Department of Chemistry, Faculty of Mathematics and Natural Sciences, Gadjah Mada University, Sekip Utara, P.O. Box Bls. 21, Yogyakarta 55281, Indonesia.
Spectrochim Acta A Mol Biomol Spectrosc. 2010 Oct 1;77(2):528-34. doi: 10.1016/j.saa.2010.06.032. Epub 2010 Jun 26.
The ct-DNA binding properties of methylene blue (MB) including binding constant, thermodynamic parameter and thermal denaturation (T(m)) have been systematically studied by spectrophotometric method. The binding of MB to ct-DNA is quite strong as indicated by remarkable hypochromicity, red shift and equilibrium binding constant (K(b)). Van't Hoff plot of 1/T versus lnK(b) suggests that the MB dye binds exothermically to ct-DNA which is characterized by large negative enthalpy and entropy changes. According to polyelectrolyte theory, the charge release (Z) when ct-DNA interacts with MB is +1.09 which corresponds very well to the one positive charge carried by the MB dye. The K(b) at a low concentration of salt is dominated by electrostatic interaction (90%) while that at a high concentration of salt is mostly controlled by non-electrostatic process (85%). However, the stabilization of the DNA binding event in both cases is governed by non-electrostatic process. A moderate stabilization of double helix ct-DNA occurs when the MB dye binds to ct-DNA as indicated by the increase in T(m) of ct-DNA of about 5.5 degrees C in the presence of MB. This suggests that MB dye possibly binds to ct-DNA via electrostatic and intercalation modes.
我们系统地研究了亚甲蓝（MB）与 ct-DNA 的 ct-DNA 结合性质，包括结合常数、热力学参数和热变性（T(m)）。分光光度法表明，MB 与 ct-DNA 的结合非常强，表现为明显的减色效应、红移和平衡结合常数（K(b)）。Van't Hoff 图 1/T 与 lnK(b)的关系表明，MB 染料与 ct-DNA 结合是放热的，其特点是焓和熵的变化均为负值。根据聚电解质理论，ct-DNA 与 MB 相互作用时释放的电荷（Z）为+1.09，这与 MB 染料所携带的一个正电荷非常吻合。低盐浓度下的 K(b)主要由静电相互作用（90%）控制，而高盐浓度下的 K(b)主要由非静电过程（85%）控制。然而，两种情况下 DNA 结合事件的稳定均由非静电过程控制。当 MB 染料与 ct-DNA 结合时，ct-DNA 的 T(m)大约增加了 5.5 摄氏度，这表明 ct-DNA 的双螺旋结构发生了适度的稳定。这表明 MB 染料可能通过静电和嵌入模式与 ct-DNA 结合。
