title: Concentration dependence of IgG-protein A affinity studied by wireless-electrodeless QCM.
abstract: The binding affinity between human immunoglobulin G (IgG) and protein A was studied by the homebuilt wireless-electrodeless quartz crystal microbalance (QCM). Protein A was immobilized on the electrodeless AT-cut quartz plate of 0.05 mm thick and its fundamental resonance frequency near 34 MHz was measured by a noncontacting manner using a line antenna. The vibrational analysis was performed to ensure higher sensitivity of the electrodeless QCM. A flow-cell system was fabricated to continuously measure the resonance frequency during the injection sequence of the IgG solutions with concentrations of 1-20,000 ng/mL. The exponential frequency changes were recorded to determine the affinity based on the Langmuir kinetics. The equilibrium constant K(A) significantly varied between 6 x 10(6) and 6 x 10(10) M(-1), depending on the IgG concentration, which is attributed to various formations of IgG-protein A complexes.
authors.affiliation: Graduate School of Engineering Science, Osaka University, Machikaneyama 1-3, Toyonaka, Osaka 560-8531, Japan. ogi@me.es.osaka-u.ac.jp
authors.forename: Hirotsugu
authors.initials: H
authors.lastname: Ogi
authors.forename: Kazuma
authors.initials: K
authors.lastname: Motohisa
authors.forename: Kenichi
authors.initials: K
authors.lastname: Hatanaka
authors.forename: Toshinobu
authors.initials: T
authors.lastname: Ohmori
authors.forename: Masahiko
authors.initials: M
authors.lastname: Hirao
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Nishiyama
mesh_terms: D000327:Adsorption; D015374:Biosensing Techniques / Q000379:methods*; D004566:Electrodes; D007074:Immunoglobulin G / Q000737:chemistry*; D011791:Quartz / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013205:Staphylococcal Protein A / Q000737:chemistry*
chemical_list: D007074:Immunoglobulin G; D013205:Staphylococcal Protein A; D011791:Quartz