基于变温紫外分光光度法研究温度对DNA凝聚过程影响

摘要

荧光单分子实验结果表明温度能够促进DNA凝聚,随着温度升高,精胺(亚精胺)-DNA凝聚体系中DNA凝聚构象趋于更加紧致、有序.为探究温度对不同高价离子-DNA凝聚体系的影响,利用自行搭建的变温紫外分光光度计,通过系统研究荧光单分子实验中采用的精胺(亚精胺)-DNA凝聚体系及去离子水中DNA在260 nm处特征吸收值随温度变化情况,确定了DNA凝聚构象与其260 nm处特征吸收值之间的对应关系为:DNA凝聚构象越紧致、有序,其对应的260 nm处紫外吸收值越低.在此基础上,系统地研究了DNA凝聚实验中常用四种钴胺化合物-DNA凝聚体系随温度变化情况,结果表明三氯六胺合钴与精胺(亚精胺)类似,其对应的DNA凝聚体系在260 nm特征吸收值,随着温度升高而逐渐降低,即DNA凝聚构象趋于更加紧致、有序.而三(乙二胺)氯化钴、反式双(乙二胺)氯化钴、五胺氯化钴的情况却不同,与其对应的DNA凝聚体系在260 nm特征吸收值,随着温度升高,呈现先增加,再降低,然后再增加的规律.%Recent fluorescent single molecule experiment indicated that temperature can facilitate DNA condensation.In the spermine (spermidine)-DNA condensation system,DNA condensation conformation became more compact and orderly with increasing temperature.In order to detect the temperature effects in DNA condensation system further,a temperature-changed ultraviolet spectrum method is developed.By applying the method to the condensation system mentioned by recent fluorescent single molecule experiment and the DNA in DI water,a conclusion is derived from the absorption value at 260 um of a condensation system will be reduced,when the corresponding system is further condensed and become compact and orderly.Based on this conclusion,effects of temperature on DNA-cobalt amine compounds used in DNA condensation experiments are detected by using temperature-changed ultraviolet Spectrum method.The results indicate that Hexaammine cobalt(lⅢ) chloride is similar to spermine and spermidine,the UV absorption value at 260 nm of DNA reduces sharply with the temperature increasing,indicating that the DNA conformation tends to be more compact and orderly.However,for the condensation system wherein the DNA is condensed by trans (ethylenediamine) cobalt(Ⅲ) chloride,trans-dichlorobis (ethylenediamine) cobalt(Ⅲ) chloride and pentaamminechloro cobalt(Ⅲ) chloride,respectively,the UV absorption value at 260 um of the corresponding condensation.System does not change with temperature monotonously,taking an increased-reduced-increased manner.