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Research Highlight

Nano-Enabled Measurement of Single Molecule Protein Binding

Nano-Enabled Measurement of Single Molecule Protein Binding
Fluorescent cAMP (fcAMP) binding to intact HCN channels in ZMWs. (a) Scanning electron microscopy (SEM) image of ZMWs. (b) Schematic (not to scale) of ZMW with deposited fluorescent protein (eGFP)-tagged pacemaker ion channel receptor (HCN) binding experiments.

Scientific Achievement

A new approach based on nanofabricated zero-mode waveguides for observing stepwise binding in multimeric proteins at physiologically relevant concentrations with single-molecule resolution is demonstrated.

Significance and Impact

The approach overcomes the current limitations of ensemble measurements and offers several key insights into the mechanism of ligand activation.

Research Details

– Cyclic adenosine monophosphate (cAMP) binding to purified pacemaker ion channels was quantified at the single-molecule level using zero-mode waveguides (ZMWs) to monitor binding. – ZMWs enabled measurements at physiologically relevant protein concentrations for extended times providing an unprecedented view of early binding transitions in these multimeric ion channels. – This technique can be broadly applied to unambiguously quantify binding cooperativity in other membrane receptors.   D. S. White, S. Chowdhury, V. Idikuda, R. Zhang, S. T. Retterer, R. H. Goldsmith, and B. Chanda, "cAMP Binding to Closed Pacemaker Ion Channels is Non-Cooperative,"  Nature (2021).