SYNTHESIS OF 6 NOVEL RETINALS AND THEIR INTERACTION WITH BACTERIOOPSIN

The synthesis and spectroscopic characterization of six novel chemical ly modified retinals, is described, prepared by a single strategy: all -E-10,12-ethanoretinal (1), all-E-10,12-propanoretinal (2), all-E-10,1 2-ethano-20-norretinal (3), all-E-20-nor-10,12-propanoretinal (4), all -E-12,14-ethano-20-norretinal (5), and all-E-20-nor-12,14-propanoretin al (6). For this strategy we developed two novel synthons, 2-(diethoxy phosphinyl) hexanedinitrile and 2-(diethoxyphosphinyl) heptanedinitril e which were prepared in their deprotonated form from hexanedinitrile and heptanedinitrile. Bacterioopsin was incubated with each of 1 to 6. Only 1 and 3 form bacteriorhodopsin analogues (bR-1 and bR-3). bR-1 s hows light-dark adaptation and an approx. 50% light-driven proton-pump action. bR-3 does not show light-dark adaptation or proton-pump actio n. It is also shown that the protein can efficiently accommodate retin al with the 10,12-ethano group whereas the corresponding retinal with the 10,12-propano group does not fit in the binding site.