Unique Mechanisms of Excitation Energy Transfer, Electron Transfer and Photoisomerization in Biological Systems

Authors: Kakitani T.¹; Kawatsu T.¹; Kimura A.²; Yamada A.¹; Yamato T.¹; Yamamoto S.³

Source: Journal of Biological Physics, Volume 28, Number 3, 2002 , pp. 367-381(15)

Publisher: Springer

Abstract:

We discuss unique mechanisms typical in the elementary processes of biological functions. We focus on three topics. Excitation energy transfer in the light-harvesting antenna systems of photosynthetic bacteria is unique in its structure and the energy transfer mechanism. In the case of LH2 of Rhodopseudomonas acidophila, the B850 intra-ring energy transfer and the inter-ring energy transfer between B800 and B850 take place by the intermediate coupling mechanism of energy transfer. The excitonic coherent domain shows a wave-like movement along the ring, and this property is expected to play a significant role in the inter-ring energy transfer between LH2's. The electron transfer in biological systems is mostly long-range electron transfer that occurs by the electron tunneling through the protein media. There is a long-standing problem that which part of protein media is used for the electron tunneling root. As a result of our detailed analysis, we found that the global electron tunneling root is a little winded with a width of a few angstrom, reflecting the property of tertiary and secondary structures of the protein and it is affected by the thermal fluctuation of protein structure. Photoisomerization of rhodopsin is very unique: The cis-trans photoisomerization of rhodopsin occurs only around the C11 = C12 bond in the counterclockwise direction. Its molecular mechanism is resolved by our MD simulation study using the structure of rhodopsin which was recently obtained by the X-ray crystallographic analysis.

Keywords: electron tunneling root; excitation energy transfer; exciton; long-range electron transfer; photoisomerization; retinal chromophore

Language: English

Document Type: Research article

Affiliations: 1: Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464–8602, Japan 2: Graduate School of Human Informatics, Nagoya University, Nagoya 464-8602, Japan 3: Faculty of Liberal Arts, Chukyo University, 101-2 Yagoto-Honmachi, Showa-ku, Nagaya 466-8666, Japan

Publication date: 2002-01-01

• In this: publication
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• In this Subject: Biology ,  Physics (General)
• By this author: Kakitani T. ;  Kawatsu T. ;  Kimura A. ;  Yamada A. ;  Yamato T. ;  Yamamoto S.

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