Fluctuation spectroscopy of giant unilamellar vesicles using confocal and phase contrast microscopy

Abstract

Bending rigidity measured with fluctuation spectroscopy is insensitive to the imaging technique: do’s and do not’s when using confocal and phase contrast imaging.

Electromechanical characterization of biomimetic membranes using electrodeformation of vesicles

“…Several experimental methods are widely used to measure bending rigidity and tension using GUVs [14]. Fluctuation spectroscopy analyzes the thermally driven membrane undulations with micron and submicron wavelength recorded with optical microscopy [15–21]. Tension and bending rigidity control the dynamics of the long and short wavelength undulations, respectively.…”

A vesicle microrheometer for high-throughput viscosity measurements of lipid and polymer membranes

“…Flickering spectroscopy is a popular technique to extract out membrane rigidity and tension due to its non-intrusive nature and well developed statistical analysis criteria. The details of the technique are given in [15, 27, 28]. Essentially, a time series of fluctuating vesicle contours is recorded on the focal plane.…”

“…The Focal depth, FD, was determined using the standard formula where the wavelength, l , of transmission light is 550 nm. This results in FD= 0.97 μ m with the non dimensionalized (vesicle size range of radius, R, 20-50 μ m) smaller than 0.05 to avoid the averaging effect of out of focus optical projections on equatorial projections [28]. The integration time effect of the camera was reduced by acquiring images at a low shutter speed of 100-200 μs.…”

“…The method for flickering spectroscopy is detailed in [75,76]. Here, we summarize the electrodeformation method to extract out membrane capacitance.…”

“…The applied frequency was kept as 0.5-1 kHz. We recorded the vesicle fluctuations for fluctuation spectroscopy [15, 27, 28] to determine the equilibrium membrane tension and bending rigidity before and after the electric field application, see SI Section I. No changes were detected due to the exposure to the electric field.…”