Date of Award

Spring 2006

Document Type

Dissertation - Restricted

Degree Name

Doctor of Philosophy (PhD)



First Advisor

Ryan, Michael D.

Second Advisor

Kincaid, James

Third Advisor

Donaldson, William A.


The sulfur cycle in nature is the means by which inorganic sulfur is incorporated in the biosphere [1, 2]. Biological utilization of sulfur requires reduction of sulfur to the oxidation level of sulfide. Assimilatory and dissimilatory sulfite reductases, found in fungi, algae and green plants are responsible for part of this process by catalyzing the reduction of sulfite to sulfide in the six-electron process of reaction ( 1.1) below: "formula" Reduced sulfur then reacts with O-acetyl serine on the biosynthetic pathway to cysteine. Sulfite reductase appears to have a unique active-site catalytic assembly: a siroheme, the site of substrate binding when in the Fe (II) state [3], coupled structurally and electronically to a Fe4S4 cluster [4-7] via a cysteinate sulfur bridge [8]. An ultimate understanding of multi-electron reductions requires identification of intermediates and products of the overall reduction process. In the case of assimilatory enzymes, no intermediates of substrate reduction are detected during catalysis. The reduction of HSO3-to H2S occurs in nature via stepwise, catalytic process in the presence of sulfite reductase enzyme [1]. Myoglobin (Mb) [9] is a heme protein that binds oxygen. Myoglobin gives slow electron transfer rate at bare electrode surfaces [10-12]. Myoglobin gives reversible voltammetry when contained in a DDAB surfactant film at basal plane graphite [13]. The surfactant didodecyl dimethyl ammonium bromide, DDAB, has the structure shown below...



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