EFFECTS OF PRESSURE ON THE DNA MINOR-GROOVE BINDING OF HOECHST-33258

We investigated the pressure perturbations of DNA minor groove binding of the antibiotic drug Hoechst 33258 -(4-methyl-1-piperazinyl)-2,5'-b i-1H-benzimidazole trihydrochlolride) on fluorescent titrations and on restriction endonuclease protection assays. Significantly, pressure e levations were found to disturb the binding of Hoechst 33258 with poly (dA).poly(dT) and poly[d(A-T)].poly[d(A-T)] in opposite directions, wh ich suggested different volume changes (sign and size) in their comple xation reactions. The ability of Hoechst 33258 to provide the restrict ion endonuclease protection for plasmid DNA was notably enhanced by th e application of pressure, implying that there is a large volume contr action following the EcoRI site-drug interaction. These data were expl ained by DNA hydration and its effects on the ligand complexation that is sequence dependent.