Thermochromatium tepidum外周捕光天线蛋白LH2在脂质体及表面活性剂胶束中的光谱性质

采用动态光散射、透射电子显微镜、紫外-可见吸收光谱和拉曼光谱对比研究了处于表面活性剂胶束和脂质体磷脂双分子层中的Thermochromatium(Tch.)tepidum LH2的光谱响应.结果表明,与在表面活性剂胶束中相比,双分子层脂膜中LH2的Spirilloxanthin(一种含有13个共轭双键的类胡萝卜素)构象有明显差异;表面活性剂及磷脂分子端基的荷电状态对B850-Qy吸收谱有显著影响;Ca2+结合导致B850 Qy吸收谱带红移和增色,而H+结合则使该吸收谱带蓝移和减色.对LH2脱辅基蛋白氨基酸序列的分析结果表明,Ca2+和H+的结合位点可能位于α脱辅基蛋白的C-端一侧.B850 Qy吸收谱带对Ca2+和H+的响应特性可能与Tch.tepidum适应其生存环境的能力有关.

Spectroscopic Properties of LH2 from Thermochromatium tepidum in Liposome and Detergent Micelles

By the use of dynamic light scattering ( DLS ) , transmission electron microscopy ( TEM ) , UV-Vis and resonance Raman spectroscopy, the properties of LH2 from Thermochromatium( Tch. ) tepidum in two de-tergent micelles and in liposome were studied, respectively. The results show that in LH2-liposome the confor-mation of spirilloxanthin, an incorporated longer chain carotenoid, is obviously different from that in detergent micelles . The charge state of the terminal groups of detergents or lipids is the key factor affecting the B850 ab-sorption. Generally, the calcium ions cause red-shift of the B850 absorption and hyperchromicity, while the proton has the opposite effect. Based on the amino acid sequence analysis, several amino acid residues on the C-terminus of α apo-protein were proposed to constitute the potential binding site for the calcium ion and pro-ton. Such Ca2+-and H+-regulated changes of B850 absorption might be an adaptive mechanism to the living environment for this species.