| Abstract
| - Very different biological activities are usually ascribed to Cr(VI) (a toxin and carcinogen) andCr(III) (an antidiabetic agent), although recent evidence suggests that both these types of actions are likelyto arise from cellular uptake of varying concentrations of Cr(VI). The first systematic study of XANES spectraof Cr(III) complexes formed in Cr(VI)-treated mammalian cells (A549, HepG2, V79, and C2C12 cell lines),and in subcellular fractions of A549 cells, has been performed using a library of XANES spectra of modelCr(III) complexes. The results of multiple linear regression analyses of XANES spectra, in combinationwith multiple-scattering fits of XAFS spectra, indicate that Cr(III) formed in Cr(VI)-treated cells is most likelyto bind to carboxylato, amine, and imidazole residues of amino acids, and to a lesser extent to hydroxo oraqua ligands. A combination of XANES and EPR spectroscopic data for Cr(VI)-treated cells indicates thatthe main component of Cr(III) formed in such cells is bound to high-molecular-mass ligands (>30 kDa,probably proteins), but significant redistribution of Cr(III) occurs during the cell lysis, which leads to theformation of a low-molecular-mass (<30 kDa) Cr(III)-containing fraction. The spectroscopic (XANES, XAFS,and EPR) properties of this fraction were strikingly similar to those of the purported natural Cr(III)-containingfactor, chromodulin, that was reported to be isolated from the reaction of Cr(VI) with liver. These datasupport the hypothesis that a chromodulin-like species, which is formed from such a reaction, is an artifactof the reported isolation procedure.
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