Single-Molecule Electrical Currents Associated with Valinomycin Transport of K<sup></sup>.
basic_science · Level V
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- Record sourced from PubMed, PMID 37068060.
- Also identified by DOI 10.1021/acsnano.3c02825.
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Abstract
A quantitative description of ionophore-mediated ion transport is important in understanding ionophore activity in biological systems and developing ionophore applications. Herein, we describe the direct measurement of the electrical current resulting from K<sup>+</sup> transport mediated by <i>individual</i> valinomycin (<i>val</i>) ionophores. Step fluctuations in current measured across a 1,2-diphytanoyl-<i>sn</i>-glycero-3-phosphocholine (DPhPC) bilayer suspended over a ∼400 nm radius glass nanopore result from dynamic partitioning of <i>val</i> between the bilayer and torus region, effectively increasing or decreasing the total number of <i>val</i> present in the membrane. In our studies, approximately 30 <i>val</i> are present in the membrane on average with a <i>val</i> entering or leaving the bilayer approximately every 50 s, allowing measurement of changes in electrical current associated with individual <i>val</i>. The single-molecule <i>val</i>(K<sup>+</sup>) transport current at 0.1 V applied potential is (1.3 ± 0.6) × 10<sup>-15</sup> A, consistent with estimates of the transport kinetics based on large <i>val</i> ensembles. This methodology for analyzing single ionophore transport is general and can be applied to other carrier-type ionophores.