Polarography and electroreduction of synthetic haemoprotein models

Abstract

Haemoprotein models, whose molecular weight was sufficiently low (3000–15000) to be amenable to polarographic investigation, have been synthesized. Two or three haem units were π-bonded to polyvinyl-imidazole and polyhistidine chains via nitrogen at two co-ordination positions which are perpendicular to the iron-porphyrin network. Oligohaemichromes-and-haemochromes were obtained in which the iron-iron spacing was 15–70 Å. The electroreduction of the oligohaemichromes at the dropping mercury cathode was 15–28 orders of magnitude slower than that of ferrihaem, ceteris paribus. Mechanistic implications are discussed, with emphasis on a plausible electron transfer path.