Investigation of Binding Energy between Myoglobin and Heme
Date Issued
2005
Date
2005
Author(s)
Wei, Shih-Chia
DOI
zh-TW
Abstract
In this report, the structure and the binding characteristics of ferri-heme as well as its complex with myoglobin have been studied by using collision-induced dissociation (CID) method in a Fourier-transform ion cyclotron resonance (FT-ICR) cell. Performing on-resonance RF excitation to the selective precursor, we monitored the dependencies of product yields of CID as a function of ion energies and determined their dissociation thresholds. By using this method, we determined unambiguously that the heme, as a major oxygen-binding site of haemprotein, is only loosely bound to myoglobin with dissociation threshold of 1.0 ± 0.12 eV. Furthermore, an early dissociation started at 0.1 ± 0.03 eV suggesting the hMb ion contains two different conformers in our measurement. In applying it to the investigation of decomposition of Fe(III)-heme+, we determined that the decomposition of two carboxymethyl groups consecutively from it require threshold energies of respectively 2.3 ± 0.24 eV and 2.9 ± 0.27 eV. Moreover, the relative bond energy of its side chains is also obtained as: carboxymethyl groups < methyl groups < ethyl groups. Theoretical prediction carried out using density functional theory (DFT) method in both B3LYP/6-31G and B3LYP/6-311++G** level basis sets agree reasonably well with our observation. This method is unique in providing a rapid, non-selective, simple, and reliable qualitative measurement of dissociation energetics of both covalent and non-covalent interactions.
Subjects
傅立葉轉換質譜儀
血紅素
肌紅蛋白
碰撞誘導解離
FT-ICR MS
Heme
Myoglobin
CAD
Type
thesis
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