Table 1.
A summary of values reported for the bending rigidity, κ, of discocytic red blood cells from the literature and our RBCcm membranes.
(Errors are expressed as standard deviations).
Fig 1.
A Schematic of a stack of fluctuating membranes and the geometry of specular (q|| = 0) and off-specular (q|| ≠ 0) X-ray scattering. B q-space X-ray intensity map of a solid supported RBCcm membrane stack, measured at 37°C. Two orders of lamellar peaks surrounded by diffuse X-ray intensity are visible. The white lines show the locations and ranges of the data used for fits. C Off-specular intensities at qz = 2q1 and qz = 2.5q1, normalized to the respective X-ray intensity at q|| = 0.01 Å−1). Fits of the structure factor S(qz, q||) following Eq (1) are shown as solid lines. Error bars represents the ± standard deviation. Intensity measured in proximity of a lamellar peak is orders of magnitude higher than intensity measured in between lamellar peaks. Since errors in scattering experiments scale with the square root of counted X-ray photons, the relative error is consequently smaller in proximity of a lamellar peak than between lamellar peaks.
Fig 2.
A. Experimental setup of the NSE experiment. 6 ml of RBCcm liposomes immersed in D2O at a concentration of 20 mg/ml were filled in custom made titanium/quartz chambers provided by the NIST Center for Neutron Research (NCNR). B Intermediate scattering function I(q, t)/I(q, 0) at q = (0.0523, 0.0664, 0.0794 and 0.0959) Å−1. Data were fitted by Eq (5). The inset shows the determined decay constant Γ as function of the scattering vector q which were fitted with a q3 dependency, as predicted by the Zilman-Granek theory. A bending modulus of 4 kBT was determined using the cholesterol model. (Error bars represents the ± standard deviation).
Fig 3.
Three-dimensional renderings of the undulation simulation after 5 μs (side-view A and top-view B).
Lipid molecules are represented by rods representing intra-molecular bonds. Each lipid species (Phosphatidylcholine, PC; Ceramide, CER; Monoglucosyl lipids, MG; Diacylglycerol lipids, DG; Fatty acids, FA; Sphingomyelin, SM; Phosphatidylethanolamine, PE; Phosphatidylserine, PS; Phosphatidylglycerol, PG; Phosphatidic acid, PA; Phosphatidylinositol, PI) are represented by different colors indicated in the legend. Cholesterol (CHOL) is symbolized by red spheres. C The fluctuation spectrum determined from the undulation simulation averaged over the last 4 μs for all three models. Fits of Eq (8) to the data are depicted as red solid line. The fit range was Q<0.2 Å−1. (Error bars represents the ± standard deviation).