AVS 47th International Symposium
    Biomaterial Interfaces Tuesday Sessions
       Session BI-TuM

Paper BI-TuM10
Determination of Surface-Protein Equilibrium Binding Constants by MALDI Mass Spectrometry

Tuesday, October 3, 2000, 11:20 am, Room 202

Session: Protein-Surface Interactions
Presenter: G.R. Kinsel, University of Texas at Arlington
Authors: G.R. Kinsel, University of Texas at Arlington
J. Zhang, University of Texas at Arlington
R.B. Timmons, University of Texas at Arlington
H. Qiu, University of Texas at Arlington
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We have recently demonstrated that matrix assisted laser desorption / ionization (MALDI) mass spectrometry offers a new approach for the characterization of surface-protein interactions. Our work demonstrates that strongly surface-retained proteins are poorly incorporated into the MALDI matrix crystals, leading to inefficient ionization of these species. In effect, the surface-deposited protein MALDI ion signal approaches zero as the quantity of deposited protein approaches the quantity strongly retained by the surface. Furthermore, as expected, the protein MALDI ion signals exhibit Langmuir type behavior as the surface concentration of the protein is reduced, i.e. the protein MALDI ion signal versus surface concentration response becomes asymptotic at low protein surface concentrations. Analysis of the protein MALDI ion signal versus surface concentration data allows the equilibrium surface-protein binding constant to be established. In our current work this approach to the determination of surface-protein binding constants has been applied to a number of smaller peptides and proteins deposited on a variety of polymeric biomaterials. Expected trends are observed, particularly with regard to the influence of electrostatic interactions between acidic or basic surfaces and basic or acidic proteins in solution. In addition, we have used the MALDI approach to examine the elutability of surface-bound proteins as a function of solvent choice. Our studies indicate that protein solubilization as a function of solvent choice is strongly influenced by the chemistry of the surface-protein interaction.