Surface-bound Light-activated Redox Enzyme Cascades

Abstract

Bioelectronics is a progressive area of research, which combines biochemistry, electronics and biotechnology, underpinning technologies such as biosensors for medical diagnostics and therapeutics; and biofuel cells for alternative sustainable energy generation. However, a fundamental challenge in this field is controlling the activity of the redox enzymes used in these devices.

This Thesis describes the development of redox enzyme cascades that can be switched on and off using light as a trigger; and used to improve our understanding of redox enzyme cascades in nature to design better bioelectronic devices. It was shown that in our design, a homogenous enzyme layer can be turned on and off using light or an electrochemical potential. These light-activated enzyme cascades could be used for novel bioelectronics devices including biofuel cells, medical devices and biosensors. In addition, they also provide a new powerful tool for the study of complex natural bio-chemical systems, such as the redox enzyme cascades found in photosynthesis and in respiratory electron transport chains.

Through the course of this work a method was developed for the one-pot dimerisation of complimentary charged (one positive, one negative) high molecular weight (> 80 kDa) protein via small non-charged spacers with fairly good yields (24%). In contrasts, if proteins with the same charge were used, none or very low yields of the target protein dimers were obtained.

Investigation of the various proteins expressed for this study also showed that the recombinant cytochrome c exhibited lower activity, due to the lack of trimethylation at the Lys72 residue. It was shown that the addition of 6×His-tag on the N-terminus of the cytochrome c and cytochrome c peroxidase affects their biological activity in comparison to that of native proteins.