Effect of light on extraction of lipid from retinal rods.

Chloroform-methanol 2:1 removes a significantly greater quantity of lipid from bleached bovine retinal rods than from a dark-adapted counterpart. The extracts contain phosphatidyl serine, phosphatidyl choline, phosphatidyl ethanolamine, sphingomyelin, and an unknown substance which, it is proposed, may be a combination of phospholipid and retinaldehyde. The difference between extracts of light-and dark-adapted rods is quantitative rather than qualitative. The data tend to confirm a model of rhodopsin suggested by Kropf and Hubbard in which isomerization of the retinaldehyde chromophore causes its displacement and opens a path to the interior of the molecule.