AVS 45th International Symposium
    Biomaterial Interfaces Group Monday Sessions
       Session BI-MoM

Paper BI-MoM5
Molecular Recognition Between Genetically-Engineered Streptavidin and Surface-Bound Biotin

Monday, November 2, 1998, 9:40 am, Room 326

Session: Protein Solid-Surface Interactions
Presenter: V.H. Perez-Luna, University of New Mexico
Authors: V.H. Perez-Luna, University of New Mexico
K.A. Opperman, University of New Mexico
P.D. Hampton, University of New Mexico
M.J. O'Brien, University of New Mexico
L. Klumb, University of Washington
P. Stayton, University of Washington
G.P. Lopez, University of New Mexico
Correspondent: Click to Email
There are fundamental differences between molecular recognition at the solid-liquid interface and in solution. In solution, ligands and receptors are randomly distributed in space, have high mobility, random orientation and, after binding, the ligand receptor pair can freely move in the solution. At the solid-liquid interface, the immobilized species is concentrated at the solid surface, has low mobility, preferential orientation for the ligand and, upon binding, the ligand-receptor pair becomes constrained to the surface region. Interactions between the immobilized biomolecules and the surface may occur or, at high densities of the immobilized receptors, attractive interactions among adjacent adsorbed ligands can give rise to cooperative effects. In this work, we study such differences with the streptavidin-biotin molecular recognition system. Binding of streptavidin to biotin-terminated self assembled monolayers (SAMs) on gold is reported. Three streptavidin mutants were used in this work: wild type, Y43A and W120A. Desorption of the bound protein molecules was obtained by incubation of the SAMs in 1 mM biotin. Desorption from disordered monolayers was incomplete, which suggests that non-specific interactions occurred either with the gold substrate or hydrophobic moieties of the thiolate after binding. Non-specific interactions did not occur on well organized monolayers and complete dissociation was achieved. Desorption of the surface bound molecules was modeled considering that the bound proteins could come off the surface either by sequential dissociation of biotin-streptavidin bonds or by simultaneous dissociation of two biotin-streptavidin bonds. The calculated dissociation constants differed by several orders of magnitude for the three mutants and they depended on the degree of coverage of surface bound biotin. The later indicating the presence of attractive interactions among adsorbed molecules at high surface coverage.