Multicomponent Nanoscale Patterning of Functional Light-Harvesting Protein Complexes by Local Oxidation Lithography

Local oxidation lithography has the potential for patterning proteins on conductive substrates such as silicon with nanometer accuracy, guided by and extending the nanoscale architectures found in native bioenergetic membranes. Such membranes foster energy and electron transfers between two or more types of protein complex, so the potential of this lithographic technique is investigated for copatterning multiple types of protein complex. Composite patterns consisting of light-harvesting 2 (LH2) and reaction center-light-harvesting 1-PufX (RCLH1) complexes purified from Rhodobacter (Rba.) sphaeroides, and light-harvesting complex II (LHCII) purified from spinach, are fabricated. Atomic force microscopy (AFM) images demonstrate the successful sequential deposition of single-molecule layers of RCLH1 and LH2 molecules. In the case of LHCII, a mixture of single-layer and multilayer patterns is found on the silicon substrate. Experimental conditions are established for the most efficient substrate surface modification and for protein immobilization. Spectral imaging and fluorescence lifetime imaging microscopy (FLIM) show that the immobilized photosynthetic complexes retain their native light-harvesting and energy transfer functions, and provide evidence for excitation energy transfer from LH2 to RCLH1. Local oxidation lithography has the capacity to pattern proteins singly, or in small domains, for fabricating bioinspired nanoscale architectures for biosensors and solar cells.