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Spectroscopic studies and a structural model for blue copper centers in proteins

Solomon, Edward I. and Hare, Jeffrey W. and Gray, Harry B. (1976) Spectroscopic studies and a structural model for blue copper centers in proteins. Proceedings of the National Academy of Sciences of the United States of America, 73 (5). pp. 1389-1393. ISSN 0027-8424. http://resolver.caltech.edu/CaltechAUTHORS:SOLpnas76

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Abstract

Low temperature absorption, circular dichroism, and magnetic circular dichroism spectral studies of the blue copper proteins Rhus vernicifera stellacyanin, bean plastocyanin, and Pseudomonas aeruginosa azurin have been made. Low energy bands attributable to the d-d transitions 2B2-.2E and 2B2-.2B1 in a flattened tetrahedral (D2d) copper-(II) center are observed in these proteins at about 5000 and 10,000 cm-1, respectively. The band positions accord well with ligand field calculations based on a tetrahedral structure that is distorted approximately 6° toward a square plane. The ligands in this flattened tetrahedral coordination unit in bean plastocyanin are identified from various spectroscopic experiments as His-38, Cys-85, His-88, and a deprotonated peptide nitrogen (N*) a few residues above His-38. Based on a comparison of absorption and CD intensities, the characteristic bands at about 13,000, 16,000, and 22,000 cm-1 in the blue proteins are assigned to the ligand to metal charge transfer transitions [pi]S->d(x^2-y^2), [sigma]S->d(x^2-y^2) and [pi](N*)->d(x^2-y^2), respectively, in the flattened tetrahedral CuN2N*S unit.


Item Type:Article
Additional Information:Copyright © 1976 by The National Academy of Sciences. Contributed by Harry B. Gray, February 4, 1976. We thank Prof. P. J. Stephens and Dr. J. Rawlings for assistance with the near-infrared CD and MCD measurements and for several helpful comments. Receipt of a preprint in advance of publication from Dr. L. Morpurgo is gratefully acknowledged. This research was supported by the National Science Foundation. E.I.S. acknowledges National Institutes of Health Research Fellowship no. lF32GM05358-01. This is Contribution no. 5266 from the Arthur Amos Noyes Laboratory.
Subject Keywords:blue copper, tetrahedral geometry, near-infrared spectra, d-d transitions, charge transfer transitions
Record Number:CaltechAUTHORS:SOLpnas76
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:SOLpnas76
Alternative URL:http://www.pnas.org/cgi/content/abstract/73/5/1389
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:608
Collection:CaltechAUTHORS
Deposited By: Archive Administrator
Deposited On:01 Sep 2005
Last Modified:26 Dec 2012 08:40

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