The surface potential on the purple membrane measured using a modified bacteriorhodopsin chromophore as the spectroscopic probe

FEBS Letters

Ebrey, Thomas G.¹  Friedman, Noga³  Sheves, Mordechai³  Ehrenberg, Benjamin² 

[1] Department of Physiology and Biophysics, University of Illinois, Urbana, IL 61801, USA;Department of Physics, Bar Ilan University, Ramat Gan 52 - 100, Israel;Department of Organic Chemistry, Weizmann Institute of Science, Rehovot, Israel

关键词: Bacteriorhodopsin;    Purple membrane;    Surface potential;    Surface charge;    Retinal;    Absorption spectroscopy;   

DOI  :  10.1016/0014-5793(89)80715-X

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The surface potential of the purple membrane was measured by a novel method by using an artificial bacteriorhodopsin whose chromophore was 13-CF₃ retinal instead of retinal. When attached to the apoprotein by a Schiff base, the intrinsic pK of the 13-CF₃ chromophore is around 7.3. The apparent p_K of this pigment depends on the surface potential and thus on the electrolyte concentration. This allowed us to determine the surface charge density using the Gouy-Chapman equation. The surface charge density was found to be −1.65 ± 0.15 × 10⁻³ electronic charges per Ų or about 2 negative charges/bacteriorhodopsin. This large value for the surface potential probably explains both part of the strong apparent association of divalent cations with the membrane and the effect of low salt concentrations on light-induced proton release from the purple membrane.

【 授权许可】

Unknown