PICKING A SINGLE MOLECULE AND APPLICATION FOR MAGNETIC FORCE MICROSCOPY, TIP-ENHANCED SPECTROSCOPY, AND SINGLE MOLECULE WRITING

Woong Kim1, Eung-Sam Kim2, and Joon Won Park1

1Department of Chemistry, Pohang University of Science and Technology, San 31 Hyoja-dong, Pohang, 790-784, Korea2Department of Life Sciences, Pohang University of Science and Technology, San 31 Hyoja-dong, Pohang, 790-784, KoreaPresenting author: Joon Won Park; jwpark@postech.ac.kr

A proper surface treatment of the substrate and the AFM tip enabled us to pick a single DNA molecule with reasonable yield (75%). The transfer of a single DNA at the apex was confirmed by recording the force-distance curve and imaging a gold nanoparticle tag with TEM. The approach was extended to pick a single-molecule ferritin. The picking placed a single ferritin protein molecule at the very end of an AFM tip. When used for magnetic force microscopy (MFM) imaging, the tips were able to detect magnetic interactions of approximately10-nm sized magnetic nanoparticles. Because the protein engineering of ferritin and the supporting coordination and conjugation chemistry are well established, we envisage that it would be straightforward to extend this approach to the development of various single magnetic particle MFM probes of different compositions and sizes.

After the picking process, a silver enhancing solution was employed to prepare an Au@Ag particle of various sizes (30 nm – 70 nm). By carrying out the tip-enhanced spectroscopic measurement, it was confirmed that such tip indeed showed plasmonic activity.

Scheme for the ferritin picking

► TEM image of AFM probes after the picking

The 3rd generation dendron(27-acid)

Single Ferritin Picking Process

References

1) Yu Jin Jung, Bong Jin Hong, Wenke Zhang, Saul J. B. Tendler, Philip M. Williams, Stephanie Allen, Joon Won Park, “Dendron Arrays for the Force-Based Detection of DNA Hybridization Events”, J. Am. Chem. Soc., 129 (2007) 9349.2) Duk Hoe Kim, Nak-Kwan Chung, Joon Won Park, “Immobilizing a Single DNA Molecule at the Apex of AFM Tips through Picking and Ligation”, Soft Matters, 6 (2010) 3979.3) Duckhoe Kim, Nak-Kwan Chung, Stephanie Allen, Saul Tendler, and Joon Won Park, “Ferritin-Based New Magnetic Force Microscopic Probe Detecting 10-nm Sized Magnetic Nanoparticles”, ACS Nano, (2012) 241.4) Eung-Sam Kim, Jung Sook Kim, Yoonhee Lee, Kwan Yong Choi, and Joon Won Park, “Following the DNA Ligation of a Single Duplex Using Atomic Force Microscopy”, ACS Nano, (2012) 6108.