Fluorescence quenching and electron spin resonance study of percolation in a two-phase lipid bilayer containing bacteriorhodopsin

Biophysical Journal
B PiknováT E Thompson

Abstract

The effect of bacteriorhodopsin (BR) on the percolation properties of dimyristoylphosphatidylcholine/distearoylphosphatidylcholine bilayers was examined by studying the quenching of a lipid-bound fluorophore by a lipid-bound quencher, and by spin-spin interactions of a nitroxide-labeled lipid using electron spin resonance (ESR). At the low concentrations of BR used, differential scanning calorimetry showed that although the transition enthalpy was reduced in a concentration-dependent manner by incorporation of BR, the solidus and fluidus phase boundaries and overall shape of the heat capacity profiles were essentially unchanged. However, fluorescence quenching and spin-label ESR data showed that the domain topology, as reflected in the percolation properties, is strongly affected by the protein. In contrast to our previous fluorescence data for the pure lipid mixtures, quenching in the coexistence region is independent of the fluid phase fraction when BR is present. In addition, the percolation threshold estimated by spin-label ESR is shifted in the presence of BR to a higher gel phase fraction at a given lipid composition. Both the fluorescence quenching and spin-label ESR data, together with the results of earlier simulations...Continue Reading

Citations

Jun 24, 1999·Bioelectrochemistry and Bioenergetics·A N Goltsov
Nov 7, 1998·Biochimica Et Biophysica Acta·T GilM J Zuckermann
Aug 1, 1997·Current Opinion in Structural Biology·O G Mouritsen, K Jørgensen
Aug 1, 1997·Current Opinion in Structural Biology·M Edidin
Apr 4, 2006·Chemistry and Physics of Lipids·Jörg H Kleinschmidt

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