Understanding and exploiting lipid-lipid interactions

我们的工作主要致力于脂质自组装的结构表征，以便更好地理解生物系统中脂质的结构-功能关系。首先，我们对在精浆中发现的一个蛋白质家族感兴趣，该家族通过一种未知的机制，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。我们提出脂质分选是基于脂质膜的局部曲率。为了检验这一假设，我们将在分子水平上探测膜曲率，使用固态2H核磁共振。我们还将使用共聚焦荧光显微镜（带有荧光标记的脂质）来确定在微观水平上，由于与这些蛋白质相互作用而产生的自组装中的脂质分布。最后，我们将通过分析由这些蛋白质提取的脂质产生的颗粒来定量地确定脂质特异性。其次，表皮顶层的脂质在很大程度上负责皮肤的不渗透性，这是一个重要的特性，与显著比例的脂质在结晶阶段有关。我们将研究这种固相的结构和形成动力学，以便更好地了解皮肤不透水性的起源。通过配备焦平面阵列的红外显微镜，可以在微观尺度上表征晶体相的形成（由温度变化或酶活性诱导）与具有异质脂质组成的结构域的形成。角质层的不同分子成分的作用将被检查。第三，我们最近发现了利用单酰基两亲体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，它们表现出非凡的不渗透性和对pH值的有趣敏感性。我们希望详细了解这些新型脂质体的分子结构，并创建这些NPL的延伸家族，其中被捕获的物质的释放可以通过各种刺激触发，包括pH值，温度和光。

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.