composition for scintillation cocktails ensuring an effective homogeneous count of radioactive water samples (0-8% V) at minimum expense of ethyl alcohol has been suggested.
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The effects of UV-light (253,7 nm) on the structure of DNP and its protein and nucleic components were studied. The formation of protein-DNA covalent bonds in DNP-200 A at low ionic strength was confirmed. Under certain irradiation conditions more than 80% of protein may be linked to the DNA; all histone fractions were linked to the same extent and at the same rates. The local denaturation of DNA in the region of photo-induced thymine-thymine dimers and other photoadducts dramatically changed the rate and specificity of the effects of staphylococcal nuclease, which directly affected the composition and size of the fragments formed. A possible application of UV-irradiated DNP for various structural investigations is discussed.
A comparative kinetic study has been made of tetranitromethane nitration of tyrosine residues in deoxyribonucleoprotein preparation (DNP) treated with EDTA and/or UV light at lambda=253.7 nm, as well as obtained by enzymatic digestion of nucleosomes. UV-light-induced protein-DNA linkages stabilize the structure of the preparation, whereas the action of chelate agents causes DNP-200 angstrom leads to DNP-100 angstrom transfer. Comparison of kinetic data and the results of the amino acid analysis of individual fractions of nitrated histones allowed to conclude that the differences observed between the degree and the rate of nitration are due to internucleosomic interactions which form the supernucleosomic structure of DNP.
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For studying distribution of drugs and their metabolites in organs of experimental animals by the method of radioactive indicators with recording of measurements of the compounds under study by means of a liquid-scintillaton counter, there is described a simple and available method of complete solubilization of a biological tissue. The method makes it possible to dissolve up to 10 g of a biological tissue without preliminary lyophilization.
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