DNA电子结构和磁性研究

【作者】 王永娟；

【导师】 李华；

【作者基本信息】 山东大学 ， 凝聚态物理， 2006， 硕士

【摘要】 1953年Watson和Crick提出了DNA的双螺旋结构模型：DNA分子由两条多核苷酸链组成，这两条核苷酸链通过碱基的互补配对相互缠绕形成一种双螺旋结构；组成双螺旋结构的每条链中都含有嘌呤和嘧啶，一条链上的嘌呤总是通过氢键与另一条链上的嘧啶相结合，而且嘌呤和嘧啶的配对方式是固定的，腺嘌呤（A）与胸腺嘧啶（T）配对，鸟嘌呤（G）和胞嘧啶（C）配对。分子遗传学上认为DNA分子是生物体遗传信息的载体，它通过编码功能蛋白质来实现遗传信息的表达。物理学上认为DNA分子的遗传信息可能是电子的某种分布形式、运动形态，或者是与自旋取向有关的某种形式。DNA分子的遗传信息的传递及信息表达过程可以看作是发生在原子、分子之间的电荷传递和迁移等微观过程。实验上还发现，DNA分子中的电子传输对于它的某些生物功能像是辐照损伤和生物合成的修复机制也是至关重要的。因此，研究DNA分子的电子结构对于生命活动的理解具有重要的意义。此外，DNA分子的直径只有2纳米，但长度可达上百微米，是典型的一维纳米材料。如果DNA分子可以导电，则可以用做纳米导线。由于DNA分子具有自组装和分子识别等特性，可以用作纳米尺度的电子器件的有源元件。可见，DNA对于纳米技术上的电路设计是非常有用的，有助于克服经典的硅基电子学在未来年代里所面临的极限。因此，研究DNA分子的电子结构在纳米科技领域也具有重要价值。 DNA序列由四种核苷酸排列组成，遗传信息就存在于其中。组成DNA的核苷酸含有四种碱基：鸟嘌呤（G）、腺嘌呤（A）、胞嘧啶（C）和胸腺嘧啶（T）。分析这四种碱基的结构，不难看出，由N、C原子构成的六环N₂C₄原子簇是这四种碱基共同的基本结构单元。我们研究这一基本结构单元的电子结构，无疑能够反映DNA分子的某些重要基本物理性质，这些物理性质很有可能与其遗传信息的基本组成以及传递过程的微观机制密切相关。本文用自旋极化的MS-Xα方法研究了折叠构型和平面构型的六环N₂C₄原子簇，并取得以下主要结果： （1） 折叠型结构的六环原子簇在其基态附近至少存在四个亚稳态。这些状态的基本物理性质是，（Ⅰ）基态：系统内能=-7.01635×10³eV，呈现弱反铁磁性(μ+更多还原

【Abstract】 Watson and Crick advanced the double helix structure model of the DNA in 1953. The DNA is made up of two pieces of nucleotide chains, which is double helix structure with complementary pairing of the bases and winding each other. Every chain is made up of two kinds of purines and pyridines. The purine in one chain is always paired with the pyridine in the other chain by the hydrogen bonds. The partnership is fixed that Adenine(A) must be paired with Thymine(T) and Guanine(G) must be paired with Cytosine(C). Based on Molecular Genetics, DNA is considered to be the carrier of the genetic information and to code for functional proteins of expression of the genetic information. In Physics, the genetic information of DNA may be-considered to be the certain forms of distribution and movement of electrons, or some other forms that may be associated with the spin-tropism etc. While the transmission and expression of the genetic information of DNA may be considered to be the transmission and transfer of the charge proceeding between the atoms or molecules. Experimentally, it was found that the electronic transport through DNA is crucial for its biological functions such as the repair mechanism after radiation damage and biosynthesis. Therefore, study on the electronic structures of DNA is of consequence to understand the life movements. Furthermore, DNA molecule is a kind of typical 1-D nanomaterials whose diameter is only two nanometers but length can ? be hundreds of micrometers. If the DNA molecule is a conductor, it can be used as the nanowire. By virtu: of the molecular recognition and self-assembling properties, DNA molecules can be used as the active components for nano-scale electronic devices. Obviously, DNA is useful in nanotechnology for the design of the electric circuits, which can help to overcome the limitations that the classical silicon-based electronics face in the coming years. Therefore, studying the electronic structures of the DNA is quite worthful in the nanotechnology field.DNA sequences are made up of four kinds of nucleotides that carry about the genetic information. These nucleotides consist of four kinds of bases: guanine (G),更多还原