硫酸铈对5′-腺嘌呤及5′-鸟嘌呤核苷酸的水解断裂的催化作用

本文用核磁共振（ＮＭＲ）波谱和化学定磷法研究了Ｃｅ（ＳＯ４）２，对５’－腺嘌呤核苷酸（５’－ＡＭＰ）及５’－鸟嘌呤核苷酸（５’－ＧＭＰ）的水解断裂作用，结果表明：Ｃｅ（ＳＯ４）２在３７℃，酸性条件下使５’－ＡＭＰ断裂为腺嘌呤核苷（Ａ）及无机磷，使５’－ＧＭＰ断裂为鸟嘌呤核苷（Ｇ）及无机磷，ＳＯ＾２－４浓度及酸强度对５’－ＡＭＰ及５’－ＧＭＰ的水解断裂程度有很大影响，并对其水解断裂机制进行了研究。     

功能化线型聚氨酯的合成及其二阶非线性光学特性的研究

功能化线型聚氨酯的合成及其二阶非线性光学特性的研究＊颜星中陈用烈梁兆熙＊＊（中山大学高分子研究所广州５１０２７５）蔡志岗杨佩青徐志凌李鹏（中山大学国家超快速激光光谱重点实验室广州５１０２７５）关键词４’－（Ｎ，Ｎ二羟乙基）－氨基－４－硝基偶氮苯，聚氨...     

Cu（Ⅱ）NEAE和Cu（Ⅱ）NACN的NIR FT－SERS光谱研究

用沉积银胶的银镜作活性载体，获得了中位－四－（４－Ｎ－乙氧羧甲基吡啶）卟啉络铜（Ⅱ）（Ｃｕ（Ⅱ）ＮＥＡＥ）、中位－四－（４－Ｎ－氰甲基吡啶）卟啉络酮（Ⅱ）（Ｃｕ（Ⅱ）ＮＡＣＮ）的近红外富里叶变换－表面增强喇曼光谱（ＮＩＲＦＴＳＥＲＳ），对其谱峰位移作了归属，并与它们的可见激光表面增强共振喇曼光谱（ＳＥＲＲＳ）作了比较。     

(R)-N-酰基四氢噻唑-2-硫酮-4-羧酸在DCC存在下与胺的反应

由Ｎ－乙酰四氢噻唑－２－硫酮－４－羧酸（［α］２０Ｄ－１０９．８３°），及Ｎ－苯甲酰四氢噻唑－２－硫酮－４－羧酸（［α］２０Ｄ－１１２．２２°），在Ｎ，Ｎ′－二环己基二亚胺（ＤＣＣ）存在下分别与环己胺、苯胺反应得到光学活性产物（Ｒ）－Ｎ－乙酰四氢噻唑－２－硫酮－４－甲酰环己胺（［α］１７Ｄ－７４．５°），及（Ｒ）－Ｎ－苯甲酰四氢噻唑－２－硫酮－４－甲酰苯胺（［α］１９Ｄ－７．０４°）。用量子化学ＰＭ３方法研究了反应物和产物的电子结构。     

芳氨基硫脲类化合物的质谱研究（Ⅱ）

本文报道了五种新的芳氨基硫脲类化合物，即１－（４－溴－２－羧基苯基）－４－烷基氨基硫脲的电子轰击质谱（ＥＩＭＳ）。结果表明，该类化合物的分子离子峰（Ｍ＋）很弱，但却具有效强的［Ｍ－Ｈ］＋峰。分子离子的断裂以Ｎ－Ｎ键和Ｃ－Ｎ键的断裂为主，并伴随着六员环或四员环过渡态氢重排，生成相应的芳氨基正离子和芳肼基正离子，这两种离子继续失水或失其它小分子，从而形成一系列特征离子，包括骨架重排离子。     

乙烯系单体自由基聚合的阻聚效应──XIX．取代哌啶羟胺和二叔丁基羟胺及其稳定自由基对苯乙烯－丙烯腈共聚合的影响

研究了二叔丁基羟胺（ＤＴＢＨＡ），二叔丁基氮氧自由基（ＤＴＢＮＯ），２，２，６，６－四甲基－４－羟基哌啶羟胺（ＴＭＨＰＨＡ）和２，２，６，６－四甲基－４－羟基哌啶－１－氧自由基（ＴＭＨＰＯ）对过氧化苯甲酰（ＢＰＯ）６０℃引发的苯乙烯（Ｍ１）－丙烯腈（Ｍ２）共聚合的阻聚物行为。结果表明，这些阻聚剂对Ｓｔ－ＡＮ共聚均表现良好的阻聚行为，其中氮氧自由基优于相应羟胺。同时观察到Ｓｔ－ＡＮ竞聚率的改变，羟胺     

酞菁-卟啉超分子的形成及光致电子转移过程

用吸收光谱的方法研究了溶液中四－（４’－Ｎ，Ｎ，Ｎ－三甲基）－苯氧基）酞菁季铵碘盐及它的锌络合物与四－（４’－磺酸基苯基）卟啉及它的锌络合物通过分子间自组装形成的新一类超分子排列的杂聚体，用Ｊｏｂ氏光度滴定的方法确定了它们的组成，为面对面的杂二聚体或三明治式的杂三聚体超分子排列，证实卟啉和酞菁的中心络合金属与溶剂分子之间的轴向配位是决定了卟啉，酞菁杂聚体的组成，发现在超分子体系中卟啉与酞菁能互相猝     

1，3－双－（介晶基）－1，1，3，3－四甲基二硅氧烷的合成和相变研究

合成了１６种１，３－双－（介晶基）－１，１，３．３－四甲基二硅氧烷（Ⅱ_（ａ，ｂ），Ⅲ_（ａ─ｇ），Ⅲ_ｊ，Ⅳ_（ａ─ｆ）．其化学结构用￣１ＮＭＲ、ＩＲ、ＵＶ和元素分析表征。通过ＤＳＣ和偏光显微镜研究了它们的相行为，除Ⅱ_（ａ，ｂ）、Ⅲ_ｄ和Ⅳ_ｄ外，其余都呈现液晶相变。用Ｘ衍射分析研究了１，３－双－（４－甲基偶氮苯氧甲基）－１，１，３，３－四甲基二硅氧烷（Ⅱ_ａ）的晶体结构。讨论了这些新型硅氧烷化合物的比学结构对液晶相变行为的影响。     

镍（Ⅱ）与meso—四（4—N—甲基吡啶基）卟啉（TMPyP）络合物的伏…

本文用循环伏安法、溶出伏安法和计时库仑法等多种电化学方法研究了合成的镍（Ⅱ）与ｍｅｓｏ－四（４－Ｎ－甲基吡啶基）卟啉（ＴＭＰｙＰ）络合物的电还原行为。结果表明，Ｎｉ（Ⅱ）ＴＭＰｙＰ的还原过程是中心离子Ｎｉ（Ⅱ）和卟啉环同时还原，其中Ｎｉ（Ⅱ）被还原为Ｎｉ（０），总电子转移数为６。比较并讨论了溶解氧对锰、铁钴、镍卟啉的不同影响。     

N－（苦基）－7－氮杂－1，4，10，13－四硫杂环十六烷的晶体结构研究

Ｎ－（苦基）－７－氮杂－１，４，１０，１３－四硫杂环十六烷的晶体结构研究秦勇，杨季秋，罗世琼（中国科学院成都有机化学研究所成都６１００４１）关键词：生色冠硫醚，晶体结构生色冠硫醚能选择性地络合过渡金属离子，从而导致其光谱行为的变化，因而此类化合物是过...     

Low molar mass poly(styrene-co-acrylic acid) amphiphilic block copolymers: synthesis and characterization

Low molar mass (∼ 4000) di- and triblock copolymers of styrene and tert-butyl acrylate were synthesized by atom transfer radical polymerization (ATRP) in bulk and solution conditions. A CuBr/N, N,N′,N″,N″-pentamethyldiethylenetriamine (PMDETA) catalyst system in conjunction with an alkyl-halide initiator were used to control the synthesis of the polystyrene macroinitiator and the subsequent copolymerization with tert-butyl acrylate. Hydrolysis of the tert-butyl acrylate blocks to acrylic acid blocks in the presence of trifluoroacetic acid resulted in the formation of an amphiphilic block copolymer. Size exclusion chromatography (SEC) and matrix assisted laser desorption ionization - time of flight - mass spectrometry (MALDI-TOF-MS) were used to determine the molar mass and molar mass distribution of the polystyrene macroinitiators and the block copolymers. ¹H NMR was used to characterize the polystyrene macroinitiators and the block copolymers, and to confirm hydrolysis of the poly(tert-butyl acrylate) blocks to poly(acrylic acid).     

Effects of ion mode and matrix additives in the identification of bacteria by intact cell mass spectrometry

Protocols for the identification of bacterial cells by intact cell matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (ICM-TOFMS) are presented. A mass range of 500 to 10,000 m/z is used. The use of formic acid and the crown ether 1, 4, 7, 10, 13, 16-hexaoxacyclooctadecane (18-crown-6) is described. Crown ether is useful for removing metal ion adducts, which degrade spectral purity, and formic acid promotes positive ions, improves spectral signal, and, hence, increases identification certainty.     

N,N′-dichloro-p-nitrobenzenesulfonamide (dichloramine-N) as a new oxidimetric reagent: Synthesis and analytical application

A new oxidimetric reagent, dichloramine-N (N,N′-dichloro-p-nitrobenzenesulfonamide; DCN) has been synthesized and its structure elucidated from the spectral data and elemental analyses. The ultraviolet, infrared, nuclear magnetic resonance, and mass spectral data have been presented. Analytical applications of DCN as a potential redox titrant in the determination of diverse reductants such as ascorbic acid, methionine, sulfite, arsenite, glutathione, and indigocarmine have been described.     

Evaluation of the quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using an equimolar mixture of uniform poly(ethylene glycol) oligomers

Quantitativeness of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was elucidated using an equimolar mixture of uniform poly(ethylene glycol) (PEG) oligomers with no molecular weight distributions. Uniform PEG oligomers with degrees of polymerization n = 6-40 were separated from commercial PEG samples by preparative super-critical fluid chromatography. MALDI-TOF mass spectra of an equimolar mixture of the uniform PEG oligomers were recorded by adding a mixture of 2,5-dihydroxybenzoic acid as a matrix reagent and four chlorinated salts, i.e. LiCl, NaCl, KCl and RbCl. Remarkable non-quantitative effects were observed in the MALDI-TOF mass spectra in both the lower and higher molecular mass regions. At higher molecular masses greater than about 10(3), PEG oligomers with larger molecular mass yielded lower spectral intensities irrespective of the species of adduct cations and higher laser powers induced larger decreases in mass spectral intensities with the increase in their molecular masses. On the other hand, in the lower molecular mass region, less than about 10(3), the observed non-quantitative effect greatly depends on the species of adduct cations, indicating that the stability of the PEG-cation complex affects the MALDI-TOF mass spectral intensities of uniform PEG oligomers.     

Determining the time needed for the vortex method for preparing solvent-free MALDI samples of low molecular mass polymers

Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry is an important technique to characterize many different materials, including synthetic polymers. MALDI mass spectral data is used to determine the polymer average molecular weights, repeat units, and end groups. The development of the vortex method of solvent-free sample preparation showed that remarkably short mixing times could prepare samples that yielded high quality MALDI mass spectra. In this paper, we use microscopy images and MALDI mass spectra to evaluate the mixing time required by the vortex method to produce mass spectra for low molecular mass polymer samples. Our results show that mixing times of as little as 10 s can generate homogeneous thin films that produce high quality mass spectra with S/N ∼ 100. In addition, ultrashort mixing times of only 2 s still produce samples with mostly smooth morphology and mass spectra with S/N ∼ 10.     

Matrix-assisted laser desorption/ionization mass spectrometric analysis of aliphatic biodegradable photoluminescent polymers using new ionic liquid matrices

In this study, two novel ionic liquid matrices (ILMs), N,N-diisopropylethylammonium 3-oxocoumarate and N,N-diisopropylethylammonium dihydroxymonooxoacetophenoate, were tested for the structural elucidation of recently developed aliphatic biodegradable polymers by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The polymers, formed by a condensation reaction of three components, citric acid, octane diol, and an amino acid, are fluorescent, but the exact mechanism behind their luminescent properties has not been fully elucidated. In the original studies, which introduced the polymer class (J. Yang et al., Proc. Natl. Acad. Sci. USA 2009, 106, 10086-10091), a hyper-conjugated cyclic structure was proposed as the source for the photoluminescent behavior. With the use of the two new ILMs, we present evidence that supports the presence of the proposed cyclization product. In addition, the new ILMs, when compared with a previously established ILM, N,N-diisopropylethylammonium α-cyano-3-hydroxycinnimate, provided similar signal intensities and maintained similar spectral profiles. This research also established that the new ILMs provided good spot-to-spot reproducibility and high ionization efficiency compared with corresponding crystalline matrix preparations. Many polymer features revealed through the use of the ILMs could not be observed with crystalline matrices. Ultimately, the new ILMs highlighted the composition of the synthetic polymers, as well as the loss of water that was expected for the formation of the proposed cyclic structure on the polymer backbone.     

Evaluation of mass discrimination effects in the quantitative analysis of polydisperse polymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry using uniform oligostyrenes

Mass discrimination effects in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) were quantitatively investigated using equiweight and equimolar mixtures of uniform polystyrene (PS) oligomers. Uniform PS oligomers were separated by preparative super-critical fluid chromatography (SFC) from commercial standard PS samples. The separated PS oligomers, with degrees of polymerization n = 2–25, have absolutely no molecular weight distributions. Equiweight and equimolar mixtures of uniform PS oligomers were accurately prepared by weighing by microbalance, and their spectra were recorded using a MALDI-TOF mass spectrometer. In the lower molecular weight region (less than about 10³) the oligomers with lower molecular weights give lower mass spectral intensities, with no correlation with laser power. In contrast, higher laser powers yield a decrease of mass spectral intensities in the higher molecular weight region. These results clearly show that mass discrimination effects occur at lower and higher molecular weights depending on the laser power, and provide quantitative information about the discrimination. Using the data on equiweight and equimolar mixtures of PS oligomers, it was possible to calibrate the MALDI-TOF mass spectral data for an analysis of molecular weight distribution of a standard monodisperse PS sample with number-averaged molecular weight of 10³, and to compare it with the molecular weight distribution measured by analytical SFC. The result from the calibrated MALDI-TOF mass spectrum, however, does not agree perfectly with that from the SFC results, because undetectable peaks in MALDI-TOF mass spectra at lower and higher molecular weights could not be included in the calibration of peak intensities. Copyright © 2001 John Wiley & Sons, Ltd.     

N2+2离子在线偏振和圆偏振强激光场中的解离

基于N+离子的飞行时间质谱, 研究了N2+2离子在线偏振和圆偏振强飞秒激光场中(45 fs, 5×1015-1×1016 W·cm-2, 800 nm)的解离. 通过对N+离子质谱和平动能的分析发现, N2+2离子在线偏振光和圆偏振光作用下具有不同的解离方式. 在线偏振光下, N2分子在平衡核间距RE处发生次序双电离生成N2+2离子, N2+2离子解离所释放的能量能够用单光子跃迁模型来解释. 而在圆偏振光下, N2分子首先电离生成N+2离子, N+2离子在核间距增大到临界核间距RC(>RE)时, 进一步被电离从而发生解离, 此时解离所释放的能量可以用库仑推斥模型来解释.     

Selective ultra-trace detection of NO and NO2 in complex gas mixtures using broad-bandwidth REMPI mass spectrometry

In this paper we demonstrate the feasibility of ultra-trace resonance enhanced multiphoton ionization (REMPI) detection employing a small broad-bandwidth solid state laser system. The results reported here are compared with measurements carried out with a conventional excimer pumped dye laser combination. Mass selected broad-bandwidth REMPI spectra for the environmentally relevant nitrogen oxides NO and NO2 are presented. Tunable broad-bandwidth laser radiation with a spectral resolution of > 10 cm(-1) in the wavelength range 560-400 nm was employed for the detection of NO2. For NO detection, the range 230-224 nm was covered. Laser radiation was generated using an optical parametric oscillator pumped by an unseeded Nd:YAG laser. A mobile time-of-flight mass spectrometer equipped with an atmospheric pressure laser ionization source allowed for mass selective parent ion detection at m/z 30 for NO and m/z 46 for NO2. The limit of detection was 10 pptV for NO and 20 pptV for NO2. A selectivity of > 2000 for both compounds with respect to N2O5, organic nitrates and NO2 in the case of NO is reported. An improved laser system currently under construction is expected to provide detection limits below pptv mixing ratios for both nitrogen oxides in a 20 s integration interval.     

Reaktionen von Glutaminsäuredimethylester im Massenspektrometer. 21. Mitteilung über das massenspektrometrische Verhalten von Stickstoffverbindungen

The mass spectral fragmentation of dimethyl glutamate ( 1 ) and its deuterated derivatives 1a , 1b and 1c has been investigated. By loss of a methoxycarbonyl group from the molecular ion an ion of m/e 116 is generated. The latter splits off methanol (m*), the resulting fragment of m/e 84 giving raise to the base peak of the spectrum. Only part of the hydrogen transferred to the leaving group originates from thc amino group, as was suggested earlier [2] [3]. Basing on experiments with deuterated compounds we propose an additional mechanism for the reaction, i.e. hydrogen transfer from C(3) to methoxyl. The fragment generated by both processes is most likely to be a pyrrolinonium ion. Thermal side reactions in the mass spectrometer (formation of pyroglutamic acid ester) followed by fragmentation may lead to the same ion. – The mechanisms discussed are supported by the mass spectral fragmentation of N-acetyl-glutamic acid diesters 3 , 3a , 3b and 3d and of the N, N-dimethyl derivatives 4 and 4a . – The fragmentation reactions investigated are similar to some of 1,3-trimethylenediamine derivatives [7]. This means that there are parallels in the mass spectral fragmentation of difunctional compounds irrespective of the nature of the functional groups.