The photoreaction of vacuum-dried rhodopsin at low temperature: evidence for charge stabilization by water |
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| Authors: | U M Ganter E D Schmid F Siebert |
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| Institution: | Institut für Biophysik und Strahlenbiologie, Albert-Ludwigs Universit?t Freiburg, F.R.G. |
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| Abstract: | 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. |
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