Heftberger Peter, Kollmitzer Benjamin, Rieder Alexander A, Amenitsch Heinz, Pabst Georg
Biophysics Division, Institute of Molecular Biosciences, University of Graz, NAWI Graz, Graz, Austria; BioTechMed-Graz, Graz, Austria.
Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria.
Biophys J. 2015 Feb 17;108(4):854-862. doi: 10.1016/j.bpj.2014.11.3488.
Biophysical understanding of membrane domains requires accurate knowledge of their structural details and elasticity. We report on a global small angle x-ray scattering data analysis technique for coexisting liquid-ordered (Lo) and liquid-disordered (Ld) domains in fully hydrated multilamellar vesicles. This enabled their detailed analysis for differences in membrane thickness, area per lipid, hydrocarbon chain length, and bending fluctuation as demonstrated for two ternary mixtures (DOPC/DSPC/CHOL and DOPC/DPPC/CHOL) at different cholesterol concentrations. Lo domains were found to be ~10 Å thicker, and laterally up to 20 Å(2)/lipid more condensed than Ld domains. Their bending fluctuations were also reduced by ~65%. Increase of cholesterol concentration caused significant changes in structural properties of Ld, while its influence on Lo properties was marginal. We further observed that temperature-induced melting of Lo domains is associated with a diffusion of cholesterol to Ld domains and controlled by Lo/Ld thickness differences.
对膜结构域的生物物理理解需要准确了解其结构细节和弹性。我们报告了一种用于分析完全水合的多层囊泡中共存的液晶有序(Lo)和液晶无序(Ld)结构域的全局小角X射线散射数据分析技术。这使得能够对膜厚度、每脂质面积、烃链长度和弯曲波动的差异进行详细分析,如在不同胆固醇浓度下对两种三元混合物(DOPC/DSPC/CHOL和DOPC/DPPC/CHOL)所展示的那样。发现Lo结构域比Ld结构域厚约10 Å,并且横向每脂质凝聚程度高20 Å(2)。它们的弯曲波动也降低了约65%。胆固醇浓度的增加导致Ld结构性质发生显著变化,而其对Lo性质的影响很小。我们进一步观察到,温度诱导的Lo结构域熔化与胆固醇向Ld结构域的扩散有关,并受Lo/Ld厚度差异控制。