An observation concerning electronically excited retinal.

The observation of Mathies and Stryer of highly polar excited electronic states of all-trans-retinal, its unprotonated Schiff base, a salt of the protonated Schiff base, and 11-cis-retinal leads us to propose a possible consequence of the existence of such species. The highly polar excited molecule may have sufficient potential to oxidize its surroundings, thus achieving a transfer of one electron. Experimental evidence is combined with crude model calculations to support the possible role of these excited states as electron transfer agents.