Helical cyclic pentapeptides constrain HIV-1 Rev peptide for enhanced RNA binding

HIV-1 Rev is a 116 residue transporter protein that enters the host cell nucleus and uses its 17 amino acid segment (Rev_34–50) to bind and capture a specific piece of RNA, the Rev Response Element (RRE), for transport to the cytoplasm. This is critical for HIV replication. In isolation, Rev_34–50 shows negligible structure in water, but is alpha helical in a mixture of water and 2,2,2-trifluoroethanol (TFE) or when bound to RRE. Here we report that helix-constrained cyclic pentapeptides, either appended to the N-terminus or incorporated within Rev_34–50, are efficient helix nucleators in water. They induce up to 90% alpha helicity for isolated Rev peptides in water and confer high RNA-binding affinity.     

Two variants of magnetic diffusivity stabilized finite element methods for the magnetic induction equation

We consider the time‐dependent magnetic induction model where the sought magnetic field interacts with a prescribed velocity field. This coupling results in an additional force term and time dependence in Maxwell's equation. We propose two different magnetic diffusivity stabilized continuous nodal‐based finite element methods for this problem. The first formulation simply adds artificial magnetic diffusivity to the partial differential equation, whereas the second one uses a local projected magnetic diffusivity as stabilization. We describe those methods and analyze them semi‐discretized in space to get bounds on stabilization parameters where we distinguish equal‐order elements and Taylor‐Hood elements. Different numerical experiments are performed to illustrate our theoretical findings.     

Bifurcation analysis and chaos control in a discrete‐time plant quality and larch budmoth interaction model with Ricker equation

We investigate the dynamics of two‐dimensional discrete‐time model of leaf quality and larch budmoth interaction with Ricker equation. More precisely, the qualitative behavior of larch budmoth model is discussed in which the effect of food source upon the moth population is through intrinsic growth rate. We find the parametric conditions for local asymptotic stability of the unique positive fixed point. It is also proved that under certain parametric conditions, the system undergoes period‐doubling bifurcation with the help of center manifold theory. The parametric conditions for existence and direction of Neimark‐Sacker bifurcation at positive fixed point is investigated with the help of standard mathematical techniques of bifurcation theory. The chaos control in the system is discussed through implementation of hybrid control methodology. Finally, numerical simulations are provided to illustrate theoretical results. These results of numerical simulations demonstrate chaotic long‐term behavior over a broad range of parameters. The computation of the maximum Lyapunov exponents confirms the presence of chaotic behavior in the system.     

Planar homogeneous systems of difference equations

This paper is concerned to additive and multiplicative systems of homogeneous difference equations of non‐negative degree. We apply a reduction in order for both additive and multiplicative systems. Then, we consider convergence and monotony of positive solutions. In fact, using convergence results on factor maps, we obtain convergence results on homogeneous systems. We will conclude that monotonic behaviour on the invariant ray (i.e. for multiplicative systems and for additive systems) may or may not be the representative of other solutions. To illustrate our results, some examples are presented by multiplicative and additive homogeneous systems of rational equations. Copyright © 2014 John Wiley & Sons, Ltd.     

复调制Zoom-FFT方法的LabVIEW实现与应用

为了对信号频谱中多个频率接近的分量进行检测,提出在LabVIEW平台上使用复调制Zoom-FFT方法,通过移频、滤波、重采样、FFT和频率调整几个步骤实现对频谱的细化。仿真表明,该方法能够灵活的选择细化频带,提高频带内的频域分辨率并有较小的计算量。将其应用到异步电机故障诊断中,实现了对转子断条故障分量的有效检测。     

各向异性介质多分量感应测井三维Born几何因子理论研究

几何因子理论被广泛运用于感应测井仪器设计、响应特征分析及高分辨率曲线处理, 现有的感应测井几何因子主要适用于二维各向同性介质, 难以满足各向异性介质多分量感应测井的研究需要. 本文基于Born近似方法将Born几何因子扩展至各向异性介质, 推导了各向异性介质多分量感应测井三维Born几何因子表达式, 随后进一步考察了多分量感应测井对地层各向异性的敏感性和探测能力. 数值模拟结果表明, 各向异性系数越大, 多分量感应测井几何因子空间分布越复杂, 其对各向异性的敏感性越高. 多分量感应测井仪器在不同倾斜角度对各向异性均具有较高的敏感性. 直井条件下, xx共面分量受各向异性影响严重, 井斜角在40°–60°时, xz/zx交叉分量对各向异性的敏感性高, 水平井中zz同轴分量则对各向异性的探测能力最强. 各向异性介质三维Born几何因子弥补了现有几何因子理论的不足, 可为国内新型多分量感应测井仪器研发及储层各向异性评价方法的发展提供有利条件.     

高效液相色谱-电感耦合等离子体质谱测定MT-like的研究

采用高压凝胶柱实现了类金属硫蛋白粗提液的分离纯化,且基于蛋白的紫外吸收及与其结合的金属元素的信号,建立了高效液相色谱-电感耦合等离子体质谱联用测定类金属硫蛋白的方法;流动相为20mmol/L Tris-醋酸缓冲溶液(pH 7.5),流速为0.5 mL/min。实验考察了牛血清蛋白、兔肝Zn-Metallothionein(Zn-MTs)组分的在线分离效果及Zn-MTs分离的重现性,研究了紫外及ICP-MS测定蛋白的线性、检出限及相关性;发现Zn-MTs组分分离重现性较好,RSD(n=6)小于5%,Zn-MTs中紫外吸收与Zn信号具有较好的量值关系,线性相关系数为0.999 5,且基于Zn的信号值测定蛋白的检出限较低。     

有机标准物质期间核查核磁共振定量分析仪器参数的研究

以磺胺对甲氧嘧啶为例,对有机标准物质期间核查核磁共振定量分析方法的仪器参数作了研究,主要包括脉冲宽度、弛豫延迟时间、扫描次数、谱宽、发射机频率偏移、时域数据长度。分别对磺胺、磺胺对甲氧嘧啶、磺胺间甲氧嘧啶、磺胺噻唑、磺胺嘧啶、磺胺吡啶、磺胺苯吡唑7种磺胺类标准物质进行期间核查含量测定,测定结果的相对误差为0.1%～0.3%,准确度与高压液相色谱方法相当。     

Chiral Induction and Amplification in Supramolecular Systems at the Liquid–Solid Interface

Chiral induction and amplification in surface‐confined supramolecular monolayers are investigated at the liquid–solid interface. Scanning tunneling microscopy (STM) proves that achiral molecules can self‐assemble into globally chiral patterns through a variety of approaches, including induction by chiral solvents or by a novel chiral amplification method. Our study demonstrates the aptness of both approaches, which have already been applied to (supramolecular) polymers in solution, to create chiral supramolecular monolayers at the liquid–solid interface.