Bending rigidities of some biological model membranes as obtained from the Fourier analysis of contour sections

We have measured the bending rigidites kc of egg lecithin (EYPC), dimyristoylphosphatidyl-ethanolamine (DMPE) and digalactosyl-diacylglycerol (DGDG) membranes in the fluid state, subjecting the fluctuations of large nearly planar bilayer sections to computerized Fourier analysis. For EYPC we found kc = 0.8 × 10 -12 erg which is less than half the value obtained earlier for egg and other lecithins from the bending fluctuations of tubular vesicles but in the range of more recent measurements on spherical lecithin vesicles. For DMPE we found kc = 0.7 x 10-12 erg at T = 60 °C, while we derived kc = 1.7 x 10-12 erg from the bending fluctuations of tubular vesicles of dilauroyl-phosphatildylethanolamine (DLPE) at T = 46 °C. As in the case of lecithins the different results seem to be mostly due to the different methods. Very low values of kc = (0.12 — 0.27) x 10-12 erg were measured for DGDG. The scatter was less but also large for the other materials.