Resonance energy transfer in a model system of membranes: application to gel and liquid crystalline phases

Abstract

Resonance energy transfer between octadecyl rhodamine B (donor) and 1,1',3,3,3',3'-hexamethylindotricarbocyanine (acceptor) was studied in a model system of membranes (large unilamellar vesicles of dipalmitoylphosphatidylcholine), using both steady-state and time-resolved techniques. In the fluid phase (temperature = 50 degrees C) the decay law and the steady-state theoretical curve for energy transfer in two dimensions are verified. In the gel phase (temperature = 25 degrees C) an apparent reduction of dimensionality is observed, which is explained on the basis of probe segregation to the defect lines (grain boundaries). An estimation of the domain size from the model recovered linear probe concentrations is approximately 1750-2000 lipid molecules. In both phases, the existence of a fractal geometry was ruled out.

Organization and Dynamics of NBD-Labeled Lipids in Membranes Analyzed by Fluorescence Recovery after Photobleaching

“…The regions of defects are characterized by greater disorder and enhanced molecular diffusion rates. 30,35,41 In the present case, the estimated diffusion coefficient of ∼2.4 × 10 -10 cm 2 s -1 could represent mobility of NBD-PE molecules in such defects in the gel phase membrane. Interestingly, the fraction of molecules exhibiting such mobility is rather low (∼15%).…”

“…Such defects are believed to be intrinsic to the gel phase membrane organization and not experimentally induced artifacts. 30,[34][35][36][37] In addition, such organization in gel phase membranes has been observed in freezefracture micrographs 39 and inferred from small-angle neutron scattering 40 and fluorescence energy transfer 41 experiments. The regions of defects are characterized by greater disorder and enhanced molecular diffusion rates.…”

Interaction of S413‐PV cell penetrating peptide with model membranes: relevance to peptide translocation across biological membranes

“…The time-resolved instrumentation (correlated single-photon timing technique) was described previously [28]. Excitation wavelength was 287 nm and emission was detected at the magic angle (54.7°) relative to the vertically polarized beam.…”

Steady-state probe-partitioning fluorescence resonance energy transfer: A simple and robust tool for the study of membrane phase behavior

“…It has long been recognized that energy transfer between fluorescent membrane probes is eminently suited to the detection and study of coexisting membrane phase domains [19], and a number of groups have adapted FRET experiments to this end during the last decade, or so [e.g., 4,[20][21][22]. Indeed, Loura, de Almeida, Fedorov and Prieto have published several excellent studies [13,[23][24][25][26][27] based on time-resolved measurements of transfer efficiency, ) (t E , and Silvius and Nabi have recently produced a comprehensive review of FRET-based studies of membrane microdomains [28].…”