一种新型的光驱动变构荧光分子探针

变构效应是生命体实现复杂生理效应的精妙调控和准确表达的重要途径.本研究利用双硫键的光致翻转特性,以双硫键为变构"枢纽"单元,设计、合成了一种具有非线性响应的光驱动变构荧光分子探针.合成的分子探针DSSB经过光照后,因双硫键翻转而形成刚性的分子内氢键网络,探针溶液的荧光显著增强;同时,由于阴离子的氢键活性,F-、AcO-和H2PO4-等阴离子的存在将促使氢键网络重组而呈现出不同的荧光响应.因此,该探针可实现对3种阴离子的分辨性荧光传感,并具有非线性响应的特性.     

Aβ_(37-42)形成二聚体的分子模拟研究

阿尔茨海默症是一种神经退行性疾病,多发病于老年人群.该疾病不但严重影响患者的健康及正常生活,还给患者家属带来极大痛苦.因此治疗该疾病成为科学界急欲攻克的难关.而治疗的基础是解析病理,大量研究表明该病患者脑内有大量纤维状Aβ蛋白质聚集物.因此研究Aβ蛋白质如何聚集是解析病理的关键.同时预防和阻止Aβ蛋白质聚集也成为治疗阿尔茨海默症的一种可选方案.本文即选取Aβ蛋白质片段,以分子动力学模拟方法,详细分析其形成稳定二聚体的完整过程.研究发现该蛋白质片段上残基侧链之间的疏水作用促使两个Aβ37-42单体相互靠近,其间会形成多种非稳态中间体,其结构经过不断调整最终才形成稳定的二聚体结构.该结构调整过程对形成稳定的二聚体结构非常重要.在此过程中两条肽链主链形成氢键的个数逐渐增加,同时伴随形成了新的残基侧链之间的相互作用.研究发现在二聚体形成的全过程中Ile41和Ala42均起到不可忽视的作用.Ile41由于其侧链具有疏水性且体积相对较大,可通过其疏水作用力促使两个单体相互靠近.而Ala42在后期结构调整中发挥了一定作用,稳定了二聚体的结构.该研究有助于更好地理解Aβ蛋白质聚集特别是其形成二聚体的过程,同时也为防治Aβ蛋白质聚集提供了一些理论依据.     

Experimental and molecular dynamics study of gas flow characteristics in nanopores

Gas flow characteristics in nanopores were investigated experimentally and numerically using molecular dynamics (MD) simulations with an emphasis on the friction factor and gas viscosity. The results show that the viscosity and the friction factor in nanopores are much lower than those in macroscale channels. The actual viscosities obtained from the MD studies showed that the gas viscosity in nanopores is less than the macroscale viscosity because collisions between gas molecules are less frequent in high Knudsen number flows and there are more collisions with the wall. The MD simulations show that the velocity profile is composed of two parts, with a much steeper velocity gradient near the wall.     

高温超导薄膜的原子尺度制备和表征

高温超导体因其丰富的物理性质和潜在的应用价值已成为30余年来凝聚态物理学备受关注的前沿方向之一.探索和发现新型高温超导体并以此建立非常规高温超导电性的物理机制是超导物理学家们长期追求的目标.本文从高温超导体的研究现状和瓶颈出发,介绍基于异质外延薄膜高温超导电性的原子尺度研究,阐述近年来分子束外延技术在高温超导薄膜制备和量子调控方面取得的研究进展.在外延薄膜超导特性表征方面,着重介绍基于原位扫描隧道显微镜对超导层的原子尺度研究.在新型高温超导体探索方面,主要介绍基于异质外延薄膜界面超导体系的构筑.本文侧重于展示实验设计思路、研究方法以及对高温超导电性微观机制的理解,力图以此启发相关领域的研究人员.     

多胺修饰?-环糊精:钕配合物对萘二胺的分子识别研究

将?-环糊精的6-OH用二乙烯三胺基取代，得到了6-脱氧-二乙烯三胺基?-环糊精(DTCD),在镧系金属NdCl3的存在下，分别与1,5-萘二胺和1,8-萘二胺反应，得到了2种三元超分子配合物，并用核磁共振氢谱对配合物进行了表征。其中主客体分子的化学计量比为2:1，客体分子等价氢原子的信号简并现象在包合前后没有发生变化，表明客体分子在主体空腔保持着对称的构象。2种三元超分子配合物均呈“三明治”式夹心结构。     

Bio-sketches and partitioning of sympatric reed frogs,genus Hyperolius (Amphibia; Hyperoliidae), in two humid tropical African forest regions

Sympatric reed frog species were studied in Gabon (Monts Cristal: Hyperolius mosaicus, H. pardalis, H. tuberculatus) and Kenya (Kakamega Forest: Hyperolius acuticeps, H. cf. cinnamomeoventris, H. kivuensis, H. lateralis, H. viridiflavus). For each taxon, a standardized diagnosis covering 11 aspects of adult and in part tadpole morphology as well as the sequence of a 560 bp fragment of mitochondrial DNA of the 16S ribosomal gene are provided. In addition, behavioural data are given for each species including measurable parameters of advertisement calls. The Monts Cristal Hyperolius species clearly differ in their spatial arrangement through the choice of breeding site. Hyperolius species at the Kakamega Forest share the same breeding sites but in part differ in their activity pattern throughout the year. Advertisement calls of sympatric species in both regions mainly differ in temporal parameters.     

First observations on the phylogeny of the families Gammaridae,Crangonyctidae, Melitidae,Niphargidae, Megaluropidae and Oedicerotidae (Amphipoda,Crustacea), using small subunit rDNA gene sequences

This study examines amphipod phylogeny based on small subunit (18S) rDNA sequence data. Complete sequences of 25 species representing six families were used to test the phylogenetic information content of this gene for reconstruction of amphipod phylogeny. The alignment proved to be informative for most of the studied taxa. The monophyly of the families Gammaridae, Crangonyctidae, Niphargidae and Oedicerotidae is supported. The Melitidae are not monophyletic in the reconstructed topologies, but weak molecular evidence for the monophyly of this group could be observed in spectra of supporting positions. A close relationship of Gammaridae + Melitidae or Gammaridae + Crangonyctidae is not supported, rather there are supporting positions for the incompatible sister-group relationship (Gammaridae + Niphargidae) and (Crangonyctidae + Niphargidae). The molecular evidence is in favour of the latter relationship. The evolution of cephalothoracic apodemes is discussed in the light of other phylogenetic hypotheses resulting from molecular data.     

Champsodontidae (Pisces: Trachinoidei) in the Eastern Mediterranean: how many species are there?

ABSTRACT

Three marine fish species of the Indo-Pacific genus Champsodon were reported as invasive species in the Eastern Mediterranean between 2009 and 2012; Champsodon nudivittis, C. vorax, and C. capensis. These are presumed to invade through the Suez Canal, but only C. nudivittis is known from the Red Sea, so the presence of C. vorax and C. capensis is surprising. To test the validity of the taxonomic identification of these two species, this study combined traditional morphology, genetic barcoding, and photography investigation. Our results demonstrate that only one species, C. nudivittis, has migrated into the Eastern Mediterranean.     

基于ITS2条形码对铁皮石斛及其混伪品分子鉴定的初步研究

通过分析铁皮石斛及其常见混伪品的ITS2序列差异，建立铁皮石斛药材真伪的快速鉴别方法．运用CodonCode Aligner V3．0软件对测序峰图进行校对拼接，基于隐马尔可夫模型的注释方法获得ITS2序列，采用MEGA5．0软件进行序列比对，种内种间距离计算及UPGMA聚类树构建，应用Koetschan等建立的ITS2数据库及网站预测ITS2二级结构．结果表明，铁皮石斛及其混淆品ITS2之间存在明显差异，所有铁皮石斛样品在UPGMA树上单独聚为一类．ITS2序列可以作为DNA条形码用于铁皮石斛与其混伪品的快速分子鉴别．     

分子动力学模拟乙醇／水二元混合物的扩散性质

采用分子动力学方法模拟乙醇／水混合物的扩散性质．模拟中乙醇分子采用点点刚性模型,水分子采用TIP4P模型,在全浓度范围内计算乙醇和水的自扩散系数,分别与实验值和文献的MD模拟值比较．水溶液中,水的自扩散系数描述为结合水分子和自由水分子的综合贡献．计算结果表明,我们采用的乙醇和水的模型对正确描述乙醇／水混合物扩散性质是可行的．