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.

Understanding protein adsorption phenomena at solid surfaces

“…The SAF technology itself (2000) [238,239], a SAF sensing instrument (2003) [240], and also a SAF imaging instrument (2007) [241,242] were recently developed. The strength of the SAF technique to study protein adsorption phenomena was demonstrated in some recent publications [44,102,118,187] or TIRF set-ups and, more recently, also with the SAF optics [244]. In relation to protein adsorption the applicability of FCS to reveal the aggregation of proteins in the solution or on the surface has been demonstrated [245,246].…”

“…That means, a freshly established protein layer is hardly resistant to elution whereas after a certain time period (scaling between a few minutes and several hours) proteins can even be found to be irreversibly attached to the surface. In this way it has been proven that the protein Immunoglobulin G (IgG) undergoes conformational changes on a variety of model surfaces [118]. By using a simple kinetic model the transition rates between the initial and the apparent equilibrium state could be quantified.…”

Investigating Alanine–Silica Interaction by Means of First‐Principles Molecular‐Dynamics Simulations

“…Already during the minimization of structure B Vac , a proton transfer from the NH 3 + group of alanine to its COO À takes place, which means that the zwitterionic form is not stable without solvent molecules. This observation is consistent with a series of investigations on the stability of glycine in the gas phase (see for example Jensen and Gordon [41] and references given therein).…”

Biotin‐Functionalized Cellulose‐Based Monolayers as Sensitive Interfaces for the Detection of Single Molecules

“…The mechanism was resolved recently and shows the difficulties of removal after adhesion due to conformational changes. [40] In this respect, providing surfaces as described here, which lead to A C H T U N G T R E N N U N G desorption prior to conformational changes, is of principal interest. [40] In summary, a novel biotin cellulose has been synthesized.…”

“…[40] In this respect, providing surfaces as described here, which lead to A C H T U N G T R E N N U N G desorption prior to conformational changes, is of principal interest. [40] In summary, a novel biotin cellulose has been synthesized. Monolayers of this compound were obtained on glass after Langmuir-Blodgett transfer and were used to detect single molecules after specific binding onto a streptavidin coating.…”