[Hybridization analysis of nucleic acids using stained latex]. / Gibridizatsionnyi analiz nukleinovykh kislot s ispol'zovaniem okrashennykh lateksov.

Method of the latex hybridization analysis has been developed: after hybridization of NA-target with biotinylated probe visualization of hybrids was carried out using latex particles, containing fluorescent dye pyronin G and coated with streptavidin. Due to encapsulation of the fluorescent dye in polymer particles sensitivity of the analysis was increased by several orders of magnitude in comparison with methods, using fluorescently labelled probes. Possessing a number of advantages, the method yields to none of any other methods of NA hybridization analysis in sensitivity.

[Non-enzymatic DNA methylation by S-adenosylmethionine results in the formation of minor thymine residues and 5-methylcytosine from cytosine]. / Neénzimaticheskoe metilirovanie DNK pod deistviem S-adenozilmetionina s obrazovaniem iz tsitozina ostatkov minornogo timina i 5-metiltsitozina.

It was found that nonenzymatic DNA methylation proceeds in water solution in the presence of S-adenosylmethionine (AdoMet). The main reaction products are thymine and 5-methylcytosine residues. It was shown that labelled thymine residues are formed also upon DNA incubation in the presence of [methyl-14C]methionine as well as [methyl-14C]cobalamine. Only cytosine reacts with AdoMet resulting in thymine production. AdoMet may be a potential mutagen that induces GC----AT transitions during DNA replication in the cell.

DNA-like duplexes with repetitions. I. Properties of concatemer duplexes formed by d(T-G-C-A-C-A-T-G).

A new class of synthetic DNA duplexes containing repeating oligonucleotide sequences, double-helical concatemers, is characterized. The UV-absorption and circular dichroism of a concatemer formed in self-association of d(T-G-C-A-C-A-T-G) have been studied. The thermodynamical parameters of complex formation are the following: delta Ho1 = -9.2 +/- 0.3 kcal/mol, delta So1 = -27 +/- 1 e.u. The data obtained show that pseudopolymeric duplexes having structures that are similar to DNA-B-type helices are formed in solutions of d(T-G-C-A-C-A-T-G). Polymerization of 32P-d(pT-G-C-A-C-A-T-G) induced by water-soluble carbodiimide has been carried out under the conditions of concatemer stability. The yield of the dimer, a 16-member oligonucleotide, was 13%.