CaltechTHESIS
  A Caltech Library Service

Electrochemical and Electron Transfer Investigations of Copper Proteins

Citation

St. Clair, Cynthia Strong (1989) Electrochemical and Electron Transfer Investigations of Copper Proteins. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/0zvh-aw13. https://resolver.caltech.edu/CaltechTHESIS:08262013-120637323

Abstract

A study of the pH and temperature dependence of the redox potentials of azurins from five species of bacteria has been performed. The variations in the potentials with pH have been interpreted in terms of electrostatic interactions between the copper site and titrating histidine residues, including the effects of substitutions in the amino acid sequences of the proteins on the electrostatic interactions. A comparison of the observed pH dependences with predictions based on histidine pK_a values known for Pseudomonas aeruginosa (Pae), Alcaligenes denitrificans (Ade), and Alcaligenes faecalis (Afa) azurins indicates that the Pae and Ade redox potentials exhibit pH dependences in line with electrostatic arguments, while Afa azurin exhibits more complex behavior. Redox enthalpies and entropies for four of the azurins at low and high pH values have also been obtained. Based on these results in conjuction with the variable pH experiments, it appears that Bordetella bronchiseptica azurin may undergo a more substantial conformational change with pH than has been observed for other species of azurin.

The temperature dependence of the redox potential of bovine erythrocyte superoxide dismutase (SOD) has been determined at pH 7.0, with potassium ferricyanide as the mediator. The following thermodynamic parameters have been obtained (T = 25°C): E°' = 403±5 mV vs. NHE, ΔG°' = -9.31 kcal/mol, ΔH°' = -21.4 kcal/mol, ΔS°' = -40.7 eu, ΔS°'_(rc) = -25.1 eu. It is apparent from these results that ΔH°', rather than ΔS°', is the dominant factor in establishing the high redox potential of SOD. The large negative enthalpy of reduction may also reflect the factors which give SOD its high specificity toward reduction and oxidation by superoxide.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Gray, Harry B.
Thesis Committee:
  • Unknown, Unknown
Defense Date:3 April 1989
Record Number:CaltechTHESIS:08262013-120637323
Persistent URL:https://resolver.caltech.edu/CaltechTHESIS:08262013-120637323
DOI:10.7907/0zvh-aw13
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7943
Collection:CaltechTHESIS
Deposited By: Benjamin Perez
Deposited On:26 Aug 2013 20:01
Last Modified:16 Apr 2021 23:30

Thesis Files

[img]
Preview
PDF - Final Version
See Usage Policy.

21MB

Repository Staff Only: item control page