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 hom 100 to 500 0 base pairs, was studied using streptavidin-coated polystyrene latex particles with diameters between 0.944 and 0.090 mu m. The experimenta l binding constants and forward rate constants of this solid-phase rea ction were determined to be several orders of magnitude lower than val ues for the biotin-streptavidin interaction in solution as expected an d were shown to depend on the size of both Ligand and substrate. An ob served inflection in the binding constant of the biotinylated DNA appe ared around 1000 base pairs, possibly indicating different surface ori entations of the macroligand above and below this critical size. This effect was more pronounced for the smaller latex particles used in thi s study and highlighted possible differences in the surface arrangemen t of streptavidin on the differently sized particles. Diffusion limita tion to the binding reaction was found to be significant in all cases. In this present work, an exponential relationship was established bet ween the experimental binding constant and the number of base pairs in the biotinylated DNA This relationship possibly provides a means to p redict capacity and binding speed in cases where adsorption, purificat ion, and release of larger DNA chains are required. (C) 1996 Academic Press, Inc.