Conformation and self-diffusion of single DNA molecules confined to two dimensions

The conformation of DNA molecules electrostatically bound to fluid cationic lipid bilayers is investigated by fluorescence microscopy. The DNA diffuse s freely in the plane and follows Rouse dynamics, D similar to 1/N, with an increasing number of base pairs N. The chain extension scales as [R-2] - N -2 nu, with nu = 0.79 +/- 0.04 in good agreement with the exact exponent nu = 3/4 for a self-avoiding random walk in two dimensions. The structure fac tor of dilute and semidilute DNA solutions shows fractal scaling behavior, S(k) similar to k(-1/nu). In highly concentrated two-dimensional DNA soluti ons, the chains were found to segregate.