An integrated molecular simulation, biophysical experimentation and toxicology bioassay approach for mechanistic understanding of toxic effects of ionic liquids

PI：Jindal ShahProposal number：1134238这项研究的主要目标是了解离子液体这一新兴工业溶剂的分子水平毒性机理，以及这种机理如何在系统水平上表现为对特定生物体的毒性。这项拟议的研究将以尚未得到证实的假设为指导，即离子液体直接与磷脂双层相互作用，从而损害膜的完整性。一个由生物学家、化学工程师和分子模型师组成的跨学科团队将在这个项目上进行合作。将进行毒理学生物测定实验，以确定与对照相比可使微生物生长减少50%的离子液体浓度EC50。单分子光谱学和成像实验将被用来确定EC50浓度附近的模型脂质双层的形态和动力学。先进的分子动力学模拟将在相同的浓度下进行，以量化脂双层的结构和动力学数量以及双层分子水平运动的细节。这些模拟还将用于确定脂质双层界面上离子液体物种的结构和动力学，这是很难通过实验获得的信息。将对两种生物进行毒理学生物检测：莱茵衣藻和细菌大肠杆菌。中性脂双层和带负电荷的脂双层将作为模型生物膜。我们将研究两种截然不同的离子液体。第一组离子液体将基于不同烷基链长的1-烷基-3-甲基咪唑阳离子与阴离子配对，如氯化物和双三氟甲基磺酰亚胺，这些阴离子已经进行了非常详细的研究，很可能会大量生产。第二组离子液体将由阳离子四丁基膦和类似的阴离子组成。与咪唑基离子液体相比，这些离子液体及其变体的毒性较小，目前正在研究作为潜在的二氧化碳捕获溶剂。这项工作的灵感来自于这样一个事实：离子液体被定义为在环境条件下是液体的纯盐？已经成为一系列技术应用的有前途的新溶剂，包括气体分离、润滑、电池和作为治疗剂。学术界和工业界离子液体研究的爆炸性增长，加上工业采用离子液体的可能性越来越大，导致迫切需要了解这些材料对环境的影响，包括它们的命运、运输和对生物体的毒性。许多毒性生物测定研究表明，烷基链长、阴离子类型和亲脂性都对离子液体的毒性起作用。然而，对于这些因素如何导致毒性以及如何操纵它们以实现离子液体所需的毒性特性，缺乏基本的分子水平的了解。为了解决这一关键的知识差距，建议的分子模拟、生物物理实验和毒性生物测定相结合的方法是非常有希望的，因为它将导致对离子液体毒性的更大的机械理解，而不是单一的技术。虽然拟议的研究针对的是两类离子液体，但所获得的基本认识具有广泛的影响，可以纳入毒性较低的离子液体的合理设计，从而导致开发减少环境足迹的化学工艺和产品。这项工作也有利于目前旨在开发离子液体的治疗特性的努力，其中离子液体与脂质双层相互作用的知识是至关重要的。这项研究将提供关于细胞膜特性的基本信息，这些特性决定了对离子液体破坏的敏感性，这最终可能使能够在细胞内运输离子液体的微生物的工程成为可能，以便对离子液体进行生物降解。这项研究的另一个主要目标是教和培训学生如何通过在跨学科的实验/计算环境中工作，在分子水平上的相互作用和这种相互作用在系统水平上的表现之间建立智能联系。从代表不足的群体中招收妇女和学生的努力将遵循皮？S行之有效的方法，并将在巴黎圣母院现有的几个项目基础上再接再厉。计划通过巴黎圣母院公共事务办公室向更广泛的受众广泛传播这项活动的成果

PI: Jindal ShahProposal Number: 1134238The primary goal of this research is to understand the molecular level mechanisms of toxicity of ionic liquids, an emerging class of industrial solvents, and how such mechanisms manifest at a systems level to result in toxicity to a given organism. The proposed research will be guided by the as-yet unproven hypothesis that ionic liquids directly interact with the phospholipid bilayer and thereby compromise membrane integrity. An interdisciplinary team of biologists, chemical engineers, and molecular modelers will collaborate on this project. Toxicological bioassay experiments will be carried out to determine the ionic liquid concentrations EC50 that cause a 50% reduction in growth of microbes relative to a control. Single molecule spectroscopy and imaging experiments will be used to determine the morphology and dynamics of model lipid bilayers around the EC50 concentrations. Advanced molecular dynamics simulations will be carried out at the same concentrations to quantify structural and dynamical quantities for the lipid bilayer along with details on the molecular-level motion of the bilayer. The simulations will also be used to determine the structure and dynamics of ionic liquid species at the lipid bilayer interface, information that is difficult to obtain experimentally. Two types of organisms will be studied for toxicological bioassays: the alga Chlamydomonas reinhardtii and the bacterium Escherichia coli. A neutral-lipid bilayer and a negatively-charged lipid bilayer will serve as model organism membranes. Two very different classes of ionic liquids will be investigated. The first set of ionic liquids will be based on 1-alkyl-3-methylimidazolium cations with varying alkyl chain length paired with anions such as chloride and bistrifluoromethylsulfonylimide, which have been studied in great detail and are likely to be manufactured in large quantities. The second set of ionic liquids will be comprised of the cation tetrabutylphosphonium with similar anions. These ionic liquids and their variations are less toxic than imidazolium-based ionic liquids and currently being studied as potential CO2 capture solvents. The work is inspired by the fact that ionic liquids defined as pure salts that are liquid at ambient conditions ? have emerged as promising new solvents for a range of technological applications including gas separations, lubrication, batteries, and as therapeutic agents. An explosion in ionic liquid research within academia and industry coupled with increasing likelihood of adoption of ionic liquids by industry has resulted in an urgent need to understand the environmental impact of these materials in terms of their fate, transport, and toxicity towards organisms. A number of toxicity bioassay studies have suggested that alkyl chain length, anion type, and lipophilicity all play a role in ionic liquid toxicity. However, a fundamental molecular level understanding of how these factors contribute to toxicity and how they can be manipulated to achieve desired toxicity characteristics of ionic liquids is lacking. To address this critical gap in knowledge, the proposed linked molecular simulation, biophysical experimentation, and toxicity bioassay approach is highly promising as it will result in a greater mechanistic understanding of ionic liquid toxicity than would be possible by a single technique alone. Although the proposed research is targeted at two classes of ionic liquids, the fundamental understanding gained has broad implications and can be integrated into the rational design of less toxic ionic liquids which will lead to development of chemical processes and products with reduced environmental footprint. This work also benefits current efforts aimed at exploiting therapeutic properties of ionic liquids, where knowledge of ionic liquid interactions with the lipid bilayer is critical. The study will provide essential information on the characteristics of the cell membrane that determine susceptibility to disruption by ionic liquids, which may ultimately enable the engineering of microorganisms able to transport ionic liquids inside the cell for biodegradation of ionic liquids. Another major goal of this research is to teach and train students how to make an intellectual connection between molecular level interactions and the manifestation of such interactions at a systems level by working in an interdisciplinary experimental/computational environment. Efforts to recruit women and students from underrepresented groups will follow the PI?s proven methods and will build on several existing programs at Notre Dame. A wide dissemination of the results from this activity to a broader audience is planned through the Notre Dame Public Affairs Office