Heme-protein active site models via self-assembly in water

Water-soluble models of heme-protein active sites are obtained via the self-assembly of cationic porphyrins 1 and tetrasulfonato calix[4]arene 2 (K-1.2 = 10(5) M-1). Selective binding of ligands either outside or inside the cavity of assemblies 1.2 via coordination to the zinc center has been observed. Small ligands such as 4-methylpyridine and 1-methylimidazole are encapsulated, while the bulkier caffeine is bound outside, Assemblies Co-1.2, in which the Zn porphyrin moiety has been replaced by a Co-II porphyrin, can act as O-2 carriers.