A surface forces study of DNA hybridization

We report the first use of a surface forces apparatus to study the hybridiz ation of DNA. We study the regime of very high ionic strength (approximate to1 M) at which commercial DNA chip operations are performed. Using a thiol end-attached single-stranded oligonucleotide, we find that exposure to the complementary strand resulted in larger thickness. In addition, the resist ance to small-amplitude shear deformations when opposed to a nonadsorbing s urface (mica) increased significantly after hybridization. The thickness at onset of significant shear resistance was, for single-stranded DNA, consid erably less than that of hybridized DNA. This could provide a new method to detect DNA hybridization efficiency.