Protein interactions with bivalent tin. 1. Hydrolysis and complexation of tin(II) ion with glycine.
The complexation between tin(II) ion and glycine was studied in 0.15 mol/dm3 NaCl medium at 310 K using potentiometric glass electrode titrations. In the pH range 1.1-4.5 and concentration range of the tin(II) between 0.2 and 5.0 mmol/dm3, with variable glycine-to-tin molar ratio up to 10:1, the experimental data were explained by the formation of the following complexes and their overall stability constants: log(beta +/- sigma): Sn(HGly)+, (12.78 +/- 0.08); Sn(Gly)+, (10.02 +/- 0.07); Sn(OH)Gly, (7.34 +/- 0.03), as well as the pure hydrolytic complex Sn4(OH)2+(6), whose stability constant was determined in separate experiments and found to be -4.30 +/- 0.08, under the same experimental conditions as for complexation study. The precipitate formed in tin(II)-glycine system at pH ca. 5.0 was characterized by chemical and TG analysis, I. R. spectra, X-ray powder diffraction, and electron scanning microscopy measurements. It has been shown that the precipitate has the composition Sn(OH)Gly and crystallizes in a tetragonal system with unit cell dimensions a = b = 1.584 nm, c = 0.597 nm. The mechanism of the complex formation in solution is discussed.
Djurdjevic
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Faculty of Science, Institute of Chemistry, Kragujevac, Yugoslavia.
Djokic
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D
D002413:Cations, Divalent / Q000737:chemistry / Q000378:metabolism; D002614:Chelating Agents / Q000737:chemistry / Q000378:metabolism; D005998:Glycine / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D066298:In Vitro Techniques; D008855:Microscopy, Electron, Scanning; D011199:Potentiometry; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D011522:Protons; D013667:Technetium / Q000737:chemistry; D014001:Tin / Q000737:chemistry / Q000378:metabolism*
D002413:Cations, Divalent; D002614:Chelating Agents; D011506:Proteins; D011522:Protons; D013667:Technetium; D014001:Tin; D005998:Glycine