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J Colloid Interface Sci. 2019 Jun 15;546:211-220. doi: 10.1016/j.jcis.2019.03.066. Epub 2019 Mar 21.

Surface functionalization of graphene oxide by amino acids for Thermomyces lanuginosus lipase adsorption.

Author information

1
State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, No. 5, Xinmofan Road, Nanjing 210009, China; College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu South Road, Nanjing 211816, China.
2
State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, No. 5, Xinmofan Road, Nanjing 210009, China; College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu South Road, Nanjing 211816, China. Electronic address: weizhuang@njtech.edu.cn.
3
Centre for Future Materials, University of Southern Queensland, Springfield, Queensland 4300, Australia.
4
State Key Laboratory of Materials-Oriented Chemical Engineering, Nanjing Tech University, No. 5, Xinmofan Road, Nanjing 210009, China; College of Biotechnology and Pharmaceutical Engineering, National Engineering Technique Research Center for Biotechnology, Nanjing Tech University, No. 30, Puzhu South Road, Nanjing 211816, China. Electronic address: yinghanjie@njtech.edu.cn.

Abstract

Graphene oxide (GO) with oxygen containing functional groups can be selectively modified by small biomolecules to achieve heterogeneous surface properties. To achieve a hyper-enzymatic activity, the surface functionality of GO should be tailored to the orientation adsorption of the Thermomyces lanuginosus (TL) lipase, and the active center can be covered by a relatively hydrophobic helical lid for protection. In this work, amino acids were used to interact with GO through reduction reaction, hydrophobic forces, electrostatic forces, or hydrogen bonding to alter the surface hydrophobicity and charge density. Characterization of the structure and surface properties confirmed that the GO samples decorated with phenylalanine (Phe) and glutamic acid (Glu) exhibited superior hydrophobicity than other modifications, whereas tryptophan (Trp) and cysteine (Cys) provided weaker reduction effects on GO. Moreover, the zeta potential of the samples modified by amino acids of lysine (Lys) and arginine (Arg) is higher than other modified samples. The adsorption amount of lipase on Glu-GO reached 172 mg/g and the relative enzymatic activity reached up to 200%. The thermodynamic data and the Freundlich isotherm model fitting showed that the lipase adsorption process on modified samples was spontaneous, endothermic and entropy increase.

KEYWORDS:

Amino acids; Freundlich isotherm model; Graphene oxide; Lipase adsorption; Surface modification

PMID:
30921675
DOI:
10.1016/j.jcis.2019.03.066

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