DEOXYRIBONUCLEIC-ACID STRUCTURES VISUALIZED BY SCANNING TUNNELING MICROSCOPY

The capability of the scanning tunneling microscope (STM) to produce atomic-resolution images makes it a powerful tool in both basic and applied science. The main application of STM has been for the analysis of structural features and electronic properties of a wide spectrum of metals and semiconductors, while only a few biological items have been investigated. With a STM operating in air at ambient pressure, we present images showing the molecular structure of naked DNA. High-resolution topographic images of linear DNA fragments reveal structures with a periodicity of ~ 38 ± 6 A and a width of 28 + 4 A, consistent with the molecular dimensions of the helical repeat of double-stranded DNA. In addition, the supreme resolving power of the STM permits visualization of the major and minor grooves. © 1990, American Vacuum Society. All rights reserved.