Structure-function relationships in hemoglobins: scientific aspects.

Both proximal and distal molecular processes which could contribute to lowered ligand affinity, and hence to cooperativity, have been identified from a comparison of macromolecular structures; most have been successfully modelled by ingenious model heme derivatives. More work is needed to decide which of these processes are operative at each stage of the ligand binding process, which is both kinetically and structurally complex.