ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A theory describing the shapes of polarized fluorescence photobleaching recovery (PFPR) curves for a population of fluorophores undergoing restricted rotational diffusion in two-dimensional systems such as planar membranes has been developed. In this model, restricted rotational diffusion of the fluorophores is described by using reflective boundary conditions, in which the fluorophores are assumed to diffuse freely but only within an angular space of width 2ω. The magnitude and apparent rate of the PFPR postbleach fluorescence curves are a function of both ω and the angle between the bleaching and observation beam polarizations ψ. It is shown that estimates of the degree of rotational restriction ω may be obtained from changes in the ψ-dependent postbleach fluorescence intensities.Using angle-dependent PFPR, slow rotational reorientations of the fluorescent lipid analogue 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine in distearoylphosphatidylcholine Langmuir-Blodgett monolayers deposited on octadecyltrichlorosilane-treated fused quartz were measured. As theoretically predicted for a rotationally restricted fluorophore population, both the initial Fψ(0) and final Fψ(∞) postbleach fluorescence intensities varied as a function of ψ, and no measurable change in the postbleach fluorescence intensities was observed for ψ = 45°. Using the theory for restricted rotational motion, the ψ-dependent variations of the final fluorescence intensities Fψ(∞) obtained at two bleaching intensities gave an average apparent ω ≍ 52°. However, to adequately fit the Fψ(0) data, inclusion of the theoretical effects of rapid (faster than the duration of the photobleaching pulse) fluorophore dynamics was also required. Best fits of the Fψ(0) and Fψ(∞) data were obtained when the fluorophores were assumed to rapidly wobble within a cone of semiangle δ ≍ 30°-50° while slowly rotating within an angular space defined by semiangle ω ≍ 35°-60°. Subsequent analysis of the time- and ψ-dependent changes in the postbleach fluorescence curves Fψ(t) gave apparent diffusion coefficients ranging from D ≍ 10-3 s-1 to 4 × 10-2 s-1. © 1993 John Wiley & Sons, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.360330106
Permalink
