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Nanoparticles synthesis using cage-shape protein as a restricted chemical chamber

Kenji Iwahori1, Keiko Yoshizawa1, and Ichiro Yamashita*, 2

1Japan Science and Technology Corporation
2Matsushita Electric Industrial Co., Ltd.

This is an abstract for a presentation given at the
11th Foresight Conference on Molecular Nanotechnology


We propose a new process using protein supramolecules to build nano-electronics devices [1]. This process employs protein supramolecules with inner cavities and one of them is a ferritin molecule. Ferritin, the major cellular iron-storage protein, is a spherical hollow shell composed of 24 polypeptide subunits and has the ability to sequester and store iron as hydrated iron oxide in the internal cavity. The inner and outer diameters of the protein shell are about 6 nm and 12 nm respectively. The molecular weight of one subunit is 18.5kDa and the whole molecule is about 450 kDa in case of horse spleen ferritin. We made use of the inner cavity of this apoferritin as a restricted chemical reaction chamber to synthesize inorganic nano-particles.

Proteins are made using genome information and have an identical structure. This gives ideal characteristics to be used as building blocks for making nano structures. However, the native apoferritin is composed of two slightly different subunits, L- and H- subunits, and their ratio varies one by one. Therefore, we have been using recombinant L-apoferritin, which is composed of only L-subunits. This recombinant L-apoferritin is stable and has atomically identical structure. Therefore, if the cavity is fully loaded, the nano-particles synthesized within the cavity would be same-size, To fulfill this purpose, buffer conditions such as pH, temperature and dissolved gas were surveyed. The wide range of survey results showed that the best buffer condition depends on the kinds of inorganic material. It is found that the pH is critical and that the temperature of the solution affects the quality of obtained nano particles. Some ion is indispensable for synthesis of some metal complex. Using the best buffer condition, the standard deviation of the nanoparticle size synthesized in the cavity is very small compared to the conventional synthesis methods. It is deemed that they are suitable for using as quantum dots of quantum-electronics devices. The application of obtained nanoparticles as electronics devices is in progress


[1] Ichiro Yamashita, "Fabrication of a Two dimensional Array of Nano-particles Using Ferritin" Thin Solid Films. Vol. 393 (2001) 12

Abstract in Microsoft Word® format 22,854 bytes

*Corresponding Address:
Ichiro Yamashita
Advanced Technology Research Laboratories,
Matsushita Electric Industrial Co., Ltd.
3-4 Hiakri-dai, Seika
Kyoto, 619-0237 Japan
Phone: +81-774-98-2513 Fax: +81-774-98-2575


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