Binding of biotinylated DNA to streptavidin-coated polystyrene latex: effects of chain length and particle size.

The binding of 5'-end biotinylated DNA, ranging in size from 100 to 5000 base pairs, was studied using streptavidin-coated polystyrene latex particles with diameters between 0.944 and 0.090 micron. The experimental binding constants and forward rate constants of this solid-phase reaction were determined to be several orders of magnitude lower than values for the biotin-streptavidin interaction in solution as expected and were shown to depend on the size of both ligand and substrate. An observed inflection in the binding constant of the biotinylated DNA appeared around 1000 base pairs, possibly indicating different surface orientations of the macroligand above and below this critical size. This effect was more pronounced for the smaller latex particles used in this study and highlighted possible differences in the surface arrangement of streptavidin on the differently sized particles. Diffusion limitation to the binding reaction was found to be significant in all cases. In this present work, an exponential relationship was established between the experimental binding constant and the number of base pairs in the biotinylated DNA. This relationship possibly provides a means to predict capacity and binding speed in cases where adsorption, purification, and release of larger DNA chains are required.