Abstract: A series of modified retinals bearing nonconjugated positive charges along the polyene were synthesized. It was found that nonconjugated charges shifted the absorption maxima of retinal chromophore as well as protonated retinal Schiff bases. The magnitude of shift observed in bacteriorhodopsin (bR), 5170 cm-', could be found in our models by the additivity of two factors:(1) interaction through space with a positive charge located in the ...
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