[Effectiveness of the modification of a single-stranded DNA fragment by alkylating derivatives of oligonucleotides]

Modification of a single-stranded DNA fragment 303 nucleotides long with addressed reagents d(pTGACCCTCTTCCC) A greater than CHRCl (I), d(pACCCTCTTCCC) A greater than CHRCl (II), d(CCTCTTCCC) A greater than CHRCl (III) and d(TCTTCCC) A greater than CHRCl (IV) complementary to the sequence 261-274 has been studied. It was shown that not only G258 residue, located near to the above sequence, but also G179 residue is modified. The latter can be explained by the vicinity of G179 and the alkylating group in the three-dimensional structure of the complex. Some modification of fragment 19-24 was observed due to non-complementary binding of the reagent. Association constants of the reagents (I)-(IV) with 261-274 sequence of the fragment were calculated using the dependence of the modification extent of G258 and G179 on the reagent concentration. The constants at 25 and 35 degrees C were found to be 260 and 31 (I), 0,5 and 2 (II), 0,46 and 0,13 (III), 0,0020 and 0,0023 (IV) microM-1.