title: Interaction of L-arginine with κ-casein and its effect on amyloid fibril formation by the protein: multi-spectroscopic approaches.
abstract: Herein, the interaction of l-arginine (ARG) with κ-casein, and its effect on amyloid fibril formation of the protein, have been investigated in vitro by resonance light scattering (RLS), fluorescence, UV-Vis absorption spectroscopy and transmission electron microscopy (TEM) under simulated physiological conditions. The results indicated that ARG inhibited fibril formation by reduced and carboxymethylated κ-casein (RCMκ-CN), and there was interaction between ARG and RCMκ-CN, proved by the observation of enhancement in RLS intensity attributed to the formation of RCMκ-CN-ARG complex. It was also demonstrated that ARG strongly quenched the intrinsic fluorescence of RCMκ-CN through a static quenching mechanism. The corresponding thermodynamic parameters (ΔH, ΔS and ΔG) were tested to show that the binding process was spontaneous and mainly enthalpy driven with an unfavorable entropy, and both hydrogen bond and van der Waals forces played a key role in the binding of ARG and RCMκ-CN. The determined value of the distance r between ARG and RCMκ-CN Trp97 residue evaluated by fluorescence resonance energy transfer (FRET) was 2.94nm. Furthermore, the conformational investigation from synchronous fluorescence showed that the RCMκ-CN Trp97 residue was placed in a less polar environment and more difficultly exposed to the solvent after addition of ARG.
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: Jianyuan
authors.initials: J
authors.lastname: Yin
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: Qin
authors.initials: Q
authors.lastname: Meng
authors.affiliation: Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130021, PR China.
authors.forename: Baohua
authors.initials: B
authors.lastname: Zeng
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*; D000818:Animals; D001120:Arginine / Q000378:metabolism* / Q000494:pharmacology*; D002364:Caseins / Q000737:chemistry* / Q000378:metabolism*; D002417:Cattle; D008745:Methylation; D011485:Protein Binding; D055503:Protein Multimerization / Q000187:drug effects*; D017433:Protein Structure, Secondary; D012997:Solvents / Q000737:chemistry; D013057:Spectrum Analysis
chemical_list: D000682:Amyloid; D002364:Caseins; D012997:Solvents; D001120:Arginine