Biomaterial Database

Visual-pigment spectra: implications of the protonation of the retinal Schiff base. 1976

B Honig, and A D Greenberg, and U Dinur, and T G Ebrey

Various models of visual-pigment spectra are critically discussed in terms of the spectral properties of protonated Schiff bases and the common structural features of most proteins. The opsin apoprotein is capable of regulating visual pigment wavelengths in ways that are difficult or impossible to reproduce in model systems. Theories based on solvent effects of the spectra of protonated Schiff bases may be misleading. Careful parameterization using known polyene spectra allows accurate calculation of the spectral properties of protonated Schiff bases. It is shown that an isolated protonated Schiff base of retinal should absorb near 600 nm and that blue-shifted spectra seen in solution arise from associated counterions or solvent molecules. We conclude that the most plausible specific model of chromophore-protein interactions is one in which the protonated Schiff base is closely associated with its counterion and where additional negatively charged or polar groups are positioned by the protein in the vicinity of the ring half of the chromophore. Pigment absorption maxima, bandwidths, and the A2-A1 pigment absorption differences arise naturally from these simple models of pigment spectra.

UI	MeSH Term	Description	Entries
D008433	Mathematics	The deductive study of shape, quantity, and dependence. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)	Mathematic
D008968	Molecular Conformation	The characteristic three-dimensional shape of a molecule.	Molecular Configuration,3D Molecular Structure,Configuration, Molecular,Molecular Structure, Three Dimensional,Three Dimensional Molecular Structure,3D Molecular Structures,Configurations, Molecular,Conformation, Molecular,Conformations, Molecular,Molecular Configurations,Molecular Conformations,Molecular Structure, 3D,Molecular Structures, 3D,Structure, 3D Molecular,Structures, 3D Molecular
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012168	Retinal Pigments	Photosensitive protein complexes of varied light absorption properties which are expressed in the PHOTORECEPTOR CELLS. They are OPSINS conjugated with VITAMIN A-based chromophores. Chromophores capture photons of light, leading to the activation of opsins and a biochemical cascade that ultimately excites the photoreceptor cells.	Retinal Photoreceptor Pigment,Retinal Pigment,Visual Pigment,Visual Pigments,Retinal Photoreceptor Pigments,Photoreceptor Pigment, Retinal,Photoreceptor Pigments, Retinal,Pigment, Retinal,Pigment, Retinal Photoreceptor,Pigment, Visual,Pigments, Retinal,Pigments, Retinal Photoreceptor,Pigments, Visual
D012545	Schiff Bases	Condensation products of aromatic amines and aldehydes forming azomethines substituted on the N atom, containing the general formula R-N:CHR. (From Grant & Hackh's Chemical Dictionary, 5th ed)	Schiff Base,Base, Schiff,Bases, Schiff
D013045	Species Specificity	The restriction of a characteristic behavior, anatomical structure or physical system, such as immune response; metabolic response, or gene or gene variant to the members of one species. It refers to that property which differentiates one species from another but it is also used for phylogenetic levels higher or lower than the species.	Species Specificities,Specificities, Species,Specificity, Species
D013053	Spectrophotometry	The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.