title: Interaction of an amino-functionalized ionic liquid with enzymes: a fluorescence spectroscopy study.
abstract: The interaction of an amino-functionalized ionic liquid, 1-(2-aminoethyl)-3-butylimidazolium bromide ([NH(2)C(2)C(4)im]Br) with two enzymes, pepsin and papain was investigated using fluorescence spectroscopic technique. It is found that [NH(2)C(2)C(4)im]Br has strong ability to quench the intrinsic fluorescence of pepsin and papain. Quenching mechanisms are considered as static quenching for papain and dynamic quenching for pepsin, respectively. The binding constants and the number of binding sites (n) of [NH(2)C(2)C(4)im]Br to papain were calculated at different temperatures. The thermodynamic parameters such as free energy change (ΔG), enthalpy change (ΔH) and entropy change (ΔS), were calculated by thermodynamic equations. The values of ΔG, ΔH and ΔS suggest that interaction of [NH(2)C(2)C(4)im]Br with the two enzymes is spontaneous. Hydrogen bonding and van der Waals interactions play important roles in the binding process of [NH(2)C(2)C(4)im]Br to papain. However, hydrophobic interaction is the main driving force for the interaction of [NH(2)C(2)C(4)im]Br with pepsin. The results of three-dimensional fluorescence spectra show that [NH(2)C(2)C(4)im]Br has no obvious effects on the polypeptide structures of the two enzymes. Additionally, the [NH(2)C(2)C(4)im]Br-containing system can slightly increase the activities of the two enzymes.
authors: College of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454003, China. yunchangfan@yahoo.com.cn
authors: Yunchang
authors: Y
authors: Fan
authors: Sheli
authors: S
authors: Zhang
authors: Qiang
authors: Q
authors: Wang
authors: Junhai
authors: J
authors: Li
authors: Haotian
authors: H
authors: Fan
authors: Dongkai
authors: D
authors: Shan
mesh_terms: D000586:Amination; D000588:Amines / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism*; D052578:Ionic Liquids / Q000737:chemistry / Q000378:metabolism*; D010206:Papain / Q000737:chemistry / Q000378:metabolism*; D010434:Pepsin A / Q000737:chemistry / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence / Q000379:methods; D013552:Swine; D013816:Thermodynamics
chemical_list: D000588:Amines; D007093:Imidazoles; D052578:Ionic Liquids; C514468:n-butylimidazolium bromide; D010206:Papain; D010434:Pepsin A