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

The conformational dynamics and adsorption/desorption behavior of individua l lambda -DNA molecules at liquid-solid interfaces were monitored by imagin g within the evanescent field laver using total internal reflection fluores cence microscopy. At a fused-silica surface, molecular conformation and ads orption behavior were found to depend on both pH and buffer composition. A histogram of individual lambda -DNA adsorption durations measured by hydrod ynamically flowing molecules along the interface exhibited asymmetry nearly identical to that of the corresponding elution peaks found in capillary li quid chromatography and capillary electrophoresis. The accessibility of the surface to the molecules, which is proportional to the capillary surface a rea-to-volume ratio, can be correlated with the capacity factor and the rel ative adsorption factor. At a Cls surface, the dynamics of individual DNA m olecules changed with the addition of organic solvent as well as with pH. H ydrophobic interaction rather than electrostatic interaction was the major driving force for adsorption of individual DNA molecules.