Fusion of purple membranes triggered by immobilization on carbon nanomembranes

René Riedel; Natalie Frese; Fang Yang; Martin Wortmann; Raphael Dalpke; Daniel Rhinow; Norbert Hampp; Armin Gölzhäuser

doi:10.3762/bjnano.12.8

Fusion of purple membranes triggered by immobilization on carbon nanomembranes

Beilstein J Nanotechnol. 2021 Jan 22:12:93-101. doi: 10.3762/bjnano.12.8. eCollection 2021.

Authors

René Riedel¹, Natalie Frese², Fang Yang³, Martin Wortmann⁴, Raphael Dalpke², Daniel Rhinow^{1

5}, Norbert Hampp¹, Armin Gölzhäuser²

Affiliations

¹ Faculty of Chemistry and Materials Sciences Center, University of Marburg, Hans-Meerwein-Strasse, D-35032 Marburg, Germany.
² Physics of Supramolecular Systems and Surfaces, Faculty of Physics, Bielefeld University, Universitätsstraße 25, D-33615 Bielefeld, Germany.
³ Nano Biomaterials Group, Ningbo Institute of Industrial Technology, Chinese Academy of Science, China.
⁴ Faculty of Engineering and Mathematics, Bielefeld University of Applied Sciences, Interaktion 1, D-33619 Bielefeld, Germany.
⁵ Max Planck Institute of Biophysics, Department of Structural Biology, Max-von-Laue-Str. 3, D-60438 Frankfurt, Germany.

Abstract

A freestanding ultrathin hybrid membrane was synthesized comprising two functional layers, that is, first, a carbon nanomembrane (CNM) produced by electron irradiation-induced cross-linking of a self-assembled monolayer (SAM) of 4'-nitro-1,1'-biphenyl-4-thiol (NBPT) and second, purple membrane (PM) containing genetically modified bacteriorhodopsin (BR) carrying a C-terminal His-tag. The NBPT-CNM was further modified to carry nitrilotriacetic acid (NTA) terminal groups for the interaction with the His-tagged PMs forming a quasi-monolayer of His-tagged PM on top of the CNM-NTA. The formation of the Ni-NTA/His-tag complex leads to the unidirectional orientation of PM on the CNM substrate. Electrophoretic sedimentation was employed to optimize the surface coverage and to close gaps between the PM patches. This procedure for the immobilization of oriented dense PM facilitates the spontaneous fusion of individual PM patches, forming larger membrane areas. This is, to our knowledge, the very first procedure described to induce the oriented fusion of PM on a solid support. The resulting hybrid membrane has a potential application as a light-driven two-dimensional proton-pumping membrane, for instance, for light-driven seawater desalination as envisioned soon after the discovery of PM.

Keywords: bacteriorhodopsin; carbon nanomembrane; electrophoretic sedimentation; proton pump; purple membrane.

Grants and funding

This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) Cluster of Excellence “Macromolecular Complexes” Frankfurt, DFG grant GO 918/14-1 to AG, DFG grant HA 2906/9-1 to NH, and DFG grant RH 134/1-1 to DR.