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. 161 .收稿日期：2012-03-15基金项目：山东省自然科学基金(ZR2010HM057)；国家863课题基金(2011AA09070104)作者简介：李莉媛，女，生于1985年，在读博士研究生，主要从事真菌活性代谢产物的提取、分离和鉴定。
E-mail：2001angel007@。
*通讯作者，顾谦群，女，硕士，教授，博士生导师。
E-mail：guqianq@文章编号：1001-8689(2013)03-0161-14多硫代二酮哌嗪类化合物的研究进展李莉媛 朱天骄 李德海 顾谦群*(中国海洋大学 医药学院 海洋药物教育部重点实验室，青岛 266003)摘要：多硫代二酮哌嗪(Epipolythiodioxopiperazines ，ETPs )是一类重要的主要由真菌产生的活性次级代谢产物，其结构特征为二酮哌嗪母核中含有硫桥；ETPs具有广泛的生物活性，例如：抗增殖、细胞毒、免疫抑制、抗病毒以及抗菌等。
大量研究表明，分子中的硫桥结构是ETP类化合物保持活性的关键药效基团。
据统计，截至2011年底，从天然界中共分离得到126个ETP 类化合物。
本文根据其结构中组成氨基酸以及修饰的不同将ETP类化合物分为15种结构类型，并就其来源、结构、生物活性、生物合成及其构效关系研究进行综述。
关键词：多硫代二酮哌嗪；真菌；生物活性；构效关系；生物合成中图分类号：R978 文献标识码： AProgress in the research of epipolythiodioxopiperazinesLi Li-yuan, Zhu Tian-jiao, Li De-hai and Gu Qian-qun(Key Laboratory of Marine Drugs, Chinese Ministry of Education, School of Medicine and Pharmacy,Ocean University of China, Qingdao 266003)Abstract Epipolythiodioxopiperazines (ETPs) are an important class of biologically active compounds mainly produced by fungi. ETPs are characterized by a bridged polysulfide piperazine ring. These metabolites have been found to possess a wide variety of biological activities, including antiproliferative, cytotoxic, immunomodulatory, antiviral, antibacterial and antifungal activities. The crucial structural element responsible for the observed biological properties has been shown to be the sul fi de linkage. According to statistic, up to the end of 2011, 126 ETPs have been isolated from fungi and lichens. In this article, 15 different kinds of ETPs are known according to the diversity of the amino acids of the the core ETP moiety and the modi fi cations of these amino acids. We review the researches on the origins, structures, biological activities, biosynthesis and structure-activity relationships of ETPs.Key words Epipolythiodioxopiperazines; Fungi; Bioactivity; Structure-activity relationship; Biosynthesis 中国抗生素杂志2013年3月第38卷第3期多硫代二酮哌嗪类化合物(e p i p o l y t h i o -dioxopiperazines, ETPs)是一类重要的生物活性化合物，主要由真菌代谢产生，其结构中都含有带硫桥的二酮哌嗪母核。
实验三十四植物叶绿体色素的提取、分离、表征及含量测定摘自王尊本主编,综合化学实验(第二版),第226-244页,北京:科学出版社,2007年9月。
实验三十四植物叶绿体色素的提取、分离、表征及含量测定[1-27]一、叶绿体色素的提取(一) 实验目的1)掌握有机溶剂提取叶绿体色素等天然化合物的原理和实验方法。
2)了解皂化-萃取提取胡萝卜素的原理。
3)了解1,4-二氧六环沉淀法提取叶绿素的原理。
(二) 实验原理植物光合作用是自然界最重要的现象,它是人类所利用能量的主要来源。
在把光能转化为化学能的光合作用过程中,叶绿体色素起着重要的作用。
高等植物体内的叶绿体色素有叶绿素和类胡萝卜素两类,主要包括叶绿素a、叶绿素b、胡萝卜素和叶黄素四种。
它们所呈现的颜色和在叶绿体中含量大约比例见表34.1。
表34.1 高等植物体内叶绿体色素的种类、颜色及含量项目叶绿素类胡萝卜素叶绿素a 叶绿素b 胡萝卜素叶黄素颜色蓝绿色黄绿色橙黄色黄色在叶绿体内各色素含量比例 3 1 2 13 1 叶绿素chlorophylls是叶绿酸的酯,它在植物进行光合作用中吸收可见光,并将光能转变为化学能。
叶绿素是植物进行光合作用所必需的催化剂。
在绿色植物中叶绿素主要以叶绿素a(C55H72O5N4Mg)和叶绿素b(C55H70O6N4Mg)两种结构相似的形式存在,其差别仅是叶绿素a中一个甲基被叶绿素b中的甲酰基所取代。
叶绿素的基本结构见图34.1。
在叶绿素分子结构中含有四个吡咯环,它们由四个甲烯基联结成卟啉环,在卟啉环中央有一个镁原子,它以两个共价键和两个配位键与4个吡咯环的氮原子结合成内配盐,形成镁卟啉。
在叶绿素分子中还有两个羧基,其中一个与甲醇酯化成COOCH3,另一个与叶绿醇酯化成COOC20H39长链。
类胡萝卜素carotenoids是一类不饱和的四萜类碳氢化合物(例如胡萝卜素,carotenes,或它们的氧化衍生物(例如叶黄素类,xanthophylls。
中文摘要基于Keap1-Nrf2通路的蛋清源抗氧化小肽筛选及其作用机制研究抗氧化肽作为一种重要的抗氧化剂，具有安全、活性好、易吸收等优点，已成为研究的热点。
但在目前的抗氧化肽的研究之中，仍存在着如其分子水平作用机制研究不足等一些问题有待解决。
在本文中，我们以优质的食物蛋白——蛋清蛋白作为抗氧化肽的蛋白来源，以可被完整吸收，活性最不易受机体吸收影响的小肽（小肽即二肽和三肽的总和）作为试验的研究目标。
结合与细胞自身抗氧化相关的重要通路Keap1-Nrf2通路，从蛋清源小肽中筛选具有抗氧化作用的蛋清源小肽并研究其对Keap1-Nrf2相互作用的影响，明确小肽基于Keap1-Nrf2通路的抗氧化作用，从分子水平上阐明小肽抗氧化作用机制，为抗氧化肽的研究和应用奠定基础。
本论文主要结论如下：（1）基于分子对接技术初次筛选能直接抑制Keap1-Nrf2相互作用的蛋清源小肽。
首先建立并优化了由8400条小肽组成的蛋清源扩展小肽库，接着以小肽库为配体，从PDB数据库中选择并优化2FLU文件中的Keap1的Kelch区域为受体，以PDB文件2FLU自带配体所形成的结合位点为基础，设计了3个新的结合位点：位点1（中心坐标为x: -4，y: 6，z: 0，半径：21Å），位点2（中心坐标为x: 5，y: 9，z: 1，半径：15Å）和位点3（中心坐标为x: 7.36，y: 8.33，z: 1.77，半径：15Å）。
使用Discovery Studio软件的CDOCKER程序在这3个结合位点上分别进行分子对接，最终筛选出抑制Keap1-Nrf2相互作用能力最强的20条小肽：二肽EK、DK、WE、DW、EY、EW与三肽DKE、QKE、DKD、EDW、DWE、DKK、EEW、EWE、ECD、DET、DEW、DWD、DDW和DKQ。
（2）基于荧光偏振技术再次筛选能直接抑制Keap1-Nrf2相互作用的蛋清源小肽并分析其作用机制。
Spectroscopic Study of the Interaction between Small Molecules and Large Proteins1. IntroductionThe study of drug-protein interactions is of great importance in drug discovery and development. Understanding how small molecules interact with proteins at the molecular level is crucial for the design of new and more effective drugs. Spectroscopic techniques have proven to be valuable tools in the investigation of these interactions, providing det本人led information about the binding affinity, mode of binding, and structural changes that occur upon binding.2. Spectroscopic Techniques2.1. Fluorescence SpectroscopyFluorescence spectroscopy is widely used in the study of drug-protein interactions due to its high sensitivity and selectivity. By monitoring the changes in the fluorescence emission of either the drug or the protein upon binding, valuable information about the binding affinity and the binding site can be obt本人ned. Additionally, fluorescence quenching studies can provide insights into the proximity and accessibility of specific amino acid residues in the protein's binding site.2.2. UV-Visible SpectroscopyUV-Visible spectroscopy is another powerful tool for the investigation of drug-protein interactions. This technique can be used to monitor changes in the absorption spectra of either the drug or the protein upon binding, providing information about the binding affinity and the stoichiometry of the interaction. Moreover, UV-Visible spectroscopy can be used to study the conformational changes that occur in the protein upon binding to the drug.2.3. Circular Dichroism SpectroscopyCircular dichroism spectroscopy is widely used to investigate the secondary structure of proteins and to monitor conformational changes upon ligand binding. By analyzing the changes in the CD spectra of the protein in the presence of the drug, valuable information about the structural changes induced by the binding can be obt本人ned.2.4. Nuclear Magnetic Resonance SpectroscopyNMR spectroscopy is a powerful technique for the investigation of drug-protein interactions at the atomic level. By analyzing the chemical shifts and the NOE signals of the protein in thepresence of the drug, det本人led information about the binding site and the mode of binding can be obt本人ned. Additionally, NMR can provide insights into the dynamics of the protein upon binding to the drug.3. Applications3.1. Drug DiscoverySpectroscopic studies of drug-protein interactions play a crucial role in drug discovery, providing valuable information about the binding affinity, selectivity, and mode of action of potential drug candidates. By understanding how small molecules interact with their target proteins, researchers can design more potent and specific drugs with fewer side effects.3.2. Protein EngineeringSpectroscopic techniques can also be used to study the effects of mutations and modifications on the binding affinity and specificity of proteins. By analyzing the binding of small molecules to wild-type and mutant proteins, valuable insights into the structure-function relationship of proteins can be obt本人ned.3.3. Biophysical StudiesSpectroscopic studies of drug-protein interactions are also valuable for the characterization of protein-ligandplexes, providing insights into the thermodynamics and kinetics of the binding process. Additionally, these studies can be used to investigate the effects of environmental factors, such as pH, temperature, and ionic strength, on the stability and binding affinity of theplexes.4. Challenges and Future DirectionsWhile spectroscopic techniques have greatly contributed to our understanding of drug-protein interactions, there are still challenges that need to be addressed. For instance, the study of membrane proteins and protein-protein interactions using spectroscopic techniques rem本人ns challenging due to theplexity and heterogeneity of these systems. Additionally, the development of new spectroscopic methods and the integration of spectroscopy with other biophysical andputational approaches will further advance our understanding of drug-protein interactions.In conclusion, spectroscopic studies of drug-protein interactions have greatly contributed to our understanding of how small molecules interact with proteins at the molecular level. Byproviding det本人led information about the binding affinity, mode of binding, and structural changes that occur upon binding, spectroscopic techniques have be valuable tools in drug discovery, protein engineering, and biophysical studies. As technology continues to advance, spectroscopy will play an increasingly important role in the study of drug-protein interactions, leading to the development of more effective and targeted therapeutics.。
应用波谱学英文Applications of spectroscopySpectroscopy has a wide range of applications across various scientific disciplines. Some of the common applications of spectroscopy include:1. Chemistry: Spectroscopy is extensively used in chemistry for the identification and analysis of chemical compounds. It helps in determining the chemical composition, molecular structure, and functional groups present in a sample.2. Pharmaceuticals: Spectroscopic techniques are crucial in the drug discovery and development process. They are used for quality control, impurity analysis, and determining the stability of pharmaceutical products.3. Environmental science: Spectroscopy plays a vital role in environmental monitoring and assessment. It is used to evaluate air quality, analyze water pollutants, and identify harmful substances in soil samples.4. Biochemistry and molecular biology: Spectroscopy is employed in studying the structure, function, and dynamics of biological molecules like proteins, nucleic acids, and carbohydrates. Techniques such as UV-Visible spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy are commonly used in this field.5. Material science: Spectroscopy helps in characterizing andstudying various materials and their properties. It is used to analyze the composition, crystal structure, and surface properties of materials such as metals, ceramics, polymers, and semiconductors.6. Astronomy: Spectroscopy is fundamental in studying the properties and composition of celestial objects. Astronomers use spectroscopic techniques to analyze the light emitted or absorbed by stars, galaxies, and other astronomical phenomena to determine their chemical composition, temperature, and motion.7. Forensics: Spectroscopic methods are employed in forensic science for the detection and analysis of trace evidence, such as drugs, explosives, and chemical residues. They are also used in analyzing questioned documents and for the identification of counterfeit or forged materials.8. Food science and agriculture: Spectroscopic techniques are used for analyzing food products, determining their quality, and detecting adulteration. They are also employed in agricultural research for monitoring plant health and analyzing soil fertility. These are just a few examples of the diverse applications of spectroscopy in various fields. Overall, spectroscopy is a powerful analytical tool that enables scientists to study and understand the properties and behavior of substances in a wide range of scientific domains.。
证实2种蛋白相互作用的高分文献在生物学研究中，蛋白质相互作用的研究对于揭示细胞内分子的功能和调控机制至关重要。
下面将介绍两种蛋白质相互作用的高分文献。
1. 文献标题：Structural basis for the recognition and ubiquitination of a single nucleosome residue by Rad6-Bre1发表日期：2024年2月13日主要内容：该文献描述了蛋白质Rad6-Bre1与核小体结构中一个特定残基的相互作用。
通过利用X射线晶体学技术，研究人员解析了Rad6-Bre1与核小体残基的结合模式，并确定了该相互作用的结构基础。
通过表征Rad6-Bre1与该残基的相互作用，研究人员发现该相互作用在细胞染色质修饰和胚胎发育中起到关键作用。
此外，研究人员还揭示了这种相互作用中的部分结构变异对于细胞分化和疾病发展的潜在影响。
2. 文献标题：Dynamic interactions between cancer cells and the endothelium in transendothelial migration mediate the metastatic cascade发表日期：2024年5月15日主要内容：该文献研究了肿瘤细胞与内皮细胞之间的相互作用对转移过程的影响。
通过多种实验方法，包括显微镜观察和细胞粘附性实验，研究人员发现在癌细胞穿越内皮细胞和逃脱血管的过程中，细胞与内皮细胞之间存在动态的相互作用。
通过展示这些相互作用的分子和细胞机制，研究人员阐明了转移级联中的细胞-细胞信号传导途径，并提供了精确控制肿瘤细胞转移的新策略。
这两篇文献都具有较高的分数和重要性，揭示了蛋白相互作用在生物学中的重要性和相关的分子机制。
这些研究为我们了解细胞内分子交互的功能和调控提供了重要的基础。
Valence band x-ray photoelectron spectroscopic studies to distinguish between oxidized aluminum speciesJohn A.Rotole and Peter M.A.Sherwood a)Department of Chemistry,Kansas State University,Manhattan,Kansas66506-3701͑Received2November1998;accepted8February1999͒The determination of the detailed chemical nature of oxidized aluminum species is an essentialrequirement for the study of many important practical aspects associated with aluminum metal andits compounds.While thick oxidizedfilms of aluminum metal can be easily characterized by x-raypowder diffraction when thefilms are crystalline,thin amorphousfilms are very difficult tocharacterize.In this article,a study of the valence band x-ray photoelectron spectrum of aluminumoxides,hydroxides,and oxyhydroxides is reported using monochromatic aluminum K␣X radiation.The valence band spectra obtained are shown to have significant differences for different oxidizedaluminum species,and can be well understood by comparison with spectra generated from clusterand band structure calculations.This study compliments earlier published studies from this researchgroup using achromatic radiation,and demonstrates how the use of monochromatic X radiationallows a more conclusive distinction to be made among oxidized aluminum species.©1999American Vacuum Society.͓S0734-2101͑99͒09004-1͔I.INTRODUCTIONAlthough aluminum metal is highly reactive in the pres-ence of water and oxygen,it is protected by a thin oxidelayer that is mechanically and chemically stable,making itextremely useful for a wide variety of industrial and com-mercial applications.The complex chemistry of thealuminum–oxygen–water corrosion system produces surfacefilms that often contain a variety of compounds.These in-clude the oxides͑␣-Al2O3and␥-Al2O3͒,hydroxides͑bay-erite,Gibbsite,and Nordstrandite͒,and oxyhydroxides͑boe-hmite and diaspore͒that are examined in this article.Thechemistry of the aluminum–water system has been exten-sively documented.1This article represents a careful re-examination of the va-lence band x-ray photoelectron spectra͑XPS͒of compoundsof the aluminum–oxygen–water system.The earlier workwith powder alumina compounds performed in this groupemployed an achromatic Mg K␣X radiation source and the spectra were interpreted with multiple scattered wave X␣cluster type calculations.2The valence band spectra were shown to be adequately explained by the cluster calculations. In this article,we extend our earlier work by collecting the data using monochromatic X radiation and a high resolution spectrometer,and have compared our results with both clus-ter and band structure calculations.Monochromatic X radia-tion has a number of advantages,especially in the valence band region,where the elimination of x-ray satellite radiation can be especially valuable.3The compounds studied have considerable ionic character making a cluster calculation ap-propriate.Nevertheless,these compounds show significant covalent character and may be expected to show some effect from longer range bonding interactions.Thus the energy bands may show some dispersion which could give rise to additional features.We reported such an effect in the case of MoO2in a recent paper.4We will show that differences in the valence band region allow these compounds to be distin-guished.II.EXPERIMENTXPS measurements were made with a VSW HA150spec-trometer͑150mm hemispherical analyzer͒,equipped with a 16-plate multichannel detector system and Al K␣X radiation ͑240W͒produced from a32quartz crystal VSW monochro-mator providing an x-ray linewidth of less than0.2eV.6The base pressure of the instrument is better than10Ϫ9Torr.The spectrometer was operated in thefixed analyzer transmission ͑FAT͒mode with a pass energy of44eV for survey scans and22eV for all core level and valence band data.The spectrometer energy scale was calibrated using copper and all spectra are referenced against the C1s peak of adventi-tious hydrocarbon at284.6eV.6,7All spectral measurements were repeated on multiple occasions with new samples to ensure reproducibility.With the exception of small varia-tions in adventitious hydrocarbon and water content,identi-cal results were obtained for each spectrum.The achromatic data for the oxidized aluminum com-pounds were collected on a VSW HA100instrument with achromic Al X radiation as described previously.2All va-lence band spectra are presented with a nonlinear back-ground removed.5Original monochromatic data with the background included have been published elsewhere.6 The aluminum compounds studied are insulators and ac-quire a severe surface charge under illumination with mono-chromatic x-ray light.A VSW Electron Flood Gun Model EG2operated at2.20A and275V͑the manufacturer’s rec-ommended operating conditions͒was used to eliminate any differential surface charging during spectral measurement.A typical narrowing of nearly0.5eV in the full width at half maximum͑FWHM͒of the Al2p core level compared to the Al2p of the achromatic data was observed,a clear indication that no sample charging occurred during data collection.a͒Electronic mail:escachem@10911091 J.Vac.Sci.Technol.A17…4…,Jul/Aug19990734-2101/99/17…4…/1091/6/$15.00©1999American Vacuum Society␣-Al2O3was purchased from Alfa Chemicals,␥-Al2O3 from Johnson Matthey Chemical and the Gibbsite from Fisher.The bayerite7͓-Al͑OH͒3͔,Nordstrandite8͓Al͑OH͒3͔,and boehmite9͑␥-AlOOH͒were prepared as de-scribed previously2and the diaspore was provided by the ALCOA Technical Center.The bulk purity of these materials was verified by powder x-ray diffraction͑XRD͒using a Scintag XDS2000diffractometer.The instrument was equipped with a Cu K␣source͑x-ray radiation wavelength ϭ1.54059Å͒and was operated at a power of1600W.The basis for diffraction pattern comparison was the on-line JCPDS data base.10The achromatic valence band data were interpreted using a multiple scattered wave X␣calculation for clusters that represented the aluminum ion and its immediate nearest neighbors.These calculations used the same parameters as those reported previously.The calculated spectra were ad-justed such that x-ray satellites are not included,but are the same in all other respects to our earlier published calcula-tions.The band structure calculations were carried out using an extensively modified version of the program CRYSTAL11 which allowed these low symmetry materials to be studied. Crystallographic information was taken from Wycoff,12and from other crystallographic references.13Calculated spectra were generated from the band structure by adjusting the den-sity of states in the valence band for each orbital symmetry type͑O2s and O2p,Al3s͒by the appropriate Scofield atomic photoelectron cross section.14The density of states was then convoluted with a50%mixed Gaussian–Lorentzian product function.15All calculations were per-formed on IBM RISC/6000computers.III.RESULTS AND DISCUSSIONA.Core level XPS studiesAs is the case in most metal systems,corrosion layers of oxidized aluminum are usually composed of rather thin sometimes amorphousfilms that cannot be examined by bulk sensitive techniques such as x-ray diffraction.Detailed knowledge of the aluminum surface composition is of criti-cal importance for various practical applications.16XPS is a surface sensitive analytical technique which allows one to easily distinguish between aluminum metal(Al0)and its oxygen containing compounds(Al3ϩ).This is due to the3 eV chemical shift between the metal and the oxide peaks in the Al2p region.17In addition,the metal peak has a substan-tially smaller FWHM than those of oxidized aluminum. These straightforward characteristics make the Al2p region easy to curvefit and numerous studies have exploited this feature to identify a percentage area resulting from metal or oxidized aluminum.It is also possible to derive an oxidefilm thickness from the area ratio of these two peaks if one is willing to employ the routine assumptions that thefilm is uniform in nature and composition.The Al2p spectra of the oxidized aluminum compounds discussed all show very small differences and the binding energy differences are not sufficiently large for a clear identification of the oxidized species.While many metals exhibit the typical separation observed in the O1s region between oxide,hydroxide,and water,these useful shifts are not present in the aluminum system where their binding energies lie within a range of about1eV,making this region of little value for XPS sur-face analysis.Whereas,in most oxides and hydroxides the hydroxide bond is substantially longer than the oxide bond, this is not the case in aluminum where the Al–O bond is about the same length for oxide and hydroxide bonds.The Al2p,O1s,and O2p binding energies and FWHM for the alumina compounds are given in Table I.As noted previously,2the core chemical shifts do not allow these com-pounds to be effectively distinguished.Significant variations are seen in the FWHM of the O1s peak shown in Table I. The narrowest FWHM of1.58eV is observed for␣-Al2O3 and the widest of3.10eV for the-oxyhydroxide,diaspore. The FWHM of the hydroxides range from1.82eV for Gibb-site up to2.46eV for bayerite.The␥oxide posseses an anomalously large FWHM of2.78eV,wider than all the hydroxides and on the order of the oxyhydroxide boehmite at2.77eV.B.Valence band XPS studiesIn an earlier paper,2we demonstrated that the valence band region below15eV binding energy provides meaning-T ABLE I.Spectral features of Al2p,O1s,and O2s XPS core levels of aluminum compounds.The binding energies͑eV͒of line͑a͒and thefirst set of FWHM͑eV͒in parentheses on line͑b͒are monochromatic data.The second set of parentheses on line͑b͒are achromic FWHM͑eV͒.Compound Al2p O1s O2s␣-Al2O3͑a͒74.14530.6823.10͑b͒͑1.35͒͑1.58͒͑1.9͒͑3.52͒͑3.85͒␥-Al2O3͑a͒74.30531.0823.57͑b͒͑2.46͒͑2.78͒͑2.9͒͑4.15͒͑4.28͒Al͑OH͒3-Nordstrandite͑a͒74.47531.4424.16͑b͒͑1.75͒͑2.22͒͑2.9͒͑4.15͒͑4.82͒-Al͑OH͒3-bayerite͑a͒74.31531.4424.70͑b͒͑1.75͒͑2.46͒͑3.0͒͑4.53͒͑4.77͒Al͑OH͒3-Gibbsite͑a͒74.63531.6824.22͑b͒͑1.58͒͑1.82͒͑2.1͒͑3.65͒͑4.33͒-AlOOH-diaspore͑a͒74.20531.4424.04͑b͒͑1.67͒͑3.10͒͑2.95͒͑5.10͒͑4.45͒␥-AlOOH-boehmite͑a͒74.47531.1624.09͑b͒͑1.59͒͑2.77͒͑2.1͒͑5.16͒͑5.24͒T ABLE II.Separation͑eV͒of the two peaks in the valence band region below1.5eV for valence band spectra excited with achromatic and mono-chromatic X radiation.Compound Achromatic separation Monochromatic separation ␣-Al2O3 4.3 4.4␥-Al2O3 3.7 3.2Al͑OH͒3-Nordstrandite 4.3 4.3-Al͑OH͒3-bayerite 4.3 3.9Al͑OH͒3-Gibbsite 3.5 3.4-AlOOH-diaspore 5.2 4.2␥-AlOOH-boehmite 4.8 3.4J.Vac.Sci.Technol.A,Vol.17,No.4,Jul/Aug1999ful differences between the compounds discussed in this ar-ticle.These earlier data,collected with achromatic Mg K ␣radiation are shown in Fig.1.Figure 1also shows how these data can be compared with spectra calculated from multiple scattered wave X ␣calculations which were reported in an earlier paper.2Figure 2shows the new valence band data collected using monochromatic Al K ␣radiation.The calcu-lated spectra shown in Fig.2have been adjusted for the different Al K ␣cross sections,and the use of monochro-matic radiation which of course has no x-ray satellites.The component peaks of the calculated spectra have a FWHM of about 1.0eV ͑reduced from 1.2eV ͒to reflect the improved linewidth of the monochromatic radiation,and the high reso-lution of the XPS instrument.K ␣3,4x-ray satellites from the O 2s region change the valence band spectrum obtained with achromatic X radiation by providing extra intensity in the outer valence band region ͑below 16eV binding energy ͒,altering apparent peak separations and linewidths.These ef-fects,together with enhanced resolution,result in substantial differences between the monochromatic and achromatic va-lence band data.The effect that the K ␣3,4x-ray satellites have on the va-lence band spectrum obtained with achromatic X radiation is illustrated in Fig.3.Significant intensity is seen to arise in the region below 15eV,especially for ␥-Al 2O 3͓Fig.3͑a ͔͒,the hydroxide Gibbsite ͓Fig.3͑b ͔͒,and the oxyhydroxide di-aspore ͓Fig.3͑c ͔͒.The figure is constructed by overlaying the X ␣cluster calculation spectrum generated with x-ray sat-ellites with the same spectrum generated in the absence of x-ray satellites.The dark portion represents the intensity re-sulting from the x-ray satellites.This surplus intensity sig-nificantly alters the spectrum by changing the relative inten-sities of the peaks in the low binding energy valence band structure of interest.Furthermore,the satellite intensity adds an additional feature in the form of a shoulder to higher binding energy.Careful examination of Fig.1reveals distinct differences among the valence band spectra of these compounds.In gen-eral,visual inspection of these valence band spectra focuses on the two peaked structure in the low binding energy region ͑below 15eV ͒of the spectra.Fluctuations in the relative intensities and separations of these two features vary among the different compounds allowing for specificity inspectralF IG .1.Achromatic XPS valence band spectra of aluminum compounds compared to X ␣cluster calculations.͑i.a,ii.a ͒␣-and ␥-Al 2O 3powder standard spectra compared to ͑i.b,ii.b ͒calculation;͑i.c,ii.c ͒the hydroxides bayerite and Gibbsite compared to ͑i.d,ii.d ͒calculation;͑i.e,ii.e ͒the oxy-hydroxides boehmite and diaspore compared to ͑i.f,ii.f ͒calculation.F IG .2.Monochromatic XPS valence band spectra of aluminum compounds compared to X ␣cluster calculations.͑i.a,ii.a ͒␣-and ␥-Al 2O 3powder standard spectra compared to ͑i.b,ii.b ͒calculation;͑i.c,ii.c ͒the hydroxides bayerite and Gibbsite compared to ͑i.d,ii.d ͒calculation;͑i.e,ii.e ͒the oxy-hydroxides boehmite and diaspore compared to ͑i.f,ii.f ͒calculation.JVST A -Vacuum,Surfaces,and Filmsassignment.Furthermore,some variation in the O 2s width is observed.Table II provides the peak separations in the va-lence band spectra of these compounds for achromatic and monochromatic X radiation.The valence band region of the spectrum provides infor-mation that is derived from the way in which atomic orbitals overlap to form energy bands.Therefore,the overall shape of this region arises from the nature of the bonding that occurs in the compound making it very sensitive to subtle changes in the chemical state.As a result,the valence band supplies complimentary and often enhancing information when used in conjunction with core level data.The variation in the va-lence band regions may be understood from a very simple viewpoint.If these compounds were completely ionic,one would expect their valence band region to be composed of two features,a single O 2s and a single O 2p .The slightly covalent nature of these compounds,however,results in the presence of some Al 3s and Al 3p characters which would be absent in a completely ionic Al 3ϩion.This interaction would lead to an Al–O bonding feature at a higher binding energy and an Al–O nonbonding feature at a lower binding energy thus providing the two observed valence band fea-tures.Slight changes in the Al–O bond strength alter the relative intensities and separation of those two features.When the Al–O bond strength weakens with lengthening of the Al–O bond,the general character of the bonding be-comes more ionic in nature and the separation between the two features is reduced.This view can continue until the Al and O atom are completely separated and only the com-pletely ionic Al 3ϩion is present leaving again a spectrum with only one distinct O 2s peak.This oversimplified picture is consistent with reduced separation of these two features in the valence band spectrum of the ␥oxide as compared to the ␣oxide.The average Al–O bond length is longer in the ␥oxide and it is observed experimentally that the separation in the ␥alumina is smaller than that of the ␣oxide.The core-like O 2s region is similar for all of these com-pounds except in the case of the oxyhydroxides boehmite and diaspore in which a distinct increase in FWHM is ob-served.In metal systems,the O 2s level is well separated from the valence levels thus causing this level to behave much like the O 1s core level.It has been shown that in some cases small amounts of chemical bonding can amplify the effects observed in the O 2s level.18Other studies by this group 19–22and others 23have discussed the use of O 2s spec-troscopy for analytical purposes.1.Oxide valence bandsOf all the compound subgroups ͑oxide,hydroxide,oxyhy-droxide ͒,the most notable differences observed are those between the alpha and the ␥oxide.The apparent difference in the separation of the two main features in the outer va-lence band region for the alpha and ␥oxides increases from 0.6to 1.2eV when monochromatic radiation is used.The O 2s FWHM is much less in spectra obtained with mono-chromatic x rays.2.Hydroxide valence bandsThe highly disordered Gibbsite structure ͑whose OH bondlengths vary from 1.8to 2.1Å͒has a calculated outer valence band region that has the least resolved ‘‘two-peak’’feature.The more ordered bayerite structure is predicted to have a clearly resolved two-peak feature in this region.The experimental data support these predictions,with the separa-tion between the two peaks being significantly less for the bayerite spectra obtained with monochromatic radiation.3.Oxyhydroxide valence bandsExamination of the achromatic data for boehmite reveals a spectrum much like that for the achromatic spectrum of bayerite.In the previous paper,2it was concluded that boeh-mite had decomposed on the surface prior to analysis to give a surface layer of the hydroxide bayerite.The spectra ob-tained with monochromatic radiation have outer valence band regions that are much narrower,and have more clearly resolved features.We believe that because the spectra ob-tained with monochromatic radiation for boehmite and di-aspore are significantly different in the outer valence band region ͑0.8eV difference in the separation in the two-peak structure ͒,and have the broadest O 2s features,that these spectra are consistent with AlOOH.All our calculations ͑cluster and band structure ͒indicate two resolved peaks in the O 2s region.While we do not observe this experimen-tally ͑perhaps because of a relatively greater FWHM in the O 2s region ͒,the greater FWHM for the O 2s region is con-sistent with two overlapping features.C.Band structure studiesThe band structure of ␣-Al 2O 3has been investigated by a number of workers 24–26and its valence band spectrum has been reported by others.27–30Band structures of the other compounds in the system,however,have not beenreported.F IG .3.Contribution of x-ray satellites to the XPS valence band spectra of ͑a ͒␥-Al 2O 3,͑b ͒Gibbsite,͑c ͒diaspore.The dark portions of the spectra represent x-ray satellite contributed intensity.J.Vac.Sci.Technol.A,Vol.17,No.4,Jul/Aug 1999Figure 4shows the calculated spectra for ␣-Al 2O 3,␥-Al 2O 3,bayerite,diaspore and boehmite generated from band struc-ture calculations compared to monochromatic data for the compounds.We have not shown a calculated spectrum for Gibbsite because we have not been able to satisfactorily complete the calculated valence band spectrum of this com-pound because of its very low symmetry.1.OxidesIn the case of ␥-Al 2O 3,we have performed two calcula-tions which recognize the uncertainty about the crystal struc-ture of this compound.The two possible structures are the defect spinel structure and the defect hausmannite structure.2One of our calculations ͑shown in Fig.4͒is based upon the spinel structure which is the most commonly quoted struc-ture for the oxide.Our calculation uses the fully populated spinel lattice,and thus has too many electrons that give rise to a very low intensity peak in the calculated spectrum at low binding energies ͑off the range shown in Fig.4͒.The other calculation used a hausmannite structure in a deficient formthat had the right number of electrons but overemphasized the number of tetrahedral sites ͑twice as many as octahedral rather than the correct number which is the reverse of this ͒.In both cases,the calculations predicted a smaller separation between the two peaks in the ␥-Al 2O 3than in the ␣-Al 2O 3form as observed experimentally.2.HydroxidesOnly one of the hydroxides ͑bayerite ͒had its band struc-ture calculated,Gibbsite has been excluded for the reasons given above.The calculated spectrum indicates a low bind-ing energy feature ͑at rather too high a binding energy ͒which may be present in the experimental spectrum as a slight shoulder.3.OxyhydroxidesThe calculated and experimental spectra show the same features,with the higher intensity low binding energy feature seen for diaspore correctly predicted in the calculated spec-trum.The outer valence band region is predicted as being somewhat narrower in boehmite ͑after setting the O 2s peak separation to be the same for both oxyhydroxides ͒as seen experimentally ͑Table II ͒.The low binding energy shoulder predicted in the calculation for boehmite can be seen in the experimental data.4.Energy bandsThe energy bands for the aluminum compounds are shown in Fig.5.To save space only one direction in the first Brillouin zone is shown.It can be seen that the bands are fairly flat indicating that the cluster model is not inappropri-ate.On the other hand,there is some significant dispersion ͑i.e.,variation from a flat band potential ͒in the bands sug-gesting that there are some effects arising from long range interactions in these solids.These potential ‘‘band structure’’effects are thus likely to be significant,especially as they may give rise to distinctive features that may assist in the distinction between similar,but characteristically different valence band spectra.We are currently working with larger basis sets,which can result in convergence problemsforF IG .4.Monochromatic XPS valence band spectra of aluminum compounds compared to band structure calculations.͑i.a,ii.a ͒␣-and ␥-Al 2O 3powder standard spectra compared to ͑i.b,ii.b ͒calculation;͑i.c ͒the hydroxide bay-erite compared to ͑i.d ͒calculation;͑i.e,ii.e ͒the oxyhydroxides boehmite and diaspore compared to ͑i.f.,ii.f ͒calculation.F IG .5.Energy bands for aluminum compounds.Only the occupied states of the valence band are shown.͑a ͒␣-Al 2O 3;͑b ͒␥-Al 2O 3;͑c ͒Al ͑OH ͒3-bayerite;͑d ͒AlOOH-boehmite;and ͑e ͒AlOOH-diaspore.JVST A -Vacuum,Surfaces,and Filmsthese low symmetry compounds,to determine if further im-provement between the experimental valence band data and calculations can be obtained.However,it is clear that the band structure calculations presented here provide a reason-able interpretation of the valence band spectra.IV.CONCLUSIONSA careful re-examination of the valence bands of the com-pounds of the aluminum–oxygen–water system was per-formed.The data were recollected with Al K␣monochro-matic radiation at high resolution.These new data provide spectra with improved linewidth and the elimination of x-ray satellite features.This allows significant additional spectro-scopic features to be identified which enhances our ability to distinguish between these compounds.The band structure calculations appear overall to provide the best description of the spectral features,and support the experimental observa-tion of differences in the valence band spectra of these com-pounds.This work clearly demonstrates that the oxides,hy-droxides,and oxyhydroxides of oxidized aluminum may be distinguished one from another through the use of valence band x-ray photoelectron spectroscopy. ACKNOWLEDGMENTSThis material was based upon work supported by the Na-tional Science Foundation under Grant No.CHE-9421068. The ernment has certain rights in this material.The authors are grateful to Dr.Brian Strohmeier of the Alcoa Technical Center for providing the diaspore sample.1Oxides and Oxide Films,edited by R.S.Alwitt and J.W.Diggle͑Marcel Dekker,New York,1974͒,Vol.4,pp.169–254.2S.Thomas and P.M.A.Sherwood,Anal.Chem.64,2488͑1992͒.3P.M.A.Sherwood,J.Vac.Sci.Technol.A15,520͑1997͒.4H.Hixson and P.M.A.Sherwood,Chem.Mater.8,2643͑1996͒.5A.Proctor and P.M.A.Sherwood,Anal.Chem.54,13͑1982͒.6J.A.Rotole and P.M.A.Sherwood,Surf.Sci.Spectra5,11͑1998͒;5,18͑1998͒;5,25͑1998͒;5,32͑1998͒;5,39͑1998͒;5,46͑1998͒;5,53͑1998͒.7Handbook of Preparative Inorganic Chemistry,edited by G.Brauer,2nd ed.͑Academic,New York,1963͒,Vol.1.8U.Z.Hauschild,Inorg.Chem.324,15͑1963͒.9T.L.Barr,Crit.Rev.Anal.Chem.22,229͑1991͒.10JCPDS,International Center for diffraction Data,1601Park Lane,Swar-thmore,PA19081-2389.11C.Pisani,R.Dovesi,and C.Roetti,Hartree-Fock Ab Initio Treatment of Crystalline Systems,Lecture Notes in Chemistry,48͑Springer,Berlin, 1988and QCPE577͒.12R.W.G.Wycoff,Crystal Structures,2nd ed.͑Interscience,New York, 1963͒,Vols.1–3.13G.Ervin,Acta Crystallogr.5,103͑1952͒.14J.H.Scofield,J.Electron Spectrosc.Relat.Phenom.8,129͑1976͒.15P.M.A.Sherwood,in Practical Surface Analysis by Auger and X-ray Photoelectron Spectroscopy,edited by D.Briggs and M.P.Seah͑Wiley, New York,1983͒,Appendix3.16N.J.Havercroft and P.M.A.Sherwood,J.Vac.Sci.Technol.A16,1112͑1998͒.17D.A.Shirley,in Advances in Chemical Physics Vol.XXIII,edited by I. 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目 录1 安全指导 (1)2 Junior-PAM组件及安装 (2)2.1 Junior-PAM组件 (2)2.2 仪器的组装及软件安装 (3)2.2.1 Junior-PAM组装 (3)2.2.2 安装WinControl-3软件 (3)3 PAM 荧光测定技术和饱和脉冲分析 (4)3.1 调制荧光（脉冲－振幅－调制） (4)3.2 饱和脉冲分析法 (6)4 基本实验 (8)4.1 Fo'-Mode的测量 (8)4.2 荧光诱导曲线 (9)5 Junior-PAM的操作 (11)5.1 初始窗口/主窗口 (11)5.1.1 Box (1)主菜单 (12)5.1.2 Box (2) 数据管理和图形形状的设定 (13)5.1.3 Box (3) 侧栏 (14)5.1.4 Box (4) 饱和脉冲分析数据 (15)5.1.5 Box (5) 在线数据 (16)5.1.6 Box (6) 饱和脉冲触发 (16)5.1.7 Box(7) 实验的参数及程序 (16)5.1.8 Box (8) 图形形状及荧光仪设置 (17)5.1.9 Box (9) 坐标轴调整 (18)5.1.10 选择纵坐标及进行文本注释 (18)5.1.11 图表区-选择数据 (18)5.2 诱导曲线窗口 (19)5.3 光响应曲线 (19)5.4 饱和脉冲图形窗口 (19)5.4.1 Box (2) 数据管理 (19)5.4.2 Box (3) 侧栏 (20)5.4.3 饱和脉冲面板 (20)5.5 报告文件窗口 (21)5.5.1 Box (11) 数据管理 (21)5.5.2 Box (12) 报告数据区域 (22)5.6 设置窗口 (23)5.6.1 Box (14) 设备名 (23)5.6.2 Box (15) 测量相关设置 (23)5.6.3 Box (16) 光源相关设置 (24)5.6.4 Box (17) 程序相关设置 (25)5.6.5 Box (18) 光强列表 (25)5.7 系统设置 (26)6 参数符号及计算公式 (27)6.1 相对荧光产量 (27)6.1.1 样品暗适应后进行测定 (27)6.1.2 对光下样品进行测量 (27)6.2 荧光淬灭参数 (28)6.3 相对电子传递速率（ETR） (29)6.4 光响应曲线 (30)6.5 本章参考文献 (32)7 JUNIOR-PAM 技术参数 (34)8 2007-2008年部分PAM文献 (35)1 安全指导1、仪器安装使用前首先阅读安全指导和操作指南2、注意所有的安全警告3、仪器要远离热源4、仪器应放在通风的环境中5、保持仪器清洁，注意防尘，远离水和潮湿的地方6、只能用干布清洁仪器7、不要自行打开仪器，仪器应由专业人员维修8、不要用光纤对着眼睛以免强光灼伤！！！9、禁止过度弯曲光纤！！！10、每次测量开始前应通过调节“Gain”、测量光光强使只打开测量光时的荧光Ft(即Fo)小于60011、不允许液体或者其它东西进入仪器内部12、仪器使用时请轻拿轻放13、仪器只允许通过USB供电（5V）2 Junior-PAM组件及安装2.1 Junior-PAM组件a) Junior-PAM主机b) USB连接线c）包含WinControl-3软件和英文版操作手册的光盘d) 英文版操作手册e）400×1.5 mm(长×直径)光纤f) 叶夹和磁性叶夹g） 荧光标准图2.1 Junior-PAM的组成2.2 仪器的组装及软件安装2.2.1 Junior-PAM组装¾将光纤较粗的一端插到Junior-PAM主机的光纤接口，轻轻的将光纤插到底，锁紧。
a rXiv:075.3638v1[astro-ph]24May27Discovery of Two Spectroscopically Peculiar,Low-Luminosity Quasars at z ∼41Eilat Glikman 2,S.G.Djorgovski 2,Daniel Stern 3,Milan Bogosavljevi´c 2,&Ashish Mahabal 2ABSTRACT We report the discovery of two low-luminosity quasars at z ∼4,both of which show prominent N IV ]λ1486˚A emission.This line is extremely rare in quasar spectra at any redshift;detecting it in two out of a sample of 23objects (i.e.,∼9%of the sample)is intriguing and is likely due to the low-luminosity,high-redshift quasar sample we are studying.This is still a poorly explored regime,where contributions from associated,early starbursts may be significant.One interpretation of this line posits photoionization by very massive young stars.Seeing N IV ]λ1486˚A emission in a high-redshift quasar may thus be understood in the context of co-formation and early co-evolution of galaxies and their su-permassive black holes.Alternatively,we may be seeing a phenomenon related to the early evolution of quasar broad emission line regions.The non-detection (and possibly even broad absorption)of N V λ1240˚A line in the spectrum of one of these quasars may support that interpretation.These two objects may signal a new faint quasar population or an early AGN evolutionary stage at high redshifts.Subject headings:quasars:emission lines —quasars:general —galaxies:evo-lution —quasars:individual (DLS1053−0528)—quasars:individual (ND-WFS1433+3408)1.IntroductionA growing body of theoretical models backed by emerging observational evidence paints a picture of joint formation and evolution of galaxies and quasars;for reviews see,e.g., the proceedings edited by Ho(2004),Djorgovski(2005),and references therein.In this picture,merger-driven build-up of massive halos trigger both vigorous star formation and fuel the central black hole igniting a quasar(Kauffmann&Haehnelt2000;Hopkins et al. 2006).AGN feedback is now believed to be an essential factor in the formation and evolution of galaxies.Understanding the AGN-starburst connection is especially interesting at high redshifts,as we probe the epoch of the initial assembly of massive galaxies.Observationally, this is challenging in the case of host galaxies of luminous Type I quasars,as the AGN activity far outshines any star formation related processes.However,by observing lower luminosity Type I quasars or Type II(e.g.,obscured)quasars,the blinding intensity of the central engine is reduced,allowing properties of the host galaxy to be studied.In this Letter,we report the discovery of two low-luminosity Type I quasars where we may be seeing evidence for a simultaneous starburst with a top-heavy IMF,and AGN activity.Both quasars show a prominent,moderately-broad N IV]λ1486˚A emission line, which is rarely seen in quasar spectra at any redshift.2.ObservationsThe two objects are low-luminosity quasars at z∼4,found in a sample of23objects used to measure the low-luminosity end of the quasar luminosity function(QLF)at z∼4 (Bogosavljevi´c et al.2007).The parent sample ranges in redshift from z=3.7to z=5.1. The candidates for this sample were selected from the NOAO Deep Wide Field Survey(ND-WFS)Bo¨o tesfield(Jannuzi&Dey1999)and the Deep Lens Survey(DLS;Wittman et al. 2002).Quasar candidates were selected based on the colors of simulated quasars in the 3.5<z<5.2redshift range,incorporating a range of spectral slopes,Lyαequivalent widths,and intervening neutral hydrogen absorbers,down to the limiting magnitude of R=24.Finding charts for the two N IV]quasars are presented in Figure1.Details of the survey and candidate selection will be presented by Bogosavljevi´c et al.(2007).We obtained spectroscopic followup for our candidates on UT2006May20through 22with the Low-Resolution Imaging Spectrometer(LRIS;Oke et al.1995)on the Keck I telescope.Only the red camera was used,with the400lines mm−1grating blazed at 8500˚A.The spectra were reduced using BOGUS,an IRAF package developed by Stern,Bunker,&Stanford1for reducing slitmask data,modified slightly for our single-slit data. DLS1053−0528was discovered in a1800second exposure of a candidate in the DLS F4field and NDWFS1433+3408was identified from a900second exposure of a candidate in the Bo¨o tesfield.Thefinal spectra are presented in Figure2and the source parameters are listed in Table1.Several things are worth noting.First is the detection of the N IV]λ1486˚A emission lines,which is particularly strong in DLS1053−0528(e.g.,in comparison with the C IV λ1549˚A line).At the same time,the commonly observed N Vλ1240˚A emission line is entirely absent,and may even be seen in absorption in DLS1053−0528(see Figure3).This latter observation is somewhat unusual since the C IVλ1549˚A line in this source does not show broad absorption.While broad absorption lines are seen in approximately10%of quasars,such quasars will show broad absorption in all permitted species.The permitted emission lines for the two N IV]quasars are narrow compared with typical quasar line-widths.A single component Voigtfit to Lyαmeasures a full-width at half-maximum(FWHM)of∼500km s−1.Since the blue side of the Lyαprofile is absorbed, we forced symmetry in the line by mirroring the red side of the line profile over the peak wavelength.To search for a broad-line component wefit a two-component Gaussian to the Lyαprofile.For DLS1053−0528,we measure a narrow-line FWHM of434km s−1 and a broad-line FWHM of1727km s−1.In NDWFS1433+3408we measure a narrow-line FWHM of713km s−1and a broad-line FWHM of3015km s−1.Therefore,while these objects have significant contribution from their narrow-line components(50%of the lineflux in DLS1053−0528and24%in NDWFS1433+3408),their broad-line velocities of >1000km s−1place them in the quasar ing the velocity widths from the broad-line component of Lyαas a proxy for C IV or Hβ,and the black hole mass estimators from Dietrich&Hamann(2004)and Vestergaard&Peterson(2006),we obtain M BH∼(5−15)×106M⊙for DLS1053−0528and M BH∼(32−77)×106M⊙for NDWFS1433+3408. Consistent with the somewhat narrow line widths(for a broad-lined quasar)and the low-luminosity,these inferred black hole masses are much lower than the masses inferred for luminous quasars.On UT2007January23we imaged DLS1053−0528with the Slit-viewing Camera (SCAM)of the NIRSPEC instrument on Keck-II.We used the J-bandfilter and imaged the source with a9-point dither pattern of120second exposures,for a total of1080sec-onds at the position of the quasar.The seeing was0.′′7.The data were reduced using the XDIMSUM package in IRAF.We calibrate our image to the2MASS J-band using a15.26magnitude point source that is detected in thefield.The quasar is not detected,with a3σmagnitude threshold of24.9(Vega)magnitudes.NDWFS1433+3408was observed as part of FLAMEX,a near-infrared survey overlap-ping4.1deg2of the Bo¨o tes area(Elston et al.2006).The quasar is detected at∼5σin both the J and K s images.In addition,this quasar was observed in the IRAC Shallow Survey, an8.5deg2Spitzer imaging survey of the Bo¨o tesfield(Eisenhardt et al.2004).The sourceis faintly(<5σ)detected at3.6µm and4.5µm at19.0and19.1(Vega)magnitudes,respec-tively.We list the4′′aperture magnitude from the FLAMEX catalog as well as the IRAC detections in Table1.The quasar is not detected in the5.8µm or8.0µm images,whose5σdetection thresholds are15.9and15.2(Vega;3′′aperture)magnitudes,respectively.Note that the[3.6]−[4.5]colors for this object are quite blue compared to typical mid-infrared colors of AGN(e.g.,Stern et al.2005).The result is not unexpected:at z∼4,Hαemissionis shifted into the shortest wavelength IRAC band,causing AGN at this redshift to have blue[3.6]−[4.5]colors.Figure4plots the spectral energy distributions(SEDs)of both objects,using all avail-able photometry.We compare this SED with the SDSS composite spectrum(Vanden Berk et al. 2001)as well as the starburst template from Kinney et al.(1996)with E(B−V)<0.1,both shifted to z=3.88.Significant deviations are seen,especially at long wavelengths where both objects appear much bluer than the average quasar and starbusrt spectra.The SED of NDWFS1433+3408seems more consistent with the starburst spectrum,at least in the rest-frame ultraviolet,but DLS1053−0528deviates strongly from both.3.DiscussionThe most striking feature in the spectra of these two faint quasars is the presence of the extremely unusual N IV]λ1486˚A emission line.The quasar population generally shows remarkable spectroscopic similarity out to the highest observed redshifts,with no obvious signs of evolution(e.g.,Fan2006).None of the published average quasar spectral templates show any trace of the N IV]λ1486˚A line(Figure5).The top spectrum(solid line)is the SDSS quasar composite from Vanden Berk et al.(2001).The quasars that contribute to this part of the spectrum are at redshifts comparable to the quasars in our sample,but they sample the bright end of the quasar luminosity function.The bottom spectrum(dotted line)is the HST UV composite spectrum from Telfer et al.(2002).The objects contributing to this part of the spectrum are low-redshift quasars(z<1).The only strong detection of this line in a quasar that we are aware of is in the nitrogenquasar Q0353−383(Osmer&Smith1980).This object has been analyzed by Baldwin et al. (2003)who derive an overabundance of nitrogen by a factor as high as5−15times solar in this object.A sample of apparently nitrogen-rich quasars was compiled by Bentz et al. (2004)from the6650quasars in the SDSS DR1database with1.6<z<4.1(allowing for the detection of N IV]λ1486˚A and N III]λ1750˚A).Bentz et al.(2004)estimate that“nitrogen-enriched”quasars make up at most0.2%−0.7%of quasars.Their sample has luminosities in the range M i=−28.07to M i=−24.63.We found two such objects in a sample of23 quasars(8.7%)that are concentrated at z∼4and are0.7magnitudes deeper than the SDSS sample.They found20quasars with equivalent widths≥2.0˚A in both nitrogen lines and 33quasars with EWs≥2.0˚A in only one of the nitrogen lines.In these quasars the N IV]λ1486˚A line is accompanied by similarly strong N Vλ1240˚A and N III]λ1750˚A,the latter of which is outside our wavelengths range.Wefit Voigt profiles to the nitrogen lines in our spectra(as well as to Lyαand C IVλ1549˚A)to determine linefluxes,equivalent widths and dispersion velocities(Table2,Figure3).The mean N IV]λ1486˚A equivalent widths for the Bentz et al.(2004)sample is3.7˚A(σEW=1.5˚A),while the equivalent widths of N IV]λ1486˚A for our quasars are280.2˚A for the DLS source and24.5˚A for the Bo¨o tes source. This,combined with the non-detection(and possible absorption)of N Vλ1240˚A in the DLS source suggests that these quasars may be of a different ilk than the“nitrogen-enriched”population.In galaxies with no AGN signature,we are aware of only two other instances of this line being seen in the high-redshift Universe.One especially telling detection is in the spectrum of the Lynx arc,a gravitationally lensed HII galaxy at z=3.357(Fosbury et al.2003).The line intensities in this object’s spectrum,strong N IV]λλ1483,1487˚A,O III]λλ1661,1666˚A, and C III]λλ1907,1909˚A,as well as the absence of N Vλ1240,favor a hot(80,000K) blackbody over an AGN as the ionizing source.The Fosbury et al.(2003)modeling of the spectrum suggests a top heavy IMF,which is especially interesting since such an IMF is now believed to be characteristic of early,metal poor star formation,e.g.Population III stars. Alternatively,Binette et al.(2003)suggest an obscured AGN as the photoionizing source of the Lynx arc.Their model invokes dense absorbing gas near a central AGN thatfilters the powerlaw and mimicks the hot blackbody suggested by Fosbury et al.(2003)This model does require at least a weak N Vλ1240˚A line detection.The second known N IV]λ1486˚A emitter is a z=5.55galaxy in the GOODS survey (Vanzella et al.2006;Fontanot et al.2007).Similar to the Lynx arc,this object shows an extremely strong Lyαline as well as N IV]λ1486˚A,while N Vλ1240˚A is absent.No detailed analysis has been published on this source as yet.An alternative possibility is that we are witnessing an evolutionary effect in the quasarbroad-emission-line region.This is suggested by the traditional broad-line shape of N IV λ1486˚A in DLS1053−0528as well the peculiar absence(or even absorption)of N Vλ1240˚A in its spectrum.Detailed modeling of such effects is beyond the scope of this paper.The detection of such a rare emission line in two out of23z∼4quasars in our sample (i.e.,∼9%of the sample)suggests that it occurs more commonly in low luminosity quasars at high redshifts,a regime which we are now exploring systematically for thefirst time.At these luminosities we are probing deep into the QLF where the effects of a luminous star-bursts can be detected more easily;if there is an evolutionary trend,such phenomena may be present at high redshifts,and not in the better studied quasar samples at z∼0−2. As the sample sizes of comparably faint AGN at these redshifts increase,we will be able to determine whether this is indeed a systematic evolutionary effect related to the early stages of co-formation and co-evolution of galaxies and AGN.We thank the referee for helpful feedback.We are grateful to the staffof W.M.Keck observatory for their assistance during our observing runs.This work was supported in part by the NSF grant AST-0407448,and by the Ajax foundation.The work of DS was carried out at Jet Propulsion Laboratory,California Institute of Technology,under a contract with NASA.REFERENCESBaldwin,J.A.,Hamann,F.,Korista,K.T.,Ferland,G.J.,Dietrich,M.,&Warner,C.2003, ApJ,583,649Bentz,M.C.,Hall,P.B.,&Osmer,P.S.2004,AJ,128,561Binette,L.,Groves,B.,Villar-Mart´ın,M.,Fosbury,R.A.E.,&Axon,D.J.2003,A&A, 405,975Bogosavljevi´c,M.,Glikman,E.,Djorgovski,S.G.,Mahabal,A.,Stern,D.,Jannuzi,B.T.&Dey,A.,2007,in preparationDietrich,M.,&Hamann,F.2004,ApJ,611,761Djorgovski,S.G.2005,in The Tenth Marcel Grossmann Meeting.,ed.M.Novello,S.Perez Bergliaffa,&R.Ruffini,Singapore:World Scientific Publishing,422 Eisenhardt,P.R.et al.2004,ApJS,154,48Elston,R.J.et al.2006,ApJ,639,816Fan,X.2006,New Astronomy Review,50,665Fontanot,F.,Cristiani,S.,Monaco,P.,Nonino,M.,Vanzella,E.,Brandt,W.N.,Grazian,A.,&Mao,J.2007,A&A,461,39Fosbury,R.A.E.et al.2003,ApJ,596,797Ho,L.C.,ed.2004,in Coevolution of Black Holes and Galaxies,Cambridge,UK:Cambridge University Press,496Hopkins,P.F.,Hernquist,L.,Cox,T.J.,Di Matteo,T.,Robertson,B.,&Springel,V.2006, ApJS,163,1Jannuzi,B.T.,&Dey,A.1999,in ASP Conf.Ser.191,Photometric Redshifts and the Detection of High Redshift Galaxies,ed.R.Weymann et al.,111Kauffmann,G.,&Haehnelt,M.2000,MNRAS,311,576Kinney,A.L.,Calzetti,D.,Bohlin,R.C.,McQuade,K.,Storchi-Bergmann,T.,&Schmitt,H.R.1996,ApJ,467,38Oke,J.B.,et al.1995,PASP,107,375Osmer,P.S.,&Smith,M.G.1980,ApJS,42,333Stern,D.et al.2005,ApJ,631,163Telfer,R.C.,Zheng,W.,Kriss,G.A.,&Davidsen,A.F.2002,ApJ,565,773Vanden Berk,D.E.et al.2001,AJ,122,549Vanzella,E.et al.2006,A&A,454,423Vestergaard,M.,&Peterson,B.M.2006,ApJ,641,689Wittman,D.E.,Margoniner,V.,Tyson,J.A.,Cohen,J.G.,Becker,A.,&Dell’Antonio,I.P.2002,in Proc.SPIE,4836,Survey and Other Telescope Technologies and Discoveries., ed.J.A.Tyson&P.S..Wolff,S.,21Table1.N IV]Emitting QuasarsR.A.Dec.R J K s[3.6][4.5] Name(J2000)(J2000)z(mag)a(mag)(mag)(mag)(mag) a AB magnitudes.All other magnitudes are Vega-based magnitudes.Table2.Quasar Line PropertiesLine Flux rest-frame EW FWHM Line(10−16erg cm−2s−1)(˚A)(km s−1)a These line widths are from the broad component of a two-component Gaussianfit to the Lyαline.See§2for details on thefitting procedure.Fig. 1.—3′×3′finding charts from the R-band images of the original survey data. DLS1053−0528is on the top(the gray stipe through the center of the image masks a bleed trail from a nearby saturated star)and NDWFS1433+3408is displayed on the bottom.In these images,north is up and east is to the left.The white circles mark the locations of the quasars.Fig.2.—Keck LRIS spectra of the N IV]λ1486˚A emitting quasars.Top:z=4.02quasar found in the DLSfield.This spectrum lacks N Vλ1240˚A in emission but the line appears present as a broad absorption line.Bottom:z=3.88quasar found in the NDWFS Bo¨o tes field.This object shows a weaker N IV]λ1486˚A line and a possible weak detection of N V λ1240˚A.Fig. 3.—Voigt profilefits(dotted lines,with continuum model shown by the dot-dashed line)to Nitrogen lines in our quasars.The linefits to DLS1053−0528are shown in the top panels and thefits to NDWFS1433+3408are shown in the bottom panels.Fig. 4.—Rest-frame spectral energy distribution(SED)for NDWFS1433+3408(squares) and DLS1053−0528(triangles)compared with the SDSS quasar composite spectrum from Vanden Berk et al.(solid line;2001)and an unobscured starburst template with E(B−V)<0.1from Kinney et al.(dashed line;1996).Fig.5.—Composite quasar spectra showing the absence of N IV]λ1486˚A.The top spectrum (solid line)is the SDSS quasar composite from Vanden Berk et al.(2001).The quasars that contribute to this part of the spectrum are highly luminous high-redshift quasars.The bottom spectrum(dashed line)is the HST UV composite spectrum from Telfer et al.(2002). The objects contributing to this part of the spectrum are low-redshift(z<1)quasars.The absence of N IV]in both composite spectra suggests that it is necessary to probe deep intothe QLF at high-reshifts to witness the interaction of star formation with AGN activity.。
