Pigment regeneration

In addition to entering the RPE from the circulation, all-lrany-retinol passes into the RPE cells through their apical surfaces during bleaching of ihodopsin in the ROS. This phase of the visual cycle is better characterized than the reverse step, namely the reverse flow of retinoid that culminates in visual pigment regeneration. 

Since the key to understanding visual pigment regeneration lies in obtaining an insight into how 11-cis-retinoid is formed from all-troiu-retinoid, this section is devoted to this difficult as yet unsolved problem. Under what circumstances do retinoids isomerize ... 

In contrast, photoisomerization as a means for visual pigment regeneration appears to be the rule in invertebrates (Schwemer ra/., 1971 Haraera/., 1981). 

Rando RR (1992) Molecular mechanisms in visual pigment regeneration. Photochem Photobiol 56 1145-1156... 

Goldstein EB (1970) Cone pigment regeneration in the isolated frog retina. Vision Res 10 1943-1951 Bunt-Milan AH, Saari JC (1983) Inununocytochemical localization of two retinoid-binding proteins in vertebrate retina. J Cell Biol 97 703-712... 

Saari JC (2000) Biochemistry of visual pigment regeneration The Friedenwald lecture. Investigative Ophthalmology and Visual Science 41 337-348. 

At high intensities this ratio becomes unity (all photoreceptor is bleached) and therefore no phototropism can occur. Equation (2) shows that the bleaching of the photoreceptor does not depend on the absolute concentration of photoreceptor. Therefore mutants with less receptor pigment will be inhibited at the same light intensity as the wild type. However, in mutants with a reduced cross section the ratio of Pbi/Ptot reach unity at higher intensities. Hence they are phototropic active at intensities where the wild type is already inhibited. The third type of mutant (iii) which has a slower regeneration as the wild type should have a normal sensitivity at low intensities but should be phototropical insensitive at higher intensities at which the unbleached... 

Bleached rhodopsin must be regenerated to maintain normal vision. Regeneration occurs by several mechanisms. The major pathway occurs in the retinal pigmented... 

SOLINOX SO,. Linde NO,] A process for removing both NOx and SOx from fluegases. The SOx is removed by scrubbing with tetra-ethylene glycol dimethyl ether, circulated in a packed tower (the Selexol process). The NOx is destroyed by Selective Catalytic Reduction ( SCR). The sorbent is regenerated with steam the SOx is recovered for conversion to sulfuric acid. Developed by Linde in 1985 and used in a lead smelter in Austria and several power stations in Germany. In 1990 it was announced that it would be used at the titanium pigment plant in The Netherlands operated by Sachtleben. 

In these spectra, the protein has been regenerated with retinal specifically 13 C labeled at positions 11,12 and 13, and in each case the retinal resonance exhibits a sharp centerband at the isotropic chemical shift and is flanked by rotational sidebands. Other lines in the spectrum are the natural-abundance 13C resonances of the protein carbonyls ca 175 ppm) and aliphatic carbons (0-100 ppm). Contributions from the Ammonyx-LO detergent in these spectra are seen in the different intensities in the 0-100 ppm region. Ammonyx-LO does not exhibit NMR resonances above 100 ppm. Spectra of the 9-cis pigment isorhodopsin are similar. Table 38 summarizes the isotropic chemical shifts from the solid-state NMR spectra of rhodopsin regenerated with retinal13 C labeled at each position along... 

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