Model Lipid Membranes Assembled from Natural Plant Thylakoids into 2D Microarray Patterns as a Platform to Assess the Organization and Photophysics of Light‐Harvesting Proteins

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 14; pp. e2006608 - n/a
• Main Authors: Meredith, Sophie A., Yoneda, Takuro, Hancock, Ashley M., Connell, Simon D., Evans, Stephen D., Morigaki, Kenichi, Adams, Peter G.
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.04.2021; John Wiley and Sons Inc
• Subjects: artificial photosynthesis; Atomic force microscopy; atomic force microscopy (AFM); biohybrids; chlorophyll fluorescence; Electron transfer; Fluorescence; fluorescence lifetime imaging microscopy (FLIM); Light-Harvesting Protein Complexes - metabolism; light‐harvesting; Lipids; Membranes; Nanotechnology; Photosynthesis; Photosystem II Protein Complex - metabolism; Plant Proteins - metabolism; Proteins; supported lipid bilayers; Thylakoids - metabolism; Tumor Necrosis Factor Ligand Superfamily Member 14 - metabolism; Two dimensional models; artificial photosynthesis; biohybrids; supported lipid bilayers; atomic force microscopy (AFM); chlorophyll fluorescence; fluorescence lifetime imaging microscopy (FLIM); light-harvesting
• DOI: 10.1002/smll.202006608
• ISSN: 1613-6810; 1613-6829

Natural photosynthetic “thylakoid” membranes found in green plants contain a large network of light‐harvesting (LH) protein complexes. Rearrangement of this photosynthetic machinery, laterally within stacked membranes called “grana”, alters protein–protein interactions leading to changes in the energy balance within the system. Preparation of an experimentally accessible model system that allows the detailed investigation of these complex interactions can be achieved by interfacing thylakoid membranes and synthetic lipids into a template comprised of polymerized lipids in a 2D microarray pattern on glass surfaces. This paper uses this system to interrogate the behavior of LH proteins at the micro‐ and nanoscale and assesses the efficacy of this model. A combination of fluorescence lifetime imaging and atomic force microscopy reveals the differences in photophysical state and lateral organization between native thylakoid and hybrid membranes, the mechanism of LH protein incorporation into the developing hybrid membranes, and the nanoscale structure of the system. The resulting model system within each corral is a high‐quality supported lipid bilayer that incorporates laterally mobile LH proteins. Photosynthetic activity is assessed in the hybrid membranes versus proteoliposomes, revealing that commonly used photochemical assays to test the electron transfer activity of photosystem II may actually produce false‐positive results. A polymerized lipid bilayer (purple) templates the self‐assembly of “hybrid membranes” from thylakoid membranes (green) and synthetic lipids (colorless). During membrane formation, transmembrane proteins migrate from thylakoids into underlying lipid bilayers, decreasing the protein concentration and uncoupling protein‐protein interactions (manifested as increased fluorescent lifetimes). These hybrid membranes are used to delineate the relationship between photophysics and structure of light‐harvesting complexes.