驱动蛋白单向运动机理

驱动蛋白马达在实验和理论上已被进行了广泛的研究. 然而, 其行进运动的微观机理仍未确定. 在本文中我们基于化学、力学和电学耦合提出了一个交臂模型来描述这种行进运动. 在该模型中，驱动蛋白两个头的ATP水解化学反应速率由作用在其颈上的力（包括内部弹性力和外部负荷）来调控. 在低外部负荷情况下, 驱动蛋白的后头的ATP水解化学反应速率远大于前头的速率, 因而两个头在ATP水解化学反应和力学周期循环中是协调的且马达以每步消耗一个ATP的方式的行走. 在大的前向负荷情况下, 两个头的ATP水解化学反应速率变得可比拟, 因而两个头在ATP水解化学反应和力学周期循环中不再很好地协调. 该模型与驱动蛋白的结构研究结果以及ATP水解化学反应路径一致. 利用此模型所估算的驱动力（约5.8 pN）与实验结果（5~7.5 pN）一致. 所估算的每步中的运动时间（约10）也与实验测量值（0~50）符合. 解释了已观察到的每步（8nm）分为两个半步的现象. 所得到的运动速度-负荷曲线与已有的实验结果一致.     

A non-Markov ratchet model of molecular motors：processive movement of single-headed kinesin KIF1A

A fluctuating ratchet model of non-Markov process is presented to describe the processive movement of molecular motors of single-headed kinesin KIF1A,where the fluctuation perturbation to the local potential is introduced and the detailed ATPase pathway of the motor is included. The theoretical results show good quantitative agreement with the previous experimental ones.     

Simultaneous Measurement of Individual ATPase and Mechanical Reactions by a Single Myosin Molecule at Work

Based on techniques for single molecule imaging and nanomanipulation by optical tweezers, we have developed a new technique that allows simultaneous measurement of individual ATPase and mechanical reactions from a single myosin molecule during force generation. We show how the ATPase reaction couples to the mechanical reaction directly at the single molecule level. The results show that the myosin head can produce force even after releasing the bound nucleotide, probably ADP, suggesting that the chemical energy driven by ATP hydrolysis can be hysteretically stored in the myosin molecule. This view does not support a widely accepted hypothesis in which the force generation is tightly coupled to ligand dissociation.This paper was originally presented as an invited paper at the seventh Meeting on Near Field Optics, which was held on July 1, 1998 at Nagoya University, Nagoya, organized by the Research Group on Near Field Optics of the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics.     

基于虚拟仪器的导弹质心定位系统设计与实现

针对传统导弹质心定位设备精度低,操作繁琐等弊端,从弹体质心定位原理出发,合理选取力矩计算参考点,建立质心定位模型;以基于PCI总线的内插式DAQ虚拟仪器测控平台为依托,突出“通用性、精确性、高效性”的设计理念,制定系统总体设计方案,围绕导弹质量测量与质心定位技术展开研究与工程实现;实际应用表明,本系统可拓展应用于多型导弹和大型圆柱形工件的称重与质心定位,满足导弹飞行控制研究和装配工艺要求。     

类氦离子V21+精细能级结构及跃迁光谱的相对论计算

采用加轨道极化修正的相对论多组态Dirac-Fock方法,计算了类氦离子 V21+的跃迁几率和跃迁波长,所得结果与实验值吻合,比较了极化对能级、能级间隔 和不同类型跃迁的影响,并讨论了轨道极化修正函数。     

Effects of high intensity unltrasound on structural and physicochemical properties of myosin from silver carp

Myosin from silver carp was sonicated with varying power output (100, 150, 200 and 250 W) for 3, 6, 9, and 12 min. The changes in the structure and physicochemical properties of myosin were evaluated by dynamic light scattering, SDS-PAGE and some physicochemical indexes. The ultrasound treatments induced a significant conversion of myosin aggregates to smaller ones with a more uniform distribution, and obvious enhancement in solubility. The structure of myosin was also notably changed by sonication, with a decrease in Ca²⁺-ATPase activity and SH content, and an increase in surface hydrophobicity. Furthermore, SH groups were oxidized, leading to a decrease in reactive SH and total SH contents. SDS-PAGE analysis revealed that ultrasound could induce the degradation of myosin heavy chain and change the protein fraction of myosin. Collectively, the ultrasonic treatment of 100 W for 3 min showed slight influence on the SH content, S₀-ANS, and electrophoretic patterns, and the extent of changes in myosin structure and physicochemical properties tended to increase with ultrasonic power and time. The integrated data indicate that ultrasonic treatment can facilitate the improvement of the solubility and dispersion of myosin, but the choice of a suitable ultrasonic condition to avoid oxidation and degradation of myosin is very important.     

A novel terbium composite nanoparticles: Preparation and selective fluorescence determination of chromium(VI)

A highly efficient ultrasonic-assisted method was successfully applied to prepare the strong fluorescence Tb/acetyl acetone (acac)/poly (2-Acrylamidoglycolic acid monohydrate) (PAAM) composite nanoparticles. Based on the fluorescence quenching of Tb/acac/PAAM by Cr(VI), an assay for the selective determination of Cr(VI), without separation of Cr(III), was developed. It is characteristic of very few interferences, stable fluorescence signals (at least 2 h), simple instrument (common spectrofluorometer) and simple step. Under optimal experimental conditions, the fluorescence intensity of the system is linearly proportional to the concentration of Cr(VI) in concentration range of 5-800 ng mL⁻¹ with a correlation coefficient of 0.9983. The limit of detection was found to be 0.5 ng mL⁻¹.The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples with satisfactory results.     

Two-photon spectroscopy and microscopy of II–VI semiconductor nanocrystals

We review our recent nonlinear spectroscopies of nanocrystals and synthetic efforts to improve their luminescence properties. A two-photon spectroscopic study of CdSe nanocrystals as a function of size is presented and compared with predictions from the effective mass model with spherical confinement. We also detail our efforts at improving the luminescence properties of nanocrystals which have culminated in a 50% fluorescence quantum yield for inorganic capping of some sizes of CdSe nanocrystals. Finally, we present the application of two-photon microscopy to resolve fluorescence from single nanocrystals at room temperature and cryogenic temperatures.     

Molecular dynamics simulation of surface melting behaviours of the V（110） plane

The modified analytic embedded-atom method and molecular dynamics simulations are applied to the investigation of the surface premelting and melting behaviours of the V（110） plane by calculating the interlayer relaxation, the layer structure factor and atomic snapshots in this paper. The results obtained indicate that the premelting phenomenon occurs on the V（110） surface at about 1800K and then a liquid-like layer, which approximately keeps the same thickness up to 2020K, emerges on it. We discover that the temperature 2020K the V（110） surface starts to melt and is in a completely disordered state at the temperature of 2140K under the melting point for the bulk vanadium.     

New energy levels and transitions for the 4s4p5p configuration in Kr VI

The spectrum of five-time ionized krypton, Kr VI, was recorded in the 240-2600 Å wavelength range, resulting in 61 new classified lines as transitions between levels of configurations 4p³, 4s²5p, 4s4p4d, 4s4p5s and 4s4p5p. All the 18 energy levels belonging to 4s4p5p configuration except one were determined. Eight new energy level values corresponding to configurations 4s4p4f and 4p24d, supported by 26 new classified lines were also determined and used in the interpretation of the observed 4s4p5p configuration. The experimental data were obtained from a capillary-discharge tube and theta pinch light sources. Multiconfiguration Hartree-Fock calculations with relativistic corrections and a least-squares fitted parametric calculation has been carried out.     

Molecular spectroscopic insight into the binding of batatasin V isomers to human serum albumin

Fluorescence, ultraviolet-visible absorption spectroscopy, circular dichroism spectrum, and molecular docking methods were employed to study the interaction mechanisms of batatasin V and its isomer with human serum albumin. The two isomers both bond reactively to the hydrophobic activity in subdomain IIA, with an approximate binding affinity. Thermodynamic parameters and molecular modeling results manifested that hydrogen bonds and van der Waals force were the main contributors to the interaction. The secondary structure of human serum albumin was altered with the obvious decreased amount of α-helix. The results overall suggested similar binding mechanisms of batatasin V isomers with human serum albumin. This work will promote the further study of batatasins for pharmacological function. It could also help to provide some useful information for further drug design based on batatasins.     

Effects of different ultrasound frequencies on the structure,rheological and functional properties of myosin: Significance of quorum sensing

Structure and rheological properties of myosin in myofibrillar protein (MP) after single frequency pulsed ultrasound (SFPU, G1-G2) and dual frequency pulsed ultrasound (DFPU, G3) were compared for the first time. Results showed SFPU and DFPU induced “stress response” through the action of cavitation on multiple myosin. In addition, there may be a certain quorum sensing among myosin, inducing a more stable β-antiparallel structure to resist negative effects of cavitation force. Results of particle size and synchronous fluorescence indicated that structure of myosin in MPs changed through stress. The increase in pH also assisted in the ultrasound process (G5-G7). Notably, DFPU induced stronger quorum sensing and formed a more stable structure. More so, effects of (−)-epigallocatechin-3-gallate (EGCG) and baicalein (BN) on the emulsion and gel properties of DFPU treated and non-treated MPs were also investigated. Results showed that ultrasound increased the stability of emulsion. Additionally, the texture and expressible moisture content (EMOC) of the gel were also improved after treatment.     

Bianchi Type VI String Cosmological Model in Saez–Ballester’s Scalar-Tensor Theory of Gravitation

An exact Bianchi type-VI string cosmological model is obtained in a scalar-tensor theory of gravitation proposed by Saez and Ballester (Phys. Lett. 113:467, 1985). Some physical properties of the model are also discussed.     

基于RAMS V6.0的非感应起电机制评估和雷暴初期电荷结构模拟

数值模式是研究雷暴内起电和电荷结构的重要工具. 本文将Takahashi (1978) 和Saunders (1991) 两种主流非感应起电机制加入最新版本的中尺度模式RAMS(Version 6.0), 建立了一个区域大气-电耦合中尺度雷暴云模式, 据此对发生于北京的一次雷暴过程首次放电前的电荷结构和水成物粒子起电情况进行了较成功的模拟. 结果表明, Takahashi (1978) 和Saunders (1991)方案模拟的雷暴电荷结构在电场达到击穿阈值时均呈现三极性特征, 但Takahashi和Saunders方案模拟的雷暴电荷结构演变过程有一定的差异, Takahashi方案的电荷结构从起电到放电都是三极性特征, Saunders方案的电荷结构从反偶极性演变为三极性. 此外, 两种方案的模拟结果均表明雨滴是雷暴云低层的正电荷载体, 聚合物和霰是高层的主要电荷载体, 霰的电荷中心分布形态与雷暴云的总电荷分布形态相似.     

几种Fe（Ⅵ）化合物的物理性质、电化学性能及稳定性研究

为深入认识高铁化合物的物理性质和电化学性能,采用化学法合成了K2FeO4、BaFeO4、SrFeO4和 K2Sr(FeO4)2等几种高铁化合物,比较研究了这几种高铁化合物的形貌、结构、在不同浓度KOH溶液中的溶解度 及其放电性能.研究结果显示,在这几种高铁化合物中,BaFeO4具有较好的电化学性能.但在实验过程中发现,除 K2FeO4外,其余几种高铁化合物均不稳定,在干燥环境中放置时会发生分解.采用量子化学从头算方法从理论上 分析了高铁化合物的稳定性变化规律.研究结果表明,高铁化合物的稳定性与阳离子对FeO42-的极化作用有很 大关系,极化作用越强,高铁化合物就越不稳定.     

基于虚拟仪器的装备ATS系统硬件平台设计与实现

在对现有维修检测设备存在不足分析的基础上,结合武器装备的维修技术保障需求,利用分块设计思想,采用虚拟仪器、人工智能、计算机通讯与控制等技术,搭建了基于虚拟仪器的装备自动测试系统硬件平台整体架构,在对系统各功能模块原理进行分析之后,对系统主控电路、电磁兼容性进行了设计。采用虚拟仪器的装备自动测试系统硬件平台,具有智能化、通用化、可视化的特点,通过试验结果分析,测试系统硬件平台能够实现装备的性能检测和故障诊断,测试数据符合任务要求,能满足各级修理机构维修测试需求。     

Facile synthesis of fluorescent carbon dots from shrimp shells and using the carbon dots to detect chromium(VI)

It is important to develop methods to sensitively and selectively determine chromium(VI) because chromium(VI) plays crucial roles in pathological and physiological processes. We developed an easy-to-perform, low-cost, and efficient method for synthesizing carbon dots from shrimp shells by calcining the shells without using any chemical reagents. The as-prepared carbon dots exhibited excitation-dependent fluorescence, with excitation and emission maxima at 350 and 400?nm, respectively. The Carbon dots were found to be excellent fluorescent probes for detecting chromium(VI) using the fluorescence quenching effect. The Carbon dots allowed chromium(VI) to be determined with a high degree of sensitivity. The chromium(VI) detection limit was 0.1?µM, and the relationship between the chromium(VI) concentration and the response was linear up to a chromium(VI) concentration of 70?µM. The method for synthesizing carbon dots is novel and the carbon dots produced offer promise for monitoring chromium(VI) in environmental matrices.     

Insight into the chemomechanical coupling mechanism of kinesin molecular motors

Kinesin is a two-headed biological molecular motor that can walk processively on microtubule via consumption of ATP molecules. The central issue for the molecular motor is how the chemical energy released from ATP hydrolysis is converted to the kinetic energy of the mechanical motion, namely the mechanism of chemomechanical coupling. To address the issue, diverse experimental methods have been employed and a lot of models have been proposed. This review focuses on the proposed models as well as the qualitative and quantitative comparisons between the results derived from the models and those from the structural, biochemical and single-molecule experimental studies.     

ICP-AES测定高砷铁矿中砷和钒

建立了用硝酸-氢氟酸-高氯酸消解,ICP-AES测定铁矿中砷和钒的方法.该方法检出限砷为50mg/kg,钒为8mg/kg;相对标准偏差(RSD)砷为4.92%以下,钒为4.37%以下;加标回收率砷在95.3%-105.0%之间,钒在96.5%-102.1%之间.本法可以对铁矿中的砷和钒进行较为理想测定.     

Extracting Structure Parameters of Dimers for Molecular Tunneling Ionization Model

We determine structure parameters of the highest occupied molecular orbital(HOMO)of 27 dimers for the molecular tunneling ionization(so called MO-ADK)model of Tong et al.[Phys.Rev.A 66(2002)033402].The molecular wave functions with correct asymptotic behavior are obtained by solving the time-independent Schr(o|¨)dinger equation with B-spline functions and molecular potentials which are numerically created using the density functional theory.We examine the alignment-dependent tunneling ionization probabilities from MO-ADK model for several molecules by comparing with the molecular strong-field approximation(MO-SFA)calculations.We show the molecular PerelomovPopov-Terent'ev(MO-PPT)can successfully give the laser wavelength dependence of ionization rates(or probabilities).Based on the MO-PPT model,two diatomic molecules having valence orbital with antibonding systems(i.e.,Cl_2,Ne_2)show strong ionization suppression when compared with their corresponding closest companion atoms.