Direct observation of a series of non-covalent complexes formed by phosphorylated flavonoid-protein interactions through electrospray ionization tandem mass spectroscopy

In the work described in this paper, 7-hydroxyflavone and chrysin were phosphoylated by a modified Atheron-Todd reaction. Three new phosphorylated flavonoids (PF) were obtained, and the structures of the target products were determined by X-ray and NMR data and electrospray ionization (ESI) tandem mass spectroscopy (MS). The mixed solutions of the phosphorylated flavonoids and different proteins such as insulin, lysozyme, and cytochrome c were injected in an ion trap mass spectrometer. The results show that all the phosphorylated flavonoids could form non-covalent complexes with the proteins mentioned above, while non-covalent complexes were not detected from the mixed solution of the chrysin or 7-hydroxyflavone with proteins. The research shows that the phosphorylated flavonoids could enhance the interaction with proteins. It may imply their important role in biological processes. The method described in this paper provides us additional information for studying such interactions for phosphorylated flavonoids in this important field. (C) 2004 Elsevier B.V. All rights reserved.