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Title: Lead(II) complex formation with l-cysteine in aqueous solution

Abstract

The lead(II) complexes formed with the multidentate chelator l-cysteine (H 2Cys) in an alkaline aqueous solution were studied using 207Pb, 13C, and 1H NMR, Pb L III-edge X-ray absorption, and UV–vis spectroscopic techniques, complemented by electrospray ion mass spectrometry (ESI-MS). The H 2Cys/Pb II mole ratios were varied from 2.1 to 10.0 for two sets of solutions with C PbII = 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 2Cys/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 Å, 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 PbS 3-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 207Pb NMR signals in the chemical shift range δ Pb = 2006–2507 ppm, which became increasingly deshielded with increasing free cysteinate concentration. One-pulse magic-angle-spinning (MAS) 207Pb NMR spectra of crystalline Pb(aet) 2more » (Haet = 2-aminoethanethiol or cysteamine) with PbS 2N 2 coordination were measured for comparison (δ iso = 2105 ppm). The UV–vis spectra displayed absorption maxima at 298–300 nm (S → Pb II charge transfer) for the dithiolate PbS 2N(N/O) species; with increasing ligand excess, a shoulder appeared at ~330 nm for the trithiolate PbS 3N and PbS 3 (minor) complexes. Finally, the results provide spectroscopic fingerprints for structural models for lead(II) coordination modes to proteins and enzymes.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Univ. of Calgary, Calgary, AB (Canada)
  2. Univ. of Ottawa, Ottawa, ON (Canada)
Publication Date:
Research Org.:
Univ. of Calgary, Calgary, AB (Canada)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1345620
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
Inorganic Chemistry
Additional Journal Information:
Journal Volume: 54; Journal Issue: 5; Journal ID: ISSN 0020-1669
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Jalilehvand, Farideh, Sisombath, Natalie S., Schell, Adam C., and Facey, Glenn A. Lead(II) complex formation with l-cysteine in aqueous solution. United States: N. p., 2015. Web. doi:10.1021/ic5025668.
Jalilehvand, Farideh, Sisombath, Natalie S., Schell, Adam C., & Facey, Glenn A. Lead(II) complex formation with l-cysteine in aqueous solution. United States. doi:10.1021/ic5025668.
Jalilehvand, Farideh, Sisombath, Natalie S., Schell, Adam C., and Facey, Glenn A. Thu . "Lead(II) complex formation with l-cysteine in aqueous solution". United States. doi:10.1021/ic5025668. https://www.osti.gov/servlets/purl/1345620.
@article{osti_1345620,
title = {Lead(II) complex formation with l-cysteine in aqueous solution},
author = {Jalilehvand, Farideh and Sisombath, Natalie S. and Schell, Adam C. and Facey, Glenn A.},
abstractNote = {The lead(II) complexes formed with the multidentate chelator l-cysteine (H2Cys) in an alkaline aqueous solution were studied using 207Pb, 13C, and 1H NMR, Pb LIII-edge X-ray absorption, and UV–vis spectroscopic techniques, complemented by electrospray ion mass spectrometry (ESI-MS). The H2Cys/PbII mole ratios were varied from 2.1 to 10.0 for two sets of solutions with CPbII = 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 H2Cys/PbII 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 Å, 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 207Pb NMR signals in the chemical shift range δPb = 2006–2507 ppm, which became increasingly deshielded with increasing free cysteinate concentration. One-pulse magic-angle-spinning (MAS) 207Pb NMR spectra of crystalline Pb(aet)2 (Haet = 2-aminoethanethiol or cysteamine) with PbS2N2 coordination were measured for comparison (δiso = 2105 ppm). The UV–vis spectra displayed absorption maxima at 298–300 nm (S– → PbII charge transfer) for the dithiolate PbS2N(N/O) species; with increasing ligand excess, a shoulder appeared at ~330 nm for the trithiolate PbS3N and PbS3 (minor) complexes. Finally, the results provide spectroscopic fingerprints for structural models for lead(II) coordination modes to proteins and enzymes.},
doi = {10.1021/ic5025668},
journal = {Inorganic Chemistry},
number = 5,
volume = 54,
place = {United States},
year = {2015},
month = {2}
}

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