以溴化乙锭(EB)为荧光探针,利用紫外-可见光谱法和荧光分光光度法等手段研究了L-半胱氨酸二肽(Cys-Cys)与DNA的相互作用,并推测了其相互作用机理和作用模式。 结果表明,随着二肽浓度的增加,DNA-Cys-Cys体系的紫外光谱先呈减色效应,继续增大其浓度时又呈增色效应;盐效应实验表明此相互作用容易受环境中离子强度的影响;随着二肽浓度的增加,EB-DNA复合体系的荧光猝灭,Stern-Volmer方程说明此过程为静态猝灭, 通过Lineweaver-Burk方程计算得到两者作用的结合常数为1.640×104 L·mol-1。 综合以上结果可知,Cys-Cys与DNA的作用方式主要为静电结合。 这一实验结果为进一步在分子水平上研究寡肽类小分子与DNA的作用提供一定的理论依据。

In the present paper the interaction mechanism and mode of biologically active cysteine dipeptide (Cys-Cys) with DNA was studied by UV-Vis spectrophotometry and fluorescence spectroscopy using ethidium bromide as a fluorescence probe. The results showed that in the buffer solution of Tris-HCl (pH 7.20),at low concentration of Cys-Cys,the ultraviolet spectrum of DNA-Cys-Cys system produced hypochromic effect with increasing the concentration of Cys-Cys. When the concentration of Cys-Cys increased to some high extent,the ultraviolet spectrum of DNA-Cys-Cys system produced hyperchromic effect. Salt-effect experiment showed that the interaction is liable to be affected by the ionic strengths,suggesting the existence of electrostatic binding between Cys-Cys and DNA. The fluorescence of EB-DNA had quenching effect with increasing the concentration of Cys-Cys,and the Stern-Volmer equation indicated that the quenching process was a static one. According to the Lineweaver-Burk equation the binding constant was determined to be 1.640×104 L·mol-1. From the above results it can be concluded that the interaction mode of Cys-Cys with DNA was mainly electrostatic binding. These findings could contribute to further investigation on the mechanism of oligopeptides interaction with DNA.