Eur. Phys. J. E (2018) 41: 77
https://doi.org/10.1140/epje/i2018-11687-6

Regular Article

Size-dependent interaction of a 3-arm star poly(ethylene glycol) with two biological nanopores

¹ Laboratory for Membrane Physiology and Technology, Department of Physiology, Faculty of Medicine, University of Freiburg, Hermann-Herder-Str. 7, 79104, Freiburg, Germany
² Ionera Technologies GmbH, Hermann-Herder-Str. 7, 79104, Freiburg, Germany
³ Institute for Macromolecular Chemistry, Stefan-Meier-Str. 31, 79104, Freiburg, Germany
⁴ Freiburg Materials Research Centre, University of Freiburg, Stefan-Meier-Str. 19, 79104, Freiburg, Germany
⁵ Freiburg Centre for Interactive Materials and Bioinspired Technologies, University of Freiburg, Georges-Köhler-Allee 105, 79110, Freiburg, Germany

^* e-mail: jan.behrends@physiologie.uni-freiburg.de

Received: 23 March 2018
Accepted: 31 May 2018
Published online: 18 June 2018

Abstract

We use two pore-forming proteins, alpha-hemolysin and aerolysin, to compare the polymer size-dependence of ionic current block by two types of ethyleneglycol polymers: 1) linear and 2) 3-arm star poly(ethylene glycol), both applied as a polydisperse mixture of average mass 1kDa under high salt conditions. The results demonstrate that monomer size sensitivity, as known for linear PEGs, is conserved for the star polymers with only subtle differences in the dependence of the residual conductance on monomer number. To explain this absence of a dominant effect of polymer architecture, we propose that PEG adsorbs to the inner pore wall in a collapsed, salted-out state, likely due to the effect of hydrophobic residues in the pore wall on the availability of water for hydration.