Cationic silanes stabilize intermediates in DNA condensation

In vitro condensation of DNA has been widely studied to gain insight into t he mechanisms of DNA compaction in biological systems such as chromosomes a nd phage heads and has been used to produce nanostructured particles with n ovel material and functional properties, Here we report on the condensation of DNA in aqueous solutions by cationic silanes, which combine the condens ing properties of polyamines with the cross-linking chemistry of silanes, D NA can be reversibly condensed into classical toroidal and rod-shaped struc tures with these agents, At low silane concentrations DNA forms a variety o f looped structures with well-defined characteristics, including flower-and sausage-shaped forms. These structures suggest that at low silane concentr ations a DNA-DNA contact in which the strands are at very large angles to e ach other is stabilized. Changes in these structures observed as a function of silane concentration suggest possible pathways for the formation of tor oids and rods. (C) 1999 Federation of European Biochemical Societies.