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Spectral and Kinetic Studies of Iron-Sulfur Proteins


Rawlings, Jill (1975) Spectral and Kinetic Studies of Iron-Sulfur Proteins. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/vv7x-np65.


Spectral studies of spinach ferredoxin and Chromatium HiPIP in the near infrared region give indications of inequivalence of the iron. The low energy spectrum of ferredoxin is interpreted in terms of one [Fe(III)S4] site, which is the reducible site, and one site, which is not tetrahedral and is nonreducible. A band at 720 nm in the oxidized protein is attributed to the first spin forbidden d-d band of a tetrahedral site, while bands at 820 and 920 nm are assigned to the distorted, nonreducible site. A band at 652 nm in the reduced protein is interpreted as an intervalence transition or a spin forbidden band of the iron(II) site.

The near infrared spectrum of reduced HiPIP has a broad band at 1040 nm. This band is absent in the model compound, (Et4N)2[Fe4S4(SCH2Ph)4] and may be indicative of a slight site inequivalence. However, magnetic studies show an antiferromagnetic coupling very similar to the model, with μe per iron for protein and model agreeing closely.

A number of redox reactions of these iron-sulfur proteins with inorganic reagents were studied. The second order rate constant 5 for the reaction of spinach ferredoxin with FeEDTA- is 3.4 x 105 M-1sec-1, while the rate constants for the HiPIP reactions are slower by a factor of 100. The rate constant is 1.7 x 103 M-1sec-1 for the reaction of HiPIP and FeEDTA2- and 2.4 x 103 M-1sec-1 for the HiPIP-Fe(CN)63- reaction. These reactions typically have very small activation enthalpies and very negative activation entropies. Electron tunneling is suggested as a possible mechanism for these reactions.

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:
  • Gray, Harry B. (chair)
Defense Date:14 October 1974
Record Number:CaltechTHESIS:11032021-211434335
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14417
Deposited By: Benjamin Perez
Deposited On:04 Nov 2021 21:40
Last Modified:04 Nov 2021 21:41

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