High-resolution scanning tunneling microscopy imaging of DNA molecules on Cu(111) surfaces

Using the pulse injection method, single-stranded DNA and double-stranded plasmid DNA have been deposited on well-defined Cu(111) surfaces under ultrahigh vacuum (UHV ) conditions to obtain high-resolution scanning tunneling microscope (STM) images. These particular UHV-STM images have revealed that DNA molecules are adsorbed directly onto a clean Cu(111) surface and exhibited the detailed structures of DNA, which has not been resolved previously. The single-stranded DNA oligomers have exhibited the images of individual internal base molecules and the helix structures made of complementary base sequences. For the double-stranded plasmid DNA, the images have shown the Watson–Crick double-helix structure. © 1999 Elsevier Science B.V. All rights reserved.