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Probing electrical properties of oriented DNA by conducting atomic force microscopy

Lintao Cai1, Hitoshi Tabata and Tomoji Kawai

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Different methods have been applied for the stretching of DNA molecules on chemically functionalized surfaces by various modified reagents, i.e. 3-aminopropyltriethanoxysilane or polylysine on mica and 2-mercaptoethylamine on Au(111)/mica by a moving interface technique, magnesium cation (Mg2+) on mica by a spin-stretching method and DNA on an atomic-level flat mica by a free-flowing method. The long λ-DNA molecule is well elongated using the moving interface technique. The DNA molecule array density can be controlled by the change of surface charge density and the DNA concentration. On the other hand, the novel free-flowing method is very useful for the alignment of short polynucleotide molecules. Shadow-mask evaporation has been used to fabricate a gold electrode contacted electrically to the oriented DNA molecules. The intrinsic electrical properties of individual DNA molecules are directly measured using a conducting probe atomic force microscope equipped with a gold-coated conductive tip. The DNA molecule is considered as a promising molecular wire.


PACS

87.14.G- Nucleic acids

87.15.B- Structure of biomolecules

82.39.Jn Charge (electron, proton) transfer in biological systems

87.64.Dz Scanning tunneling and atomic force microscopy

Subjects

Medical physics

Biological physics

Chemical physics and physical chemistry

Dates

Issue 3 (September 2001)

Received 28 October 2000, in final form 18 June 2001

Published 14 August 2001



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