Poster The 5th Prato Conference on Pore Forming Proteins 2021

Ligand exchange and peptide sensing with metallic clusters in a nanopore sensor (#101)

Madhav L Ghimire 1 , Bobby D Cox 1 , Massimo F Bertino 1 , Joseph E Reiner 1
  1. Virginia Commonwealth University, Richmond, VA, United States

Resistive-pulse nanopore sensing provides a unique methodology to study ligand dynamics on thiolate-capped metallic clusters. Small gold nanoclusters (D ~ 2 nm) can be trapped in the vestibule region of an alpha hemolysin nanopore under sufficient applied transmembrane potential.  These clusters remain trapped for tens of seconds and ligand-induced structure fluctuations of the nanoclusters can be observed as step-like transitions between numerous quantized nanopore current states.  The isolation and monitoring of these cluster dynamics permits the observation of a variety of surface reactions on water-soluble nanoclusters.  Here we present our studies of ligand exchange processes at the single cluster limit.  Target ligands are ejected onto the pore-bound cluster through a micron-sized pipette capillary and the ensuing exchange process can be monitored at the single ligand-limit.  The observed exchange kinetics are consistent with the expected energetics of the exchange process and the corresponding current steps that result from the ligand exchange suggest a way to detect and characterize the exchanging ligands.  We provide proof-of-concept demonstration of peptide detection by ejecting the tripeptide glutathione onto a tiopronin-capped gold nanocluster that is isolated and trapped in an alpha hemolysin pore.  This presentation will highlight our ligand exchange kinetic studies along with our demonstration of peptide sensing, both of which illustrate that nanopore sensing provides a unique tool for monitoring ligand dynamics of nanoconfined metallic clusters.