Photosynthetic compounds have been a paradigm for biosolar cells and biosensors and for application in photovoltaic and photocatalytic devices. However, the interconnection of proteins and protein complexes with electrodes, in terms of electronic contact, structure, alignment and orientation, remains a challenge. Here we report on a deposition method that relies on the self-organizing properties of these biological protein complexes to produce a densely packed monolayer by using Langmuir-Blodgett technology. The monolayer is deposited onto a gold electrode with defined orientation and produces the highest light-induced photocurrents per protein complex to date, 45 μA/cm(2) (with illumination power of 23 mW/cm(2) at 880 nm), under ambient conditions. Our work shows for the first time that a significant portion of the intrinsic quantum efficiency of primary photosynthesis can be retained outside the biological cell, leading to an internal quantum efficiency (absorbed photon to electron injected into the electrode) of the metal electrode-protein complex system of 32%.
Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils.
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