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2007
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In the Laboratory
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Complexation of Copper(II) Ion with Tetraglycine as Followed by Electronic Absorption Spectroscopy
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A Bioinorganic Chemistry Experiment
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Eugenio Garribba and Giovanni Micera
Department of Chemistry, University of Sassari, I-07100 Sassari, Italy
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May 2007
Vol. 84 No. 5
p. 832
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| Abstract |
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The complexation of Cu(II) ion with tetraglycine (TetraGly) is studied by electronic absorption spectroscopy as a function of pH. In an equimolar solution, tetraglycine forms a sequence of 1:1 chelated species: [CuL]+ around pH 5.4, [CuLH-1] around pH 6.4, [CuLH-2]- around pH 8.0, and [CuLH-3]2- above pH 11.0. They are characterized, respectively, by the equatorial donor sets [(NH2, CO); H2O; H2O], [(NH2, N-, CO); H2O], [NH2, N-, N-, CO], and [NH2, N-, N-, N-], where NH2 is the amino, CO the carbonyl, and N- the deprotonated amide group. The electronic absorption spectra exhibit a single band in the visible region, which becomes sharper and shifts to higher energy values as the complexation proceeds and the water molecules are replaced by stronger donors. The experimental λmax value can be calculated through Billo's equation, which assigns a different contribution to the equatorial water, carbonyl-O, carboxylate-O, amino-N, and deprotonated amide-N. Two biological applications, the interaction of Cu(II) with prion and the transport of copper by albumin, are presented.
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| Supplement |
A more detailed description of the Cu(II)–TetraGyl experiment, along with additional background material, is available. Details of an alternative experiment between Cu(II) and GlyGlyHis, a model of Human Serum Albumin (HSA), are also available.
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| More Information |
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Citation |
Garribba, Eugenio; Micera, Giovanni. J. Chem. Educ. 2007, 84, 832.
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Keywords |
Aqueous Solution Chemistry; Biochemistry; Bioinorganic Chemistry; Coordination Compounds; Copper; Hands-On Learning / Manipulatives; Inorganic Chemistry; Instrumental Methods; Laboratory Instruction; Proteins / Peptides; Upper-Division Undergraduate; UV-Vis Spectroscopy
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History |
Created:
Last Updated: |
3/22/2007
4/9/2007
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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