时间分辨光谱技术研究亚甲基蓝与小牛胸腺DNA的相互作用

Interaction Between Methylene Blue and ctDNA by Time-resolved Spectroscopy

采用时间分辨光谱技术研究了亚甲基蓝(MB)与小牛胸腺DNA(ctDNA)在重水混合体系中MB敏化单态氧(1O2)动力学过程,并探讨了MB与DNA的相互作用方式.结果表明,低浓度ctDNA和高浓度ctDNA的单态氧磷光动力学曲线存在明显不同,这些差异被归结为MB与DNA之间结合方式和作用机制的不同.在低浓度ctDNA条件下,MB分子和ctDNA形成离子型结合物,MB的吸收带出现显著的减色效应,敏化1O2产量随ctDNA浓度的增加而急剧下降,但ctDNA与1O2未发生明显的相互作用;而在高浓度ctDNA时,MB分子与ctDNA之间的作用方式以嵌插式结合为主,激发态MB与ctDNA间的能量转移和介质的黏度效应改变了1O2的动力学特性,大大降低了光敏剂MB敏化1O2的产量,但1O2不为ctDNA所猝灭.以上结果表明,在MB和DNA的混合体系中,敏化单态氧损坏DNA的Ⅱ型反应不是主要的光动力疗法(PDT)作用机制.

The singlet oxygen（1O2） kinetics process of methylene blue（MB）-ctDNA mixed solutions in D2O was studied by time-resolved spectroscopy,which helped to further investigate the interaction of MB and DNA.The results showed that 1O2 phosphorescence kinetic curves of MB-ctDNA solutions at low concentrations of ctDNA and high concentrations of ctDNA had obvious differences,these differences were ascribed to the change of MB and DNA binding mode and the interaction mechanism.At low ctDNA concentration,ionic conjugate formed between MB molecules and ctDNA,significant hypochromic effect was observed in MB absorption band,and 1O2 production dropped sharply with ctDNA concentration increasing,but there were no obvious interaction between ctDNA and 1O2;at high ctDNA concentration,interaction mode between MB molecules and ctDNA changed to intercalative binding,energy transfer between the excited state MB molecules and ctDNA as well as the effect of medium viscosity changed property of the 1O2 dynamics,which greatly decreased the production of 1O2,but ctDNA did not quench the 1O2 apparently.These results indicated that type Ⅱ photosensitization of 1O2 damaging DNA was not the major mechanism of photodynamic therapy（PDT） action in MB-DNA solutions.