Qu X, Chaires J B
Department of Biochemistry, University of Mississippi Medical Center, 2500 North State Street, Jackson, Mississippi 39216-4505, USA.
J Am Chem Soc. 2001 Jan 10;123(1):1-7. doi: 10.1021/ja002793v.
The hydration changes that accompany the DNA binding of five intercalators (ethidium, propidium, proflavine, daunomycin, and 7-aminoactinomycin D) were measured by the osmotic stress method with use of the osmolytes betaine, sucrose, and triethylene glycol. Water uptake was found to accompany complex formation for all intercalators except ethidium. The difference in the number of bound water molecules between the complex and the free reactants (Deltan(w)) was different for each intercalator. The values found for Deltan(w) were the following: propidium, +6; daunomycin, +18; proflavine, +30; and 7-aminoactinomycin D, +32. For ethidium binding to DNA a value of Deltan(w) = +0.25(+/-0.3) was found, indicating that within experimental error no water was released or taken up upon complex formation. Intercalation association constants measured in D2O were found to increase relative to values measured in H2O for all compounds except ethidium. A positive correlation between the ratio of binding constants (K(D2O)/K(H2O)) and Deltan(w) was found. These combined studies identify water as an important thermodynamic participant in the formation of certain intercalation complexes.
采用渗透压法，使用渗透压调节剂甜菜碱、蔗糖和三甘醇，测定了五种嵌入剂（溴化乙锭、碘化丙啶、硫酸原黄素、柔红霉素和7-氨基放线菌素D）与DNA结合时伴随的水合变化。结果发现，除溴化乙锭外，所有嵌入剂在形成复合物时都会吸水。每种嵌入剂形成复合物和游离反应物之间结合水分子数量的差异（Δn(w)）各不相同。所得到的Δn(w)值如下：碘化丙啶为+6；柔红霉素为+18；硫酸原黄素为+30；7-氨基放线菌素D为+32。对于溴化乙锭与DNA的结合，发现Δn(w)值为+0.25(±0.3)，这表明在实验误差范围内，形成复合物时既没有释放也没有吸收水。结果发现，除溴化乙锭外，所有化合物在D2O中测得的嵌入缔合常数相对于在H2O中测得的值都有所增加。发现结合常数之比（K(D2O)/K(H2O)）与Δn(w)之间存在正相关。这些综合研究表明，水是某些嵌入复合物形成过程中重要的热力学参与者。
