Architecture and Attributes of Gas Vesicles

ID: MPS/DMR/BMAT(7623) 1305713 PI: Herzfeld， Judith ORG: Brandeis university标题：气体囊泡的结构和属性技术：水生微生物的空心纺锤形漂浮囊泡具有显着的物理性质。2.0 nm厚的蛋白质壁不透水，但可以渗透比水大得多的气体分子。宽度为75纳米，长度为1000纳米的囊泡可以承受高达10个大气压的静水压力。该壁几乎完全由高度疏水的7kda气体囊泡蛋白A （gvpA）的重复单元组装而成，不能用洗涤剂溶解。虽然很难想象自然界是如何实现这些机械、界面和渗透性特性的，但从所有生物体中gvpA的强烈同源性来看，很明显，自然界并没有找到很多方法来实现这一点。此外，与其他蛋白质的同源性缺失表明该气体囊泡结构是一种非常特殊的结构。该项目的总体目标是了解导致其性质的气体囊泡的结构特征。将研究两种系统，一种适应淡水，另一种适应高盐条件。这项工作将采用固态核磁共振实验和原子模型。固体核磁共振的优点是能够在不适合溶解或结晶的体系中测量核间距离。这些信息将允许对完整的结构和气体囊泡壳的界面特性进行建模，充分考虑到囊泡壁的周期性和不对称环境。比较适应淡水的囊泡和适应高盐条件的囊泡将有助于为不同的结构特征分配功能意义。非技术：从实际的角度来看，水生微生物的气体囊泡在许多情况下都有直接的用途。特别是，它们已被用于赋予通常不漂浮的细胞浮力，用于改善锚定依赖性细胞培养中的氧灌注，并作为疫苗接种载体。预计对气体囊泡结构的详细了解将允许这些直接应用在与野生型囊泡的工程相互作用或选择突变囊泡方面进行微调。此外，了解大自然是如何设计气体囊泡的，可能会激发利用相同基本原理设计新材料的灵感。特别令人感兴趣的是囊泡壁对洗涤剂和蛋白酶的抵抗力的起源，它们的机械强度，它们对气体的高渗透性，以及它们内表面预期的极端脱湿行为。与此项目相关的教育和推广活动将包括布兰代斯大学科学团队项目的本科生在夏季直接参与，为学生提供动手活动，让他们从大波士顿地区服务不足的高中到校园实地考察，以及在Kroka探险项目中进行动手活动的指导，该项目主要为来自新罕布什尔州和佛蒙特州的青少年提供服务。

ID: MPS/DMR/BMAT(7623) 1305713 PI: Herzfeld, Judith ORG: Brandeis UniversityTitle: Architecture and Attributes of Gas VesiclesTechnical: The hollow, spindle-shaped floatation vesicles of aquatic micro-organisms have remarkable physical properties. The 2.0 nm thick proteinaceous wall is impermeable to water but permeable to gas molecules considerably larger than water. Vesicles measuring 75 nm in width and up to 1000 nm in length can withstand as much as 10 atmospheres of hydrostatic pressure. The wall, assembled almost exclusively from repeating units of the highly hydrophobic 7 kDa gas vesicle protein A (gvpA), cannot be solubilized with detergents. While it is difficult to imagine how nature achieves these mechanical, interfacial, and permeability properties, it is also clear, from the strong homology among gvpA's across all organisms, that nature has not found many ways of doing it. Furthermore, the absence of homology with other proteins indicates that the gas vesicle construct is a very special one. The general goal of the project is to understand the structural features of gas vesicles that are responsible for their properties. Two systems will be studied, one adapted to fresh water and the other adapted to highly saline conditions. The work will employ solid state NMR experiments and atomistic modeling. Solid state NMR has the advantage of being able to measure internuclear distances in systems not amenable to either solubilization or crystallization. This information will allow modeling of the complete structure and the interfacial properties of the gas vesicle shell, taking fully into account the periodicity and the asymmetric environment of the vesicle wall. Comparisons between vesicles adapted to fresh water and vesicles adapted to highly saline conditions will help in assigning functional significance to different structural features. Non-Technical: From a practical point of view, the gas vesicles of aquatic micro-organisms are finding direct use in a number of contexts. In particular, they have been used to confer buoyancy in cells that normally do not float, to improve oxygen perfusion in anchorage-dependent cell cultures, and as vaccination vehicles. It is expected that detailed knowledge of gas vesicle structure will allow these direct applications to be fine-tuned with respect to engineering interactions with wild type vesicles or choosing mutant vesicles. In addition, understanding how nature has designed gas vesicles may inspire the design of new materials that make use of the same underlying principles. Of particular interest are the origins of the resistance of the vesicle walls to detergents and proteases, their mechanical strength, their high permeability to gases, and the anticipated extreme dewetting behavior of their inner surface. Education and outreach activities associated with this project will include direct involvement of undergraduates from the Brandeis University Science Posse program during the summer, hands-on activities for students in field trips to campus from underserved high schools in the greater Boston area, and instruction with hands-on activities in the Kroka Expeditions program that serves teens primarily from New Hampshire and Vermont.