Imaging of single extended DNA molecules on flat (aminopropyl)triethoxysilane-mica by atomic force microscopy

Long strands of DNA have been deposited, extended, and immobilized on chemically modified mica for study with an atomic force microscope (AFM). By employing a modified ''molecular combing'' technique and carefully silanized mica, we show that DNA molecules may be distributed uniformly, adsorbed in extended conformations, and bound with great tenacity. When maintained in a buffer solution, these strands remained stable for > 5 h. Scanning the surface with high loads applied to an AFM tip induced fragmentation in the strands, but remaining pieces never relinquished their original positions. Further imaging applications, such as after treatment of the DNA by molecular hybridization or DNA synthesis and labeling in situ, are discussed.