Surface plasmon resonance measurement of binding and dissociation of wild-type and mutant streptavidin on mixed biotin-containing alkylthiolate monolayers

The attachment of recognition elements to surfaces through streptavidin-biotin links has potential applications in sensor technology. Surface plasmon resonance (SPR) was used to monitor the kinetics of binding of streptavidin (SA) to mixed biotin-containing alkylthiolate monolayers (BTMs) on gold and the subsequent competitive desorption kinetics. Various binary compositions of BTMs were prepared from a mixture of biotinylated alkylthiol (BAT) and a poly(ethylene oxide) (PEO) alkylthiol. Differences in both the amount of adsorbed protein and the relative desorption rates between a low-binding affinity mutant (W120A) and wild-type streptavidin (WT) were observed as a function of the composition of the BTM. The rates of WT and W120A desorption from these mixed BTMs were correlated with the amount of biotin present on the surface. The results confirm the specific nature of the bonds which attach streptavidin to the biotinylated surface in the mixed BAT/PEO monolayer. However, when the PEG-terminated alkylthiolate was replaced with a simple methyl-terminated alkylthiolate, non-specific adsorption of the streptavidin dominates. (C) 1999 Elsevier Science S.A. All rights reserved.