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AFM visualization of 2D topological exclusion acting on non-supercoiled DNA molecules. Non-supercoiled DNA molecules were gently adsorbed to mica surface under conditions resulting in a low (a) or high (b and c) density of deposition. Notice that at high density of deposition most of the molecules are much more elongated than at the low density of deposition. Panel (c) shows at higher magnification a region demarked in panel (b).
