Carbon-13 magic-angle spinning NMR studies of bathorhodopsin, the primary photoproduct of rhodopsin-猫眼课题宝

红视紫红质（视紫红质的主要光产物）的碳 13 魔角旋转 NMR 研究

DOI：

发表时间：

1991

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作者：

Steven O. Smith;Jacques Courtin;H. de Groot;R. Gebhard;J. Lugtenburg

Magic-angle spinning NMR spectra have been obtained of the bathorhodopsin photointermediate trapped at low temperature (<130 K) by using isorhodopsin samples regenerated with retinal specifically {sup 13}C-labeled at positions 8, 10, 11, 12, 13, 14, and 15. Comparison of the chemical shifts of the bathorhodpsin resonances with those of an all-trans-retinal protonated Schiff base (PSB) chloride salt show the largest difference (6.2 ppm) at position 13 of the protein-bound retinal. Small differences in chemical shift between bathorhodopsin and the all-trans PSB model compound are also observed at positions 10, 11, and 12. The effects are almost equal in magnitude to those previously observed in rhodopsin and isorhodopsin. Consequently, the energy stored in the primary photoproduct bathorhodopsin does not give rise to any substantial change in the average electron density at the labeled positions. The data indicate that the electron and structural properties of the protein environment are similar to those in rhodopsin and isorhodopsin. In particular, a previously proposed perturbation near position 13 of the retinal appears not to change its position significantly with respect to the chromophore upon isomerization. The data effectively exclude charge separation between the chromophore and a protein residue as the main mechanism for energy storagemore » in the primary photoproduct and argue that the light energy is stored in the form of distortions of the bathorhodopsin chromophore.« less