Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published October 15, 1984 | Published
Journal Article Open

Preparation and characterization of pentaammineruthenium-(histidine-83)azurin: Thermodynamics of intramolecular electron transfer from ruthenium to copper

Abstract

The reaction between a5RuH2O2+ (a is NH3) and Pseudomonas aeruginosa azurin at pH 7, followed by oxidation, yields a5Ru(His-83)3+-azurin(Cu2+) as the major product. Spectroscopic measurements (UV-visible, CD, EPR, and resonance Raman) indicate that the native structure is maintained in the modified protein. The site of ruthenium binding (His-83) was identified by peptide mapping. The a5RuHis/Cu ratio in the modified protein, determined from the EPR spectrum, is 1:1, and the reduction potentials (vs. normal hydrogen electrode, pH 7.0, 25 degrees C) are blue copper (Cu2+/1+), 320 ± 2 mV; a5Ru(His-83)3+/2+, 50 ± 10 mV. From measurements of the reduction potentials at several temperatures in the 5-40 degrees C range, delta-H degrees for intramolecular Ru2+ --> Cu2+ electron transfer was estimated to be -12.4 kcal mol(-1) (1 cal = 4.184 J). Analysis of kinetic data in light of the electron transfer exothermicity indicates that the reorganizational enthalpy of the blue copper site can be no larger than 7.1 kcal mol(-1).

Additional Information

© 1984 by the National Academy of Sciences. Contributed by Harry B. Gray, May 29, 1984. We thank Stephen Mayo for Fig. 3, Vance Morgan for help with the CD measurements, Tin Wu Tang for assistance with cyclic voltammetry, and Ting Lin Kao for a sample of Na[Co(EDTA)]. Helpful comments were provided by Walther Ellis, Karl Freed, Michel Goldberg, Brian Hoffman, John Hopfield, Noel Hush, Sven Larsson, George McLendon, Bo Malmstrom, and Rudy Marcus. This research was supported by National Institutes of Health Grants AM19038 (H.B.G.) and HL02558 (W.A.S.). This is contribution no. 7033 from the Arthur Amos Noyes Laboratory. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.

Attached Files

Published - MARpnas84.pdf

Files

MARpnas84.pdf
Files (1.1 MB)
Name Size Download all
md5:c11ea152eb6af12e540a50e95d2706b7
1.1 MB Preview Download

Additional details

Created:
August 22, 2023
Modified:
October 13, 2023