Lipid - rhodopsin vesicles

In 1985 Tyminski etal. [55, 56] reported that two-component lipid vesicles of a neutral phospholipid, e.g. DOPC, and a neutral polymerizable PC, bis-DenPC (15), formed stable homogeneous bilayer vesicles prior to photopolymerization. After photopolymerization of a homogeneous 1 1 molar lipid mixture, the lipid vesicles were titrated with bovine rhodopsin-octyl glucoside micelles in a manner that maintained the octyl glucoside concentration below the surfactant critical micelle concentration. Consequently there was insufficient surfactant to keep the membrane protein, rhodopsin, soluble in the aqueous buffer. These conditions favor the insertion of transmembrane proteins into lipid bilayers. After addition and incubation, the bilayer vesicles were purified on a... 

A different vesicular photoimaging material consists of an assembly of lipid vesicles sensitized with rhodopsin. In one system the vesicles can be filled with a solution containing Co2+, and the solution outside the vesicles can be free of metal ions but contain a chelating indicator dye such as xylenol orange (101). The whole assembly can be coated, and when exposed to actinic radiation the vesicles are disrupted in exposed areas and release Co2+ ions, which are complexed by the dye indicator, thereby forming an image.253... 

DHA is very abundant in excitable membranes in the retina and brain, particularly in PL of the rod outer segment of retina and of synaptic vesicles, and is important in vision. However, the mechanism by which DHA functions in retina is not well understood. Chen et al. (Y. Chen, 1993) suggest that DHA in retina might be involved in shuttling 11-c/j-retinal to photoreceptors, whereas Niu et al. (S. Niu, 2004) propose that DHA in PL increases the efficiency of G-protein-mediated signal transduction of rhodopsin. In humans, supplementation of infant formula with DHA accelerates the development of visual functions in pre-term infants. The novel protective lipid mediator docosanoids, namely, Protectin D1 (C. Serhan, 2002) and 17S-hydroperoxy-DHA (V. Marcheselli, 2003), have been suggested to mediate the beneficial effects of DHA. 

The thermal stability of rhodopsin, defined as the temperature at which in 10 min 50% of the 500 nm absorbance is lost, is indeed sensitive to changes in lipid environment (Table II, 2nd column). Whereas native rhodopsin has a high thermal stability (70°C), affinity chromatography and phospholipase-C treatment lower this parameter to 53 C and 59 C, respectively. Reconstitution of such delipidated preparations with egg phosphatidylcholine (66 mol per mol rhodopsin) to rhodopsin-lipid vesicles leads to full recovery of the thermal stability. 

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