A Soret Marker Band for Four-Coordinate Ferric Heme Proteins from Absorption Spectra of Isolated Fe(III)-Heme+ and Fe(III)-Heme+(His) Ions in Vacuo

In this work, we report the absorption spectra in the Soret band region of isolated Fe(III)-heme+ and Fe(III)-heme+(His) ions in vacuo from action spectroscopy. Fe(III)-heme+ refers to iron(III) coordinated by the dianion of protoporphyrin IX. We find that the absorption of the five-coordinate compl...

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Bibliographic Details
Published in:Journal of the American Chemical Society 2008-09, Vol.130 (36), p.11856-11857
Main Authors: Lykkegaard, Morten Køcks, Ehlerding, Anneli, Hvelplund, Preben, Kadhane, Umesh, Kirketerp, Maj-Britt Suhr, Nielsen, Steen Brøndsted, Panja, Subhasis, Wyer, Jean Ann, Zettergren, Henning
Format: Article
Language:English
Subjects:
Ferric Compounds - chemistry
Heme - chemistry
Hemin - chemistry
Histidine - chemistry
Spectrophotometry - methods
Static Electricity
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Summary:In this work, we report the absorption spectra in the Soret band region of isolated Fe(III)-heme+ and Fe(III)-heme+(His) ions in vacuo from action spectroscopy. Fe(III)-heme+ refers to iron(III) coordinated by the dianion of protoporphyrin IX. We find that the absorption of the five-coordinate complex is similar to that of pentacoordinate metmyoglobin variants with hydrophobic binding pockets except for an overall blueshift of about 16 nm. In the case of four-coordinate iron(III), the Soret band is similar to that of five-coordinate iron(III) but much narrower. These spectra serve as a benchmark for theoretical modeling and also serve to identify the coordination state of ferric heme proteins. To our knowledge this is the first unequivocal spectroscopic characterization of isolated 4c ferric heme in the gas phase.
ISSN:0002-7863
1520-5126
DOI:10.1021/ja803460c