title: Effect of metal ions on the binding reaction of (-)-epigallocatechin gallate to β-lactoglobulin.
abstract: The effects of metal ions (Cu2+, Sn2+, Zn2+, Mn2+, Al3+and Fe3+) on the interaction between (-)-epigallocatechin-3-gallate (EGCg) and β-lactoglobulin (β-Lg) were investigated via fluorescence and circular dichroism (CD) spectroscopy. The results of the fluorescence titration experiment demonstrated that the addition of Cu2+increases the quenching efficiency of EGCg to β-Lg by more than EGCg alone, while Mn2+, Al3+and Zn2+decrease the quenching efficiency of EGCg to β-Lg by less than EGCg alone. [β-Lg-Mn], [β-Lg-Al], [β-Lg-Zn] and [β-Lg-Sn] obviously decreased the apparent binding affinities (Ka) of EGCg to β-Lg by 95.53%, 81.94%, 44.66% and 38.58%, respectively, whereas [β-Lg-Cu] significantly increased the Kaof EGCg for β-Lg by 115.44%. The results of CD spectroscopy experiment showed the α-helix content of β-Lg decreased with the addition of Cu or Al, indicating that the β-Lg-Cu and β-Lg-Al interaction resulted in unfolding of the secondary structure of β-Lg.
authors.affiliation: Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China. Electronic address: zhll20086@163.com.
authors.forename: Liangliang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Chemistry and Biochemistry Department, Miami University, Oxford, OH 45056, USA.
authors.forename: Indra Dev
authors.initials: ID
authors.lastname: Sahu
authors.affiliation: Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China.
authors.forename: Man
authors.initials: M
authors.lastname: Xu
authors.affiliation: Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China.
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Institute of Chemical Industry of Forest Products, CAF, Nanjing 210042, China.
authors.forename: Xinyu
authors.initials: X
authors.lastname: Hu
mesh_terms: D002392:Catechin / Q000031:analogs & derivatives* / Q000737:chemistry; D007477:Ions; D007782:Lactoglobulins / Q000737:chemistry*; D008670:Metals; D017433:Protein Structure, Secondary
chemical_list: D007477:Ions; D007782:Lactoglobulins; D008670:Metals; D002392:Catechin; C045651:epigallocatechin gallate
keywords: (−)-Epigallocatechin gallate; CD spectroscopy; Fluorescence; Metal ions; β-Lactoglobulin