Rondelli V, Del Favero E, Motta S, Cantù L, Fragneto G, Brocca P
Department of Medical Biotechnologies and Traslational Medicine, University of Milan, Segrate, Italy.
Eur Phys J E Soft Matter. 2013 Jul;36(7):73. doi: 10.1140/epje/i2013-13073-4. Epub 2013 Jul 16.
The determination of the structure of membrane rafts is a challenging issue in biology. The selection of membrane components both in the longitudinal and transverse directions plays a major role as it determines the creation of stable or tunable platforms that host interactions with components of the outer environment. We focus here on the possibility to apply neutron scattering to the study of raft mimics. With this aim, we realized two extreme experimental models for the same complex membrane system (phospholipid : cholesterol : ganglioside GM1), involving two of the characteristic components of glycolipid-enriched rafts. One consists of a thick stack of tightly packed membranes, mixed and symmetric in composition, deposited on a silicon wafer and analyzed by neutron diffraction. The other consists of a free floating individual membrane, mixed and asymmetric in composition in the two layers, studied by neutron reflection. We present here results on the ganglioside-cholesterol coupling. Ganglioside GM1 is found to force the redistribution of cholesterol between the two layers of the model membranes. This causes cholesterol exclusion from compositionally symmetric ganglioside-containing membranes, or, alternatively, asymmetric cholesterol enrichment in raft-mimics, where gangliosides reside into the opposite layer.
细胞膜筏结构的确定是生物学中一个具有挑战性的问题。膜成分在纵向和横向方向上的选择起着主要作用，因为它决定了稳定或可调平台的形成，这些平台承载着与外部环境成分的相互作用。我们在此关注将中子散射应用于筏模拟物研究的可能性。为此，我们针对同一复杂膜系统（磷脂：胆固醇：神经节苷脂GM1）实现了两种极端实验模型，该系统包含富含糖脂的筏的两个特征成分。一种由紧密堆积的厚膜堆叠组成，成分混合且对称，沉积在硅片上并通过中子衍射进行分析。另一种由自由漂浮的单个膜组成，两层成分混合且不对称，通过中子反射进行研究。我们在此展示关于神经节苷脂 - 胆固醇偶联的结果。发现神经节苷脂GM1会促使胆固醇在模型膜的两层之间重新分布。这导致胆固醇从成分对称的含神经节苷脂膜中被排除，或者在模拟筏中不对称富集胆固醇，其中神经节苷脂位于相反的层中。
