Fluorescence depolarization studies of molecular dynamics using pulsed synchrotron radiation

Analysis of time-resolved fluorescence anisotropy measurements on TMA-DPH molecules in POPC vesicles in terms of the rotational diffusion model reveals two distinct chi2 minima which are statistically equivalent. The ambiguity in the interpretation is resolved by carrying out angle-resolved fluorescence depolarization experiments on planar POPC multibilayers in the time domain. It is shown that the order parameters of the probe molecules are higher in the multibilayers than in the vesicles. Furthermore the reorientational motion of the probes is considerably slower in the multibilayer sample. These differences are ascribed to the effects of the curvature and hydration of the bilayers in the vesicle systems