Resistive-pulse nanopore sensing enables label free single molecule analysis.  The sensor is based on the Coulter-counter principle applied at the nanoscale.  Briefly, a nano-sized hole in a membrane separates two electrolyte solutions, and an applied transmembrane voltage establishes a stable open-pore current.  Individual molecules, commensurate in size with the pore, enter and reduce the flow of charge, which yields short-lived current blockades whose magnitude and duration can be used to infer information about the molecular size, shape, charge and conformation.  The majority of nanopore-based single molecule analysis utilizes voltage dependent studies to probe the molecules of interest.  Varying the temperature of the solution provides more information as it allows one to separate the entropy and enthalpy components of the free energy change of the molecule/pore interaction.  However, nanopore-based temperature studies are limited by solvent evaporation and the long-times required to heat large solution volumes.   Recently, our group described the use of infrared laser heating to facilitate the analysis of short duplex DNA strands with a wild type alpha hemolysin pore.  This work showed the advantages of laser heating, which enables rapid temperature changes over tightly confined volumes.  Our approach eliminates issues related to bulk heating and provides a means for quantifying the thermodynamic interaction between the analyte molecule and pore.  In this presentation we will describe more recent efforts on the application of the laser-based heating protocol to the analysis of polymer-pore and polymer-(pore-cluster) interactions.  The goal is to better understand the interaction between analyte molecules such as PEG and other peptides with the alpha hemolysin pore and to extract details about the mechanism of residence time enhancement seen with thiolate-capped gold clusters in the pore.

Analyzing single molecule thermodynamics from laser-induced nanopore heating

254th National Meeting (2017)

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