Interactions of Bismuth Compounds with Biological Molecules

The biochemical fate of bismuth is speculated to include BiOCl in the stomach, Bi2O2CO3 in the small intestine and BiS3 in the large intestine.43 Bismuth is known to concentrate in the kidneys and the liver, with trace amounts in the skeleton and other organs. The binding of bismuth with proteins of exposed ulcer tissue and the formation of a protective coating is a likely mode of action for the anti-ulcer behavior exhibited by some bismuth compounds. In this context, the chemistry of bismuth complexes involving biological molecules as ligands represents an important component in understanding aspects of bio-activity. Interactions of bismuth with methionine,44 cysteine (Figure 27.1),45,46 glutathione (Figure 27.1),46 48 metallothionein,49 human serum transferin,50 53 lactoferin54 and other serum proteins55 have been studied using IR, UV, fluorescence, 1H NMR and 13C NMR spectroscopy, inductively coupled plasma mass spectroscopy (ICP-MS), ESI-MS and extended X-ray absorption fine structure spectroscopy. The pronounced thiophilicity of bismuth highlights conjugates of thiol-carboxylic acids as obvious sites for interaction of bismuth with biological molecules. In this context, in situ ESI-MS (Figure 27.9) of solutions containing Bi(NO3)3 and glutathione (Figure 27.1) confirm the existence of the complex ions [Bi(GSH)2-2H]+ and [Bi(GSH)-2H]+,46 and X-ray crystallographic data confirm the interaction of a dianionic penicillaminate (a derivative of cysteinate) with bismuth (Figure 27.7f).56

513.9

307.9

385.0

821.1

385.0

200 250 300 350 400 450 500

Figure 27.9 ESI-MS of a reaction mixture containing Bi(NO3)3 and glutathione in aqueous solution. Assignments for m/z peaks: 821.1 [Bi(GSH)2-2H]+; 513.9 [Bi(GSH)-2H]+

/.'fi'.,i'..r .'.i) "!^ ii"i ¥i'i"im/z 550 600 650 700 750 800 850 900

200 250 300 350 400 450 500

Figure 27.9 ESI-MS of a reaction mixture containing Bi(NO3)3 and glutathione in aqueous solution. Assignments for m/z peaks: 821.1 [Bi(GSH)2-2H]+; 513.9 [Bi(GSH)-2H]+

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