Journal of Photoscience
- 제9권2호
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- Pages.51-54
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- 2002
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- 1225-8555(pISSN)
Analysis of Cis- Trans Photoisomerization Mechanism of Rhodopsin Based on the Tertiary Structure of Rhodopsin
- Yamada, Atsushi (Department of Physics, Nagoya University) ;
- Yamato, Takahisa (Department of Physics, Nagoya University) ;
- Kakitani, Toshiaki (Department of Physics, Nagoya University) ;
- Yamamoto, Shigeyoshi (Faculty of Liberal Arts, Chukyo University)
- 발행 : 2002.08.01
초록
We propose a novel mechanism (Twist Sharing Mechanism) for the cis-trans photoisomerization of rhodopsin, based on the molecular dynamics (MD) simulation study. New things devised in our simulations are (1) the adoption of Mt. Fuji potentials in the excited state for twisting of the three bonds C9=C10, C11=C12 and C13=14 which are modeled using the detailed ab initio quantum chemical calculations and (2) to use the rhodopsin structure which was resolved recently by the X-ray crystallographic study. As a result, we found the followings: Due to the intramolecular steric hindrance between 20-methyl and 10-H in the retinal chromophore, the C12-C13 and C10-C11 bonds are considerably twisted counterclockwise in rhodopsin, allowing only counterclockwise rotation of the C11 =C12 in the excited state. The movement of 19-methyl in rhodopsin is blocked by the surrounding three amino acids, Thr 118, Met 207 and Tyr 268, prohibiting the rotation of C9=C10. As a result only all-trans form of the chromophore is obtainable as a photoproduct. At the 90
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