Electronic states and magnetism of doped DNA

近年来，关于DNA的物理性质的各种调查都有报道。也就是说，这些引人注目的争议聚集了人们对DNA内在本质的强烈科学兴趣。这个项目的目的是揭示DNA的内在物理性质，并研究DNA对纳米线的潜在应用，这可能会在不久的将来支持电子学的进一步工业发展。为了避免在DNA研究中提出的问题，我们计划利用ESR和SQUID磁强计等磁性手段。(1)天然DNA的内在物理性质我们已经开始研究从两种不同纯度的睾丸中提取的鲑鱼DNA：一种是粗鲑鱼DNA粉，另一种是鲑鱼DNA纤维。鲑鱼DNA粉的ESR谱具有相对较强的强度，约为每DNA碱基对(BP)0.2%。然而，我们从sa…获得了极弱的电子自旋共振信号。低于50ppm/BP的鲑鱼DNA纤维较多，这可归因于鲑鱼DNA纤维中杂质的影响。这一发现表明，应该重新考虑那些具有类似金属行为甚至令人兴奋的邻近效应的关于稀土电极超导电性的报道。因此，我们得出结论，天然鲑鱼DNA是一种具有较大带隙的半导体，正如最近报道的光学吸收数据一样，其带间吸收能超过4 eV。(2)二价金属离子掺杂的DNA的物理性质也引起了人们的极大兴趣，因为它作为纳米线潜在地应用于纳米电子学。DNA在设计碱基排列时表现出高度的灵活性和良好的自组织能力。到目前为止，八面体结构的纳米结构已有报道。然而，正如上面所揭示的那样，天然的DNA是半导体。然后，我们必须将载流子引入到天然DNA中。在这里，我们应用了二价金属离子在碱基对的碱基之间掺杂的方法。我们用多种金属离子，如M=Ca、Mg、Zn、Cu、Mn、Co、Ni等制备了M-DNA，并测定了它们的ESR和SQUID磁化率。由于计算结果表明，大部分金属离子都是以二价掺杂的，因此不能确定基带π中存在载流子掺杂。然而，3D金属离子为研究磁相互作用提供了有趣的模板。此外，我们还发现在Fe-DNA中发生了从Fe到碱基π-带的净电荷转移。另一方面，在Mn-DNA中，我们发现与天然DNA一样，也发生了从B型到A型的相变。在A型Mn-DNA中，我们证实了类AF磁性相变的存在。我们想进一步揭示潜在应用于纳米电子学的可能性。较少

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 DNAWe 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 … More 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 DNADNA 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