X-ray absorption spectroscopy of cuprous-thiolate clusters in proteins and model systems

Journal Article · Wed May 01 00:00:00 EDT 2002 · Journal of the American Chemical Society

DOI:https://doi.org/10.1021/ja00074a014· OSTI ID:1450190

Pickering, Ingrid J.; George, Graham N.; Dameron, Charles T.; Kurz, Boris; Winge, Dennis R.; Dance, Ian G.

Cuprous-thiolate mutlimetallic clusters exist in a range of different biological molecules for which no structural information exists from X-ray crystallography. Spectroscopic tools such as X-ray absorption spectroscopy have provided the major structural insights into this family of biological molecules. Recent nuclear magnetic resonance data on silver substituted metallothionein, thought to be analogous with the copper proteins, have suggested the presence of digonal coordination marula, S. S.; Mehra, R. K.; Winge, D. R.; Armitage, I. M. J. Am. Chem. Sot. 1991, 113, 9354-93581. In order to test this in the copper case, we have examined a series of structurally characterized cuprous-thiolate model compounds, containing different proportions of digonal and trigonal copper sites using copper K-edge X-ray absorption spectroscopy. The edge spectra, which have been previously used as a probe for the average copper coordination environment in proteins, show little variation between the models, indicating that these are not useful as a probe of coordination environment in the case of cuprous thiolate clusters (as opposed-to isolated metal sites). We show that systematic trends in the average Cu-S bond length from EXAFS curve-fitting analysis can be used to obtain an estimate of the fraction of digonal, and trigonal copper sites. This correlation is applied to a series of different proteins containing $ cuprous thiolate clusters which are found to contain significant fractions of digonal copper.

• Research Organization: SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: AC02-76SF00515
• OSTI ID: 1450190
• Report Number(s): SLAC-PUB-6251
• Journal Information: Journal of the American Chemical Society, Journal Name: Journal of the American Chemical Society Journal Issue: 21 Vol. 115; ISSN 0002-7863
• Country of Publication: United States
• Language: English