Marky L A, Macgregor R B
Department of Chemistry, New York University, New York 10003.
Biochemistry. 1990 May 22;29(20):4805-11. doi: 10.1021/bi00472a009.
We report differences in the interaction of two structurally similar phenanthroline intercalators, ethidium and propidium, with poly(dA).poly(dT) and poly[d(A-T)] as a function of ionic strength based on titration microcalorimetry, fluorescence titration, and hydrostatic pressure measurements. Both ethidium and propidium bind more strongly to poly[d(A-T)].poly[d(A-T)] than to poly(dA).poly(dT). Ethidium intercalation into the latter polymer displays titrations with positive cooperativity; this is not found with propidium. The enthalpy of intercalation (delta H degrees) is exothermic for both dyes with poly[d(A-T)].poly[d(A-T)]; however, the value of this parameter is nearly zero in the case of poly(dA).poly(dT). The molar volume change (delta V degrees) accompanying dye intercalation is negative under all conditions for poly[d(A-T)].poly[d(A-T)] whereas it is positive for poly(dA).poly(dT). The changes observed in delta V degrees correlate well with the entropy changes derived from the titration and calorimetric data for this reaction. The results, interpreted in terms of the relative hydration of these two polymers, are consistent with a higher extent of hydration of poly(dA).poly(dT) relative to poly[d(A-T)].poly[d(A-T)].
我们基于滴定微量热法、荧光滴定法和静水压力测量，报告了两种结构相似的菲咯啉嵌入剂（溴化乙锭和碘化丙啶）与聚（dA）·聚（dT）和聚[d（A - T）]的相互作用随离子强度的差异。溴化乙锭和碘化丙啶与聚[d（A - T）]·聚[d（A - T）]的结合都比与聚（dA）·聚（dT）的结合更强。溴化乙锭嵌入后一种聚合物时显示出具有正协同性的滴定；碘化丙啶则未发现这种情况。两种染料与聚[d（A - T）]·聚[d（A - T）]的嵌入焓（ΔH°）都是放热的；然而，在聚（dA）·聚（dT）的情况下，该参数的值几乎为零。对于聚[d（A - T）]·聚[d（A - T）]，在所有条件下，染料嵌入伴随的摩尔体积变化（ΔV°）都是负的，而对于聚（dA）·聚（dT）则是正的。观察到的ΔV°变化与该反应滴定和量热数据得出的熵变很好地相关。根据这两种聚合物的相对水合作用来解释这些结果，与聚（dA）·聚（dT）相对于聚[d（A - T）]·聚[d（A - T）]具有更高程度的水合作用是一致的。
