东方弧菌荧光酶的分离纯化和性质研究

东方弧菌518菌株于20℃摆床液体培养十六小时,菌数达最大,菌体内荧光素酶含量也较高,此时收获菌体.用超声波振动破碎细胞从中提取荧光酶粗液,经DEAE-纤维索和DEAE-sephadex柱层析得到纯化的酶.用葡聚糖凝胶层析法测得该酶分子量为87000道尔顿,用SDS-PAGE法测得该酶两个亚基分子量分别为44000(α)和41000(β). 该酶在pH6.8、18℃时活性最佳,对热不稳定.以FMNH2为底物催化发光反应,最高发射波长为490nm左右.其光谱特征与文献报道的东方孤菌整体发光的光谱相一致.     

光谱法表征蛋白酶K的热变性过程

用不同温度处理蛋白酶K,以变性酪蛋白底物法测定酶活力,稳态/瞬态荧光光谱法和圆二色谱法测定空间构象和二级结构,研究温度对蛋白酶K酶活力和构象的影响。温度由25 ℃升高至65 ℃过程中,蛋白酶K的酶活力逐渐降低,半衰期缩短;发射光谱荧光强度降低,峰位由335 nm红移至354 nm;色氨酸残基同步荧光强度降低,酪氨酸残基同步荧光强度增大;色氨酸残基荧光寿命由4.427 1 ns降低至4.032 4 ns;α-螺旋百分含量降低。结果表明：采用稳态/瞬态荧光光谱法和圆二色谱法能较简便、准确的描述蛋白酶K的热稳定性变化;蛋白酶K的热变性过程符合三态模型,存在一个中间态;蛋白酶K分子内部存在酪氨酸残基对色氨酸残基的共振能量转移作用;α-螺旋是维系蛋白酶K活性中心构象稳定性的主要结构。     

石墨烯/碳化硅异质界面热学特性的分子动力学模拟

为了调控石墨烯/碳化硅异质界面传热特性,采用非平衡态分子动力学方法研究温度、尺寸、材料缺陷率对界面热导的影响,通过声子态密度和声子参与率对界面热导变化的原因进行阐述分析.研究表明:两种界面作用力下界面热导均随温度升高而增大,但共价键的异质界面热导要高于范德瓦耳斯作用力下的界面热导.异质界面的界面热导随着碳化硅层数的增加而降低,当层数从10层增加到20层时,界面热导下降30.5%;4层时异质结构界面热导最低,分析认为中低频段更多的声子从局域进入离域模式.空位缺陷的引入可以有效地提高界面热导,随着碳化硅和石墨烯缺陷率的增加,界面热导均先升高再降低.300 K时当碳化硅和石墨烯缺陷率分别为20%和35%时界面热导达到最大值,分析认为缺陷的引入会阻碍中频声子的热输运.研究结果揭示可以通过尺寸效应和空位缺陷来进行异质界面的改性研究,有利于第三代半导体微纳器件的设计和热管理.     

多肽和蛋白质酰胺-I带振动频率图的温度依赖性

利用高温分子动力学模拟和红外光谱实验手段,研究了一个基于分子力学力场的酰胺-I带振动频率图的温度依赖性. 结果表明,基于298 K所建立的频率图可以应用上至500 K的分子动力学轨迹,所模拟的红外光谱能够很好地重复88 oC时的实验光谱. 另外还模拟了两个含有天然和非天然氨基酸残基的三肽分子的红外光谱,与实验结果相比得到了较好的符合. 结果表明,所建立的频率图能够用于获得多肽体系在不同温度下的酰胺-I带局域模振动频率及其分布,有助于深入认识多肽的热去折叠物种的红外光谱特征.     

头孢他啶与牛血清白蛋白(BSA)的相互作用

采用荧光、紫外及红外光谱法研究了头孢他啶与牛血清白蛋白(BSA)的结合反应.头孢他啶对BSA的色氨酸残基和酪氨酸残基均具有猝灭作用,其猝灭机理为静态猝灭,两者之间形成新的复合物是导致BSA荧光猝灭的主要原因.获取了复合物的结合常数(298K:1.27×10~4L·mol~(-1);310K:1.33×10~41·mol~(-1)).BSA Ⅱ A结构域的site I位点是其唯一可能结合位点.同步荧光光谱表明头孢他啶造成BSA的酪氨酸残基的极性增强.红外光谱表明头孢他啶引起了BSA二级结构的改变,使其α-螺旋含量降低.     

6066Al/SiCp复合材料内耗性能研究

用粉末冶金方法制备了6066Al合金和不同SiCp含量的6066Al/SiCp复合材料,用多功能内耗仪在200～600 K温度区间内测试了所研究材料在升温过程中的内耗变化趋势,探讨了6066 Al /SiCp复合材料在不同温度区间的内耗机制.结果表明6066Al/SiCp的内耗值比6066Al合金内耗值高,特别是在高温阶段比6066Al合金内耗值高得多;6066Al/SiCp和6066Al合金在300～470 K时的内耗主要是位错与第二相颗粒交互作用引起的位错内耗,在高温下内耗主要由Al/Al、Al/SiC的界面微滑移引起.     

界面尺寸对铜/石墨烯界面热导的影响

采用原子格林函数(AGF)方法研究了界面尺寸对铜/单层石墨烯(SLG)界面热导的影响。建立了有限和无限界面尺寸的AGF计算模型,计算得到的界面热导均在铜的迪拜温度(343 K)附近收敛,但两者计算得到的透射系数和界面热导存在明显差别:有限界面尺寸时计算得到的透射系数在1.5 THz附近达到峰值0.84,而无限界面尺寸时计算得到的透射系数在5 THz附近存在峰值0.58,且前者数据波动较大,总体数值也大于后者;无限界面热导收敛为17.6 MW·m^?2·K,显著小于有限界面面积的计算结果(41.9 MW·m^?2·K^?1)。     

超导磁体预冷回热组件设计与动态模拟

为满足强流重离子加速器装置(HIAF)中各类超导磁体300～80 K的预冷需求,设计一套液氮为冷源、氦气为循环介质的预冷回热组件。采用Aspen HYSYS对预冷回热组件300～80 K降温过程进行动态模拟,分析了组件模式切换时三种典型工况下系统的瞬态热工水力特性。结果表明预冷回热组件在最大流量30 g/s时可实现温度300～80 K连续可调,调节精度优于±3 K,可为HIAF各类磁体测试提供稳定可靠的冷源。     

利用瞬态热栅技术研究Sr2FeMoO6的热扩散系数及其温度效应

为研究Sr2FeMoO6的热扩散系数及其温度效应,利用瞬态热栅法研究了不同温度下Sr2FeMoO6热扩散系数变化,发现在温度300～360 K范围内,Sr2FeMoO6热扩散系数随着温度升高缓慢减小;在居里温度Tc～380 K附近,热扩散系数剧烈下降;在温度400～450 K范围内,热扩散系数随着温度升高基本保持不变....     

温度对金刚石涂层膜基界面力学性能的影响

利用分子动力学方法建立了硬质合金基底金刚石涂层膜基界面模型, 并采用Morse势函数和Tersoff势函数相互耦合的方法来表征模型内原子间的相互作用关系, 在此基础上对不同温度(0–800 K)条件下硬质合金基底金刚石涂层膜基界面的力学性能进行了分子动力学仿真计算. 结果表明: 当温度由0 K上升到800 K的过程中, 金刚石涂层膜基界面拉伸强度呈下降趋势, 并且在0–300 K范围内下降趋势明显, 在300–800 K范围内下降趋势缓和; 体系能量随温度的变化具有相同的下降趋势.     

In situ X-Ray study of thermal expansion and phase transition of iron at multimegabar pressure

The density of varepsilon-iron has been calculated at pressures and temperatures up to 300 GPa and 1300 K, respectively. We observe varepsilon to beta phase transition at pressures between 135 and 300 GPa and temperature above 1350 K; the pattern can be interpreted in terms of double hexagonal close-packed structure. The density calculated at high pressure and temperature (330-360 GPa and 5000-7000 K) closely matches with preliminary reference Earth model density, thereby imposing constraint on the composition of the Earth's inner core.     

High temperature defects in electron irradiated semiconductors HgCdTe,PbSnTe

The peculiarities of defect formation in n- and p-type conductivity HgCdTe and PbSnTe crystals after electron irradiation (2 MeV, 300 K) up to 2 × 10¹⁸ cm^-2 are examined. It has been found that irradiation results in formation of n-type conductivity crystals with final parameters that are determined by the composition of initial samples. The annealing of radiation defects occurs in the 360–470 K temperature range. It has been believed that the change of HgCdTe, PbSnTe properties after electron irradiation at 300 K are connected with formation of radiation defects, including Te vacancies.     

Role of remote Coulomb scattering on the hole mobility at cryogenic temperatures in SOI p-MOSFETs

The impacts of remote Coulomb scattering(RCS)on hole mobility in ultra-thin body silicon-on-insulator(UTB SOI)p-MOSFETs at cryogenic temperatures are investigated.The physical models including phonon scattering,surface roughness scattering,and remote Coulomb scatterings are considered,and the results are verified by the experimental results at different temperatures for both bulk(from 300 K to 30 K)and UTB SOI(300 K and 25 K)p-MOSFETs.The impacts of the interfacial trap charges at both front and bottom interfaces on the hole mobility are mainly evaluated for the UTB SOI p-MOSFETs at liquid helium temperature(4.2 K).The results reveal that as the temperature decreases,the RCS due to the interfacial trap charges plays an important role in the hole mobility.     

Specific features in supersonic nonlinear dynamics of domain walls in rare-earth orthoferrites

Physics of the Solid State - The dynamics and temperature dependences of the mobility of domain walls in EuFeO3 (from 4.2 to 300 K), TmFeO3 (from 100 to 300 K), LuFeO3 (300 K), YFeO3 (460 K), and...     

Influence of the interface structure on the barrier height of homogeneous Schottky contacts

Unreconstructed interfaces may be prepared by evaporation of thick Pb films onto surfaces at room temperature. Current-voltage and capacitance-voltage characteristics of such Schottky contacts were measured in the temperature range between 140 and 300 K. The experimental data are analyzed by applying the thermionic-emission theory of inhomogeneous metal-semiconductor contacts as well as the “standard” thermionic-emission theory. From both methods the Schottky barrier height of laterally homogeneous contacts results as 0.724 eV. This value is by 74 meV larger than the previously observed barrier heights of laterally homogeneous interfaces. Similar differences were reported for unreconstructed and reconstructed Al- and contacts. The reduced barrier heights of all these interfaces are explained by the electric dipole associated with the stacking faults of reconstructions at surfaces and interfaces. Received: 14 May 1998 /Revised and Accepted: 7 September 1998     

Low temperature measurements by infrared spectroscopy in CoFe2O4 ceramic

This paper presents results of new far-infrared and middle-infrared measurements (wavenumber range of 4000?C100 cm^?1) of the CoFe₂O₄ ceramic in the temperature range from 300 K to 8 K. The band positions and their shapes remain constant across the wide temperature range. The quality of the sample was investigated by X-ray, EDS and EPMA studies. The CoFe₂O₄ retains the cubic structure (Fd - 3m) across the temperature range from 85 K to 360 K without any traces of distortion. Based on current knowledge the polycrystalline CoFe₂O₄ does not exhibit any phase transitions across the temperature range from 8 K to 300 K.     

Polydimethylsiloxane at the interfaces of fumed silica and zirconia/fumed silica

Polydimethylsiloxane (PDMS)/fumed silica A-300 and PDMS/ZrO₂/A-300 were studied using adsorption, thermogravimetry, temperature-programmed desorption (TPD) mass-spectrometry, infrared spectroscopy, XRD, and broadband dielectric relaxation spectroscopy. ZrO₂ was synthesized on fumed silica with zirconium acetylacetonate in CCl₄ at 350 K for 1 h and calcinated at 773 K for 1 h (1-4 reaction cycles). PDMS (5-40 wt.%) was adsorbed onto silica and zirconia/silica from hexane solution and then dried. Grafted zirconia changes the chemistry of the surface (because of its catalytic capability) and the topology of secondary particles (because of occupation of voids in aggregates of primary silica particles by zirconia nanoparticles) responsible for the textural porosity of the powders. Therefore, many properties (such as structural characteristics of the composites, reactions on heating in air and vacuum, interfacial relaxation phenomena, hydrophobicity as a function of treatment temperature, etc.) of PDMS/zirconia/silica strongly differ from those of PDMS/A-300. Broadening of the α-relaxation of PDMS at the interfaces of disperse oxides suggests both weakening of the PDMS-PDMS interaction and strengthening of the PDMS-oxide interaction.     

Changes of properties of the soliton with temperature under influences of structure disorder in the α-helix protein molecules with three channels

The changes of property of solitons in α-helix protein molecules with three channels under influences of fluctuations of structure parameters and thermal perturbation of medium are extensively investigated using dynamic equations in the improved theory, numerical simulation and Runge-Kutta method. In this investigation the peculiarities of the solitons are given first in the motions of short-time and long-time and its collision features at T = 0 K and biological temperature T = 300 K. This study shows that the solutions of dynamic equations are solitons, which are very stable at T = 0 and 300 K, although its amplitudes and velocity are somewhat decreased relative to that at T = 0 K, the soliton can transport over 1000 amino acid residues, its lifetime is, at least, 120 ps. Subsequently, studies are made of the changes of properties of the soliton with variations of temperature of the medium and fluctuations of structure parameters including mass sequence of amino acid residues and the coupling constant, force constant, dipole–dipole interaction, chain–chain interaction and ground state energy in the α-helix proteins. The investigations indicate that the soliton has high thermal stability and can transport along the molecular chains retaining amplitude, energy and velocity, although the fluctuations of the structure parameters and temperature of the medium increase continually. However, the solitons disperse in larger fluctuations at T = 300 K and higher temperatures than 315 K. Thus it is determined that the critical temperature of the soliton is 315 K. Finally reasons are given for the generation of high thermal stability of the soliton and the correctness of the improved model is demonstrated. It is concluded that the soliton in the improved model is very robust against structure disorder and thermal perturbation of the α-helix protein molecules at 300 K, and is a possible carrier of bio-energy transport, and the improved model is maybe a candidate for the mechanism of this transport.     

Investigation of collision-induced absorption in the vibrational fundamental bands of O2 and N2 at elevated temperatures

Collision-induced absorption has been measured for the vibrational fundamental bands of N₂ and O₂ at temperatures up to 360 K. These data when combined with previously obtained lower temperature data show that the integrated band intensity of the O₂ fundamental increases as the temperature is raised above 300 K. The integrated intensity of the N₂ band also increases, but at a much lower rate with temperature.