Nature of the Fe-O Bonding in Oxy-Myoglobin: Effect of the Protein.
The nature of the Fe-O bonding in oxy-myoglobin was probed by theoretical calculations: (a) QM/MM (hybrid quantum mechanical/molecular mechanical) calculations using DFT/MM and CASSCF/MM methods and (b) gas-phase calculations using DFT (density functional theory) and CASSCF (complete active space se...
| Publicado en: | Journal of the American Chemical Society Vol. 130; no. 44; pp. 14778 - 14791 |
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| Autores principales: | , , |
| Formato: | Artículo |
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American Chemical Society
11/5/2008
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=35419301&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 35419301 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 11/5/2008 vid: 130 iid: 44 pid: 997 pub: American Chemical Society artinfo: ui: 35419301 10.1021/ja805434m ppf: 14778 ppct: 13 formats: tig: atl: Nature of the Fe-O Bonding in Oxy-Myoglobin: Effect of the Protein. aug: au: Chen, Hui Ikeda-Saito, Masao Shaik, Sason affil: Department of Organic Chemistiy and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel, and Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Katahira, Sendai 980-8577, Japan su: Myoglobin Proteins Quantum theory Density functionals Charge exchange sug: subj: Myoglobin Proteins Quantum theory Density functionals Charge exchange ab: The nature of the Fe-O bonding in oxy-myoglobin was probed by theoretical calculations: (a) QM/MM (hybrid quantum mechanical/molecular mechanical) calculations using DFT/MM and CASSCF/MM methods and (b) gas-phase calculations using DFT (density functional theory) and CASSCF (complete active space self-consistent field) methods. Within the protein, the O is hydrogen bonded by His64 and the complex feels the bulk polarity of the protein. Removal of the protein causes major changes in the complex. Thus, while CASSCF/MM and DFT/MM are similar in terms of state constitution, degree of O charge, and nature of the lowest triplet state, the gas-phase CASSCF(g) species is very different. Valence bond (VB) analysis of the CASSCF/MM wave function unequivocally supports the Weiss bonding mechanism. This bonding arises by electron transfer from heme-Fe to O and the so formed species coupled then to a singlet state Fe-O that possesses a dative σ(Fe-O) bond and a weakly coupled π(Fe-O) bond pair. The bonding mechanism in the gas phase is similar, but now the σ(Fe-O) bond involves higher back-donation from O to Fe, while the constituents of π(Fe-O) bond pair have greater delocalization tails. The protein thus strengthens the Fe-O character of the complex and thereby affects its bonding features and the oxygen binding affinity of Mb. The VB model is generalized, showing how the protein or the axial ligand of the oxyheme complex can determine the nature of its bonding in terms of the blend of the three bonding models: Weiss, Pauling, and McClure-Goddard. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2008 holdings: @attributes: islocal: N |
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