Wednesday, July 3, 2013

1307.0367 (Benjamin Kollmitzer et al.)

Monolayer Spontaneous Curvature of Raft-Forming Membrane Lipids    [PDF]

Benjamin Kollmitzer, Peter Heftberger, Michael Rappolt, Georg Pabst
Monolayer spontaneous curvatures for cholesterol, DOPE, POPE, DOPC, DPPC, DSPC, POPC, SOPC, and egg sphingomyelin were obtained using small-angle X-ray scattering (SAXS) on inverted hexagonal phases (HII). Spontaneous curvatures of bilayer forming lipids were estimated by adding controlled amounts to a HII forming template following previously established protocols. In our analysis we compared two methods, based either on the calculation of the electron density map, or simple measurement of the lattice parameter. Within uncertainty of the measurement both methods yielded good agreement. Spontanous curvatures of both phosphatidylethanolamines and cholesterol were found to be one order of magnitude more negative than those of phosphatidylcholines, whose J0 is close to zero. Interestingly, a significant positive J0 value (+0.1 1/nm) was retrieved for DPPC at 35 {\deg}C. We further determined the temperature dependence of the spontaneous curvatures J0(T) in the range from 15 to 55 {\deg}C, resulting in a quite narrow distribution of -1 to -3 * 10^-3 1/nm{\deg}C for all investigated lipids. The data allowed us to estimate the monolayer spontaneous curvatures of ternary lipid mixtures showing liquid ordered / liquid disordered phase coexistence. We report spontaneous curvature phase diagrams for DSPC/DOPC/Chol, DPPC/DOPC/Chol and SM/POPC/Chol and discuss effects on protein insertion and line tension.
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