含平面胺配体的反式二价钯配合物与DNA碱基的作用

含大的平面胺配体的二价钯金属配合物在当前的抗肿瘤药物设计中代表着一类具有重要发展前途的先导结构. 由于大的平面胺配体具有较大的空间位阻, 目前主要的问题是这类化合物能否和DNA碱基结合形成单功能和双功能加合物. 我们采用密度泛函理论和等电聚焦连续极化(IEF-PCM)溶剂化模型研究了trans-PdCl2L2(L:2-羟基吡啶)的钯配合物与DNA碱基的作用. 该化合物与DNA形成单功能和双功能加合物反应的活化自由能均低于铂类抗肿瘤药. 所有反应在水溶液中均为放热反应. 结果表明, 这一大的平面胺配体不会阻碍该化合物与DNA碱基形成双功能加合物, 而且该化合物与DNA的单功能和双功能结合的速率会大于铂类化合物.     

Increasing the Sensitivity and Single‐Base Mismatch Selectivity of the Molecular Beacon Using Graphene Oxide as the “Nanoquencher”

Here, we report a novel, highly sensitive, selective and economical molecular beacon using graphene oxide as the “nanoquencher”. This novel molecular beacon system contains a hairpin‐structured fluorophore‐labeled oligonucleotide and a graphene oxide sheet. The strong interaction between hairpin‐structured oligonucleotide and graphene oxide keep them in close proximity, facilitating the fluorescence quenching of the fluorophore by graphene oxide. In the presence of a complementary target DNA, the binding between hairpin‐structured oligonucleotide and target DNA will disturb the interaction between hairpin‐structured oligonucleotide and graphene oxide, and release the oligonucleotide from graphene oxide, resulting in restoration of fluorophore fluorescence. In the present study, we show that this novel graphene oxide quenched molecular beacon can be used to detect target DNA with higher sensitivity and single‐base mismatch selectivity compared to the conventional molecular beacon.     

Solid-Phase Molecular Recognition of Cytosine Based on Proton-Transfer Reaction

Abstract  The proton-transfer molecular adducts cytosine/isoorotic acid (1:1) dihydrate (CytIsor) and cytosine/maleic hydrazide (2:2) dihydrate (CytMal) have been studied by X-ray diffraction methods. CytIsor crystallizes in the orthorhombic system, space group Pbnb, a = 7.4859 (4), b = 12.7977 (9), c = 26.4573 (16) ?, V = 2534.7 (3) ?³. CytMal crystallizes in the triclinic system, space group P − 1, a = 6.7767 (9), b = 12.063 (2), c = 12.937 (3) ?, α = 78.58 (2), β = 75.87 (2), γ = 75.63 (1)°, V = 982.8 (3) ?³. In both compounds protonation occurs at the N3 atom of the cytosine aminooxo tautomer as a result of the proton-transfer process from the acidic hydroxy groups of the counterions. In the crystal structure, both cocrystals are stabilized by a plethora of N–H···O, N–H···N and O–H···O hydrogen bonds. It is shown the ability of cytosine to form large organic assemblies, with the appropriate guest, due to solid-state recognition involving synthons based on hydrogen bonding between functional groups as sites of proton-transfer reactions. Index Abstract  The proton-transfer molecular adducts of cytosine with isoorotic acid and with maleic hydrazide have been synthesized in the solid state and their hydrogen-bonding patterns have been studied by X-ray diffraction methods.      

熊猫型保偏光纤中应力区失配对光纤性能影响的研究

采用弹性力学理论和复变函数法导出了熊猫型保偏光纤应力双折射的近似解析表达式.利用有限元法数值分析了熊猫型保偏光纤的双折射特性,结果表明,与采用纤芯中心应力相比,采用芯区平均应力表示光纤的双折射较为精确,且结果与解析法导出的芯区中心应力双折射计算结果相比误差小于0.18%.在此基础上进一步分析了应力区失配对熊猫型保偏光纤的双折射所产生的影响,并通过实验测试证明了分析结果的正确性. 关键词： 偏振保持光纤 应力区失配 双折射 拍长     

（La0．6Nd0．4）0．7Sr0．3MnO3薄膜的厚度依赖的结构与输运性

厚度为6～100 nm的(La0.6Nd0.4)0.7,Sr0.3MnO3(LNSMO)薄膜是由脉冲激光沉积生长在SrTiO3[STO(001)]衬底上.X-射线衍射(XRD)线扫描、ω-摇摆曲线和倒空间衍射显示,随着膜厚(t)的变化,薄膜的结构经历了由完全应变到部分弛豫的变化.电阻测量显示存在两个不同的厚度依赖的金属-绝缘体转变温度(Tp),对于应变的薄膜(t≤17 nm),Tp敏感地依赖于双轴应变和膜厚;而对较厚的薄膜(t≥35nm),Tp对于膜厚是较小敏感的.这个厚度依 赖的输运性的变化可被解释为菱形LNSMO的角度畸变诱导的应变和弛豫.我们的结果表明金属-绝缘体转变温度和相分离都受薄膜的应变态控制.     

The effect of phase mismatch on two-pump fiber optical parametrical amplifier

In the paper, the effect of phase mismatch on two-pump fiber optical parametric amplifier is investigate based on analytic solutions of parametric gain. The phase mismatch is mainly induced by the fiber losses, the fourth-order dispersion and zero-dispersion wavelength fluctuations. The fiber losses reduce the pump powers resulting in a fall of the parametric gain, and make the phase mismatch vary with propagation distance leading to an obvious gain ripple. When the fiber losses are taken into account, the fourth-order dispersion produces a deeper ripple on the parametric gain and deteriorates the gain flatness. Zero-dispersion wavelength fluctuations result in variations of gain spectrum, and the long-scale fluctuations are more devastating than the short-scale ones.     

The molecular orientation of DNA bases on H-passivated Si(1 1 1) surfaces investigated by means of near edge X-ray absorption fine structure spectroscopy

Layers of the DNA bases adenine, cytosine, and guanine were deposited onto hydrogen passivated Si(1 1 1) surfaces. The average tilt angles of these molecules with respect to the substrate surface were determined by the angular dependence of the Near Edge X-ray Absorption Fine Structure (NEXAFS) of the carbon K-edge. The interpretation of the NEXAFS spectra was assisted by a semi-empirical approach to the calculation of the π^∗-transition region which employs density functional theory calculations and core level photoemission data.     

Mismatch Negativity and Stimulus-Preceding Negativity in Paradigms of Increasing Auditory Complexity: A Possible Role in Predictive Coding

The auditory mismatch negativity (MMN) has been considered a preattentive index of auditory processing and/or a signature of prediction error computation. This study tries to demonstrate the presence of an MMN to deviant trials included in complex auditory stimuli sequences, and its possible relationship to predictive coding. Additionally, the transfer of information between trials is expected to be represented by stimulus-preceding negativity (SPN), which would possibly fit the predictive coding framework. To accomplish these objectives, the EEG of 31 subjects was recorded during an auditory paradigm in which trials composed of stimulus sequences with increasing or decreasing frequencies were intermingled with deviant trials presenting an unexpected ending. Our results showed the presence of an MMN in response to deviant trials. An SPN appeared during the intertrial interval and its amplitude was reduced in response to deviant trials. The presence of an MMN in complex sequences of sounds and the generation of an SPN component, with different amplitudes in deviant and standard trials, would support the predictive coding framework.     

高通量条件下KDP晶体三倍频参数的优化

 采用四阶龙格-库塔（R-K）数值计算方法,以Ⅰ／Ⅱ角度失谐和Ⅱ／Ⅱ偏振失配两种三倍频方案为例,给出了入射基频光为平面方波,功率密度5GW/cm²的情况下 ,KDP晶体三倍频参数的优化结果。