(55e) Functional Reconstitution and Characterization of Artificial Proton Channels in Artificial Membranes

Functional
reconstitution and characterization of artificial proton channels
in artificial membranes

Yue-xiao Shen¹,
Istvan Kocsis², Mihail Barboiu², Manish Kumar*¹

¹Department of Chemical Engineering, Pennsylvania State Univerity,
University Park, PA, 16802, USA

²Institut Europeen des Membranes, ENSCM-UMII-UMR CNRS 5635, Place Eugene
Bataillon CC047, Montpellier, 34095, France

*Corresponding author: 155
Fenske Laboratory, Pennsylvania State Univerity, University Park, PA, 16802,
USA, (814) 865-7519, manish.kumar@psu.edu

Artificial
proton channels mimicking M2 Influenza
proton channels present in biological membranes could be new materials for water
treatment membranes, ion exchange membranes or pH sensors in the future. Here
we report on a series of imidazole compounds with urea ribbons which are
proposed to assemble into imidazole quartet channel in artificial membranes.
The proposed quartet structures mimic the His-37 selectivity filter in M2
Influenza proton channel (Fig. A). In lipid membranes, these imidazole
based molecules could self-assemble into channel structures (Fig. A) that mimic
the 4 His tetrad of M2 proton channels and the resulting artificial channels were
able to transport ∼10⁶
water molecules per second, rejecting all ions except protons and showed
similar proton transport rates as M2 proton channels.¹ We also demonstrated that these
imidazole channels could be functionally incorporated into lipid bilayer-like poly(butadiene)-b-poly(ethylene
oxide) block copolymer membranes (Fig. B).² Because block copolymers are more
mechanically and chemically stable than lipids, and offer customizable polymer
types, membrane thicknesses and terminal functional groups, the self-assembled
artificial channels in these membranes can be an ideal platform for engineering
applications such as separation, sensing and drug delivery.

Figure. (A) M2 proton channel is a highly pH
sensitive and proton selective transmembrane protein existing in Influenza A virus. When the protein is in acidic environment, the His
tetrad is protonated and the pore is opened to proton transport. Here we
provide a series of imidazole compounds (HCn, n means
different carbon chains) that can mimic the His tetrad structure in M2 and have
both water and proton transport activities. (B) Water-transport activity of one
imidazole channel (S-HC8) in polymer vesicles. The selected imidazole compounds
formed channels in poly(butadiene)-b-poly(ethylene oxide) (PB₂₂-PEO₁₄)
block copolymer vesicles. After abrupt exposure to a hypertonic solution
containing 200 mM extra NaCl, the light-scattering experimental traces of the
PB₂₂-PEO₁₄ polymersomes without and with channels
indicated the water permeability through these self-assembled channels.

References

1          Licsandru,
E. et al. Salt-Excluding Artificial
Water Channels Exhibiting Enhanced Dipolar Water and Proton Translocation. J. Am. Chem. Soc. 138, 5403-5409, (2016).

2          Shen,
Y.-x. et al. Artificial proton
channels in block copolymer membranes. In
preparation.