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THE EFFECT OF PERIPHERAL SUBSTITUTION ON THE BATHOCHROMIC SHIFT OF THE Q y TRANSITION OF BACTERIOCHLOROPHYLL DIMERS; in vitro MODELS OF THE PROTEIN EFFECT ON THE SPECTRUM OF PIGMENT CENTERS IN THE LIGHT‐HARVESTING COMPLEXES *
Author(s) -
RosenbachBELKIN V.,
Scherz A.,
MlCHALSKI T. J.,
Schiffer M.,
Norris J.
Publication year - 1994
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.1751-1097.1994.tb02987.x
Subject(s) - bathochromic shift , chemistry , bacteriochlorophyll , crystallography , circular dichroism , photochemistry , stereochemistry , hydrogen bond , pigment , fluorescence , molecule , organic chemistry , physics , quantum mechanics
— The effect of chemical modifications in the side groups of the isocyclic ring V on the formation, optical absorption and circular dichroism of bacteriochlorophyll (Bchl) dimers was examined in a mixture of formamide and water containing TritonX–100 and variable amounts of pyridine. Substitution of the carbomethoxy group in the C13 2 position with a hydrogen atom, had no effect on the dimerization constant but increased the shift of the Q y transition by 1000 cm ‐1 with respect to the native Bchl. Substitution of the C13 hydrogen atom with OH decreased the shift of the Q y transition by 400 cm ‐1 . The similarity between the spectra of the modified Bchl dimers and Bchl dimers in vivo indicates that protein binding to the side groups at Bchl dimers may profoundly affect the energy of their Q y transition but have minor effects on the Q y transitions of the monomelic Bchl.