Pattern photobleaching recovery

The fluidity of LB monolayers on solid supports was characterized by measuring the long-range (> 10 xm) translational diffusion of dissolved fluorescent lipids using fluorescence pattern photobleaching recovery (FPPR). In this technique, an area of the membrane is illuminated with a spatially striped intensity. After irreversibly photobleaching, fluorescence recovery occurs, as unbleached molecules from nonilluminated stripes move into the illuminated stripes . In fluid-like LB films, translational diffusion coefficients... 

Diffusion coefficients of the tracer molecules have been measured also by fluorescence recovery after fringe pattern photobleaching recovery. The fluorescence recovery curves are pure exponentials but the diffusion... 

FRAPP fluorescence recovery after pattern photobleaching... 

Unambiguous determination of the conditions under which slippage occurs requires a technique able to measure the velocity of the fluid in the immediate vicinity of the solid wall over a thickness comparable to the size of a polymer chain, i.e. a few tens of nanometers. Classical laser Doppler velocimetry does not meet this requirement even if it allows for the determination of velocity profiles which clearly reveal a non-zero velocity within typically a few 10 pm from the wall. We have developed a new optical technique. Near Field Velocimetry (N.F.V.) [14], which combines Evanescent Wave Induced Fluorescence (E.WF.) [27] and Fringe Pattern Fluorescence Recovery After Photobleaching (F.P.F.R.A.P.) [28]. The former technique gives the spatial resolution normal to the solid wall, while the latter one enables the determination of the local velocity of the fluid. A major constraint of the technique is that it needs polymer molecules labelled with an easily photobleachable fluorescent probe. 

II.1. Experimental Procedure. The micelles self-diffusion coefficient has been determined by fluorescence recovery after fringe pattern photobleaching (FRAP). A fluorescent probe was incorporated in the micelles it was checked that its finite residence time in the micelle did not affect the diffusion process. 

Jourdainne, L., Sn, Lecuyer, Amtz, Y., Picart, C., Schaaf, P., Senger, B., Voegel, J.-C., Lavalle, P., Charitat, T. Dynamics of poly(l-lysine) in hyaluronic acid/poly(l-lysine) multilayer films studied by fluorescence recovery after pattern photobleaching. Langmuir 24, 7842-7847 (2008)... 

Such an approach has been used to determine the average a-relaxation time based on second harmonic generation measurements [60, 61] and fluorescence recovery after pattern photobleaching measurements [62, 63]. 

Since the information on the velocity close to the solid wall is contained in the recovery dynamics and not in the absolute values of the fluorescence intensities, the intensity axis is scaled such that the recovery curves range from I(%) = 0 to I(%) = 100. The flow pattern of photobleached probes is strongly affected by the fast diffusion during the fluorescence recovery time (x 50 ms) a probe travels by... 

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