hPRS1蛋白酶的同步辐射真空紫外圆二色光谱研究

人的PRPP合成酶1(hPRS1:Human phosphoribosylpyrophosphate synthetase)是与人体核苷酸代谢途径密切相关的一种重要合成酶.本文利用同步辐射真空紫外圆二色光谱(SRCD)实验方法研究hPRS1二级结构特征,以及通过添加反应底物,观察hPRS1二级结构的变化.研究发现,在添加相应底物的条件下,显示出hPRS1二级结构富有弹性,在外界因素发生改变时,二级结构相应发生较大变化,这个结果表明hPRS1蛋白二级结构的改变对于发挥功能作用是必需的.     

同步辐射圆二色谱研究氧化石墨烯与腐殖酸的相互作用

应用同步辐射真空紫外圆二色光谱、紫外-可见及红外光谱等技术研究了氧化石墨烯(Graphene Oxide,GO)与腐殖酸(Humic Acid,HA)在水溶液中的相互作用,探讨了不同配比、溶液p H及不同温度条件下GO与HA之间的相互作用对GO在水溶液中形态的影响。研究表明,一定条件下GO在水溶液中显示出圆二色性,其强弱与GO在水溶液中的形态结构有关。HA可通过极性相互作用和π-π相互作用吸附在GO表面,形成GO-HA复合物,改变体系的圆二色性,这种影响与二者的质量比、水环境p H和温度相关。GO-HA与GO相比,厚度增加,分散性提高,圆二色信号降低;GO-HA体系p H值升高和温度降低,有利于GO-HA折叠构象的形成,使得体系的圆二色信号升高。     

NSRL真空紫外圆二色光谱实验站设计及性能测试

本文介绍了中国科学技术大学国家同步辐射实验室(NSRL)真空紫外圆二色光谱测量装置的设计及安装调试结果,包括光学设计、样品池、数据采集系统、以及标准样品测量的结果。该实验站连接在弯铁光源和正入射单色器光束线的末端,在0.5nm光谱分辨下样品点的光子通量大于1012s-1。采用线性起偏器获得线偏振同步辐射,经过光弹调制器(PEM)获得重复频率约50kHz、左右旋交替的圆偏振光。通过高压伺服使得光电倍增管平均输出电流不变;使用锁相放大器采集与PEM同频的交流信号,得到圆二色光谱信号。常规实验条件(氮气氛保护、水作为溶剂、标准样品池)下,可测试的光谱范围是178—300nm。通过采用特殊溶剂、超短光程氟化物样品池等手段,可以将测试的短波限推至140nm。     

同步辐射圆二色谱法研究Fe3O4纳米颗粒对细胞色素C结构的影响

四氧化三铁纳米颗粒(Fe3O4-NPs)在生物医学领域有着广泛的应用。通过同步辐射真空紫外圆二色谱(SRCD)和紫外可见(UV-Vis)吸收谱技术研究了Fe3O4纳米颗粒的粒径(10 nm和40 nm)对细胞色素C(Cyt c)结构的影响。结果表明,随着Fe3O4-NPs颗粒物浓度的增大,Cyt c在408 nm处的吸光度值逐渐下降。SRCD结果显示Cyt c与Fe3O4-NPs作用后,蛋白的α螺旋含量减少,β折叠含量增加;Fe3O4-NPs与Cyt C的作用强度具有尺寸依赖性,小尺寸的Fe3O4-NPs作用更为明显。     

NSRL软X射线磁性圆二色光束线

本文对合肥同步辐射（NSRL）二期工程软X射线磁性圆二色光束线进行了介绍。束线主要包括斩波器系统、前置镜系统、单色器系统、后置镜系统、真空系统、软件及电子学系统。光束线的预期指标为：光通量10^8s^-1,实验站的波长范围为100-1000eV,圆偏振度0．6-0．8（随波长变化而变化）,在1000ev处的能量分辨率为1000,在实验站的焦点处光斑大小为水平方向3mm,垂直方向1mm。     

同步辐射反射法测定液体结构方法研究

用北京同步辐射装置4W1C光束线Huber五圆测角仪反射法测定液体结构的实验方法.以Na2SO4溶液的散射实验为例,简单介绍了样品池构造、散射几何布局、样品准直、扫描条件和扫描方式;详尽叙述了实验散射强度数据的校正方法,如样品池窗口净吸收、空气散射、偏振校正、吸收校正和几何校正等;演示了溶液结构函数和径向分布函数的计算方法,包括Compton散射强度和乱真峰的扣除技巧.研究表明,用同步辐射反射法获得了高质量的X射线散射数据.     

端粒DNA形成不同构象的关键因素

端粒DNA与细胞的衰老、死亡、癌变密切相关,人体端粒DNA富含G和C单链可分别形成G-四链体(G-quadruplex)和I-motif四链体结构。它们与端粒酶活性、着丝粒DNA、RNA夹层结构等有直接关系,且可作为药物的靶点,因此研究其形成条件有重要意义。本文用圆二色谱谱研究富G和C单链及其混合状态下形成不同四链构象的关键影响因素。结果表明,dAG3(T2AG3)3是否形成G-quadruplex主要取决于溶液中金属阳离子,d(C3TA2)3C3T形成I-motif则与溶液pH密切相关,而在dAG3(T2AG3)3/d(C3TA2)3C3T混合溶液中很易形成双螺旋(duplex)结构,在一定条件下也可形成G-quadruplex、I-motif混合态。     

螺旋线圈在同步辐射光源冷却系统中的应用

在冷却流体管道中插入铜质线圈的强化冷却方法可以较为显著地提高管道的对流换热系数,从而增强冷却效果,此法已在国际上的同步辐射光源中得以应用。根据现有相关文献,总结介绍了此种强化冷却方法,阐述该机构的关键结构参数与强化冷却工作机理,并对其在国际上各同步辐射光源的应用情况作出描述,同时指出关键技术问题与未来的发展趋势,从而为此强化冷却方法在我国同步辐射装置,特别是高能高热的第三代同步辐射装置冷却系统的应用提供前瞻与有益的探索。     

同步辐射X射线形貌术在晶体生长和缺陷研究中的应用

本介绍了同步辐射光源的特点,以及在应用于X射线形貌术时带来的各种好处。并通过介绍在北京同步辐射装置上所做的若干实验成果,扼要叙述了同步辐射X射线形貌术在晶体缺陷研究和晶体生长中的应用。     

类金刚石薄膜的同步辐射光电子能谱研究

利用同步辐射光电子能谱全电子产额模式(TEY)对石墨、金刚石薄膜和类金刚石薄膜(DLC)的ClsX射线吸收谱进行了研究。在高真空里表面净化处理后,在类金刚石薄膜的Cls吸收谱中分别观察到对应于金刚石sp^3杂化结构成分和石墨sp^2杂化结构成分的特征峰,说明了类金刚石薄膜是由碳sp^2、sp^3两种杂化结构无序混合形成的非晶碳结构;然后,测量了一系列类金刚石薄膜样品的ClsX射线光电子能谱(XPS),得到了每组样品的sp^2、sp^3成分比。     

Development of vacuum ultraviolet spectroscopy for measuring edge impurity emission in the EAST tokamak

The dominant wavelength range of edge impurity emissions moves from the visible range to the vacuum ultraviolet(VUV) range, as heating power increasing in the Experimental Advanced Superconducting Tokamak(EAST). The measurement provided by the existing visible spectroscopies in EAST is not sufficient for impurity transport studies for high-parameters plasmas. Therefore, in this study, a VUV spectroscopy is newly developed to measure edge impurity emissions in EAST. One Seya-Namioka VUV spectrometer(McPherson 234/302) is used in the system, equipped with a concave-corrected holographic grating with groove density of 600 grooves mm~(–1). Impurity line emissions can be observed in the wavelength range ofλ=50–700 nm, covering VUV, near ultraviolet and visible ranges. The observed vertical range is Z=-350–350 mm. The minimum sampling time can be set to 5 ms under full vertical binning(FVB) mode. VUV spectroscopy has been used to measure the edge impurity emission for the 2019 EAST experimental campaign. Impurity spectra are identified for several impurity species, i.e., lithium(Li), carbon(C), oxygen(O), and iron(Fe). Several candidates for tungsten(W) lines are also measured but their clear identification is very difficult due to a strong overlap with Fe lines. Time evolutions of impurity carbon emissions of CII at 134.5 nm and CIII at97.7 nm are analyzed to prove the system capability of time-resolved measurement. The measurements of the VUV spectroscopy are very helpful for edge impurity transport study in the high-parameters plasma in EAST.     

揭示生命能量之源--ATP合酶三维结构的同步辐射研究

在英国Daresbury同步辐射实验室获得的线粒体F1-ATPase原子分辨率（0.28nm)的三维结构是1997年诺贝尔化学奖成果之一，并且是第一个基于同步辐射研究而获得诺贝尔奖的研究成果。同步辐射具有的高通量、高准直性以及波长连续可调等优点必将会在已经到来的后基因组时代发挥巨大的作用。     

Use of synchrotron radiation in archaeometry

A synchrotron X-ray producing device such as the National Synchrotron Light Source at Brookhaven National Laboratory will present the research worker in the field of archaeometry with a number of new possibilities. These derive from the fundamental characteristics of the extracted X-ray beam: (a) its extraordinary intensity, four to five orders of magnitude greater than that of bremsstrahlung produced by X-ray tubes, (b) its polarization in the plane of the synchrotron ring and, (c) its energy tunability.Among the archaeometric applications one may readily identify: (a) very fast, sensitive, bulk analyses of materials such as ceramic and stone, for provenance research, (b) spot (microprobe) analytical capability, for obtaining structural information on artifacts, (c) scanning applications leading to images of the distributions of particular elements and, (d) element speciation on a micro scale. There is every reason to believe that this instrument will quickly take a prominent place in archaeometric research.     

Crystal structure and grain size of Zr oxide characterized by synchrotron radiation microdiffraction

Zirconium oxides formed on Zirclaoy-4 and Zr-1.5Nb (in wt%) were characterized by the microbeam X-ray diffraction using a synchrotron radiation. The phase fraction and the grain size were determined as a function of the position in the oxide. It was found that Zr-1.5Nb showed the better corrosion resistance than Zircaloy-4 in 360 °C pure water although the tetragonal phase was more stabilized to a further distance from the metal/oxide interface in the oxide of Zircaloy-4. The calculation of the grain size revealed that the oxide of the Zr-1.5Nb had larger grains than that of Zircaloy-4 with the tetragonal phase being smaller than the monoclinic one. It seems reasonable to suppose that the superior corrosion resistance of Zr-1.5Nb was attributed to the lager grain size of the oxide in which the oxygen diffusion is expected to be lowered when compared to the smaller grain size of the oxide on Zircaloy-4.     

Spin light identification in the presence of power synchrotron radiation

The relativistic radiation theory of the intrinsic magnetic moment of an electron (which is known as spin light) from the point of view of the correspondence principle of classical, semi-classical and quantum theory of radiation is discussed. It is shown that after separation of terms unbound with a spin in the power of the total radiation of electrons (with the example of the synchrotron radiation of an electron) the correspondence principle holds accurate within a second approximation by Plank’s constant. The formulas for the angular distribution, linear polarization and spectral structure of radiation obtainable here with an allowance for spin can find application for non-trivial problems of experimental identification of spin light.