| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
In recent years, variety of investigations has been reported on the physical nature of DNA. That is, the striking controversies have gathered the strong scientific interest on the intrinsic nature of DNA. The aim of this project is to unveil the intrinsic physical properties of DNA and research the potential applicability of DNA to nanowires which might support further industrial developments of electronics in the near future. To avoid the suggested issues in the DNA investigations, we have planed to utilize the magnetic means such as ESR and SQUID magnetometer.
(1) Intrinsic physical properties of natural DNA
We have started our project to study the salmon DNA extracted from a testis with two different grades of purification: one is the crude salmon DNA powder and the other is the fine salmon DNA fiber. The ESR spectra in the salmon DNA powder have a relatively strong intensity, approximately 0.2 % per base pair (bp) of DNA. However, we obtained the extremely weak ESR signal from the sa
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lmon DNA fiber less than 50 ppm/bp, which could be ascribed to the effect of impurities in the salmon DNA fiber. This finding suggests that the reports with the metallic-like behavior or even exciting proximity effect of the superconductivity of the Re-metal electrodes should be reconsidered. Thus, we concluded that the natural salmon DNA is a semiconductor with a large band gap, as in the recently reported optical absorption data with more than 4 eV of the inter-band absorption energy.
(2) Physical properties of divalent metal ion doped DNA
DNA also attracts a lot of interest in these years because of the potential application to the nanoelectronics as nanowires. DNA shows high flexibility in design of base arrangements and excellent ability of self-organization. The nano architecture with octahedral structure has been reported so far. However, as revealed in the above, the natural DNA is a semiconductor. Then, we have to introduce the charge carriers into the natural DNA.
Here, we applied the doping method with the divalent metal ions in between the bases of a base pair. We prepared M-DNA with a variety of metal ions, such as M=Ca, Mg, Zn, Cu, Mn, Co, Ni, etc. and measured both of ESR and SQUID susceptibility. Since the result suggests that almost of the metal ions are doped keeping the valence two, we cannot establish the charge carrier doping into the base π-band. However, 3d metal ions provided the interesting templates for studying the magnetic interactions. Furthermore, we found that in Fe-DNA the net charge transfer from Fe to the base π-band has occurred. On the other hand, in Mn-DNA, we discovered that the phase transition from the B-form to the A-form takes place as in the natural DNA. In the A-form Mn-DNA, we confirmed the presence of AF-like magnetic phase transition. We would like to proceed further to unveil the possibility of potential application to nano-electronics. Less
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