In part 2 we have tried to pinpoint some of the ways in which the presence of a protein may affect the reactivity of transition-metal complexes. We have examined in some detail three case studies chosen to illustrate how the protein can vary (1) the thermodynamics of an individual step (for example, the equilibrium constant for the co-ordination of O2 by Fe(II) in Hb and Mb-chapter 7), (2) the kinetics of individual steps (for example, the reactions of the Fe in peroxidase and catalase with H2O2 and other substrates-chapter 8) and (3) the thermodynamics of the overall reaction (for example driving the endothermic reduction of N2 to N2H2 with a second thermodynamically favourable reaction-chapter 9). In each case we have also considered what the simple protein-free complex or ion can and cannot do, and hence what problems nature has to overcome and how she has solved them. This has thrown up additional examples of the ways in which the protein can affect thermodynamic and kinetic properties.
KeywordsAxial Ligand Homolytic Fission COOH COOH Porphyrin Ligand COOH COOH COOH
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