Supplementary Information Files for Transmembrane transport of bicarbonate unravelled

Supplementary Information Files for Transmembrane transport of bicarbonate unravelledAnion receptors can be used to transport ions across lipid bilayers, which has potential for therapeutic applications. Synthetic bicarbonate transporters are of particular interest, as defects in transmembrane transport of bicarbonate are associated with various diseases. However, no convenient method exists to directly observe bicarbonate transport and study the mechanisms involved. Here, an assay is presented that allows the kinetics of bicarbonate transport into liposomes to be monitored directly and with great sensitivity. The assay utilises an encapsulated europium(III) complex, which exhibits a large increase in emission intensity upon binding bicarbonate. Mechanisms involving CO2 diffusion and the dissipation of a pH gradient are shown to be able to lead to an increase in bicarbonate concentration within liposomes, without transport of the anion occurring at all. By distinguishing these alternative mechanisms from actual bicarbonate transport, this assay will inform the future development of bicarbonate transporters.碳酸氢盐跨膜转运解析补充信息文件 阴离子受体可介导离子跨脂质双分子层转运，该方向具备治疗应用潜力。人工合成碳酸氢盐转运体尤为引人关注，因为碳酸氢盐跨膜转运缺陷与多种疾病密切相关。然而目前尚无便捷方法可直接观测碳酸氢盐转运并研究其相关作用机制。本研究提出一种检测分析法，可直接且高灵敏度地监测碳酸氢盐转运进入脂质体（liposomes）的动力学过程。该分析法采用包封于脂质体内的铕(III)配合物（europium(III) complex），其结合碳酸氢盐后发射强度会显著提升。研究表明，仅依靠二氧化碳扩散以及pH梯度消散的机制，即可在完全不发生阴离子转运的情况下，提升脂质体内的碳酸氢盐浓度。通过区分此类替代机制与真实的碳酸氢盐转运过程，该分析法可为碳酸氢盐转运体的后续开发提供指导。