TY - JOUR
T1 - On the Mössbauer spectra of isopenicillin N synthase and a model {FeNO}7 (S = 3/2) system
AU - Zhang, Yong
AU - Oldfield, Eric
PY - 2004/8/11
Y1 - 2004/8/11
N2 - 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.
AB - 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.
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U2 - 10.1021/ja0401242
DO - 10.1021/ja0401242
M3 - Article
C2 - 15291525
AN - SCOPUS:3543051872
SN - 0002-7863
VL - 126
SP - 9494
EP - 9495
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 31
ER -