Understanding and exploiting lipid-lipid interactions

我们的努力主要致力于脂质自组装的结构表征，以更好地了解生物系统中脂质的结构-功能关系。 首先，我们感兴趣的是在精浆中发现的一个蛋白质家族，其通过未知的机制选择性地从精子膜中提取磷脂酰胆碱和胆固醇，这是精子成熟的关键步骤。 我们建议脂质分选是基于脂质膜的局部曲率。 为了验证这一假设，我们将使用固态2 H NMR在分子水平上探测膜曲率。 我们还将使用共聚焦荧光显微镜（荧光标记的脂质），以确定在微观水平上，脂质分布在自组装与这些蛋白质的相互作用所产生的。 最后，我们将通过分析由这些蛋白质的脂质提取产生的颗粒来定量确定脂质特异性。 其次，表皮顶层的脂质在很大程度上决定了皮肤的不渗透性，这是一个与结晶相脂质的大部分相关的重要特性。 我们将研究这种固相形成的结构和动力学，以便更好地了解皮肤不渗透性的起源。 通过使用配备有焦平面阵列的红外显微镜，将有可能表征结晶相的形成（由温度变化或酶活性诱导），同时在微观尺度上形成具有异质脂质组合物的结构域。 将检查角质层的不同分子组分的作用。 第三，我们最近发现了使用单酰化两亲物和甾醇形成非磷脂脂质体（NPL）的可能性。 这些NPL具有非常高的胆固醇含量，它们显示出显着的不渗透性和有趣的pH敏感性。我们希望开发这些新型脂质体的分子结构的详细了解，并创建这些NPL的扩展家族，其中所捕获的材料的释放可以通过各种刺激，包括pH，温度和光来触发。

Our efforts are primarily devoted to the structural characterization of lipid self-assemblies in order to gain a better understanding of the structure-function relationships for lipids in biological systems. First, we are interested in a family of proteins found in the seminal plasma, which extract selectively, by an unknown mechanism, phosphatidylcholine and cholesterol from sperm membranes, a critical step in the sperm maturation. We propose that the lipid sorting is based on the local curvature of the lipid membranes. To examine this hypothesis, we will probe the membrane curvature at the molecular level, using solid-state 2H NMR. We will also use confocal fluorescence microscopy (with fluorescent labelled lipids) to determine at the microscopic level, the lipid distribution in the self-assemblies resulting from the interactions with these proteins. Finally we will determine quantitatively the lipid specificity by the analysis of the particles resulting from the lipid extractions by these proteins. Second, the lipids of the top layer of the epidermis are largely responsible for the skin impermeability, a vital property linked to the significant proportion of lipid in crystalline phase. We will examine the structure and the dynamics of the formation of this solid phase in order to gain a better understanding of the origin of skin impermeability. By using an infrared microscope equipped with a focal plane array, it will be possible characterize the formation of the crystalline phases (induced by temperature changes or enzymatic activity) in parallel with the formation of domains with heterogeneous lipid compositions at the microscopic scale. The role of different molecular components of the stratum corneum will be examined. Third, we recently discovered the possibility to form non-phospholipid liposomes (NPL) using monoacylated amphiphiles and sterols. These NPL have a very high cholesterol content, they display a remarkable impermeability and an interesting sensitivity to pH. We want to develop a detailed understanding of the molecular structure of these novel liposomes and to create an extended family of these NPL for which the release of the entrapped material can be triggered by various stimuli, including pH, temperature, and light.