Diffusion in two-dimensional colloid-DNA systems

Diffusion in quasi-two-dimensional colloid-DNA systems are studied by enhanced video microscopy and image analysis. The colloidal particles are polystyrene spheres and DNA is linear or circular bacteriophage λ-DNA. Dyed linear DNA molecules in pure linear DNA solutions are tracked by fluorescence microscopy. The diffusivities of the colloidal particles and of the DNA molecules are found to decrease sharply at low DNA concentration; the diffusivities of the colloidal particles in both linear and circular DNA exhibit a change in slope as the DNA concentration increases.