On the Mössbauer spectra of isopenicillin N synthase and a model {FeNO}7 (S = 3/2) system

Yong Zhang, Eric Oldfield

Research output: Contribution to journalArticlepeer-review


We have carried out a series of density functional theory (DFT) calculations to predict the 57Fe Mössbauer quadrupole splittings (ΔEQ) and isomer shifts (δFe) for the nitrosyl complex of isopenicillin N synthase with the substrate δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine (IPNS·ACV·NO) and an {FeNO}7 (S = 3/2) model system, FeL(NO)(N3)2 (L = N,N′,N″-trimethyl-1,4,7-triazacyclononane). B3LYP predictions on the model compound are in almost exact agreement with experiment. The same DFT methods did not enable the prediction of the experimental ΔEQ and δFe results for IPNS·ACV·NO when using the experimental protein crystal structure but did permit good predictions of ΔEQ, δFe, and the asymmetry parameter (η) when using a fully optimized structure. This optimized structure also enabled good predictions of the Mössbauer spectra of the photodissociation product of IPNS·ACV·NO. Mulliken and natural bonding orbital (NBO) spin density analyses indicate an electronic configuration of FeII (S = 2) anti-ferromagnetically coupled to NO (S = 1/2) in the protein as well as in the model system and the geometry optimized structure helps explain part of the enzyme reaction.

Original languageEnglish (US)
Pages (from-to)9494-9495
Number of pages2
JournalJournal of the American Chemical Society
Issue number31
StatePublished - Aug 11 2004

ASJC Scopus subject areas

  • Catalysis
  • General Chemistry
  • Biochemistry
  • Colloid and Surface Chemistry


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