Cooperative reactions of poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion

The interaction of the alpha-helical poly-L-lysine-heme complex with molecular oxygen, carbon monoxide, or cyanide ion was studied. Binding equilibrium curve and activation parameters for the reactions were determined. Sigmoid responses were observed for the absorption of molecular oxygen or carbon monoxide by the complex and the cooperative parameter was found to be 2.1. This indicated a cooperative interaction between hemes situated on a cylindrical alpha-helix of poly-L-lysine. But those of other polymer-ligand-heme complexes were 1.0. The cooperative reaction mechanism, in which an alpha-helical poly-L-lysine plays an important role, was suggested.

Complexes between synthetic polymer ligands and ferri-delta and ferro-protoporphyrin IX

The complexes of synthetic polymer ligands, i.e. poly-L-lysine, poly-4-vinyl-pyridine, poly-N-vinyl-2-methylimidazole and the higher branched polyethyleneimine, with ferri- or ferro-protoporphyrin IX were studied from the standpoint of polymer ligand effects by comparison with those of their monomeric model ligand complexes and poly-gamma-benzyl-L-glutamate containing an imidazole nucleus at the chain end. The coordination numbers and formation constants were determined optically and their structures were also estimated. The coordination number of a poly-L-lysine complex was two, but those of other polymer ligand complexes were one. One of the polymer effects, which was indicated by the large formation constants of the polymer complexes, was caused by the increment of the local ligand concentration around the polymer chain. Another was caused by the conformational effect of an alpha-helical structure in the poly-L-lysine complexes. The interaction of a poly-L-lysine-heme complex with molecular oxygen was also studied. An observed pseudo-allosteric phenomenon may be due to the specific structure of a poly-L-lysine complex which is different from those of other polymer ligand complexes.