title: Interaction of the ginsenosides with κ-casein and their effects on amyloid fibril formation by the protein: Multi-spectroscopic approaches.
abstract: The interaction of the ginsenosides (GS) including ginsenoside Rg1, Rb1 and Re with κ-casein and the effects of GS inhibiting amyloid fibril formation by κ-casein have been investigated in vitro by fluorescence and ultraviolet spectra. Results showed that Rg1 and Rb1 had dose-dependent inhibitory effects on reduced and carboxymethylated κ-casein (RCMκ-CN) fibril formation, while Re resulted in an increase in the rate of fibril formation. The enhancement in RLS intensity was attributed to the formation of new complex between GS and RCMκ-CN, and the corresponding thermodynamic parameters (ΔH, ΔS and ΔG) were assayed. The steady-state ultraviolet-visible absorption spectra had also been tested to observe if the ground-state complex formed, and it showed the same result as RLS spectra. The binding constants and the number of binding sites between GS and RCMκ-CN at different temperatures had been evaluated from relevant fluorescence data. According to the Förster non-radiation energy transfer theory, the binding distance between RCMκ-CN and GS was calculated. The fluorescence lifetime of RCMκ-CN was longer in the presence of GS than in absence of GS, which was evident that the hydrophobic interaction plays a major role in the binding of GS to RCMκ-CN. From the results of synchronous fluorescence, it could be deduced that the polarity around RCMκ-CN Trp97 residue decreased and the hydrophobicity increased after addition of Rg1 or Rb1. Based on all the above results, it is explained that Rg1 and Rb1 inhibited amyloid fibril formation by κ-casein because the molecular spatial conformation and physical property of κ-casein changed causing by the complex formation between GS and κ-casein.
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Fanbo
authors.initials: F
authors.lastname: Chen
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Yunhua
authors.initials: Y
authors.lastname: Wang
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Miao
authors.initials: M
authors.lastname: Yang
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Jianyuan
authors.initials: J
authors.lastname: Yin
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Qin
authors.initials: Q
authors.lastname: Meng
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Fengquan
authors.initials: F
authors.lastname: Bu
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China.
authors.forename: Dandan
authors.initials: D
authors.lastname: Sun
authors.affiliation: College of Pharmacy, Jilin University, Changchun 130021, PR China. Electronic address: liujh@jlu.edu.cn.
authors.forename: Jihua
authors.initials: J
authors.lastname: Liu
mesh_terms: D000682:Amyloid / Q000737:chemistry / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002364:Caseins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D000067493:Dynamic Light Scattering; D036145:Ginsenosides / Q000737:chemistry / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D000682:Amyloid; D002364:Caseins; D036145:Ginsenosides
keywords: Amyloid fibril; Fluorescence spectroscopy; Ginsenoside; Inhibition; Interaction; κ-Casein