19F NMR AND UV-VIS ABSORPTION SPECTROSCOPIC STUDIES OF FLUORINATED OCTOPUS RHODOPSIN AND ITS PHOTOPRODUCTS

Isomeric octopus pigment analogues from 9-cis and 11-cis 10-fluoro ret inal have been prepared and their photochemical as well as other prope rties examined. While most of the properties of the fluorinated analog ues remained similar to those of the parent system, the following diff erences were noted. Fluorine substitution at the 10-position increased the UV opsin shift (UV OS) values of the pigments and increased the f luorine opsin shift (FOS) compared to that in bovine rhodopsin. For th e 9-cis 10-fluoro octopus pigment, a reduction in photosensitivity and in FOS were observed compared to that in bovine rhodopsin. These resu lts suggest that in octopus rhodopsin the environment around the fluor ine probe in the 11-cis chromophore is more sterically hindered compar ed to that in bovine, while the opposite is likely for the 9-cis.