Abstract
Macromolecular crowding is known to modulate chemical equilibria, reaction rates, and molecular binding events, both in aqueous solutions and at lipid bilayer membranes, natural barriers that enclose the crowded environments of cells and their subcellular compartments. Previous studies on the effects of macromolecular crowding in aqueous compartments on conduction through membranes have focused on single-channel ionic conduction through previously formed pores at thermodynamic equilibrium. Here, the effects of macromolecular crowding on the mechanism of pore formation itself were studied using the droplet interface bilayer (DIB) technique with the voltage-dependent pore-forming peptide alamethicin (alm). Macromolecular crowding was varied using 8 kDa molecular weight polyethylene glycol (PEG8k) or 500 kDa dextran (DEX500k) in two aqueous droplets on both sides of the bilayer membrane. In general, voltage thresholds for pore formation in the presence of crowders in the droplets decreased compared to their values in the absence of crowders, due to excluded volume effects, water binding by PEG, and changes in the ordering of water molecules and hydrogen-bonding interactions involving the polar lipid headgroups. In addition, asymmetric crowder loading (e.g., PEG8k-DEX500k on either side of the membrane) resulted in transmembrane osmotic pressure gradients that either enhanced or degraded the ionic conduction through the pores.
Original language | English |
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Pages (from-to) | 5095-5102 |
Number of pages | 8 |
Journal | Journal of Physical Chemistry B |
Volume | 124 |
Issue number | 25 |
DOIs | |
State | Published - Jun 25 2020 |
Funding
G.T. and W.M. acknowledge support from the Bredesen Center for Interdisciplinary Research. All authors acknowledge support by way of manuscript review and feedback from S. A. Sarles, J. S. Najem, and D. Bolmatov. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Notice: This manuscript has been authored by UT-Battelle, LLC, under Contract No. DE-AC0500OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for the United States Government purposes.
Funders | Funder number |
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Bredesen Center for Interdisciplinary Research | DE-AC0500OR22725 |
U.S. Department of Energy |