Biphasic kinetics of aurothionein formation from gold sodium thiomalate: a novel metallochromic technique to probe zinc(2+) and cadmium(2+) displacement from metallothionein

Abstract

isolation of The incorporation of a Pt-S bond in a well-defined complex prior to any administration may have considerable effects on this biology and the fact that Pt-S complexes are antitumor active may be relevant to the mechanisms of some of the above-mentioned effects. An interesting point to note here also is that albumin, the predominant agent responsible for tissue binding of Pt complexes, has been used (as protein BSA) as a template for the preparation of chiral sulfoxides.37 It is therefore axiomatic that chiral sulfoxide complexes will react differently with this enzyme. The chemical aspects of the biodistribution, tissue binding, and metabolism of platinum antitumor complexes are not as well understood as those of DNA binding, but it is clear that these properties may vary quite widely between, (35) Zwelling, L. A. Biological Consequences of Platinum-DNA Crosslinks in Mammalian Cells. In Platinum, Gold, and Other Metal Chemoth-

Characterization of the ZnII Binding to the Peptide Amyloid‐β1–16 linked to Alzheimer's Disease

“…The Zn chelator Zincon (Zi) has been shown to be appropriate for Zn-protein complexes. [34,35] Figure 7 shows the titration experiments (see Experimental Section). The upper panel showed the absorption at 620 nm from the Zn-Zi with addition of increasing amounts of Ab [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] .…”

A Fungal Metallothionein Is Required for Pathogenicity of Magnaporthe grisea

“…The release of Zn 2þ from Mmt1 by ebselen, a selenium compound that very effectively releases zinc from mammalian MT (Jacob et al, 1998a), was investigated. For this assay, Mmt1 and ebselen were incubated in the presence of the metallochromic dyes pyridylazoresorcinol (PAR) and Zincon, which form colored complexes with free Zn 2þ , and this was used to calculate the number of protein-bound Zn 2þ ions (Jacob et al, 1998a;Shaw et al, 1990). The average ratios of zinc ions:thiols per protein were 0.347 (60.026) and 0.3512 (60.039) using the PAR and Zincon assay, respectively.…”

“…This metallochromic dye acts as a zinc acceptor, and by following the reaction spectrophotometrically, it was possible to detect formation of the Zn(PAR) 2 complex (Shaw et al, 1990) as metal was released from the MT. Figure 7A shows that after addition of 1 mM H 2 O 2 , Zn 2þ is gradually released by Mmt1 and becomes bound to PAR, resulting in a color change that is detected spectrophotometrically at 500 nm and is shown in Figure 7A as a curve.…”

Zinc transfer potentials of the α- and β-clusters of metallothionein are affected by domain interactions in the whole molecule

“…PAR (200 M) was incubated with clusters (2 M) in 0.2 M Tris⅐HCl, pH 7.4, and the formation of the Zn(PAR) 2 complex followed at 500 nm (18). Kinetics were analyzed by using semilog plots of (A ϱ Ϫ A t )͞(A ϱ Ϫ A 0 ), where A t is the observed absorbance at time t, A 0 is the absorbance at t ϭ 0, and A ϱ is the absorbance at completion of the reaction as evaluated with the method of Guggenheim (19).…”