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Proceedings Paper

Cholestatrienol Time Resolved Fluorescence In Phosphatidylcholine Bilayers
Author(s): Friedhelm Schroeder; George Nemecz; Yechezkel Barenholz; Enrico Gratton; Thomas E Thompson
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Paper Abstract

Multifrequency phase and modulation fluorometry and a fluorescent sterol analogue,▵5,7,9 (11) cholestatrien-3$-ol (CTE), were used to examine properties of sterols in l-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) small unilamellar vesicles (SUV). The fluorescence decay of CTE in POPC SUV was examined both by sum of exponentials and by distributional analyses. The data best fit a continuous distribution of lifetimes with a two component Lorentzian function. The centers of lifetime distribution were near c1=0.86 ns and c2=3.24 ns, fractional intensities f1=0.96 and f2=0.04, and peak widths were very narrow. The centers of lifetime distribution, fractional intensities, and peak width at half-height were highly dependent on cholesterol content and vesicle curvature. In the range 0-6 mole %, CTE underwent a concentration dependent transition characterized by red shifted wavelengths of absorption maxima as well as altered ratios of absorbance maxima and fluorescence excitation maxima at 338nm/325nm. Fluorescence intensity of CTE increased up to 6 mole % CTE in POPC SUV while other parameters remained relatively constant. In contrast, between 6-33 mole % CTE, the CTE interacted to self-quench thereby decreasing fluorescence intensity, quantum yield, steady state anisotropy, limiting anisotropy, and rotational relaxation time without decreasing lifetime. The results were consistent with the interpretation that below 6 mole % sterol, the sterols behaved as monomers exposed to some degree to the aqueous solvent in POPC SUV. At higher concentrations the sterol partially segregated. At low mole %, CTE was an excellent probe molecule for determination of the motional properties of sterols in POPC membranes.

Paper Details

Date Published: 24 June 1988
PDF: 9 pages
Proc. SPIE 0909, Time-Resolved Laser Spectroscopy in Biochemistry, (24 June 1988); doi: 10.1117/12.945428
Show Author Affiliations
Friedhelm Schroeder, University of Cincinnati (United States)
George Nemecz, University of Cincinnati (United States)
Yechezkel Barenholz, University of Virginia (United States)
Enrico Gratton, University of Illinois (United States)
Thomas E Thompson, University of Illinois (United States)

Published in SPIE Proceedings Vol. 0909:
Time-Resolved Laser Spectroscopy in Biochemistry
Joseph R. Lakowicz, Editor(s)

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