TY - JOUR
T1 - Electronic Structure of the Ferryl Intermediate in the α-Ketoglutarate Dependent Non-Heme Iron Halogenase SyrB2
T2 - Contributions to H Atom Abstraction Reactivity
AU - Srnec, Martin
AU - Wong, Shaun D.
AU - Matthews, Megan L.
AU - Krebs, Carsten
AU - Bollinger, J. Martin
AU - Solomon, Edward I.
N1 - Funding Information:
The project was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Numbers R01GM040392 to E.I.S. and R01GM69657 to J.M.B. and C.K., by the National Science Foundation (MCB-642058 and CHE-724084 to J.M.B. and C.K.), and by the Grant Agency of the Czech Republic (Grant No. 15-10279Y to M.S.). M.S. is also grateful to the Rulíšek/Havlas groups for access to their computational clusters at IOCB in Prague and to the Czech Academy of Sciences for the Purkyně fellowship.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/5/4
Y1 - 2016/5/4
N2 - Low temperature magnetic circular dichroism (LT MCD) spectroscopy in combination with quantum-chemical calculations are used to define the electronic structure associated with the geometric structure of the FeIV=O intermediate in SyrB2 that was previously determined by nuclear resonance vibrational spectroscopy. These studies elucidate key frontier molecular orbitals (FMOs) and their contribution to H atom abstraction reactivity. The VT MCD spectra of the enzymatic S = 2 FeIV=O intermediate with Br- ligation contain information-rich features that largely parallel the corresponding spectra of the S = 2 model complex (TMG3tren)FeIV=O (Srnec, M.; Wong, S. D.; England, J; Que, L; Solomon, E. I. Proc. Natl. Acad. Sci. USA 2012, 109, 14326-14331). However, quantitative differences are observed that correlate with π-anisotropy and oxo donor strength that perturb FMOs and affect reactivity. Due to π-anisotropy, the FeIV=O active site exhibits enhanced reactivity in the direction of the substrate cavity that proceeds through a π-channel that is controlled by perpendicular orientation of the substrate C-H bond relative to the halide-FeIV=O plane. Also, the increased intrinsic reactivity of the SyrB2 intermediate relative to the ferryl model complex is correlated to a higher oxyl character of the FeIV=O at the transition states resulting from the weaker ligand field of the halogenase.
AB - Low temperature magnetic circular dichroism (LT MCD) spectroscopy in combination with quantum-chemical calculations are used to define the electronic structure associated with the geometric structure of the FeIV=O intermediate in SyrB2 that was previously determined by nuclear resonance vibrational spectroscopy. These studies elucidate key frontier molecular orbitals (FMOs) and their contribution to H atom abstraction reactivity. The VT MCD spectra of the enzymatic S = 2 FeIV=O intermediate with Br- ligation contain information-rich features that largely parallel the corresponding spectra of the S = 2 model complex (TMG3tren)FeIV=O (Srnec, M.; Wong, S. D.; England, J; Que, L; Solomon, E. I. Proc. Natl. Acad. Sci. USA 2012, 109, 14326-14331). However, quantitative differences are observed that correlate with π-anisotropy and oxo donor strength that perturb FMOs and affect reactivity. Due to π-anisotropy, the FeIV=O active site exhibits enhanced reactivity in the direction of the substrate cavity that proceeds through a π-channel that is controlled by perpendicular orientation of the substrate C-H bond relative to the halide-FeIV=O plane. Also, the increased intrinsic reactivity of the SyrB2 intermediate relative to the ferryl model complex is correlated to a higher oxyl character of the FeIV=O at the transition states resulting from the weaker ligand field of the halogenase.
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U2 - 10.1021/jacs.6b01151
DO - 10.1021/jacs.6b01151
M3 - Article
C2 - 27021969
AN - SCOPUS:84966417260
VL - 138
SP - 5110
EP - 5122
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 15
ER -