Direct observation of B-form and Z-form DNA by scanning tunneling microscopy

Abstract
Using a scanning tunneling microscope (STM) of atomic resolution, we have directly observed variant conformations of DNA, including normal B-form and Z-form DNA, with a modified working condition. STM images of natural fish sperm and calf thymus B-form DNA and poly (dG-me5 dC) and bromized poly dCG Z-form DNA have been obtained at a subnatural environment. These results have provided some new evidence that images characteristic of DNA molecules can be obtained with STM.