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Interactions between l-arginine/l-arginine derivatives and lysozyme and implications to their inhibition effects on protein aggregation

Authors

  • Ming-Tao Gao,

    1. Dept. of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
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  • Xiao-Yan Dong,

    1. Dept. of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
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  • Yan Sun

    Corresponding author
    1. Dept. of Biochemical Engineering and Key Laboratory of Systems Bioengineering of the Ministry of Education, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
    • Correspondence concerning this article should be addressed to Y. Sun at ysun@tju.edu.cn.

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Abstract

l-Arginine (Arg), l-homoarginine (HArg), l-arginine ethylester (ArgEE), and l-arginine methylester (ArgME) were found effective in inhibiting protein aggregation, but the molecular mechanisms are not clear. Herein, stopped-flow fluorescence spectroscopy, isothermal titration calorimetry, and mass spectroscopy were used to investigate the folding kinetics of lysozyme and the interactions of the additives with lysozyme. It was found that the interactions of ArgME and ArgEE with lysozyme were similar to that of guanidine hydrochloride and were much stronger than those of Arg and HArg. The binding forces were all mainly hydrogen bonding and cation-π interaction from the guanidinium group, but their differences in molecular states led to the significantly different binding strengths. The additives formed molecular clusters in an increasing order of ArgEE, ArgME, HArg, and Arg. Arg and HArg mainly formed annular clusters with head-to-tail bonding, while ArgME and ArgEE formed linear clusters with guanidinium groups stacking. The interactions between the additives and lysozyme were positively related to the monomer contents. That is, the monomers were the primary species that participated in the direct interactions due to their intact guanidinium groups and small sizes, while the clusters performed as barriers to crowd out the protein–protein interactions for aggregation. Thus, it is concluded that the effects of Arg and its derivatives on protein aggregation stemmed from the direct interactions by the monomers and the crowding effects by the clusters. Interplay of the two effects led to the differences in their inhibition effects on protein aggregation. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1316–1324, 2013

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