Date of Completion

11-24-2014

Embargo Period

11-20-2014

Keywords

electrochemistry

Major Advisor

James F. Rusling

Associate Advisor

Harry A. Frank

Associate Advisor

Challa V. Kumar

Field of Study

Chemistry

Degree

Doctor of Philosophy

Open Access

Open Access

Abstract

Direct voltammetry of the redox cofactors in bacterial reaction center (RC) proteins and spinach PSII core complex was investigated in this dissertation. Peak assignments were made through the use of comparisons with multiple control experiments involving isolated proteins, those depleted of specific cofactors and those affected by exogenous chemical reagents. RCs having undergone site-specific mutagenesis were examined by cyclic voltammetry (CV) and square wave voltammetry (SWV) methods. The heterogeneous electron transfer rate constants were extracted from the datasets and simulations were used to determine the number of electrons transferred between the cofactor and the electrode. The work seeks to provide a deeper understanding of the dynamic electrochemical processes undergone by redox active proteins. In addition, the PSII core complex provided the basis for a novel photo-biofuel cell.

Chapter 2 describes direct voltammetry study of the electrochemical properties of bacterial RC in lipid dimyristoylphosphatidyl choline (DMPC) or as layer by layer (LbL) films with polyions. SWV of site-directed mutants RC films showed shifts in oxidation peak potential of primary electron donor that correlated reasonably with those reported from electrochemical titration experiment.

Chapter 3 focuses on direct thin film voltammetry of spinach PSII complex also in lipid and polyion films. CV experiments were also carried out on isolated cytochrome b-559, Mn depleted PSII and purified Chl to help in the assignment of the peaks. These assignments were further supported by fitting the voltammetric data to appropriate simulation models which also provided heterogeneous electron transfer rate constants.

Chapter 4 explores the kinetic properties of DMPC-WTRC films on a propyl-aminomethoxysilane (AS) modified slide and an indium tin oxide (ITO) slide. We compared results in films with those in RC solutions to check whether the fabricated films change the kinetic spectral properties.

Chapter 5 reports the first application of spinach protein Photosystem II (PSII) core complex in lipid films in a photoelectrochemical device. PSII in DMPC film on a pyrolytic graphite (PG) worked as anode, and Pt black mesh cathode was used as cathode, which can produce voltage and power respectively higher than and comparable to a previous published report of a PSII photobiofuel cell.

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