[New method of determining parameters of oligonucleotide complex formation with nucleic acids according to the results of alkylation in complexes. Comparison with the method of equilibrium dialysis].

Binding constants of oligonucleotides with nucleic acids can be determined using data of nucleic acids alkylation with 2',3'-O-4-(N-2-chloroethyl-N-methylamino)benzylidene oligonucleotides. The latter bind to complementary sequences of nucleic acids, the binding constants of which are close to that of oligonucleotides. The extent of alkylation allows to determinate the equilibrium concentration of the binding with small corrections by an equation given, and hence to estimate the binding constants by standard modes. The binding constants of oligoadenylate and oligocytydilate derivatives with 23S RNA and rRNA have been determined at 0 degrees and 20 degrees by the method suggested and by the method of equilibrium dialysis. The binding constants are consistent of the magnitudes, as well as of the plots of the binding constants versus the oligomer and RNA concentrations and versus the oligomer length. The data obtained indicate that alkylation within the complexes of tri-hexamers with rRNA proceeds under the condition of an established equilibrium. Limits of the method suggested are evaluated.