Cholestatrienol Time Resolved Fluorescence In Phosphatidylcholine Bilayers

Friedhelm Schroeder; George Nemecz; Yechezkel Barenholz; Enrico Gratton; Thomas E Thompson

doi:10.1117/12.945428

24 June 1988 Cholestatrienol Time Resolved Fluorescence In Phosphatidylcholine Bilayers

Friedhelm Schroeder, George Nemecz, Yechezkel Barenholz, Enrico Gratton, Thomas E Thompson

Proceedings Volume 0909, Time-Resolved Laser Spectroscopy in Biochemistry; (1988) https://doi.org/10.1117/12.945428
Event: 1988 Los Angeles Symposium: O-E/LASE '88, 1988, Los Angeles, CA, United States

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.

Citation Download Citation

Friedhelm Schroeder, George Nemecz, Yechezkel Barenholz, Enrico Gratton, and Thomas E Thompson "Cholestatrienol Time Resolved Fluorescence In Phosphatidylcholine Bilayers", Proc. SPIE 0909, Time-Resolved Laser Spectroscopy in Biochemistry, (24 June 1988); https://doi.org/10.1117/12.945428

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