Question

for the degradation of formic acid to CO and water on various metal surface were tested, commonly known volcano diagram, from the result precious metals have greater activities toward the reaction. on the other hand these metals are seldom found in metalloenzymes. can you discuss possible reason why biological systems uses Fe Ni Cu instead of Ir Pt Pd Rh from all different aspect. how does the biological system overcome low activities issue.

Answer 1

The transition metals Fe Ni Cu are used in biological systems as specific metalloproteins has triggered off research into the preparation and reactivity of many model compounds such as square-planar cobalt complexes (cf. vitamin B12) and iron-sulphur clusters (cf. ferredoxin). The interest of electronic spectroscopists has been stimulated by such problems as the very high absorbance coefficients found in the 'blue' copper proteins. Kineticists have been involved in studying the catalytic activities of many metalloenzymes, and theoretical chemists have been examining the reasons for the specific reactivities of the metal centres.

It is possible and in some cases essential to consider the way in which the chemistry of the metal ion affects complete mammalian systems, whole organs or intact cells. For example some squareplanar platinum complexes are effective anti-cancer agents but only cis complexes with specific ligand labilities have high activities and it is now generally believed that these complexes work by bridging between two nitrogen bases on DNA by substitution of the more labile pair of ligands. This suggestion gains support from studies in vitro, which demonstrated that reactions of this type are feasible within the cell.

The chemistry of the metal ion held in a well-defined environment in specific proteins has been investigated successfully in vitro in many instances.Proteins with specific roles in metal metabolism such as membrane metal transporters, metalloregulators, and metallochaperones were characterized.