Guided assembly of functional macromolecular building blocks: Carbon NanoMembranes (CNM) and Purple Membranes (PM)

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The assembly of biomolecular macromolecules to surfaces of various kinds is state-of-the-art today. However, controlled arrangement of 'free-standing' supramolecular assemblies is still in its infancy, mainly because the building blocks of that kind have a too high molecular mass to utilize Brownian motion only to bring them into contact, so that they can react with each other, and assemble them. We aim to move towards this vision by assembling carbon nanomembranes (CNM) and purple membranes (PM). CNM are monomolecular cross-linked layers of aromatic amphiphilic molecules with lateral dimensions of several square centimeters and a thickness of about 1 nm. PM from Halobacterium salinarum is a membrane-assembly of bacteriorhodopsin (BR), which is a light-driven proton pump, and lipids. Several ten thousand BRs are arranged in form of a hexagonal crystalline lattice in the lipid bilayer of the PM.The goal of this project is to build hybrid structures comprising CNM as a functional substrate and oriented covalently assembled PMs. Such a hybrid structure is of general interest (i) concerning the techniques of its preparation and (ii) in view of its photoelectric properties and as a mesoscopic building block for example in light-driven sea-water desalination.The choice of CNMs as substrates for these supramolecular assemblies is motivated by their tensile strength, the possibility to produce them with large areas, i.e. in the square centimeter range, the existence of a manifold of ways for the chemical modification of their surface, the electric conductivity of the CNMs and their expected proton conductivity. The choice of PM as the biological organelle-like supramolecular assembly is because of the preorientation of the embedded BR molecules and their easy genetic modification, the PMs attractive functional properties, i.e. photoelectric voltage generation and light-driven proton transport, and the physico-chemical robustness of the PM.The functional assembly obtained should not require any additional mechanical support so that it can be used as a building block in more complex systems later on.