A Caltech Library Service

Electrochemical Methods to Study Iron-Sulfur Cluster Proteins


Segal, Helen Muriel (2016) Electrochemical Methods to Study Iron-Sulfur Cluster Proteins. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z92Z13HT.


Electron transfer between proteins is an important mechanism in multiple biological processes. In this thesis, methods were developed to study electron transfer in two biological contexts: 1) DNA-mediated signaling between DNA binding proteins with 4Fe-4S clusters and 2) nitrogenase.

The first portion of this thesis focuses on the spectroscopic and electrochemical characterization of the iron-sulfur cluster in Dna2. Dna2 is a helicase-nuclease that is involved in Okazaki fragment maturation, double strand break repair, mitochondrial genome maintenance, and telomere maintenance. Dna2 is one of multiple DNA repair and replication proteins that contain a 4Fe-4S cluster, a cofactor that generally participates in electron transfer processes. It has been proposed that these enzymes may use their 4Fe-4S clusters to signal one another over large molecular distances to coordinate their activity on biological time scales through DNA-mediated redox chemistry. A combination of EPR and UV-visible absorption spectroscopy along with electrochemistry studies on DNA-modified gold electrodes was performed to provide insight into the chemical characteristics of the 4Fe-4S cluster in Dna2. These studies also provide a foundation for how DNA charge transport might coordinate the action of eukaryotic DNA repair and replication proteins with 4Fe-4S clusters.

The second portion of this thesis describes the development of electrochemical methods to study nitrogenase, the enzyme that catalyzes the reduction of atmospheric dinitrogen to bioavailable ammonia. First, flavodoxin II, the biological reductant of the Fe-protein of nitrogenase, was characterized using a combination of electrochemical and structural methods to determine the molecular interactions that facilitate reduction of the nitrogenase iron protein. Second, two electrochemical methods, edge-plane pyrolytic graphite electrodes and single crystal gold electrodes modified with ω-functionalized alkane-thiols, were adapted to study the redox chemistry at the iron-sulfur cluster of the Fe-protein. These studies provided insight into both the fundamental characteristics of electron transfer reactions involving nitrogenase, as well as insight into how to better study this enzyme using electrochemical methods.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Nitrogenase; Protein Electrochemistry; Flavodoxin; Dna2; DNA Repair; Iron-Sulfur Cluster
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Rees, Douglas C.
Thesis Committee:
  • Rees, Douglas C.
  • Gray, Harry B. (chair)
  • Campbell, Judith L.
  • Cai, Long
Defense Date:18 May 2016
Funding AgencyGrant Number
NIHGM 49216
NIH NRSA5 T32 GM 7616-34
NIHGM 045162
Record Number:CaltechTHESIS:05252016-131059745
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for appendix 4
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9753
Deposited By: Helen Segal
Deposited On:09 Mar 2017 18:13
Last Modified:04 Oct 2019 00:13

Thesis Files

PDF - Final Version
See Usage Policy.


Repository Staff Only: item control page