Positively charged surface induces discontinuous transition for the high order structure in duplex DNA

Interaction of DNA molecules with solid surface was studied with single molecular observation by use of fluorescence microscopy. Drastic change in the conformation of DNA chain was induced by the interaction with the positively charged surface. It was found that unfolded DNA chain in aqueous solution changes into compacted globule accompanied with the adsorption onto the positively charged surface. A brief discussion is represented concerning the mechanism of the transition from the physico-chemical point of view.