The photoreaction of vacuum-dried rhodopsin at low temperature: evidence for charge stabilization by water.
The photoreaction of vacuum-dried rhodopsin was monitored by UV-visible absorption spectroscopy. The results indicate that in dry rhodopsin, isorhodopsin and lumirhodopsin a protonation equilibrium exists between the protonated and the non-protonated Schiff base. On hydration the water stabilizes the protonated forms. In metarhodopsin-I the protein itself is able to stabilize the protonated Schiff base. The direct involvement of water in the retinal binding site was demonstrated by measuring the rhodopsin-bathorhodopsin FTIR difference spectra of rhodopsin hydrated with H2O and H2(18)O. The results are discussed with respect to the problem of charge stabilization and energy storage.
Ganter
U M
UM
Institut für Biophysik und Strahlenbiologie, Albert-Ludwigs Universität Freiburg, F.R.G.
Schmid
E D
ED
Siebert
F
F
D000818:Animals; D002417:Cattle; D005612:Freeze Drying; D007536:Isomerism; D008027:Light; D010777:Photochemistry; D012168:Retinal Pigments / Q000528:radiation effects*; D012243:Rhodopsin / Q000031:analogs & derivatives / Q000528:radiation effects*; D013053:Spectrophotometry; D014466:Ultraviolet Rays
D012168:Retinal Pigments; C042882:isorhodopsin; C018586:lumirhodopsin; C015017:bathorhodopsin; D012243:Rhodopsin