title: Electrochemical quartz crystal impedance and fluorescence quenching studies on the binding of carbon nanotubes (CNTs)-adsorbed and solution rutin with hemoglobin.
abstract: Electrochemical quartz crystal impedance (QCI) technique was utilized to monitor in situ the adsorption of rutin (RT) onto a carbon nanotubes (CNTs)-modified gold electrode and to study the binding process of solution hemoglobin (Hb) to RT immobilized on the electrode. Time courses of the QCI parameters including crystal resonant frequency were simultaneously obtained during the RT adsorption and Hb-RT binding. In contrast to the negligible RT adsorption at a bare gold electrode, the modification by CNTs notably enhanced the amount of adsorption, and almost all of the adsorbed RT molecules were found to be electroactive. On the basis of the frequency response from the binding of adsorbed RT to solution Hb and the diminished electroactivity of adsorbed RT after the formation of the electrochemically inactive RT-Hb adduct, the average binding molar ratio of adsorbed RT to Hb was estimated to be 23.9:1, and the association constant (Ka) for the binding was estimated to be 2.87 x 106 (frequency) and 3.92 x 106 (charge) L mol-1, respectively. Comparable results were obtained from fluorescence quenching measurements in mixed solutions containing RT of fixed concentration and Hb of varying concentrations, demonstrating that the interfacial RT here behaved equivalently in the RT-Hb binding activity compared to that in solution. This work may have presented a new and general protocol involving CNTs to study many other electroactive natural antioxidants or drugs that are at the interface or in solution, their binding with proteins or other biomolecules, and changes of their antioxidant activity after the binding.
authors.affiliation: Key Laboratory of Chemical Biology and Traditional Chinese Medicine Research, Ministry of Education of China, College of Chemistry and Chemical Engineering, Hunan Normal University, Changsha 410081, PR China.
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Su
authors.forename: Qingji
authors.initials: Q
authors.lastname: Xie
authors.forename: Qin
authors.initials: Q
authors.lastname: Yang
authors.forename: Xinman
authors.initials: X
authors.lastname: Tu
authors.forename: Zhijun
authors.initials: Z
authors.lastname: Cao
authors.forename: Xue'en
authors.initials: X
authors.lastname: Jia
authors.forename: Zhaohong
authors.initials: Z
authors.lastname: Su
authors.forename: Youyu
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wenhua
authors.initials: W
authors.lastname: Meng
authors.forename: Shouzhuo
authors.initials: S
authors.lastname: Yao
mesh_terms: D000327:Adsorption; D001665:Binding Sites; D003198:Computer Simulation; D017097:Electric Impedance; D004563:Electrochemistry / Q000379:methods*; D006454:Hemoglobins / Q000737:chemistry*; D008856:Microscopy, Fluorescence / Q000379:methods*; D008956:Models, Chemical; D037742:Nanotubes, Carbon / Q000737:chemistry*; D011485:Protein Binding; D011791:Quartz; D012431:Rutin / Q000737:chemistry*; D012995:Solubility; D012996:Solutions
chemical_list: D006454:Hemoglobins; D037742:Nanotubes, Carbon; D012996:Solutions; D011791:Quartz; D012431:Rutin