Vision visual pigments

Partridge, J. De Grip, W. (1991) A new template for rhodopsin (vitamin A, based) visual pigments Vision Renvoi. 31, pp 619-630... 

Rhodopsin is a seven ot-helix trans-membrane protein and visual pigment of the vertebrate rod photoreceptor cells that mediate dim light vision. In this photoreceptor, retinal is the chromophore bound by opsin protein, covalently linked to Lys296 by a Schiff base linkage. Kpega et al.64 have studied NMR spectra of Schiff bases being derivatives of all-frans retinal and amino-p-cyclodextrins as a model of rhodopsin, where p-cyclodextrin plays a role of a binding pocket. On the basis of analysis of the chemical shift differences for the model compound in the presence and in the absence of adamantane carboxylate, it has been shown that the derivative of 3-amino-p-cyclodextrin forms dimer in water and retinoid is inserted into p-cyclodextrin cavity [31]. 

A deficiency of vitamin A leads to vision defects, including a visual impairment at low light levels, termed night blindness. For the processes of vision, retinol needs to be converted first by oxidation into the aldehyde retinal, and then by enzymic isomerization to cw-retinal. c -Retinal is then bound to the protein opsin in the retina via an imine linkage (see Section 7.7.1) to give the red visual pigment rhodopsin. 

Photochemical cis-trans isomerization in a conjugated polyene system is thought to be the crucial primary process in vision. The visual pigment (rhodopsin) is derived from 11 -crs-retinal by reaction of the aldehyde group with an amino substituent in a protein (opsin). There is considerable distortion in the geometry of this chromophoric group anyway, because of the spatial requirements of the protein... 

Stavenga, D. Smits, R. Hoenders, B. (1993) Simple exponential functions describing the absorbance bands of visual pigment spectra Vision Res vol. 33, no. 8, pp 1011-1017... 

Figure 5.5.10-1 The calculated absorption spectra of the Rhodonines, the visual pigments of animal vision, when configured as found in the Outer Segments of the human photoreceptor cells. The parameters of these spectra are those of TABLE 5.5.10-1.

Hawryshyn, C. Harosi, F. (1994) Spectral characteristics of visual pigments in rainbow trout (Oncorhynchus mykiss), Vision Res. vol. 34, no. 11, pp 1385-1392... 

Nathans, J. (1987) Molecular biology of visual pigments Ann Rev Neurosci vol. 10, pp 163-194 191Nathans, J. Piantinida, T. Eddy, R. Shows, T. Hogness, D. (1986) Molecular genetics of inherited variation in human color vision Science, vol. 232, pp 203-210... 

Figure 32.26. Cone-Pigment Absorption Spectra. The absorption spectra of the cone visual pigment responsible for color vision.

J. Nathans. 1994. In the eye of the beholder Visual pigments and inherited variation in human vision Cell 78 357-360. (PuhMed)... 

J. Nathans. 1999. The evolution and physiology of human color vision Insights from molecular genetic studies of visual pigments Neuron 24 299-312. (PubMed)... 

Thu molecular mechanism of action of vitamin A in the visual process has been under investigation for many years. Wald in 1(168 and Morton in 1972" characterized this mechanism of action. The chemistry of vision was reviewed comprehensively in Accotmi.t of Clwmical Research (1975) by numerous investigators. These reviews include theoretical studies of the visual chromophorc. characleri/alion of ihfldopsin in synthetic systems, dynamic processes in vertebrate rod visual pigments and their membranes, and the dynamics of the visual protein opsin. ""... 

Retinal as Visual Pigment Model Spectroscopy and Physical Chemistry. As in previous years, several theoretical, spectroscopic, and photochemical studies of retinal (136) and related compounds, especially Schiffs bases, have been reported,and in many cases the main aim was to obtain information relevant to the functioning of rhodopsin and related visual pigments. Particularly valuable are surveys of the year s literature on the photochemistry of polyenes, excited states of biomolecules,and recent developments in the molecular biology of vision. 

W.B.A. Muntz, G.S.V. Mouat (1984). Annual variations in the visual pigments of brown trout inhabiting lochs providing different light environments. Vision Res., 24, 1575-1580. 

K.L. Carlton, F.I. Harosi, T.D. Kocher (2000). Visual pigments of African cichlid fishes evidence for ultraviolet vision from microspectrophotometry and DNA sequences. Vision Res., 40, 879-890. 

W.N. McFarland, E.R. Loew (1994). Ultraviolet visual pigments in marine fishes of the family Pomacentridae. Vision Res., 34,1393-1396. 

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