期刊
INORGANIC CHEMISTRY
卷 54, 期 5, 页码 2160-2170出版社
AMER CHEMICAL SOC
DOI: 10.1021/ic5025668
关键词
-
资金
- U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences [DE-AC02-76SF00515]
- DOE Office of Biological and Environmental Research
- National Institutes of Health (NIH), National Institute of General Medical Sciences (NIGMS) [P41GM103393]
- National Science and Engineering Research Council of Canada (NSERC)
- Canadian Foundation for Innovation (CFI)
- Province of Alberta (Department of Innovation and Science)
- University of Calgary (Faculty of Science)
The lead(II) complexes formed with the multidentate chelator l-cysteine (H(2)Cys) in an alkaline aqueous solution were studied using Pb-207, C-13, and H-1 NMR, Pb L-III-edge X-ray absorption, and UVvis spectroscopic techniques, complemented by electrospray ion mass spectrometry (ESI-MS). The H(2)Cys/Pb-II mole ratios were varied from 2.1 to 10.0 for two sets of solutions with C-Pb(II) = 0.01 and 0.1 M, respectively, prepared at pH values (9.1-10.4) for which precipitates of lead(II) cysteine dissolved. At low H(2)Cys/Pb-II mole ratios (2.1-3.0), a mixture of the dithiolate [Pb(S,N-Cys)(2)](2) and [Pb(S,N,O-Cys)(S-HCys)](-) complexes with average Pb-(N/O) and Pb-S distances of 2.42 +/- 0.04 and 2.64 +/- 0.04 angstrom, respectively, was found to dominate. At high concentration of free cysteinate (>0.7 M), a significant amount converts to the trithiolate [Pb(S,N-Cys)(S-HCys)(2)](2-), including a minor amount of a PbS3-coordinated [Pb(S-HCys)3]- complex. The coordination mode was evaluated by fitting linear combinations of EXAFS oscillations to the experimental spectra and by examining the Pb-207 NMR signals in the chemical shift range delta(Pb) = 2006-2507 ppm, which became increasingly deshielded with increasing free cysteinate concentration. One-pulse magic-angle-spinning (MAS) Pb-207 NMR spectra of crystalline Pb(aet)(2) (Haet = 2-aminoethanethiol or cysteamine) with PbS2N2 coordination were measured for comparison (delta(iso) = 2105 ppm). The UV-vis spectra displayed absorption maxima at 298-300 nm (S - Pb-II charge transfer) for the dithiolate PbS2N(N/O) species; with increasing ligand excess, a shoulder appeared at similar to 330 nm for the trithiolate PbS3N and PbS3 (minor) complexes. The results provide spectroscopic fingerprints for structural models for lead(II) coordination modes to proteins and enzymes.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据