Preparation and reactivity studies of synthetic microperoxidases containing b-type heme

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title = "Preparation and reactivity studies of synthetic microperoxidases containing b-type heme",
abstract = "In order to create a heme environment that permits biomimicry of heme-containing peroxidases, a number of new hemin–peptide complexes—hemin-2(18)-glycyl-l-histidine methyl ester (HGH), hemin-2(18)-glycyl-glycyl-l-histidine methyl ester (HGGH), and hemin-2,18-bis(glycyl-glycyl-l-histidine methyl ester) (H2GGH)—have been prepared by condensation of glycyl-l-histidine methyl ester or glycyl-glycyl-l-histidine methyl ester with the propionic side chains of hemin. Characterization by means of UV/vis- and 1H NMR spectroscopy as well as cyclic- and differential pulse voltammetry indicates the formation of five-coordinate complexes in the case of HGH and HGGH, with histidine as an axial ligand. In the case of H2GGH, a six-coordinate complex with both imidazoles coordinated to the iron center appears to be formed. However, 1H NMR of H2GGH reveals the existence of an equilibrium between low-spin six-coordinate and high-spin five-coordinate species in solution. The catalytic activity of the hemin–peptide complexes towards several organic substrates, such as p-cresol, l-tyrosine methyl ester, and ABTS, has been investigated. It was found that not only the five-coordinate HGH and HGGH complexes, but also the six-coordinate H2GGH, catalyze the oxidation of substrates by H2O2. The longer and less strained peptide arm provides the HGGH complex with a slightly higher catalytic efficiency, as compared with HGH, due to formation of more stable intermediate complexes.",
author = "Ekaterina Ryabova and Alexander Dikiy and Hesslein, {Ashley E} and Bjerrum, {Morten J} and Stefano Ciurli and Ebbe Nordlander",
year = "2004",
doi = "10.1007/s00775-004-0532-5",
language = "English",
volume = "9",
pages = "385--395",
journal = "Journal of Biological Inorganic Chemistry",
issn = "1432-1327",
publisher = "Springer",
number = "4",