DNA PHOTOMODIFICATION WITH A PERFLUOROARY LAZIDO OLIGONUCLEOTIDE DERIVATIVE

The kinetics of photomodification of oligodeoxyribonucleotide pd(GTGTG A) with a derivative of the complementary oligodeoxyribonucleotide pd( CACACA) bearing a 3-(n-azidotetrafluorobenzoylamino)propylamine residu e (ArN3) at the terminal phosphate group was studied at 20 degrees C. It was found that the target's G(3) residue is preferentially modified . Along with the transformation of the arylazide moiety, degradation o f the oligonucleotide fragment of the reagent occurred with a partial loss of affinity. With the use of the reagent labeled at the 5'-end, s ites of photomodification were found. From the dependence of the modif ication level on the reagent concentration at the initial time of irra diation, the association constant (K-x = (1.40 +/- 0.24) x 10(5) M-1) was determined. From the dependence of the modification level on the c oncentration of the pre-irradiated reagent, the constant of the transf ormed reagent-target association in solution (K-r= (2.49 +/- 0.30) x 1 0(4) M-1) was determined. From the time-dependence of the modification level [PZ]/p(0), the rate constant for the limiting step of photomodi fication (k(0) = (5.31 +/- 0.28) x 10(-4) s(-1)) and the modification efficiency of the target in the complex with the reagent (gamma = 1) w ere found.