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05:21
The Effect of Ultraviolet Radiation on the Chemical Bath Deposition of Bis(thiourea) Cadmium Chloride Crystals and the Subsequent CdS Obtention
Published on: August 30, 2018
Cadmium(II) complex formation with cysteine and penicillamine
Farideh Jalilehvand1, Bonnie O Leung, Vicky Mah
1Department of Chemistry, University of Calgary, Calgary, AB, Canada T2N 1N4. faridehj@ucalgary.ca
Inorganic Chemistry
|May 28, 2009
Summary
Cadmium(II) forms different complexes with cysteine and penicillamine, influencing their biological roles. Cysteine-rich proteins capture cadmium, while penicillamine does not, explaining differing toxicological effects.
Area of Science:
- Coordination Chemistry
- Bioinorganic Chemistry
- Spectroscopy
Background:
- Cadmium(II) is a toxic heavy metal with significant environmental and health implications.
- Cysteine and penicillamine are thiol-containing ligands that can bind to metal ions.
- Understanding metal-ligand interactions is crucial for explaining biological and toxicological effects.
Purpose of the Study:
- To investigate the complex formation between cadmium(II) and cysteine (H(2)Cys) versus penicillamine (H(2)Pen).
- To elucidate the coordination geometries and bonding characteristics of these cadmium(II) complexes.
- To explain the differential efficacy of cysteine and penicillamine in biological systems concerning cadmium.
Main Methods:
- (113)Cd Nuclear Magnetic Resonance (NMR) spectroscopy.
- Cadmium K- and L(3)-edge X-ray absorption spectroscopy (XAS).
- Studies conducted in aqueous solutions at controlled pH (7.5 and 11.0) and varying ligand-to-metal ratios.
Main Results:
- Cysteine forms predominantly CdS(4) complexes at high ligand excess, with mean Cd-S bond distances of 2.53 Å.
- Penicillamine forms chelating CdS(3)(N/O) complexes at pH 7.5, with mean Cd-S distances of 2.53 Å and Cd-(N/O) of 2.30-2.33 Å.
- Differences in coordination geometry and ligand binding explain cysteine's ability to sequester cadmium compared to penicillamine.
Conclusions:
- The study reveals distinct coordination behaviors of cadmium(II) with cysteine and penicillamine.
- Cysteine-rich metallothioneins effectively capture cadmium(II) due to specific complexation.
- Penicillamine's ineffectiveness against cadmium poisoning is attributed to its different binding modes.
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