同步辐射(软X射线)辐照玉米的细胞学效应研究

利用同步辐射(软X射线)辐照玉米自交系H65和H14D种子,研究其M1代的细胞学效应,并以60Co-γ射线作对照。结果表明,软X射线辐照处理后,不仅能够诱发玉米M1代根尖细胞内核畸变和染色体畸变,而且还能够诱发染色体多种类型的变异,其变异频率随辐照剂量的增加而增大,辐照剂量与细胞总畸变率呈正相关。软X射线对玉米根尖细胞的有丝分裂具有明显地抑制作用,辐照剂量与细胞分裂指数呈负相关。软X射线辐照的细胞学效应与γ射线基本相似,但在诱发的细胞畸变率和染色体变异类型上存在一定的差异。两个供试品系对辐射的敏感性为H14D>H65。     

同步辐射软X射线对枯草杆菌的诱变效应

采用同步辐射软X射线对枯草芽孢杆菌(Bacillus subtilis)1831菌株进行辐照处理,研究了不同剂量下3．1nm的软X射线对其芽孢的失活和诱变作用。结果表明：同步辐射软X射线对枯草杆菌芽孢的剂量存活曲线表现为典型的“肩型”,对芽孢的失活作用属于“单靶多击”方式,失活击中数等于3。根据脱脂牛奶平板上蛋白酶活力大小的测量统计,以变异系数作为诱变效应指标,软X射线对芽孢具有一定的诱变作用。     

药物设计与同步辐射

当代药物设计是通过阐明药物与靶标相互作用的机理,对药物先导化合物进行改造和优化。利用晶体X射线衍射的方法获得药物与靶标复合物的结构,为药物设计提供最直接有力的依据。同步辐射凭借其高强度、低发散性、波长可调谐性等得天独厚的优势,实现了对药物与靶标复合物结构的高通量测定,大大提高了基于结构的药物设计效率。     

热胁对海藻作用的荧光研究

本文用荧光方法研究了不同海藻对热胁的反应。在40℃的热处理下,红藻海膜（Halymenia Sinensis)的叶绿素荧光动力学曲线随时间呈规律性的变化,荧光强度先下降后上升,并有荧光的聚升现象,在达到最大值后,荧光就逐步跌落且不可逆转,此时藻体的荧光发射光谱发生了显著变化,藻红朊的荧光发射峰增高,蓝藻朊的发射下降,表明激发能由前者向后者的传递受阻,对绿藻孔石莼（Ulva pertusa)的比较研究表明,未见有荧光的聚升现象,且在受热过程中藻体的荧光光谱没有显著的变化,因而热胁对两类海藻的作用机制可能不全相同。     

同步辐射在显微CT中的应用

计算机X射线断层成像技术（CT）是利用X射线的穿透能力对物体进行扫描,所得信号经过反投影的算法而得到物体二维分布的一种成像方法,已经在医学诊断、工业探伤等领域广泛应用。但是由于实验室光源的低通量,光源点大小及其单色性等限制了其向高分辨发展,通常其分辨率在0．5mm左右。利用微焦点X射线源作为光源的显微CT分辨率可以达到微米量级,但是由于其光通量低且为非单色光,对不同样品有不同程度的束线硬化,影响了其真实分辨率。同步辐射作为一种新兴的光源有高亮度、高光子通量、高准直性、高极化性、高相干性及宽的频谱范围的特点,配合高分辨的X射线探测器,可以发展同步辐射显微CT,其分辨率可达10μm以下。利用同步辐射的高空间相干性开展位相衬度显微CT的研究,对低吸收物质也可以清晰三维成像。新建的上海光源的X射线成像及生物医学应用线站开展了三维显微CT方面的研究,经过初步试验,得到了较好的结果。     

培养液中钙对碳纳米材料细胞毒性作用机制的同步辐射初步研究

本工作研究了细胞培养液中钙离子和多壁碳纳米管,以及纳米碳黑的相互作用,采用钙荧光标记的显微成像技术和同步辐射X射线荧光技术,研究了HeLa细胞内钙离子浓度的增高及其相关机制。实验结果指出,细胞培养介质中的钙能被碳纳米颗粒(CNPs)大量吸附并载带进入细胞内,因此,CNPs向细胞内输送过量的钙离子可能是造成CNPs细胞毒性的重要原因。本工作为正确检测和评估碳纳米材料细胞毒性提供了新思路。     

相干X射线成像进展

X射线显微技术能够弥补光学显微镜分辨率的不足和电子显微镜成像深度的不足,具有很大的应用潜力.本文对已有文献进行综合,从透射、散射、衍射等成像原理方面介绍X射线显微技术,包括透射X射线显微成像、小角X射线散射成像、相干X射线衍射成像、X射线全患术等技术.本文同时介绍了多个技术的结合应用,如扫描透射X射线显微成像与相干X射...     

安徽琅琊山铜矿蝶类重元素X荧光分析

为了研究安徽琅琊山铜矿环境中重元素污染的状况,利用同步辐射X射线荧光,对于采自安徽安徽琅琊山铜矿的9种蝴蝶的翅样品进行重元素分析。结果显示,9种蝴蝶体内重元素含量的差别变化明显,蝴蝶可以富集重元素Hg和Pb,其Cu、Zn元素的比值与环境污染程度相关。结果表明该方法样品处理简便,灵敏度高。     

几种海藻和赤潮藻的DCMU增益荧光比率及其与增殖速率的关系

本文研究了红藻海膜(Halymenia sinensis)，绿藻孔石莼(Ulva pertusa)，褐藻裙带(Underia pinnatifida)及蓝藻钝顶螺旋藻(Spirulina platersis)的DCMU增益荧光比率(FD／FN)。其中海膜的比率最高(3．9)，石莼及螺旋藻次之(2．5和2．8)，裙带(采自夏季)的比率最低(1.7)。脱水及热处理下和藻体老化时，FD／FN值显著下降。在实验室条件下分批培养的两种赤潮藻海洋原甲藻(Prorocertrum micans)和微小角毛藻(Chaetoceras minutissmus)，其增殖过程中最大增益荧光比率较最大增殖速率出现早，这一结果为赤潮的预报提供了依据。     

团头鲂成熟卵的超微结构和X射线微区分析研究

本文应用扫描电镜、透射电镜及X射线微分析技术,对团头鲂成熟卵的超微结构和离子元素含量进行了研究.结果表明,在团头鲂成熟卵的卵膜上具有许多卵膜孔,胞质内有丰富的管状嵴线粒体和游离核糖体;在质膜下的皮质区内有皮质小泡、微管和微丝结构.卵的表面含有Na、Mg、Al,Si、S、Cl、K和Ca,含量分别为6.65±0.47,0.39±0.06,5.51±0.83,0.51±0.01,76.41±0.94,9.24±1.39,0.71±0.24和0.96±0.05.卵的胞质内含有Na、Mg、Si、P、S、Cl、K、Ca和Fe,其含量分别为10.26±0.15,3.04±0.12,19.48±1.23,1.17±0.32,13.42±1.59,14.83±2.32,20.26±3.15,10.02±1.69和7.52±1.83.     

X-ray fluorescence analysis using synchrotron radiation at the photon factory

X-ray fluorescence experiments at the Photon Factory in Japan are described. An energy-dispersive X-ray fluorescence system was combined with various excitation modes, i.e., a continuum and a monochromatic excitation, which consist of a crystal monochromator or a wide band pass monochromator. These excitation modes provide a wide range of band width and photon flux of excitation beams. Minimum detection limits obtained for a thin sample were less than 0.1 ppm and 0.1 pg when there was no line interference. Advantages of using monochromatic excitation are discussed, with emphasis on the possibility of chemical state analysis. Grazing incidence X-ray fluorescence is a technique very appropriate to synchrotron radiation characteristics. Near-surface analysis and trace analysis of solution samples placed on a total reflection support were made. Future plans are discussed, including microbeam analysis, tomography, X-ray excited optical fluorescence, and applications of insertion devices (undulator and wiggler).     

Investigation of elemental content distribution in femoral head slice with osteoporosis by SRXRF microprobe

A synchrotron radiation X-ray fluorescence microprobe analysis technique was used to scan a slice of the femoral head from its periphery to its center, via cartilage, compact, and spongy zones in order to determine the distribution and the way inorganic substances are lost in bone tissue. The sample preparation and experimental apparatus are described in detail. The quantitative computerized tomography of elemental distribution, such as Ca, P, K, Fe, Zn, Sr, and Pb in bone slice tissue, including cartilage, substantial compact, and substantial spongy, is investigated. Combined with the correlation among, P, K, Zn, Sr, and Ca, the route of loss of minerals and the physiological functions of some metal elements in bone are also discussed.     

The influence of electrical stimulation of vagus nerve on elemental composition of dopamine related brain structures in rats

Recent studies of Parkinson's disease indicate that dorsal motor nucleus of nerve vagus is one of the earliest brain areas affected by alpha-synuclein and Lewy bodies pathology. The influence of electrical stimulation of vagus nerve on elemental composition of dopamine related brain structures in rats is investigated. Synchrotron radiation based X-ray fluorescence was applied to the elemental micro-imaging and quantification in thin tissue sections. It was found that elements such as P, S, Cl, K, Ca, Fe, Cu, Zn, Se, Br and Rb are present in motor cortex, corpus striatum, nucleus accumbens, substantia nigra, ventral tectal area, and dorsal motor nucleus of vagus. The topographic analysis shows that macro-elements like P, S, Cl and K are highly concentrated within the fiber bundles of corpus striatum. In contrast the levels of trace elements like Fe and Zn are the lowest in these structures. It was found that statistically significant differences between the animals with electrical stimulation of vagus nerve and the control are observed in the left side of corpus striatum for P (p = 0.04), S (p = 0.02), Cl (p = 0.05), K (p = 0.02), Fe (p = 0.04) and Zn (p = 0.02). The mass fractions of these elements are increased in the group for which the electrical stimulation of vagus nerve was performed. Moreover, the contents of Ca (p = 0.02), Zn (p = 0.07) and Rb (p = 0.04) in substantia nigra of right hemisphere are found to be significantly lower in the group with stimulation of vagus nerve than in the control rats.     

The role of trace elements in the pathogenesis and progress of pilocarpine-induced epileptic seizures

X-ray fluorescence microscopy was applied for topographic and quantitative elemental analysis within the areas of the rat brain that undergo neurodegenerative changes in consequence of pilocarpine-induced seizures. Significant changes in levels of selected elements were observed in epileptic animals. They included an increased tissue content of Ca in the CA1 and CA3 regions of the hippocampus and in the cerebral cortex. The opposite relation was observed for the Cu level in the dentate gyrus and for Zn in the CA3 region of the hippocampus and in the dentate gyrus.     

XANES study of iron displacement in the haem of myoglobin

The XANES (X-ray absorption near edge structure) spectra of deoxy human adult haemoglobin (HbA) and myoglobin (Mb) have been measured at the wiggler beam line of the Frascati synchrotron radiation facility. The XANES are interpreted by the multiple scattering cluster theory. The variations in the XANES between HbA and Mb are assigned to changes in the Fe-porphyrin geometry.     

Microtubule assembly and oscillations induced by flash photolysis of caged-GTP

Microtubule assembly and oscillations have been induced using the rapid liberation of GTP by UV flash photolysis of caged-GTP and monitored by time-resolved X-ray scattering. The flash photolysis method of achieving assembly conditions is much faster than the temperature jump method used earlier (msec vs. s range). However, the structural transitions and their rates are similar to those described previously. This means that the rates of the transitions in microtubule assembly observed before are determined by the protein itself, and not by the rate at which assembly conditions are induced. The advantages and limitations of using the photolysis of caged-GTP in microtubule assembly studies are compared with temperature jump methods. Caged-GTP itself reduces the rate of microtubule assembly and oscillations at mM concentrations, consistent with a weak interaction between the nucleotide analogue and the protein. X-rays are capable of slowly liberating GTP and other breakdown products from caged-GTP, even in the absence of UV flash photolysis, thus causing an apparent X-ray-induced microtubule assembly. This effect depends on the X-ray dose but is independent of the caged-GTP concentrations used here (mM range), suggesting that the breakdown of caged-GTP is caused not by the direct absorption of X-rays by the compound but by another intermediate reaction such as the generation of radicals by the X-rays.Abbreviations DTT dithiothreitol - EGTA ethylene glycol-O,O-bis (2-amino ethyl ether)-N,N,N,N-tetraacetic acid - GDP guanosine-5-diphosphate - GTP guanosine-5-triphosphate - caged-GTP P³-1-(2-nitrophenyl) ethyl ester of GTP - HPLC high performance liquid chromatography - Mt-protein microtubule protein (=tubulin +MAPs) - MAP(s) microtubule-associated protein(s) - PC-tubulin phosphocellulose-purified tubulin - PIPES piperazine-1,4-bis(2-ethane sulfonic acid) - UV ultraviolet light Offprint requests to: E. Mandelkow     

黄土区次生植被恢复对土壤有机碳官能团的影响

以植被空间排列顺序推断时间演替顺序,采用同步辐射软X射线探讨子午岭林区典型植物样地白羊草(Bothriochlor ischaemum)狼牙刺(Sophora viciifolia)辽东栋群落(Quercus liaotungensis)演替过程中土壤有机碳官能团变化。图谱定性分析显示,恢复过程中各植被条件下0-5 cm和20-40 cm土层土壤脂肪-C、酮-C吸收强度明显增加;0-5 cm土层土壤脂肪-C吸收较20-40 cm强,而土壤酮-C吸收较20-40 cm弱。半定量分析结果显示,随植被演替进程,0-5 cm土层土壤各官能团相对百分含量都有所增加,如芳香-C、脂肪-C、酮-C呈现逐渐增加趋势,至辽东栎群落时,20-40 cm土层土壤脂肪-C相对百分含量明显增加。植被恢复过程中,各样地SOC官能团组成基本一致,但植被恢复影响土壤SOC官能团数量变化;植被恢复能促进0-5 cm和20-40 cm土层土壤脂肪-C、酮-C含量增加,并且这种作用随着植被恢复时间的延长逐渐增强,说明植被演替增强了土壤有机碳化学稳定性。