Understanding and exploiting lipid-lipid interactions

我们的工作主要致力于脂类自组装的结构表征，以便更好地了解生物系统中脂类的结构-功能关系。首先，我们对精浆中发现的一系列蛋白质感兴趣，这些蛋白质以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。我们认为，脂类的分类是基于脂膜的局部曲率。为了验证这一假设，我们将使用固态2H核磁共振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(带有荧光标记的脂类)在微观水平上确定与这些蛋白质相互作用所产生的自组装中的脂类分布。最后，我们将通过对这些蛋白质提取脂类所产生的颗粒的分析来定量确定脂类的特异性。其次，表皮顶层的脂类在很大程度上导致了皮肤的不通透性，这是一种重要的属性，与晶相中大量的脂类有关。为了更好地了解皮肤不通透性的起源，我们将研究这种固相形成的结构和动力学。通过使用配备焦平面阵列的红外显微镜，将有可能在微观尺度上表征晶相的形成(由温度变化或酶活性引起)以及具有不同类脂成分的结构域的形成。角质层的不同分子成分的作用将被检测。第三，我们最近发现了使用单酰化两亲化合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，它们表现出显著的不渗透性和对pH的有趣敏感性。我们想要对这些新型脂质体的分子结构有一个详细的了解，并创建一个这些NPL的大家族，对于这些NPL，包埋的材料可以被各种刺激触发释放，包括pH，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.