Anaëlle Rongier
Protein self-assembly for bioelectronics: Study of charges transport in amyloid fibers
Published on 13 February 2018
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Thesis presented February 13, 2018
Abstract:
Amyloid fibers are very promising biomaterials for bioelectronics, especially for interfacing with biological systems. These self-assembled proteins fibers are easy to synthetize, to tune and to functionalize. Their physical properties such as stability and mechanical strength are noticeable. We studied charge transport processes in HET-s(218-289), the only amyloid fibers we know the atomic structure. The samples were characterized as “dried” films by electrical measurement and electrochemistry. The influence of several parameters such as temperature, humidity or light was investigated. We demonstrated that the fiber organization allows intrinsic charge transport mechanisms in which water plays a crucial role. Furthermore, the dominant charge carriers would be protons. Molecular dynamic simulation and neutron diffusion experiments run in parallel show strong water-fibers interactions. In particular, H-bonded water wires can be formed along the fibers and support proton transport according to a Grotthuss-like mechanism. Proton production would result from electrochemical reactions, especially from water electrolysis. Therefore a catalytic current is detected when the bias exceeds a certain threshold. In addition, two photoelectric phenomena were observed when the fibers are irradiated with near UV light (200-400nm). The first one is a photocurrent probably due to water photo-splitting. The other occurs specifically at 280nm wavelength and in the presence of molecular oxygen. It leads to a decrease of the sample conductivity. This likely results from chemical reaction(s) between triplet-state tryptophan and oxygen that consumes protons.
Keywords:
bioelectronics, nanofiber, electronic transport, organic semiconductors, bioinspired model systems
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