Unique Mechanisms of Excitation Energy Transfer, Electron Transfer and Photoisomerization in Biological Systems
Unique Mechanisms of Excitation Energy Transfer, Electron Transfer and Photoisomerization in Biological Systems
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DOI：
10.1023/a:1020356404203
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发表时间：
2002-09
影响因子：
1.8
通讯作者：
T. Kakitani;T. Kawatsu;A. Kimura;A. Yamada;T. Yamato;S. Yamamoto
中科院分区：
文献类型：
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作者：
T. Kakitani;T. Kawatsu;A. Kimura;A. Yamada;T. Yamato;S. Yamamoto
我们讨论了在生物功能的基本过程中典型的独特机制。我们关注三个主题。光合作用细菌捕光天线系统中的激发能量传递在其结构和能量传递机制上是独一无二的。在嗜酸红假单胞菌LH2的情况下，B850环内能量转移和B800与B850之间的环间能量转移是通过能量转移的中间耦合机制进行的。激子相干域表现出沿环的波状运动，这一性质有望在LH2‘S之间的环间能量转移中发挥重要作用。生物系统中的电子转移主要是电子通过蛋白质介质隧穿发生的远程电子转移。一个长期存在的问题是，蛋白质的哪一部分被用来作为电子隧道根。通过详细的分析，我们发现全局电子隧道根部略有弯曲，宽度为几埃，反映了蛋白质的三级结构和二级结构的性质，并受到蛋白质结构热涨落的影响。视紫红质的光致异构化是非常独特的：视紫红质的顺反光异构化只发生在逆时针方向的C11=C12键附近。通过我们最近用X射线晶体分析得到的视紫红质结构的分子动力学模拟研究，解决了它的分子机制。
We discuss unique mechanisms typical in the elementary processes ofbiological functions. We focus on three topics. Excitation energytransfer in the light-harvesting antenna systems of photosyntheticbacteria is unique in its structure and the energy transfer mechanism. Inthe case of LH2 ofRhodopseudomonas acidophila, the B850 intra-ringenergy transfer and the inter-ring energy transfer between B800 and B850take place by the intermediate coupling mechanism of energy transfer. Theexcitonic coherent domain shows a wave-like movement along the ring, andthis property is expected to play a significant role in the inter-ringenergy transfer between LH2's. The electron transfer in biological systemsis mostly long-range electron transfer that occurs by the electrontunneling through the protein media. There is a long-standing problem thatwhich part of protein media is used for the electron tunneling root. As aresult of our detailed analysis, we found that the global electron tunnelingroot is a little winded with a width of a few angstrom, reflecting theproperty of tertiary and secondary structures of the protein and it isaffected by the thermal fluctuation of protein structure. Photoisomerizationof rhodopsin is very unique: Thecis-transphotoisomerization ofrhodopsin occurs only around the C11 = C12 bond in the counterclockwisedirection. Its molecular mechanism is resolved by our MD simulation studyusing the structure of rhodopsin which was recently obtained by the X-raycrystallographic analysis.