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Valeria Balogh-Nair John D. Carriker Barry Honig Vinayak Kamat Michael G. Motto Koji Nakanishi Ranjan Sen Mordechai Sheves Maria Arnaboldi Tanis Kazuo Tsujimoto 《Photochemistry and photobiology》1981,33(4):483-488
Abstract— The difference (in cm−1 ) in absorption maxima between the protonated Schiff base of retinals and the pigment derived therefrom has been defined as the opsin shift. It represents the influence of the opsin binding site on the chromophore. The analysis of the opsin shifts of a series of dihydrobacteriorhodopsins has led to the external point-charge model, which in addition to a counter anion near the Schiff base ammonium, carries another negative charge in the vicinity of the β-ionone ring. This is in striking contrast to the external point-charge model proposed earlier for the bovine visual pigment. The absorption maxima of rhodopsins formed from bromo- and phenyl retinals support the two models. A retinal carrying a photoaffinity label has yielded a nonbleachable bacteriorhodopsin. 相似文献
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Furan-terminated cationic cyclizations allylic alcohols, enones, and N-acyl iminium ions as initiators have been explored as routes to highly functionalized spiro[4,5]decanes, spiro[5,5]undecanes, spiro[4,6]undecanes, and spiro[5,6]dodecanes. 相似文献
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Ratios for target Ar K-shell ionization associated with single and double electron capture, as well as the ratios corresponding to total capture and the projectile K x rays, were determined for 1.8- to 2.2-MeV/u F7 + ,8 + ,9+ projectiles. This work was performed at Western Michigan University with the tandem Van de Graaff accelerator. Coincidences between emitted K-shell X-rays (both target and projectile) and the corresponding charge-changed particles were observed. The F9+ Ar K X-ray coincidence ratios for double to single capture are found to well exceed unity over the limited energy range of the measurements. Possible explanations for this anomalous behavior are discussed. 相似文献
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The preparation and utilization of butenolide anion equivalents 5 and 6 in alkylation sequences is described. Treatment with CH3CO3H unmasks a latent butenolide moiety providing a general route to 3- and 4-alkyl 2(5H)-furanones. 相似文献