Selective Receptors for the Transmembrane Transport of Bicarbonate Anion

碳酸氢根(HCO3-)离子在许多生化过程中起核心作用，维持细胞内外稳定的pH水平，激活精子受精，并在囊性纤维化等疾病中发挥作用。然而，尽管它的重要性显而易见，但令人惊讶的是，关于有机受体化合物对HCO3-的选择性配位作用知之甚少。同样，合成转运蛋白对HCO3-的跨膜转运尚未得到解决。尽管重碳酸盐的超分子化学很重要，但它在很大程度上还没有被探索过。受到碳酸氢盐在关键的生物和环境过程中的核心作用的启发，我们建议研究这种中心阴离子的结合和跨膜运输。据我们所知，这是第一个全面的研究计划，旨在了解重要的碳酸氢根(HCO3-)阴离子的分子识别和跨膜运输。该项目将结合两个现有研究小组的专业知识，首次对碳酸氢盐的分子识别和超分子化学进行全面研究，从而解决这两个挑战。菲利普·盖尔是英国南安普顿大学的无机化学家。盖尔是超分子化学领域的国际领先者。他在阴离子受体复合体的合成和结构测定方面享誉全球。来自美国马里兰大学的Jeffery Davis带来了在超分子组件的合成和表征方面的经验，该组件旨在结合离子和中性分子并通过磷脂膜传输。来自英国和美国的这种专业知识的结合将把合成膜运输器的开发带入促进碳酸氢盐运输的新领域。我们将设计和合成不同类型的受体，这些受体能够选择性地结合碳酸氢盐，并继续展示这些化合物通过脂膜运输HCO3-的能力-这些受体将包括被设计为跨膜载体和通道的化合物。载体化合物将由脂溶性有机受体组成，旨在与HCO3形成互补的氢键阵列-或通过可逆的共价键形成结合这种阴离子。我们还将设计载体来结合碳酸氢盐二聚体/固态碳酸氢盐通常观察到的结构基序。还将合成跨越脂质双层的通道，促进HCO3-在使用可修改的共价键形成的膜上的扩散。此外，我们还将开发一系列新的技术来测定碳酸氢盐的跨膜转运。这将包括使用以前被用来监测NO3-和Cl2-运输的所谓的“基本脉冲分析”。新的方法将包括使用碳酸氢盐敏感染料，如芘功能化的环糊精，使用13C[HCO3-]的核磁共振方法和囊外顺磁试剂，允许监测泡内和囊外碳酸氢盐的种群，以及膜片钳实验，使我们能够明确确定运输剂的作用机制。产生的化合物将成为科学家研究囊性纤维化等疾病模型的有用工具。这些系统的其他应用可以包括在囊泡环境中涉及HCO3的合成，这里开发的系统控制重碳酸盐进入包封的反应混合物。直接应用这些新体系，我们选择性地将HCO3-输送到脂质体中，作为形成结晶CaCO3的模板，作为生物矿化的模型体系。

The bicarbonate (HCO3-) anion plays a central role in many biochemical processes maintaining stable pH levels inside and outside cells, activating sperm for fertilization and playing roles in diseases such as cystic fibrosis. Despite its obvious importance, however, there is surprisingly little known about the selective coordination of HCO3- by organic receptor compounds. Similarly, the transmembrane transport of HCO3- by synthetic transporters has not yet been tackled. Despite its importance, the supramolecular chemistry of bicarbonate is largely unexplored. Inspired by bicarbonate's central role in crucial biological and environmental processes, we propose to study the binding and transmembrane transport of this central anion. This is, to our knowledge, the first comprehensive research program aimed at understanding the molecular recognition and transmembrane transport of the important bicarbonate (HCO3-) anion. The project will tackle both these challenges by combining the expertise from two established research groups in the first comprehensive study of the molecular recognition and supramolecular chemistry of bicarbonate. Philip Gale is an inorganic chemist at the University of Southampton in the UK. Gale is an international leader in the field of Supramolecular Chemistry. He has an established worldwide reputation in the synthesis and structural determination of anion-receptor complexes. Jeffery Davis, from the University of Maryland in the US, brings experience in the in the synthesis and characterization of supramolecular assemblies designed to bind and transport ions and neutral molecules across phospholipid membranes. This combination of expertise from the UK and the US will take the development of synthetic membrane transporters into the new area of facilitated bicarbonate transport. We will design and synthesize different types of receptors that are able to selectively bind bicarbonate and go on to demonstrate the ability of these compounds to transport HCO3- across lipid membranes - these receptors will include compounds designed to function as transmembrane carriers and channels. Carrier compounds will consist of lipid soluble organic receptors designed to have complementary hydrogen bonding arrays to HCO3- or to bind this anion via reversible covalent bond formation. We will also design carriers to bind bicarbonate dimers / a structural motif commonly observed with bicarbonate in the solid state. Channels will also be synthesised that span the lipid bilayer facilitating the diffusion of HCO3- across the membrane that employ revisable covalent bond formation.In addition we will develop a range of new techniques to assay for the transmembrane transport of bicarbonate. This will include using so-called 'base pulse assays' that have previously been used to monitor NO3- and Cl- transport. New methods will include the use of bicarbonate sensitive dyes such as pyrene functionalised cyclodextrins, NMR methods employing 13C[HCO3-] and extravesicular paramagnetic reagents allowing the populations intravesicular and extravesicular bicarbonate to be monitored, and patch-clamp experiments that will allow us to unambiguously determine the mechanism by which the transport agents function. The compounds produced will be useful tools for use by scientists studying models of diseases such as cystic fibrosis. Other applications of these systems could include synthesis involving HCO3- inside a vesicle environment with the systems developed here controlling the entry of bicarbonate to an encapsulated reaction mixture. Applying these new systems directly, we selectively transport HCO3- into liposomes as a means to template the formation of crystalline CaCO3 as a model system for biomineralization.