XAFS OF SILVER(I) METALLOTHIONEIN

Silver K-edge XAFS has been measured on Ag-17-MT formed by adding Ag(I ) to Zn-7-MT at pH 7. The nearest neighbor bond length and coordinatio n number are determined by curve-fitting using theoretical scattering amplitude and phase. It is found that the silver atom is coordinated w ith two sulfurs at 2.43 +/- 0.024 Angstrom and one Ag at 2.91 +/- 0.05 Angstrom. The results are compared to those of Zn-7-MT, Cd-7-MT, Hg-7 -MT and Hg18B-MT. The generality of the coordination geometry of Ag-S clusters in various metallothioneins is noted.