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ANALYZING THE RED‐SHIFT CHARACTERISTICS OF AZULENIC, NAPHTHYL, OTHER RING‐FUSED AND RETINYL PIGMENT ANALOGS OF BACTERIORHODOPSIN *
Author(s) -
Liu R. S. H.,
Krogh Erik,
Li XiaoYuan,
Mead Dennis,
Colmenares L. U.,
Thiel J. R.,
Ellis Jeannette,
Wong Darren,
Asato A. E.
Publication year - 1993
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.1751-1097.1993.tb04955.x
Subject(s) - bacteriorhodopsin , chromophore , protonation , chemistry , pigment , stereochemistry , crystallography , photochemistry , biochemistry , organic chemistry , ion , membrane
Prompted by the near infrared‐absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring‐fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (α RS ): perturbation of the basic chromophore (SB shift, ΔSB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red‐shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer‐simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red‐shifted bR and possible application to visual pigment analogs are discussed.