title: Analysis of the factors that influence the C=N stretching frequency of polyene Schiff bases. Implications for bacteriorhodopsin and rhodopsin.
abstract: In this study quantum mechanical calculations of force constants and normal mode analysis are used to elucidate the factors that influence the C=C and C=N stretching frequencies in polyenes and in protonated Schiff bases. The C=N stretching frequency is found to depend on both the C=N stretching force constant and the C=N-H bending force constant. Due to the contributions of these two modes, the C=N stretching frequency is particularly sensitive to the magnitude of the Schiff base counterion interactions and to the hydrogen bonding environment of the Schiff base nitrogen. Models for chromophore-protein interactions in the retinal binding site and for the photochemical transformations of bacteriorhodopsin and rhodopsin are evaluated in light of these results.
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032.
authors.forename: H S
authors.initials: HS
authors.lastname: Gilson
authors.forename: B H
authors.initials: BH
authors.lastname: Honig
authors.forename: A
authors.initials: A
authors.lastname: Croteau
authors.forename: G
authors.initials: G
authors.lastname: Zarrilli
authors.forename: K
authors.initials: K
authors.lastname: Nakanishi
mesh_terms: D001436:Bacteriorhodopsins; D001665:Binding Sites; D006860:Hydrogen Bonding; D011485:Protein Binding; D011487:Protein Conformation; D012168:Retinal Pigments; D012172:Retinaldehyde; D012243:Rhodopsin; D012545:Schiff Bases; D013059:Spectrum Analysis, Raman
chemical_list: D012168:Retinal Pigments; D012545:Schiff Bases; D001436:Bacteriorhodopsins; D012243:Rhodopsin; D012172:Retinaldehyde