title: Study of fluorescence quenching mechanism between quercetin and tyrosine-H(2)O(2)-enzyme catalyzed product.
abstract: Because of catalysis of horseradish peroxidase, the tyrosine reacted with H(2)O(2) to form the product S which was a strong fluorescence substance. To the product S, the quercetin was acted as a quencher. The fluorescence quenching mechanism was studied by the measurement of fluorescence lifetime and based on the Stern-Volmer plot. The reaction mechanism, which was the static quenching process between quercetin and product S, was studied. The binding constant, K=4.03 x 10(5) L mol(-1) and the number of binding sites n=1.09, were obtained against this reaction. The thermodynamic parameters were estimated. The data, DeltaH=-75.68 kJ mol(-1), DeltaS=-147.9JK(-1) mol(-1) and DeltaG=-29.17 kJ mol(-1) showed that the reaction was spontaneous and exothermic. What is more, both DeltaH and DeltaS were negative values indicated that van der Waals interaction and hydrogen bonding were the predominant intermolecular forces between quercetin and product S.
authors.affiliation: College of Chemistry, Chemical Engineering and Materials Science, Shandong Normal University, Jinan 250014, PR China.
authors.forename: Miao
authors.initials: M
authors.lastname: Zhang
authors.forename: Qingluan
authors.initials: Q
authors.lastname: Lv
authors.forename: Ningning
authors.initials: N
authors.lastname: Yue
authors.forename: Huaiyou
authors.initials: H
authors.lastname: Wang
mesh_terms: D001665:Binding Sites; D002384:Catalysis; D005453:Fluorescence; D006735:Horseradish Peroxidase / Q000378:metabolism; D006860:Hydrogen Bonding; D006861:Hydrogen Peroxide / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D015394:Molecular Structure; D011485:Protein Binding; D011794:Quercetin / Q000378:metabolism*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D055672:Static Electricity; D013816:Thermodynamics; D014443:Tyrosine / Q000737:chemistry*
chemical_list: D014443:Tyrosine; D011794:Quercetin; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase