Poster The 5th Prato Conference on Pore Forming Proteins 2021

Laser-based thermodynamic studies of polymer-nanopore systems (#113)

Christopher E Angevine 1 , Joseph WF Robertson 2 , Joseph E Reiner 1
  1. Virginia Commonwealth University, Richmond, VA, United States
  2. Biophysical and Biomedical Measurement Group, National Institute of Standards and Technology, Gaithersburg, MD, USA

Neutral polymer interactions with transmembrane proteins are of particular interest for developing single molecule biosensors.  Temperature studies of polymer-pore interactions could provide greater insight into the free energy barrier to escape by isolating the entropic and enthalpic components of the barrier.  Difficulties associated with membrane and solvent stability have limited temperature studies to a small number of demonstrations.  To address this problem, we have developed an infrared laser-based heating methodology to probe polymer-pore interactions as a function of solution temperature in and around an isolated nanopore.  As proof of concept, we demonstrate the technique with polyethylene glycol (PEG) and show that the free energy barrier for escape is dominated by entropy while studies with several water-soluble peptides (angiotensin 1, angiotensin 2 and neurotensin) are dominated by enthalpy.  We additionally use the laser-based heating methodology to probe polymer interactions with a gold-cluster occupied pore.  These studies show that the cluster enhances the enthalpic interaction for the PEG verifying that PEG behaves as a polycation under the high ionic strength conditions typically used for nanopore sensing.  Our laser heating methodology applied to these systems highlights the role that temperature studies could provide for better understanding the entropic and enthalpic components of the polymer-pore free energy landscape.  This presentation will report on these results and suggest means for improving nanopore sensors with temperature-based characterization of the polymer-pore interaction.