Extracted visual pigments

Action Spectroscopy Absorption and Fluorescence Microspectroscopy Biochemical and Spectroscopic Study of Extracted Visual Pigments Molecular Biology Investigations... 

Biochemical and Spectroscopic Study of Extracted Visual Pigments... 

Resonance Raman Spectroscopy. A review of the interpretation of resonance Raman spectra of biological molecules includes a consideration of carotenoids and retinal derivatives. Another review of resonance Raman studies of visual pigments deals extensively with retinals. Excitation profiles of the coherent anti-Stokes resonance Raman spectrum of j8-carotene have been presented. Resonance Raman spectroscopic methods have been used for the detection of very low concentrations of carotenoids in blood plasma and for the determination of carotenoid concentrations in marine phytoplankton, either in situ or in acetone extracts. ... 

Fig. 8. A nonisomerizing procedure for the extraction of retinals from their binding sites in visual pigments [90],...

Both the 9-cw and 9,13-dim isomers of 30 formed visual pigment analogs [165], with Amax at 460 nm and 455 nm (mixed diastereomers), respectively. Moreover, upon incubation of a ca. 1 1 diastereomeric mixture of 30 (the 9-cis isomers) followed by extraction of the bound chromophore by the CH2C12 procedure and... 

Visual excitation (1) in both vertebrates and invertebrates is initiated via light absorption by visual pigments consisting of a chromophore covalently bound to an apo-protein, opsin. Biochemical extraction studies have shown that in all pigments the chromophore is a Schiff base derivative of 11-cis retinal (Fig. 

C. contribute to energy transfer in photosynthesis, as well as providing protection against light. They are also important as precursors of vitamin A and the visual pigments. C. are isolated from plant material by extraction with organic solvents and adsorption chromatography. Partial and total syntheses of P-carotene are carried out on an industrial scale. Some C. (in particular P-carotene) are used as food, pharmaceutical and cosmetic colorants. 

Here, we briefly describe and compare spectroscopic and biochemical techniques that were used to define the Ught-absorbing properties of visual pigments, either in vivo (single cell or cell population) or in vitro (extracted material). To provide a clear perspective on the efficacy of different techniques as tools for the study of photoreceptive structures, a discussion of the pros and cons, the advantages and limitations, of each technique is included (see also Chapter 9). 

Extraction of visual pigments (chromophore and/or protein), either by means of detergents such as digitonin and Triton [57], or by organic solvents, could be the best method for providing large quantities of photoreceptive pigments in an accessible in vitro form for subsequent detailed biochemical analysis. 

Fong, S.L., Tsin, A.T. C., Bridges, C.D. B., and Liou, G.l. Detergents for extraction of visual pigments types, solubilization and stability, in Methods in Enzymology, 81, Biomembranes, part H, Packer, L., Ed., Academic Press, 1982, 133-140. 

The objective indication of color differences in foods has usually been attempted in a simplified, indirect way that involves a comparison of some physical characteristic of the samples or, more often, an extracted fraction that is assumed or has been proved to be largely responsible for the associated color characteristics. Although such a method does not measure the actual visual color of the samples, a measure of relative amounts of color-characteristic pigments or a comparison of physical properties of extracts of color-critical fractions (which may be mixtures of several pigments) may prove to be very sensitive indications of differences that are closely related to color. 

For durum wheats, the rapid quautitatiou of caroteues is performed using a spectrophotometer or colorimeter (AACC Method 14-50). The yellow pigmentation can be quantified by overnight extraction in aqueous n-butauol followed by measurement of absorbance at 435.8 nm (Dexter and Matsuo 1978). More frequently, the color of semolina is judged visually or with refractive light colorimeters (Allen et al. 1989, Symons and Dexter 1991). 

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