Measurement of DNA Morphological Parameters at Highly Entangled Regime on Surfaces

The morphology of circular DNA deposited from a solution on the mica surface is analyzed from the power spectrum density (PSD) of the atomic force microscopy (AFM) images. Sample morphology is modulated in a broad range of concentration C from isolated molecules to highly entangled networks. DNA exhibits a multiaffine behavior with two correlation length scales: the persistence length P which remains constant (≈50 nm) within the C range and the intermolecular distance ξ which exhibits a decay with increasing C. Applying a diffusion based model in which ξ scales as ξ ≈ D −0.25·C −0.5, we extracted the DNA diffusion coefficient D ≈ 2 × 10−7 cm2/s. This value is consistent with a high-molecular-weight plasmid DNA supercoiled in the solution.