Liquid Crystalline Orientational Excitations in Biological Membranes

生物膜被认为是生命形成和增殖的关键。在膜上的物质交换负责其平衡操作以及动作电位的传播。了解这些过程的潜在机制对我们对抗许多疾病至关重要。同时，组成生物膜的分子的取向顺序已经与液晶（LC）进行了比较。然而，在lc中发生的各种激发模式的机制与生物组织（如生物膜）中发生的类似过程没有进一步的详细比较。我们认为LC材料的各向异性特性在生物膜中应该有非常重要的相似之处。也就是说，离子在“简单”分子双层膜（类似于向列LCs）中各向异性扩散的临界差异与髓鞘分子“堆叠”平面（类似于近晶LCs）的情况相比，是一个很好的例子，可以利用我们对向列和近晶LCs的物理知识来更好地理解各种生物膜中发生的过程。此外，我们最近还发现了具有长距离传播距离的定向分子微扰的存在。这使我们有希望更好地理解髓鞘、Ranvier节点以及离子通道在动作电位传播过程中的触发机制。一旦我们更好地理解了这些机制，我们计划使用光激活的两亲性无毒偶氮苯来控制这些分子系统（膜）中的取向顺序，从而控制材料（离子等）在它们之间的交换机制。事实上，我们已经开始了一些这样的实验，我们用大肠杆菌获得的第一批结果非常令人鼓舞。我们已经证明，光可以用来控制它们的游泳速度，这是它们毒性的关键因素。我们认为这种控制是通过偶氮苯分子的光异构化离子通道的不稳定而获得的。在拟进行的研究中，我们将首先使用lc和人工脂质双分子层进行基础研究。然后，我们将研究在偶氮苯分子存在下，在允许控制这些分子的反式和顺式居群之间平衡的各种激发机制下，这些材料中的电荷迁移率。然后我们将研究具有双层膜的细菌。最后，我们将开发光遗传学工具，允许在大脑富含髓磷脂的区域注射和选择性光激活偶氮苯分子，试图局部控制大脑激活水平。我们希望这些研究将有助于开发光电工具和技术（过程），以在许多医学应用中主动控制生物组织。

The biological membrane is considered as key for the formation and proliferation of life. The material exchange across this membrane is responsible for its equilibrium operation as well as during the action potential's propagation. The understanding of underlying mechanisms of these processes is paramount for our fight against many diseases. In the same time, the orientational order of molecules, composing the biological membrane, has already been compared with liquid crystals (LC). However, there was no further detailed comparison of the mechanisms of various excitation modes, taking place in LCs, with respect to similar processes taking place in the biological tissue, such as the biological membrane. We think that the anisotropic properties of LC materials should have very important analogies in biological membranes. Namely, the critical difference of anisotropic diffusion of ions in "simple" molecular double layer membranes (similar to nematic LCs) compared with the case of molecular "stacking" planes of myelin sheaths (similar to smectic LCs) is a good example of the possible use of our knowledge of the physics of nematic and smectic LCs to better understand the processes taking place in various biological membranes. In addition, we have recently discovered the existence of orientational molecular perturbations with long range propagation distances. This gives us the hope to better understand the role of myelin sheaths, the nodes of Ranvier and the triggering mechanism of ionic channels during the action potential's propagation. Once we understand these mechanisms better, we are planning to use photo activated amphiphilic non-toxic azobenzenes, to control the orientational order in such molecular systems (membranes) and thus the mechanisms of material (ionic, etc.) exchange across them. In fact, we have already started some of these experiments and our very first results, obtained with the Ecoli bacteria, are very encouraging. We have shown that light can be used to control their swimming speed which is a key factor for their virulence. We think that this control is obtained by the destabilization of ionic channel via the photoisomerization of azobenzene molecules. In the proposed research, we shall first use LCs and artificial lipid bilayers for our basic studies. Then, we shall study the charge mobility in these materials in the presence of azobenzene molecules during various excitation regimes allowing the control of the equilibrium between Trans and Cis populations of these molecules. Then we shall work with bacteria with bilayer membranes. Finally, we shall develop optogenetic tools allowing the injection and the selective photo activation of azobenzene molecules in myelin rich regions of the brain, trying to control locally the brain activation level. We hope that these studies will help to develop optoelectronic tools and techniques (processes) for the active control of the biological tissue with numerous medical applications.