Associate Professor, Department of Applied Chemistry, Faculty of Engineering, Kyushu University
DNA conjugate for single-molecular electronic, bioelectrochemical devices
From the viewpoint of molecular electronic devices, we have been engaging in the study of DNA nanomaterials that possess electronic conductivity. Our approach has taken advantage of DNA conjugate formation with redox-active, small molecules. The DNA-bound redox molecules function as an array of electron shuttles to ensure electronic conduction along the DNA double-helix axis (Fig. 1). Recently, we have focused on psoralen compounds that bind covalently to double-stranded DNA through photochemical reactions with DNA nucleotides, and we have synthesized new ferrocene- or Ru(bpy)32+-modified psoralen derivatives. The resulting DNA (5 mer)-ferrocene conjugate has been examined by atomic force microscopy in contact current measurement mode. We have demonstrated for the first time that the formation of a ferrocene-conjugate causes DNA to become conductive.
We now have plans to prepare DNA molecular devices using ‘dip-pen nanolithography’. In the course of our research, we have found that plasmid pBR322 DNA molecules aggregate divergently to form inter-molecularly-wound, well-developed network structures (Fig. 2). Thus, we have applied ‘dip-pen’ style operations to a 2D network of DNA with psoralen derivatives. In other words, single or network structured DNA has been partially converted to a ferrocene conjugate to give conductive and nonconductive areas within the structure. Results will be reported elsewhere.
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| Fig. 1 Large Image |
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| Schematic illustration of electronic conduction in DNA conjugate. The DNA-bound ferrocene moiety functions as an array of electron shuttles to ensure electronic conduction along the axis of the DNA double- helix. |
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| Fig. 2 |
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| Two-dimensional network formation of DNA. Plasmid pBR322 DNA molecules were first treated in aqueous solution and then were fixed onto mica disks for AFM experiments. The AFM image shows that the pBR322 DNA, which originally takes circular or supercoiled circular structures, aggregates divergently to form inter-molecularly-wound, well-developed network structures. |
Relevant papers
- Nakano, K., Shirakawa, S., Taguchi, S. & Maeda, M.
Redox-Labeling of DNA by Photoadduct Conjugate Formation with Ferrocene Derivatized Psoralen
Anal. Sci. 17 (Supplement), i291-i292 (2001). - Koji Nakano
Molecular Recognition of DNA and Biosensor Applications
“Liquid Interfaces in Chemical, Biological, and Pharmaceutical Applications”, A. G.
Volkov Ed., Marcel Dekker, New York, 2001, pp.515-532. - Nakayama, M., Ihara, T., Nakano, K. & Maeda, M.
DNA Sensors using a Ferrocene-Oligonucleotide Conjugate
Talanta 56 (5), 857-866 (2002).
