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ABSORPTION OF METHYLBACTERIOPHEOPHORBIDE a SINGLE CRYSTALS: SPECTRAL SHIFTS DUE TO π‐π INTERACTIONS
Author(s) -
Hanson Louise Karle,
Hofrichter James
Publication year - 1985
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1985.tb03481.x
Subject(s) - bacteriochlorophyll , chromophore , chemistry , spectral line , absorption (acoustics) , crystal (programming language) , absorption spectroscopy , absorption band , hydrogen bond , single crystal , photochemistry , crystallography , analytical chemistry (journal) , photosynthesis , molecule , optics , physics , organic chemistry , astronomy , computer science , biochemistry , programming language
— Polarized absorption spectra were obtained for a single crystal of methylbacteriophorbide a (MeBPhide a). The Q y band is red‐shifted ? 1660 cm ‐1 (? 110 nm) relative to MeBPhide a in a CH 2 Cl 2 /benzene solution. This is equivalent to the largest red shifts observed for in vivo bacteriochlorophyll a. The Soret band exhibits a smaller red shift and a significant reduction in intensity, and the Q x band is not observed. The crystal spectra are qualitatively similar to spectra reported for several other aggregated (bacterio)chlorophyll and bacteriopheophytin systems. Since crystalline MeBPhide a contains no Mg, water or hydrogen bonding (Barkigia etal. , 1981), these results demonstrate that the spectral changes associated with the aggregation of photosynthetic chromophores can arise solely from IT‐IT interactions between macrocycles.