Ion-Ion Interactions and the Reverse Hofmeister Effect

项目概要 尽管对溶解的有机溶质和盐的性质的研究已有 130 多年的历史，但我们 对它们如何相互作用的规律知之甚少。例如，考虑 NaI 可以导致 增加蛋白质的溶解度（霍夫迈斯特效应）或导致溶解度降低并导致 蛋白质沉淀（逆霍夫迈斯特效应，RHE）。本申请涉及后者。 我们对 RHE 背后的分子相互作用的了解是有限的。确实，只是在最后 十年来，已证实关键的非共价相互作用是阴离子之间的相互作用 盐和溶质上带正电的基团。除此之外，细节很少：我们对 此类相互作用的强度以及它们是否以库仑相互作用或色散相互作用为主；我们 对可能主导溶质沉淀的特定离子对的存在知之甚少；而我们 对聚集和沉淀途径的机制知之甚少。开发一个 我们概述了对这些的理解：1) 旨在从结构上探测离子-离子配对的模型宿主的研究 和热力学，从而揭示它们如何导致聚集和沉淀的细节； 2） 分子动力学 (MD) 模拟旨在揭示这些离子对的原子细节以及水的作用 调节它们相互作用的热力学； 3）基于我们的蛋白质研究 了解模型宿主和 MD 模拟，将开始系统地限定和量化 RHE 明显存在于蛋白质中，以及这种现象背后的特定离子-离子相互作用。 这些研究将解决以下科学问题： · 与 RHE 相关的特定离子间相互作用有哪些？ · 这些离子-离子相互作用的具体结构特征和热力学是什么？ · 离子对的性质与聚集和聚集之间是否存在定性和定量的联系 小分子沉淀？ · 阴离子-蛋白质相互作用是否会影响特定蛋白质的结构、稳定性和聚集？ 可确定的方法？ · 蛋白质中的 RHE 能否用作表征/鉴定蛋白质的特征？ · 蛋白质中的 RHE 能否归因于特定的阴离子-蛋白质相互作用？ 回答这些问题将提高我们对常见小分子溶解度的理解 制药行业中经常令人困惑和矛盾的 RHE 得到更清晰的认识 蛋白质。后一点不仅是确定纯化和结晶蛋白质的新方法的关键，而且也是 对于理解朊病毒疾病和血栓形成中蛋白质的不可逆沉积至关重要。

Project Summary Although the properties of dissolved organic solutes and salts have been studied for over 130 years, we know little of the laws governing how they interact. Consider for example the fact that NaI can lead to an increase in the solubility of a protein (the Hofmeister Effect) or bring about a decrease in solubility and lead to precipitation of a protein (the Reverse Hofmeister Effect, RHE). This application concerns the latter. Our understanding of the molecular interactions behind the RHE is limited. Indeed, it is only in the last decade that it has been confirmed that the key non-covalent interactions are those between the anion of the salt and positively charged groups on the solute. Beyond this, details are sparse: We know little about the magnitude of such interactions and whether they are dominated by Coulombic or dispersion interactions; we know little about the existence of specific ion-pairs that might dominate the precipitation of a solute; and we know little about the mechanisms of the aggregation and precipitation pathway(s). To develop an understanding of these we outline: 1) studies with model hosts designed to probe ion-ion pairing structurally and thermodynamically, and hence reveal details of how these lead to aggregation and precipitation; 2) molecular dynamics (MD) simulations designed to reveal atomistic details of these ion pairs, and the role water plays in modulating their thermodynamics of interaction, and; 3) studies with proteins that, building on our understanding of model hosts and MD simulations, will begin to systematically qualify and quantify how the RHE is manifest in proteins, and the specific ion-ion interactions behind this phenomenon. These studies will address the following scientific questions: · What are the specific ion-ion interactions pertinent to the RHE? · What are the specific structural features and thermodynamics of these ion-ion interactions? · Are there qualitative and quantitative links between the nature of ion pairing and the aggregation and precipitation of small molecules? · Do anion-protein interactions influence the structure, stability, and aggregation of proteins in specific, determinable ways? · Can the RHE in proteins be used as a signature to characterize/identify proteins? · Can the RHE in proteins be attributed to specific anion-protein interactions? Answering these questions will improve our understanding of the solubility of small molecules common to the pharmaceutical industry, and lead to a clearer picture of the often bewildering and contradictory RHE in proteins. This latter point is not only key to determining new ways to purify and crystallize proteins, but is also crucial to understanding the irreversible deposition of proteins in prion diseases and thrombosis.