Group IB Cu, Ag, Au

Gopper, when present in aerobic ecosystems as Gu(II), is reduced by most microbial cells to Gu(I), which is the predominant form in the cytoplasm. This easy one-electron redox reaction makes copper very useful as cofactor for the reaction with radicalic compounds such as molecular oxygen. The last enzyme complex of the respiratory chain in mitochondria and in many fully aerobic bacteria is that of cytochrome c oxidase. This contains two copper centers one for uptake of electrons from cytochrome c (Cu A center) the other (Cu B center) for the reduction of molecular oxygen to water using these electrons. This reaction generates a proton-motive force that may be used for the synthesis of ATP (Iwata et al. 1995, Michel et al. 1998, Ostermeier and Michel 1997). 

The main advantage of copper - its radicalic character - also brings about danger. Copper is able easily to form hydroperoxide radicals (Rodriguez Montelongo et al. 1993), interact with the cell membrane (Suwalsky et al. 1998), and also bind to thiol compounds (Nies 2003). The use of copper is therefore strictly controlled by the cells. Similar to nickel, anabolic copper is bound to copper chaperones (O Halloran and Culotta 

Silver is a highly toxic-only metal, ranking in toxicity second only to mercury (Nies 

Zinc as trace element is as important as iron, but the biochemical function of zinc is opposite to that of iron while iron is the most important redox-active transition metal, zinc is the most important redox-inactive one. Zn(II) is used as Lewis acid and to tether domains of macromolecules into a distinct and concise structure. This ability of zinc results from the completely filled 3d-orbitals of the zinc atoms. 

The apparent Zn(II) concentration in bacterial cells is probably higher than 200 xM and up to 1 or 2 mM (Nies 2003). In E. coli, 200000 Zn(II) per cell are needed only for eight of the 48 known zinc-containing enzymes, for example the RNA polymerase that binds 10000 Zn(II) (Outten and O Hal-loran 2001). Surplus Zn(II) cations were thought to be bound to cellular compounds, but free zinc also seems to exist in bacterial cells (Nies 2003). 

---

Group-IB (Cu, Ag, Au) or -IIB (Zn, Cd, Hg)-Transition-Metal Bonds 8.3.3. Group IIB-Transition- and Inner-Transition-Metal Bonds 8.3.3.4. by Insertion into a Bond Insertion of a Group-IIB Element... 

Neogrady, P., Kello, V., Urban, M., and Sadlej, A. J. (1996). Polarized basis sets for high-level-correlated calculations of molecular electric properties VII. Elements of the group Ib Cu, Ag, Au. Theor. Chim. Acc., 93, 101-129. 

---