Real-time dynamics of single-DNA molecules undergoing adsorption and desorption at liquid-solid interfaces.

The conformational dynamics and adsorption/desorption behavior of individual lambda-DNA molecules at liquid-solid interfaces were monitored by imaging within the evanescent field layer using total internal reflection fluorescence microscopy. At a fused-silica surface, molecular conformation and adsorption behavior were found to depend on both pH and buffer composition. A histogram of individual lambda-DNA adsorption durations measured by hydrodynamically flowing molecules along the interface exhibited asymmetry nearly identical to that of the corresponding elution peaks found in capillary liquid chromatography and capillary electrophoresis. The accessibility of the surface to the molecules, which is proportional to the capillary surface area-to-volume ratio, can be correlated with the capacity factor and the relative adsorption factor. At a C18 surface, the dynamics of individual DNA molecules changed with the addition of organic solvent as well as with pH. Hydrophobic interaction rather than electrostatic interaction was the major driving force for adsorption of individual DNA molecules.