Height measurement of DNA molecules with lift mode AFM

摘要

The height of double-stranded DNA (dsDNA) is measured by lift mode AFM combined with conventional tapping mode AFM. While the tip scan height is raised step by step, the tip pressure on sample is decreased gradually. As a result, the deformation of the DNA strands decreases, and the height of double-stranded DNA (dsDNA) molecule can be deduced by the tip lift height. The measured height of dsDNA is 1.5 ± 0.2 nm in lift mode, but only 0.8 ± 0.2 nm in conventional tapping mode. This demonstrates thatthe tip pressure is a key factor in soft sample height measurement resulting in artificating lower values via conventional tapping mode.