Supramolecular mimics of metalloproteins, viz. cytochrome P-450 and ironsulfur proteins are described. The cytochrome P-450 mimic consists of a Mn porphyrin and a Rh complex which are incorporated within a vesicle membrane in water. This system catalyses the reductive activation of molecular oxygen in the epoxidation of alkenes at Mn, with reducing equivalents derived from the simultaneous Rh catalysed oxidation of formate to carbon dioxide. In the mimics for iron-sulfur proteins, iron-sulfur clusters are encapsulated in diphenylglycoluril and cyclotriveratrylene cavitands. The encapsulation by the cavitands modifies the electrochemical parameters, e.g. the redox potential, of the iron-sulfur clusters, in a way that has certain analogies to the effects of encapsulation by the protein in ferredoxins and high-potential iron-sulfur proteins.