Electrostatic force microscopy: imaging DNA and protein polarizations one by one.
We present electrostatic force microscopy images of double-stranded DNA and transcription complex on an insulating mica substrate obtained with molecular resolution using a frequency-mode noncontact atomic force microscope. The electrostatic potential images show that both DNA and transcription complexes are polarized with an upward dipole moment. Potential differences of these molecules from the mica substrate enabled us to estimate dipole moments of isolated DNA and transcription complex in zero external field to be 0.027 D/base and 0.16 D/molecule, respectively. Scanning capacitance microscopy demonstrates characteristic contrast inversion between DNA and transcription complex images, indicating the difference in electric polarizability of these molecules. These findings indicate that the electrostatic properties of individual biological molecules can be imaged on an insulator substrate while retaining complex formation.
Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan.
Eriko
E
Mikamo-Satoh
Fumihiko
F
Yamada
Akihiko
A
Takagi
Takuya
T
Matsumoto
Tomoji
T
Kawai
D004247:DNA / Q000737:chemistry*; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D018625:Microscopy, Atomic Force / Q000379:methods*; D011506:Proteins / Q000737:chemistry*; D055672:Static Electricity; D014481:United States
D011506:Proteins; D004247:DNA