Impact of N-Terminal Tags on De Novo Vimentin Intermediate Filament Assembly

Vimentin, a type III intermediate filament protein, is found in most cells along with microfilaments and microtubules. It has been shown that the head domain folds back to associate with the rod domain and this association is essential for filament assembly. The N-terminally tagged vimentin has been widely used to label the cytoskeleton in live cell imaging. Although there is previous evidence that EGFP tagged vimentin fails to form filaments but is able to integrate into a pre-existing network, no study has systematically investigated or established a molecular basis for this observation. To determine whether a tag would affect de novo filament assembly, we used vimentin fused at the N-terminus with two different sized tags, AcGFP (239 residues, 27 kDa) and 3 × FLAG (22 residues; 2.4 kDa) to assemble into filaments in two vimentin-deficient epithelial cells, MCF-7 and A431. We showed that regardless of tag size, N-terminally tagged vimentin aggregated into globules with a significant proportion co-aligning with β-catenin at cell–cell junctions. However, the tagged vimentin aggregates could form filaments upon adding untagged vimentin at a ratio of 1:1 or when introduced into cells containing pre-existing filaments. The resultant filament network containing a mixture of tagged and untagged vimentin was less stable compared to that formed by only untagged vimentin. The data suggest that placing a tag at the N-terminus may create steric hinderance in case of a large tag (AcGFP) or electrostatic repulsion in case of highly charged tag (3 × FLAG) perhaps inducing a conformational change, which deleteriously affects the association between head and rod domains. Taken together our results shows that a free N-terminus is essential for filament assembly as N-terminally tagged vimentin is not only incapable of forming filaments, but it also destabilises when integrated into a pre-existing network.     

基于免疫否定选择算法的机场航班延误状态检测与实现

把免疫算法中的否定选择算法运用到航班延误状态的诊断检测与预测中,将生物免疫系统机制与机场航班运行机制联系起来,建立了相应的自体集合、检测细胞、抗原信息及它们之间的匹配模型,给出了检测方法。首先根据机场航班运行数据生成航班检测的成熟检测器和记忆检测器,然后用否定选择算法和航班数据对检测器进行训练和改进,最后利用检测器中的信息对机场航班状态分段进行预测,获得每个时段的航班延误状况,为机场有关部门对航班延误应急处理提供决策支持。仿真实验表明,该方法能较准确地预测航班的延误状态,且实时性好。     

多孔材料润湿性设计与油水分离应用研究进展

清洁的水资源对人类社会生产发展至关重要,溢油事故和工业含油废水的排放等对水资源造成严重威胁,因此油水分离技术备受关注。传统的油水分离方法如生物处理、吸附、离心、气体浮选和原位燃烧等,存在程序复杂、能耗高、分离效率低等缺点,亟需开发更加环保高效的新方法。仿生材料的设计与制备是多功能材料的重要研究方向。受荷叶结构与功能启发,基于润湿性能调控的先进多孔材料的设计与开发已成为当前研究的热点之一,并在油水分离领域中展现出巨大的应用潜力。通过调控多孔材料的表面结构和化学状态,可实现对水相和油相的不同分离特性,进而选择性去除或者吸附水相或油相,甚至包括极其稳定的油包水或水包油乳液的分离。全面综述了多孔材料的制备方法,以及其在油水分离领域的最新研究与应用。重点介绍了疏水或超疏水/超亲油的多孔海绵、多孔棉织物、多孔木材、多孔泡沫、多孔气凝胶和多孔陶瓷等先进油水分离材料的制备方法和研究进展,旨在对功能性多孔材料的发展进行回顾和深入探讨,为多孔材料在油水分离方面的研究提供指导。总结了目前多孔材料研究存在的一些问题,探讨了该领域面临的挑战,并对其应用发展趋势进行了展望。     

列车控制系统的抗拒绝服务攻击弹性控制策略

当遭受拒绝服务(DoS)攻击时,分布式列车控制系统的弹性控制问题受到广泛关注.本文提出了一种基于分布式领导车状态观测器和障碍李雅普诺夫函数的弹性控制策略,不仅可以避免列车碰撞,同时实现了编队控制的目标.首先,给出了一种分布式的领导车状态观测器设计方法,用于实时估计领导车的状态.理论分析表明,在DoS攻击满足一定约束的条件下,该状态观测器的估计误差具有指数稳定特性.在此基础上,通过将列车碰撞避免问题转化为状态受限问题,提出一种基于障碍李雅普诺夫函数的状态受限控制律,解决了DoS攻击下确保碰撞避免的车队控制问题.最后,数值仿真证实了本文方法的有效性.     

BDN染料的锁模特性和基态恢复时间

本文报道了国产BDN染料的碘乙烷溶液、吡啶溶液和二甲亚砜溶液的锁模特性和基态恢复时间。     

NMR Characterization of Long-Chain Fatty Acylcarnitine Binding to the Mitochondrial Carnitine/Acylcarnitine Carrier

The mitochondrial carnitine/acylcarnitine carrier (CAC) transports short-, medium- and long-carbon chain acylcarnitines across the mitochondrial inner membrane in exchange for carnitine. How CAC recognizes the substrates with various fatty acyl groups, especially long-chain fatty acyl groups, remains unclear. Here, using nuclear magnetic resonance (NMR) technology, we have shown that the CAC protein reconstituted into a micelle system exhibits a typical six transmembrane structure of the mitochondrial carrier family. The chemical shift perturbation patterns of different fatty acylcarnitines suggested that the segment A76–G81 in CAC specifically responds to the long-chain fatty acylcarnitine. Molecular dynamics (MD) simulations of palmitoyl-L-carnitine inside the CAC channel showed the respective interaction and motion of the long-chain acylcarnitine in CAC at the cytosol-open state and matrix-open state. Our data provided a molecular-based understanding of CAC structure and transport mechanism.     

大型移动复杂装备状态监测系统研究

实现对大型移动复杂装备的完整实时在线状态监测是一个非常有意义的研究课题。对用于大型装备局部状态监测的系统特点进行了描述，指出了其局限性；将传统的完整状态监测系统归纳为集中式完整状态监测系统，并依据装备端检测装置功能结构的不同，将集中式完整状态监测系统分为三类，指出了灰匣子系统的优势，以及在现有大型移动复杂装备上应用的难点。在对各类系统进行分析比较的基础上，提出了适用于现有复杂装备的分散式完整状态监测系统，对系统的基本思想进行了阐述。实例说明，该系统适于对现有复杂装备的完整状态监测。     

基于VMD和卷积神经网络的变工况轴承故障诊断方法

针对变工况条件下轴承故障数据无法大量获取以及诊断困难的问题,提出了基于变分模态分解和卷积神经网络的轴承故障诊断方法,使用稳态工况获取的数据训练,能对变工况下的数据实现有效诊断.首先对轴承振动信号进行变分模态分解,以获得有限带宽的固有模态函数;然后构建卷积神经网络模型,采用优化技术提高模型适应性,实现对固有模态函数的自适...     

砂土强度和剪胀性的颗粒力学分析

基于广义塑性理论与临界状态概念,研究提出了一个统一三维砂土本构模型,通过一组参数实现了砂土由压缩至剪切过程中状态参量的统一表述。基于ABAQUS提供的用户自定义材料子程序UMAT接口,利用Fortran语言编程实现了该三维弹塑性本构关系模型在软件中的二次开发。分别利用Toyoura砂、Fuji River砂以及Tokachi砂的剪切试验数据与数值模拟结果进行对比,结果表明：提出的有限元计算模型可以有效反映加载过程中不同围压和砂土初始密度对应力-应变曲线的影响,能够准确描述密砂的剪胀特性与应变软化特性以及松砂的剪缩特性与应变硬化特性,从而更加真实地反映三维应力状态下土的变形和强度特性。研究成果进一步扩展了ABAQUS在岩土工程中的应用范围,能够为岩土工程领域的数值分析计算提供更加快捷的解决方案。     

中热固相法制备掺杂钛的钒酸锂正极材料

以Li2CO3和V2O5为原料,用中热固相法制备了掺杂Ti4+的锂离子电池正极材料Li1.1V3―yTiyO8(y=0.05、0.1、0.2),并对其电化学性能进行了研究。研究表明,掺杂Ti能够很好地改善中热固相法产品的电化学性能,且当y=0.1时,Li1.1V3―yTiyO8循环性能最好,首次放电比容量高达250.9 mAh/g。