Atomic force microscopy of complex DNA knots

Complex knots on circular closed DNA molecules extracted from virus capsids have been observed by Atomic Force Microscopy after being adsorbed onto a surface. A characterization of the knot conformation according to the adsorption procedure is presented. The adsorption procedure has been previously characterized by measuring the scaling properties of a linear DNA molecule belonging to a different virus. The high resolution of the AFM images has allowed us to identify the chirality of some DNA crossings without any specific sample treatment. The high complexity of the knot population prevents us from identifying the knot types. The present results concern the determination of the three dimensional knot conformation from the two dimensional images.