Asymmetric Distyrylpyridinium Dyes as Red‐Emitting Fluorescent Probes for Quadruplex DNA

The interactions of three cationic distyryl dyes, namely 2,4‐bis(4‐dimethylaminostyryl)‐1‐methylpyridinium ( 1 a ), its derivative with a quaternary aminoalkyl chain ( 1 b ), and the symmetric 2,6‐bis(4‐dimethylaminostyryl)‐1‐methylpyridinium ( 2 a ), with several quadruplex and duplex nucleic acids were studied with the aim to establish the influence of the geometry of the dyes on their DNA‐binding and DNA‐probing properties. The results from spectrofluorimetric titrations and thermal denaturation experiments provide evidence that asymmetric (2,4‐disubstituted) dyes 1 a and 1 b bind to quadruplex DNA structures with a near‐micromolar affinity and a fair selectivity with respect to double‐stranded (ds) DNA [K_a(G4)/K_a(ds)=2.5–8.4]. At the same time, the fluorescence of both dyes is selectively increased in the presence of quadruplex DNAs (more than 80–100‐fold in the case of human telomeric quadruplex), even in the presence of an excess of competing double‐stranded DNA. This optical selectivity allows these dyes to be used as quadruplex‐DNA‐selective probes in solution and stains in polyacrylamide gels. In contrast, the symmetric analogue 2 a displays a strong binding preference for double‐stranded DNA [K_a(ds)/K_a(G4)=40–100), presumably due to binding in the minor groove. In addition, 2 a is not able to discriminate between quadruplex and duplex DNA, as its fluorescence is increased equally well (20–50‐fold) in the presence of both structures. This study emphasizes and rationalizes the strong impact of subtle structural variations on both DNA‐recognition properties and fluorimetric response of organic dyes.     

Mild and Efficient Solvent‐Free Friedel–Crafts Acylation of Reserpine

The first mild, efficient, solvent‐free Friedel–Crafts acylation of reserpine has been developed, which resulted in the synthesis of 10‐ and 12‐acylated homologues in high overall yields.     

雪卡毒素毒性机理的分子对接及分子动力学研究

采用分子对接和分子动力学方法,研究了雪卡毒素与其毒性作用靶点之一钠通道的结合模式,并与钠通道阻滞剂奎尼丁比较.研究结果表明,雪卡毒素、奎尼丁与钠通道作用方式有所不同.分子动力学模拟表明,对接受体-配体复合物体系在2.5 ns的模拟过程中稳定.奎尼丁在钠通道中央与GLU1784,THR1858各形成1个稳定氢键,吡啶环与...     

基于基本不变量神经网络势能面的H+C2D2反应漫游机理研究

基于最近发展的基本不变量神经网络方法构建的精确全维势能面,本文对H+C₂D₂→HD+C₂D/D₂+C₂H反应开展了广泛的准经典轨线计算. 发现了直接抽取反应途径对整体反应性的影响很小,与漫游路径相比可以忽略不计. 乙炔促进的漫游路径在总体反应性中占主导地位,而亚乙烯基促进的漫游路径贡献很小. 结果表明,虽然漫游路径可以通过短寿命或长寿命的复合物形成过程进行,但是产物HD与D₂的分支比与2：1很接近,这意味着漫游动力学主要是由长寿命的复合物形成过程促成的. 并且,这两个产物通道的角分布也完全不同. 这些计算结果为深入了解同位素效应在双分子反应漫游动力学中的重要性提供了有价值的见解.     

振动和转动激发对N2在Fe(111)表面解离吸附的影响

N₂的解离化学吸附是工业合成氨的速控步骤. 基于最近构建的六维势能面,本文研究了N₂的初始振动激发和转动激发在Fe(111)表面的反应性的作用. 由于该反应具有重要的量子效应,通过六维量子动力学计算研究了入射能量低于1.6 eV 时振动激发的效应. 并采用准经典轨线计算揭示了高入射能量下的振动和转动激发的影响. 通过这些研究发现增加平动能量在一定程度上能提高解离几率,振动激发或转动激发能更有效地促进解离. 这项研究为重原子分子-表面反应的模式特异性动力学提供了有价值的见解.     

Noncommutativity, Generalized Uncertainty Principle and FRW Cosmology

We consider the effects of noncommutativity and the generalized uncertainty principle on the FRW cosmology with a scalar field. We show that, the cosmological constant problem and removability of initial curvature singularity find natural solutions in this scenarios.     

液相色谱法分离制备环烯醚萜化合物

液相制备色谱;分离;液相色谱法分离制备环烯醚萜化合物     

芴-硫芴共聚物的电子结构和光谱性质的理论研究

用DFT-B3LYP方法对低聚物(PF30T)_n [n(芴)∶n(硫芴)＝2∶1, 物质的量之比, n＝1～4], (PF50T)_n [n(芴)∶n(硫芴)＝1∶1, 物质的量之比, n＝1～4]体系全优化, 得到两系列低聚物的电离能(IP_(a,v))、电子亲和势(EA_(a,v))、空穴抽取能(HEP)、电子抽取能(EEP). 在此基础上用ZINDO和TD-DFT方法计算吸收光谱, 分析了两个系列的HOMO-LUMO能隙随着n递增的变化趋势及硫芴含量对低聚物电子结构和光谱性质的影响, 推断了高聚物的电子和光谱性质. 用ab initio CIS方法优化了低聚物的S₁激发态结构并分析了其与发射光谱的关系. 研究显示: 2,8位引入的硫芴基团, 破坏了链的共轭, 而且随着硫芴含量的增加, HOMO-LUMO能隙变大, 光谱蓝移; 激发态结构趋于共面化.