A Biomimetic Copper Corrole – Preparation, Characterization, and Reconstitution with Horse Heart Apomyoglobin
Résumé
A copper corrole with biomimetic propionate side chains was prepared as a novel heme analog by metalation of the respective ligand as the dimethylester with copper(II) acetate hydrate and subsequent saponification with LiOH. The metalated dimethylester was characterized by spectroscopic and crystallographic means and shown by comparison to contain a divalent copper ion, antiferromagnetically coupled to the radical-dianionic organic ligand. The molecular structure of this complex is characterized by a saddled macrocycle conformation. In addition, the methylpropionate side chains are not stretched out but bent to thesame side of the mean copper corrole plane. In buffered solution, the saponified propionate complex slowly forms an equilibrium mixture with small, insoluble aggregates. The compound cleanly binds in 1:1 stoichiometry to horse heart apomyoglobin without a support by proximal histidin binding. The binding in the protein pocket is rather weak, and the biohybride compound tends to decompose under the slightly acidic conditions of mass spectrometry. Reduction of the copper corrole was achieved with sodium dithionite inside the protein pocket and yielded an air- and buffer stable, monoanionic, and protein bound copper corrolate complex which could be identified by its EPR spectrum.
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