An evaluation of the charge transfer model for the chromophores of the retinal containing proteins rhod opsin and bacterio rhod opsin
Johnston, D.S.; Clark, A.D.; Kemp, C.M.; Chapman, D.
Biochimica et Biophysica Acta 679(3): 400-403
The chromophores of rhodopsin and bacteriorhodopsin apparently to result from an electrostatic interaction between the protonated Schiff base of retinal and amino acid side chains. It was proposed from ESR measurements on rhodopsin and model studies using retinal and tryptophan that the interaction is one of charge transfer and that the amino acid involved in tryptophan. Reexamination of this work does not support the existence of a charge-transfer complex. Additional similarities between the model system and bacteriorhodopsin were observed. Further studies in this area may yield information about the nature of the protein chromophores.