title: Characterization of interaction between amino acids and fulvic-like organic matter by fluorescence spectroscopy combining thermodynamic calculation.
abstract: Dissolved organic matter (DOM), as a very fine colloidal suspension, could inevitably affect the transformation process of dissolved organic nitrogen (DON) in drinking water treatment. Tryptophan and tyrosine were used as representatives of DON to investigate the interactions between amino acids and fulvic-like components of fluorescent DOM using titration experiments. The fluorescence intensity decreased significantly with the increasing fulvic acid (FA) concentration, suggesting that FA could greatly quench the intrinsic fluorescence of amino acids such as tryptophan and tyrosine. The absolute spectrum peaks of amino acids (AA) were changed in the presence of FA, possibly being resulted from non-covalent interactions between amino acids and FA. The specific hydrogen bonding and van der Waals forces played dominant roles in the interactions according to the results of theoretical analysis and thermodynamic calculation. The distance between donor and acceptor was 1.25 and 1.14 nm for the FA-tyrosine and FA-tryptophan system, indicating the energy transfer from tyrosine or tryptophan to FA. The association constant (K) decreased with the increase of temperature and pH value, while the change of ionic strength had no obvious influence on K value.
authors.affiliation: Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Hohai University, Nanjing, 210098, People's Republic of China. hit_lintao@163.com.|College of Environment, Hohai University, Nanjing, 210098, People's Republic of China. hit_lintao@163.com.
authors.forename: Tao
authors.initials: T
authors.lastname: Lin
authors.affiliation: Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Hohai University, Nanjing, 210098, People's Republic of China.|College of Environment, Hohai University, Nanjing, 210098, People's Republic of China.
authors.forename: Bingwei
authors.initials: B
authors.lastname: Hou
authors.affiliation: Yixing Water Group, Xiying, 214221, People's Republic of China.
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.affiliation: Yixing Water Group, Xiying, 214221, People's Republic of China.
authors.forename: Yaqun
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Ministry of Education Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes, Hohai University, Nanjing, 210098, People's Republic of China.|College of Environment, Hohai University, Nanjing, 210098, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000596:Amino Acids / Q000032:analysis / Q000737:chemistry; D001578:Benzopyrans / Q000032:analysis / Q000737:chemistry; D009584:Nitrogen / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D001578:Benzopyrans; D009584:Nitrogen; C005023:fulvic acid
keywords: Amino acids; Dissolved organic nitrogen; Fluorescence quenching; Fulvic acids; Hydrogen bonding