Mimicking a Light-Harvesting Complex to Accelerate Photooxidation in Asymmetric Lipid Membrane Nanoreactors

In nature, photosynthesis is driven by solar light and a large proportion of the visible spectrum is absorbed by the light harvesting complexes (LHCs), which then transfer the energy to the reaction center. Inspired by nature, we implemented a light harvesting energy transfer cascade within biomimetic lipid bilayers of liposomes built with DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), using membrane-anchored fluorescein, 2-(3,6-dihydroxy-9H-xanthen-9-yl)-5-dodecanamidobenzoic acid (FlC₁₂) as primary absorber and membrane anchored eosin Y, hexadecyl 2-(2,4,5,7-tetrabromo-3,6-dihydroxy-9H-xanthen-9-yl)benzoate (EYC₁₆), as energy acceptor to sensitize oxygen and generate the reactive oxygen species ¹O₂. Finally, the model substrate nicotinamide adenine dinucleotide (NADH) is oxidized by ¹O₂ within the compartmentalizing liposome nanoreactors. It was observed that our metal-free LHC system has only a minor effect on the photooxidation rate of NADH when the nanoreactor membrane is functionalized symmetrically. By contrast, asymmetric membrane functionalization of the liposome nanoreactor membranes leads to acceleration by 16% to 27% when using multi-colored light emitting diodes (LED) or simulated solar light, respectively.