Noncontact Atomic Force Microscopy - Yale School of Engineering ...

Fr-1140
Molecular-scale Investigations of Biomolecules in Liquids by FM-AFM
Shinichiro Ido 1 , Noriaki Oyabu 1,2 , Kei Kobayashi 2,3 , Yoshiki Hirata 4 , Masaru Tsukada 5 ,
Kazumi Matsushige 1 , and Hirofumi Yamada 1,2
1 Department of Electronic Science and Engineering, Kyoto University, Kyoto, Japan
2 Japan Science and Technology Agency /Adv. Meas. & Analysis, Japan
3 Innovative Collaboration Center, Kyoto University, Kyoto, Japan
4 National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan
5 Advanced Institute for Materials Research,Tohoku University ,Sendai, Japan
Recent, rapid progress in high-resolution frequency modulation atomic force
microscopy (FM-AFM) in liquid environments has opened a new way to directly
investigate "in vivo" biological processes with molecular resolution [1,2]. In this study,
submolecular-resolution imaging of DNA molecules and proteins has been conducted
toward the molecular scale analysis of DNA-protein interactions dominating site-specific
binding of proteins to DNA. In addition, three-dimensional (3D) hydration structures on
the biomolecules have been visualized for exploring the roles of water molecules in the
biological functions.
A low-thermal-drift FM-AFM developed based on a commercial AFM apparatus
with a home-built low-noise electronics system. Figure 1(a) shows an FM-AFM image of
a pUC18 plasmid DNA (2686 bp) adsorbed onto a mica surface in a buffer solution
containing 50 mM NiCl2. The major grooves (2.2 nm wide) indicated by the gray arrows
and the minor grooves (1.2 nm wide) indicated by the white arrows along the DNA
chains were clearly resolved. Figure 1(b) shows an FM-AFM image of bR trimers on the
cytoplasmic side of a purple membrane patch on a mica substrate in a phosphate buffer
solution. A two-dimensional (2D) frequency shift (Δf) mapping image (X-Z) on the
membrane was also shown.
a) b)
Figure 1: (a) FM-AFM image of pUC18 plasmid DNA on a mica substrate in 50mM NiCl2
solution. Image size: 48.4 nm × 20.0 nm. Inset: simulated structural model of DNA taking the tip
size effect into account. Image size: 10.0 nm × 5.5 nm. (b) FM-AFM image (image size: 29.1 nm
× 29.1 nm) and 2D frequency shift mapping image (image size: 29.1 nm × 2.5 nm) of a purple
membrane patch in buffer solution.
[1] T. Fukuma, K. Kobayashi, K. Matsushige, and H. Yamada. Appl. Phys Lett. 87, 034101 (2005).
[2] S. Rode, N. Oyabu, K. Kobayashi, H. Yamada, A. Kuhnle. Langmuir 25, 2850 (2009).
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