title: Conformational reorientation of immunoglobulin G during nonspecific interaction with surfaces.
abstract: To achieve a better understanding of the nonspecific adsorption process of proteins on solid surfaces, the mechanism of this interaction was investigated by a model system comprising the structurally flexible ("soft") protein goat anti-rabbit immunoglobulin G and a set of chemically defined surfaces. The thermodynamic properties of both protein and surfaces were derived from contact angle measurements by applying the Lifshitz-van der Waals acid-base approach, and the Gibbs free enthalpy of interaction was calculated. The protein shows two conformational states, one hydrophobic and the other hydrophilic. The interaction energy indicates that the hydrophobic conformation favorably adsorbs onto the surfaces. With real-time binding kinetics, measured by a supercritical angle fluorescence biosensor, we show that during the nonspecific adsorption the protein performs a reorientation in its three-dimensional amino acid structure from a hydrophilic to a hydrophobic molecular structure. Unlike the rates of adsorption and desorption, the transition rate is independent of the type of surface and only influenced by the structural reorganization of the protein.
authors.affiliation: Institute of Physical Chemistry, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Rankl
authors.forename: Thomas
authors.initials: T
authors.lastname: Ruckstuhl
authors.forename: Michael
authors.initials: M
authors.lastname: Rabe
authors.forename: Georg R J
authors.initials: GR
authors.lastname: Artus
authors.forename: Andreas
authors.initials: A
authors.lastname: Walser
authors.forename: Stefan
authors.initials: S
authors.lastname: Seeger
mesh_terms: D000327:Adsorption; D007074:Immunoglobulin G / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000737:chemistry; D010316:Particle Size; D013237:Stereoisomerism; D013499:Surface Properties; D013500:Surface Tension; D013816:Thermodynamics
chemical_list: D007074:Immunoglobulin G; D017646:Organosilicon Compounds