Technetium metallothionein: Spectroscopic and EXAFS study of {sup 99}TcO{sup 3+} binding to Zn{sub 7}-metallothionein
- Univ. of Cincinnati, OH (United States)
- Dartmouth College, Hanover, NH (United States)
- E.I. DuPont de Nemours & Co., North Billerica, MA (United States)
Vibrational, absorption, circular dichroism, and Tc K-edge extended X-ray absorption fine structure (EXAFS) measurements have been made on three samples of metallothionein (MT) containing 1.6, 3.9, and 6.2 mol equiv of {sup 99}Tc, prepared by the metal displacement (transchelation) reaction of TcO(glucoheptonate){sub 2}{sup {minus}} with Zn{sub 7}-MT. For all three samples the TcO{sup 3+} ion is bound to the protein in a square pyramidal coordination with equatorial ligands consisting of {approximately}2 cysteine thiolates and, surprisingly, {approximately}2 O/N donor ligands. As the Tc content increases, there is very little change in the Tc coordination, except for a decrease in the number of cysteine ligands per TcO{sup 3+} for Tc{sub 6.2}-MT. The unusual ligand set for this metal ion when it is bound to MT, the absence of bridging cysteine ligands, and the significant number of cysteines not involved in binding TcO{sup 3+}, indicate that transchelation does not involve a simple substitution of TcO{sup 3+} for Zn(II).
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 47959
- Journal Information:
- Inorganic Chemistry, Vol. 33, Issue 24; Other Information: PBD: 23 Nov 1994
- Country of Publication:
- United States
- Language:
- English
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