Amphiphilic Copolymer Membranes Promote NADH:Ubiquinone Oxidoreductase Activity: Towards an Electron‐Transfer Nanodevice

Abstract

Nanoscale devices for energy conversion require the transfer of electrons from one compartment to another. The enzyme complex I, which in vivo mediates electron transfer from NADH to ubiquinone, is an intriguing candidate for this role in nanodevices. However, complex I normally requires the presence of lipids to remain active, potentially limiting its application. Here we demonstrate for the first time that complex I can be actively reconstituted in the synthetic membrane of amphiphilic triblock copolymer vesicles. The functionality of the reconstituted protein was characterized by EPR and activity assays. Its activity is strongly influenced by the molar mass and the block length of the membrane‐forming polymers, and increases with increasing membrane thickness.magnified image

Recent trends in the tuning of polymersomes’ membrane properties

“…Recently it has been shown that the oxidoreductase activity of the NADH:ubiquinone complex (complex 1), when reconstituted into PMOXA-b-PDMS-b-PMOXA polymersomes membrane, not only keeps its activity as in a phospholipid membrane environment but can also be modulated by the respective sizes of the hydrophobic and hydrophilic blocks [96]. Typically an increase of hydrophobic length increases its activity whereas the opposite is observed by increasing the hydrophilic length.…”

Bio-Decorated Polymer Membranes: A New Approach in Diagnostics and Therapeutics

“…It is interesting to note that delipidated protein recovered its activity in the presence of polymeric bilayers, which proves that the synthetic membrane represents a useful mimic of biological membranes. Complex I activity exhibited obvious dependence on the molecular composition of the block copolymer, with significant influence being observed in the hydrophobic domain (Figure 9(a)) [37]. This indicates that the polymer membrane was able to adapt to and stabilize the complex I arm, which is naturally inserted in the membrane (Figure 9(b)).…”

“…The shape of such a membrane can either be planar or spherical. Complex I PMOXA-PDMS-PMOXA Membrane insertion [37] F0F1-ATP synthase PEtOz-PDMS-PEtOz Membrane insertion [38] Bacteriodopsin PEtOz-PDMS-PEtOz Membrane insertion [38] The immobilization of the biomolecule on, or in the polymeric membrane, can be performed either before or after the polymer matrix is created. However, the preferred way is to add biomolecules on/into the polymer membrane afterwards, due to the fragility of the biomolecules under conditions that are different from those in nature [19].…”

“…The PMOXA-PDMS-PMOXA membrane is impermeable to small molecules, including water [36], and its permeability was increased by reconstituting channel proteins, allowing the transport of various molecules through the polymeric membrane (Figure 7). Similarly, other membrane proteins have been successfully reconstituted in PMOXA-PDMS-PMOXA membranes: LamB, FhuA, Tsx, AqpZ, Complex I [34,36,37,59], as shown by the movement of different molecules (water, NADH, nucleotides, DNA, enzyme substrates) through the polymeric membrane. F0F1-ATP synthase and bacteriorhodopsin reconstituted in poly(2-ethyl-2-oxazoline)-bpoly(dimethylsiloxane)-b-poly(2-ethyl-2-oxazoline) (PEtOz-PDMS-PEtOz) polymeric vesicles are further examples of transmembrane proteins that retained their activity after reconstitution in polymer membranes [38].…”

Interfacing Functional Systems

“…Polymersomes or liposomes equipped with membrane proteins, synthetic pores or photosystems are secondary systems (14). [3,[24][25][26][27] For example, the insertion of the ion selective bio-pore gramicidin into PMOXA-b-PDMS-b-PMOXA polymersomes allowed H + , Na + or K + ions to pass through the membrane and quench the fluorescence of encapsulated pyranine. The ion-dependent variation of the fluorescence intensity emerges from interfacing polymersomes with fluorophores, and biopores.…”