TD-DFT calculations of the potential energy curves for the trans-cis photo-isomerization of protonated Schiff base of retinal |
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Authors: | Tachikawa Hiroto Iyama Tetsuji |
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Affiliation: | Division of Molecular Chemistry, Graduate School of Engineering, Hokkaido University, Kita-ku, Sapporo 060-8628, Japan. hiroto@eng.hokudai.ac.jp |
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Abstract: | One-dimensional potential energy curves for the isomerization of protonated Schiff base of retinal (PSBR) in bacteriorhodopsin (bR), i.e., isomerization from all-trans- to 13-cis-forms, have been calculated by means of time-dependent density functional theory (TD-DFT) calculations, in order to elucidate the mechanism of initial step in photo-absorption. The transition state of the isomerization in the first excited state is located at theta(13-14)=58 degrees , where theta(13-14) means twist angle around the C(13)=C(14) double bond of PSBR The potential barrier is formed by the avoided crossing between S(1) (B(u)-like) and S(2) (A(g)-like) states. The mechanism of the isomerization was discussed on the basis of theoretical results. |
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