Molecular forces for the binding and condensation of DNA molecules.
Atomic force microscopy has been used to investigate the binding between a double-stranded DNA and bilayers of cationic lipids and zwitterionic lipids in low ionic-strength solutions. The binding of a DNA molecule to freshly cleaved mica surface in solution has also been measured. The binding of DNA molecules to cationic lipid bilayers has a minimal strength of approximately 45 pN. On zwitterionic lipid bilayers and mica surface, the minimal binding strength is approximately twice that value. The binding also has a dynamic nature, with only a certain percentage of recorded force curves containing the binding characteristics. Divalent Mg(2+) ions enhance the binding by increasing that percentage without any effect on the binding strength. We have also observed a long-range attraction between DNA molecules and cationic lipid bilayers with a strength much larger than the minimum force and a range well over 50 nm, possibly related to the driving force responsible for the two-dimensional condensation of DNA.
Cai
Xian-E
XE
Physics Department, University of Vermont, Cook Building, Burlington, Vermont 05405, USA.
Yang
Jie
J
D001665:Binding Sites; D004247:DNA / Q000737:chemistry*; D008051:Lipid Bilayers / Q000737:chemistry; D018625:Microscopy, Atomic Force; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry
D008051:Lipid Bilayers; D004247:DNA