光谱法研究Cu2+与肌红蛋白的相互作用

用紫外吸收光谱、荧光光谱、同步荧光光谱及圆二色(CD)谱研究了Cu2+与肌红蛋白(Mb)的相互作用. 结果发现, Cu2+使Mb的紫外吸收增强, 峰位蓝移, 说明Cu2+与Mb发生了较强的相互作用; Mb的特征荧光峰猝灭, 且随着温度升高猝灭常数Ksv降低, 表明Cu2+对Mb的荧光猝灭机制属于静态猝灭; 计算了不同温度下的结合常数和结合位点数; 由van′t Hoff方程计算出ΔH和ΔS分别为-11.60 kJ/mol和33.77 J·(mol·K)-1, 得出二者之间的作用力主要为静电力; 并依据Förster非辐射能量转移理论确定了给体-受体间的结合距离r=2.56 nm. 同步荧光光谱表明, Cu2+对Mb的构象产生影响, 使色氨酸残基的疏水性下降. CD光谱测得加入Cu2+后, 二级结构发生改变, 使α-螺旋含量降低.

Spectroscopic Studies on the Interaction of Cu2+ with Myoglobin

The interaction of Cu2+ with Myoglobin(Mb) was investigated by UV-Vis absorption spectra, fluorescence spectra, synchronous fluorescence spectra and circular dichroism(CD) spectra. It is shown that Cu2+ enhanced the intensity of UV absorption peak of Mb, accompanied with blue shift. The fluorescence spectrum shows that Mb fluorescence at 323 nm was quenched regularly with the addition of Cu2+. The quenching belongs to the static fluorescence quenching. The binding constants and the numbers of the binding sites at different temperatures were calculated. The thermodynamic parameters were calculated(ΔH＝-11.60 kJ/mol, ΔS＝33.77 J·mol-1·K-1) according to van′t Hoff equation, which indicate that the static interaction played major roles in the binding process. The binding distance r between Cu2+ and Mb was obtained(2.56 nm) on the basis of Förster theory of non-radiation energy transfer. The effect of Cu2+ on the conformation of Mb was further analyzed by synchronous fluorescence spectra and circular dichroism. The results indicate that Cu2+ had a strong impact on Mb conformation with the change of the microcircumstance of aromatic amino residues and decreases of α-helical content of the protein.