INTERACTION OF DERIVATIVES OF SHORT OLIGO NUCLEOTIDES WITH NUCLEIC-ACIDS - III - SOME FEATURES OF MODIFICATION OF TARGET DNA BY ALKYLATING OLIGONUCLEOTIDE DERIVATIVES IN TANDEM COMPLEXES

The influence of effecters [octanucleotides and their 3',5'-di-N-(2-hy droxyethyl)phenazinium derivatives] on the modification of a target DN A by alkylating oligonucleotide derivatives forming duplexes of differ ent stability with the target was studied. It is shown that, being in tandem complexes immediately adjacent to the reactive group of an olig onucleotide reagent possessing a high hybridization capacity, the effe ctor, on the one hand, enhances the stability of the reagent . target duplex, and on the other hand, changes the site-specificity of alkylat ion and decreases the efficiency of the the target modification at tem peratures that provide a high extent of the target association with th e reagent. Conversely, in the case of oligonucleotide reagents forming weak complexes with the target, effecters enhance both the stability of the target . reagent duplex and the extent of the target throughout the temperature range tested. The data indicate that the varying infl uence of effecters on the target . modification by reagents with diffe rent hybridization capacities is due to conformational features of the target reagent duplexed regions. Increasing the rigidity of the targe t reagent duplex reduces the efficiency of the target modification in tandem complexes.