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在DNA光损伤产物中,有一种特殊的UV诱导生成的嘧啶二聚体(SP).尽管胞嘧啶C和胸腺嘧啶T在分子结构上非常相似,在实验中还没有发现DNA相邻的C和T之间形成类似的SP产物.用密度泛函理论,以DNA中的片段CpT为模型分子,在B3LYP/6-311++G(d,p)//B3LYP/6-31G(d,p)计算水平上从理论的角度揭示 了阻碍CpT生成SP类似物的关键因素. 与生成类似SP产物相比较,CpT更倾向于通过光物理失活途径回到基态反应物  相似文献
2.
用时间分辨傅立叶变换红外发射光谱(TR-FTIR)和G3MP2//B3LYP/6-311G(d,p)水平的电子结构计算研究了环境化学中重要的二氯代乙烯自由基C2HCl2和O2分子的基元反应通道和机理. 通过0.5 cm-1高分辨的TR-FTIR发射光谱观察到三种振动激发态产物CO2、CO和HCl,由光谱拟合得到CO和HCl的振动态分布,结合电子结构计算的反应势能曲线,提出反应机理和能量上最可能的反  相似文献
3.
采用密度泛函方法在6-31G*水平上,对一系列不同链长的低聚呋喃分子在外电场作用下的性质进行了理论计算研究。结果表明电场的引入提高了呋喃分子共轭性,电场的诱导使偶极增加,SCF能量降低和HOMO-LUMO能隙变窄.进一步通过硫原子将呋喃分子与金电极相连接,利用非平衡格林函数方法对其在0.0~2.0V偏压下电子输运特征进行了研究.讨论链长效应对这些性质的影响.  相似文献
4.
Pb(Zr0.53,Ti0.47)O3 (PZT) films with thicknesses of 0.8μm, 2μm and 4μm are prepared by a sol-gel method and their longitudinal piezoelectric coefficients are analysed. The results show that the PZT thick films, whose density is closer to bulk PZT, has the better crystallization, with d33 and density much larger than those of PZT thin films. A piezoelectric microcantilever actuated by a 4-μm-thick PZT film is fabricated and its displacement is measured in different frequencies and voltages. The displacement increases linearly with the increasing bias, and the maximum displacement of 0.544μm is observed at 30kHz for 5V bias. The resonant frequency obtained in the experiment matches quite well with the theoretical result, and it is shown that the resonant frequency of PZT microcantilever could be controlled and predicated.  相似文献
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Among all the DNA components, extremely redox-active guanine (G) and adenine (A) bases are subject to facile loss of an electron and form cation radicals (G and A) when exposed to irradiation or radical oxidants. The subsequent deprotonation of G and A can invoke DNA damage or interrupt hole transfer in DNA. However, compared with intensive reports for G, studies on the deprotonation of A are still limited at present. Herein, we investigate the deprotonation behavior of A by time-resolved laser flash photolysis. The deprotonation product of A(N6-H)· is observed and the deprotonation rate constant, (2.0±0.1)×107 s-1, is obtained at room temperature. Further, the deprotonation rate constants of A are measured at temperatures varying from 280 K to 300 K, from which the activation energy for the N6-H deprotonation is determined to be (17.1±1.0) kJ/mol by Arrhenius equation. In addition, by incorporating the aqueous solvent effect, we perform density functional theory calculations for A deprotonation in free base and in duplex DNA. Together with experimental results, the deprotonation mechanisms of A in free base and in duplex DNA are revealed, which are of fundamental importance for understanding the oxidative DNA damage and designing DNA-based electrochemical devices.  相似文献
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