Probing biological redox chemistry with large amplitude Fourier transformed ac voltammetry

Abstract

Biological electron-exchange reactions are fundamental to life on earth. Redox reactions underpin respiration, photosynthesis, molecular biosynthesis, cell signalling and protein folding. Chemical, biomedical and future energy technology developments are also inspired by these natural electron transfer processes. Further developments in techniques and data analysis are required to gain a deeper understanding of the redox biochemistry processes that power Nature. This review outlines the new insights gained from developing Fourier transformed ac voltammetry as a tool for protein film electrochemistry.

Fig. 1. Biological electron transfer in (A) photosynthesis and (B) respiration.

Fig. 2. Protein–electrode attachment strategies.

Fig. 3. Protein film electrochemistry set-up.

Fig. 4. Direct current cyclic voltammetry (dcV). (A) Applied potential, and (B) non-Faradaic current.

Fig. 5. Ideal Faradaic-only current responses for (A) reversible electron transfer and (B) redox catalysis.

Fig. 6. Voltammetric responses showing (A) catalytic bias and (B) overpotential.

Fig. 7. Comparison of FTacV and dc voltammetry techniques.

Fig. 8. Deconvolution of catalytic and electron transfer current by FTacV.

Fig. 9. dc and 1st to 3rd harmonic components of a surface confined 1e^– transfer.

Fig. 10. (A) Crystal structure of Escherichia coli YedY (PDB ; 1XDQ) including active site detail and cartoon depiction of DMSO electrocatalytic reduction reaction. (B) Simultaneous measurement of catalytic and non-catalytic redox chemistry via PF-FTacV.

Fig. 11. Non-catalytic redox activity of Escherichia coli YedY as assessed by (A) dcV, and (B) PF-FTacV.

Fig. 12. (A) Structure of Escherichia coli HypD including detail of postulated reaction centers, and cartoon depiction of reversible disulfide redox reaction. (B) Comparison of the measurement sensitivity of (i) high harmonic PF-FTacV signals versus (ii) dcV.

Fig. 13. Overlay of experimental (exp.) and data-optimized simulation (sim.) of high harmonic FTacV data for Escherichia coli HypD.

Fig. 14. (A) Crystal structure of Escherichia coli Hyd-1 (PDB ; 3UQY) including detail of the redox active metal centers. (B) High frequency is required to separately isolate the catalytic and non-catalytic redox reactions.

Fig. 15. Illustration of how simulation of the high harmonic FTacV signals permits extraction of enzyme turnover rates from simulation of the aperiodic-dc catalytic currents.