Dioxygen Binding to Protonated Heme in the Gas Phase, an Intermediate Between Ferric and Ferrous Heme.
Chemistry
; 23(54): 13493-13500, 2017 Sep 27.
Article
em En
| MEDLINE
| ID: mdl-28744916
ABSTRACT
With a view to characterizing the influence of the electronic structure of the Fe atom on the nature of its bond with dioxygen (O2 ) in heme compounds, a study of the UV/Vis action spectra and binding energies of heme-O2 molecules has been undertaken in the gas phase. The binding reaction of protonated ferrous heme [FeII -hemeH]+ with O2 has been studied in the gas phase by determining the equilibrium of complexed [FeII -hemeH(O2 )]+ with uncomplexed protonated heme in an ion trap at controlled temperatures. The binding energy of O2 to the Fe atom of protonated ferrous heme was obtained from a van't Hoff plot. Surprisingly, this energy (1540±170â
cm-1 , 18.4±2â
kJ mol-1 ) is intermediate between those of ferric heme and ferrous heme. This result is interpreted in terms of a delocalization of the positive charge over the porphyrin cycle, such that the Fe atom bears a fractional positive charge. The resulting electron distribution on the Fe atom differs notably from that of a purely low-spin ferrous heme [FeII -heme(O2 )] complex, as deduced from its absorption spectrum. It also differs from that of ferric heme [FeIII -heme(O2 )]+ , as evidenced by the absorption spectra. Protonated heme creates a specific bond that cannot accommodate strong σ donation.
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Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Compostos Férricos
/
Compostos Ferrosos
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Gases
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Heme
Idioma:
En
Ano de publicação:
2017
Tipo de documento:
Article