中性介质中中性红与双链DNA作用的光谱

通过分子吸收、荧光发射和共振光散射测定,表征了在水溶液介质中中性红(NR)与双 螺旋DNA的作用.在pH 7.63和离子强度低于0.01的水溶液介质中,随着NR与DNA的摩尔比(R)变 化,存在有两种结合方式.第一种结合方式发生在R > 2.22,此时获得共振光散射光谱增强信 号,表明NR在DNA分子表面发生聚集,集聚特性可使用RLS测定数据进行Scatchard分析;第二种 结合方式发生在R < 2.22,此时NR内嵌到DNA分子的双链碱基对之间,具有特征波长红移和分 子吸收增色效应,发生了从DNA到NR的分子能量转移,能观察到荧光增强.

Spectra of the Supramolecular Interaction of Neutral Red with Double-stranded DNA in a Neutral Medium

With the spectral measurements of molecular absorption, fluorescence, and resonance light scattering, the binding mode of neutral red (NR) with double stranded DNA has been characterized in a neutral aqueous medium. Depending on the molar ratio R of NR: DNA, it was found that the binding involves in two processes at pH 7.63 and ionic strength lower than 0.01. The first process occurs in R > 2.22, where enhanced resonance light scattering was found, indicating the aggregation of NR molecules on the molecular surface of double stranded DNA. Scatchard plot was used to discuss the aggregation features based on the measurements of RLS data. The second process occurs in R <2.22, characterized by bathochromic and hyperchromic molecular absorption of the interacting system, indicating the intercalative binding of NR into the base pairs of the double stranded DNA molecules. Energy transfer from DNA to NR molecules in the second interacting process occurs, resulting in strong enhancement of fluorescence, which proves NR can be used as a fluorescent probe as DNA structure.