2.B.68. The Organoplatinum Compound (Anion-Tuneable Uphill Hydroxide Transporter)
A transport process fuelled by organometallic compounds creates a pH gradient (Chen et al. 2022). The hydrolysis reaction of Pt(II) complexes results in the formation of aqua complexes that established rapid transmembrane movement ('flip-flop') of neutral Pt-OH species, leading to protonation of the OH group in the inner leaflet, generating OH- ions, and thus increasing the pH in the intravesicular solution. The organoplatinum complex effectively transports bound hydroxide ions across the membrane in a neutral complex. The initial net flow of the Pt(II) complex into the vesicles generates a positive electric potential that can further drive uphill transport because the electric potential is opposed to the chemical potential of OH-. The OH- ions equilibrate with this transmembrane electric potential but cannot remove it due to the relatively low permeability of the charged species. As a result, effective hydroxide transport against its concentration gradient can be achieved, and multiple additions can continuously drive the generation of OH(-) against its concentration gradient up to deltapH>2. The external addition of different anions can control the generation of OH- depending on their anion binding affinities. When anions displayed very high binding affinities towards Pt(II) compounds, such as halides, the external anions could dissipate the pH gradient. In contrast, a further pH increase was observed for weak binding anions, such as sulfate, due to the increase of the positive electric potential (Chen et al. 2022).