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Molecular mechanical study of structural-energetical aspects of the complementary addressed modification of nucleic acids by reactive 4-[N-(2-chloroethyl)-N-methylamino]benzyl 3'- or 5'-phosphoroamido derivatives of oligonucleotides
Yu. N. Vorobjov
Institute of Bioorganic Chemistry, Siberian Division, Academy of Sciences of the USSR, Novosibirsk
Abstract: Calculations of probabilities of the complementary addressed modification of target NA by 3'- or 5'-reactive derivatives of oligonucleotides carrying a 4-[N-(2-chloroethyl)-N-methyl]aminobenzyl group attached to the 3'- or 5'-terminal phosphates through a phosphoroamide linkage have been made. It is shown that the structural basis of the high efficiency and positional specificity depending on the NA target base sequence is the extent of structural correspondence of the energetically optimal conformation of the active group in the complex to the mutual arrangement of the active group and nucleophilic site needed for the chemical reaction. The 3'-derivative has the highest dependence of efficiency and positional specificity of the alkylation on the target NA base sequence. The maximal positional specificity of the alkylation is found for the modification of the cytidine at the first position from the terminal complementary base pair at the 5'-end of the target NA. For the 5'-derivative, the alkylating ability was determined to depend on the insertion of additional methylene bridges into the standard phosphoroamide linker: two methylene groups provide for the maximal increase of the modification ability of the nucleophilic site of the target NA in the double-stranded part of the complex. The efficiency of alkylation of a target NA in a three component complex with oligonucleotide-effector also complementary to the target NA have been studied. It was found that formation of the three-component complex leads to an additional stabilization of the conformation needed for the reaction of the active group, in comparison with two-component complex, by means of the intercalation of the phenyl group of the reagent in the gap between the oligonucleotide derivative and the oligonucleotide effector.
Russian Journal of Bioorganic Chemistry 1991, 17 (2):197-210