AVS 46th International Symposium
    Biomaterial Interfaces Group Tuesday Sessions
       Session BI-TuM

Paper BI-TuM10
A Multi-Parameter QCM Technique for Investigations of Protein and Surface Interactions

Tuesday, October 26, 1999, 11:20 am, Room 613/614

Session: Protein Solid-Surface Interactions II
Presenter: F. Höök, Chalmers Univ. of Tech. and Göteborg Univ., Sweden.
Authors: F. Höök, Chalmers Univ. of Tech. and Göteborg Univ., Sweden.
M. Rodahl, Q-Sense AB, Sweden
B. Kasemo, Chalmers University of Technology, Sweden
Correspondent: Click to Email
Protein molecules in contact with solid, non-biological materials, is a situation of broad scientific interest and technological importance, and there is a growing need for new tools to study these interactions. For instance, if the influence from the surface is large enough, the conformational-free-energy minimum for a protein attached on a surface might correspond to a conformation that differs from that of the native protein. It is thus likely that a protein-surface interaction might affect the conformation and hence the function of the proteins. We have developed a sensor system based on the traditional quartz crystal micro balance (QCM) technique, but where both the resonant frequency (f) and the energy dissipation (D) are measured simultaneously for a non-driven (freely oscillating) sensor crystal. This offers a possibility to investigate changes in the viscoelastic properties of adsorbed proteins in real time, which are further directly related to the conformation of the adsorbed proteins. Examples of how this type of measurements contributes with such information are presented using examples of: (i) Hemoglobin (Hb) adsorbed with and without the ligand carbon monoxide, which is known to slightly effect the conformation and stability against denaturation of Hb in solution. (ii) Antibody-antigen reactions, where we emphasize the added value from this type of multi-parameter analysis for immuno-sensing or of recognition events in general. (iii) Adsorption and enzymatic induced cross-linking of a mussel adhesive protein. We also demonstrate how additional information about these and similar types of measurements are obtained by simultaneously also measure at different frequencies, since different conformational states in some situations respond differently at different frequencies. We also demonstrate the importance of multi-parameter analysis in order to be able theoretically treat the QCM response upon adsorption of non-rigid biomolecules.