MPA/CINT/Manual Lujan Jr. Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, New Mexico.
Department of Chemistry, Gettysburg College, Gettysburg, Pennsylvania; Department of Chemistry, Institute for Biophysical Dynamics, and James Franck Institute, The University of Chicago, Chicago, Illinois.
Biophys J. 2018 Mar 13;114(5):1103-1115. doi: 10.1016/j.bpj.2017.12.044.
The influence of carbohydrate structure on the ordering of glycosphingolipids (GSLs) and surrounding phospholipids was investigated in monolayers at the air-water interface. Binary mixtures composed of GSLs, chosen to span a range of carbohydrate complexity, and zwitterionic dipalmitoylphosphatidylcholine phospholipid, were studied. X-ray reflectivity was used to measure the out-of-plane structure of the monolayers and characterize the extension and conformation of the GSL carbohydrates. Using synchrotron grazing incidence x-ray diffraction, the in-plane packing of the lipid acyl chains and the area per molecule within ordered domains were characterized at different mole ratios of the two components. Our findings indicate that GSL-containing mixtures, regardless of the carbohydrate size, enhance the ordering of the surrounding lipids, resulting in a larger fraction of ordered phase of the monolayer and greater dimensions of the ordered domains. Reduction of the averaged area per molecule within the ordered domains was also observed but only in the cases where there was a size mismatch between the phospholipid headgroups and GSL components, suggesting that the condensation mechanism involves the relief of steric interactions between headgroups in mixtures.
我们研究了在气液界面的单层中碳水化合物结构对糖脂 (GSL) 和周围磷脂有序排列的影响。选择组成二元混合物的 GSL 跨越了一系列的碳水化合物复杂度范围，并选择了两性离子二棕榈酰基磷脂酰胆碱磷脂。使用掠入射 X 射线反射法测量了单层的面外结构，并表征了 GSL 碳水化合物的延伸和构象。使用同步加速器掠入射 X 射线衍射，在不同的两种成分摩尔比下，对脂质酰基链的面内堆积和有序域内每个分子的面积进行了表征。我们的研究结果表明，含有 GSL 的混合物无论碳水化合物的大小如何，都能增强周围脂质的有序排列，从而使单层的有序相比例更大，有序域的尺寸更大。在有序域内每个分子的平均面积也观察到减少，但仅在磷脂头部基团和 GSL 成分之间存在大小不匹配的情况下，这表明凝聚机制涉及混合物中头部基团之间的空间相互作用的缓解。
