title: Scanning tunneling microscopy and spectroscopy of plasmid DNA.
abstract: We present scanning tunneling microscope (STM) images of uncoated deoxyribonucleic acid (DNA) electrochemically mounted on highly-oriented pyrolytic graphite (HOPG) and imaged in air. Images of linear abnormalities inherent to HOPG surfaces that can be confused with DNA are also presented. Scanning tunneling spectroscopic (STS) images generated by superimposing a small, high frequency ac bias onto the dc tunnel bias and recording the ac current signal were taken simultaneously with the topographic images. These spectroscopic images reveal contrast due to local conductivity variations and can be used to differentiate DNA molecules from graphite artifacts.
authors.affiliation: Oak Ridge National Laboratory, TN 37831.
authors.forename: D P
authors.initials: DP
authors.lastname: Allison
authors.forename: J R
authors.initials: JR
authors.lastname: Thompson
authors.forename: K B
authors.initials: KB
authors.lastname: Jacobson
authors.forename: R J
authors.initials: RJ
authors.lastname: Warmack
authors.forename: T L
authors.initials: TL
authors.lastname: Ferrell
mesh_terms: D002244:Carbon; D004270:DNA, Circular / Q000235:genetics / Q000648:ultrastructure*; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D010957:Plasmids / Q000235:genetics*; D013057:Spectrum Analysis / Q000379:methods*
chemical_list: D004270:DNA, Circular; C009139:pyrolytic carbon; D002244:Carbon