Molecular recognition mechanism on biomembrane surface in primary biological functioning

微观结构和热力学方法是研究生物膜表面生物功能的重要手段。从这个角度出发，我们开发了一种同时进行X射线衍射和差示扫描量热测量的方法。我们将该方法应用于磷脂和磷脂/磷脂酰甘油水分散体的研究。在前者中，我们得到了X射线衍射强度与相变热成正比的结果。在后者中，我们发现了在生物功能中起重要作用的H&lt；II&gt；结构的存在。作为磷脂分子与小分子相互作用的例子，我们研究了磷脂/醇和磷脂/糖的体系。在前者中，我们分析了交指结构，并提出了一个微观结构模型。在后者中，根据糖的不同，揭示了稳定液晶相的条件。此外，作为磷脂分子与小分子相互作用的一个例子，我们用热分析和X射线衍射法研究了磷脂/水体系。从这项研究中，我们发现了水分子在夹层中的数量。此外，我们还用原子分辨扫描隧道显微镜研究了在石墨表面形成的单层脂肪酸的结构，为原子尺度上的相互作用研究提供了可能。

Microscopic structure and thermodynamic approach is quite important to investigate biological functioning on biomembrane surface. From this point of view, we developed a method to perform simultaneous X-ray diffraction and differential scanning calorimetry measurements. We applied this method to studies on aqueous dispersions of phospholipid and phospholipid/phosphatidylglycerol. In the former, we obtained the results that the X-ray diffraction intensity is proportional to the transition enthalpy. In the latter, we found the existence of H_<II> structure that plays an important role in biological functioning. As examples for interaction between a phospholipid molecule and a small molecule, we studied systems of phospholipid/alcohol and phospholipid/sugar. In the former, we analyzed the interdigitated structure and proposed a micro-structural model. In the latter, depending on sugars the condition that stabilizes liquid-crystalline phase was revealed. Furthermore, as an example of interaction between a phospholipid molecule and a small molecule, we studied a system of phospholipid/water by thermal analysis and X-ray diffraction. From this study, we found the number of water molecule incorporated in the interbilayer. Furthermore, we studied the structure of a monolayer of fatty acids formed on a graphite surface by scanning tunneling microscopy with atomic resolution and this method offers possibility to carry out a study on interaction at atomic scale.