The binding of retinal to opsin

The regeneration in vivo of visual pigments is a complex and yet not well understood part of the process of dark adaptation. In vitro regeneration using isolated retinas, 

Rhodopsin can be regenerated in vitro by adding 1 l-c -retinal to bleached rod outer segment membranes (ROS) in suspension or in a suitable detergent. The requirements for efficient regeneration are the following  

In order to ascertain the nature of the bound chromophore, the pigments can be hexane-washed at low temperature to eliminate excess unbound retinal, and the bound retinal can then be extracted by shaking with methylene chloride procedure [90] (Fig. 8), which denatures the protein but does not isomerize the chromophore. Another procedure in which isomerization of the chromophore is unlikely to occur used ethanol denaturation at 0°C to identify 1 l-cfs-retinal as the chromophore in rhodopsin [91]. 

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