天然有机化合物X. 糖苷快原子轰击质谱中的碱金属加合离子应 用技术的研究

在对糖苷的FAB分析技术的研究中发现,如果在样品中同时加入适量的NaCl和LiCl水溶液进样时,其FAB谱中会出现[M+Na]^+和[M+Li]^+两个强峰,两峰之质量差为16(Na和Li原子量之差值),并且发现其谱图中找不到明显的碎片离子和Na^+及Li^+的加合离子,而只有糖苷分子和Na^+及Li^+的加合离子。所以很容易在FAB谱中识别它们。因而不需联谱解析而仅凭FAB谱就可准确、快速地定出糖苷的分子量。此技术国内外尚未见报道。     

天然有机化合物——Ⅹ.糖苷快原子轰击质谱中的碱金属加合离子应用技术的研究

在对糖苷的FAB分析技术的研究中发现,如果在样品中同时加入适量的NaCl和LiCl水溶液进样时,其 FAB 谱中会出现[M+Na]~+和[M+Li]~+两个强峰,两峰之质量差为16(Na 和 Li 原子量之差值),并且发现其谱图中找不到明显的碎片离子和 Na~+及 Li~+的加合离子,而只有糖苷分子和Na~+及 Li~+的加合离子.所以很容易在 FAB 谱中识别它们,因而不需联谱解析而仅凭 FAB 谱就可准确、快速地定出糖苷的分子量.此技术国内外尚未见报道.     

糖苷混合物FAB质谱分析技术的研究

我们曾阐明了糖苷单-化合物分子量的简明, 快速确定方法, 根据糖苷化合物中引入碱金属离子的FAB正离子的加合离子峰而难于找到碎片的加合离子峰, 现在我们在糖苷混合物中, 同时引入两种碱金属离子Na^+和Li(两元素原子量之差为16), 由此得到的糖苷混合物的FAB正离子谱中, 就出现两个一组的多组强峰, 且每组的两峰之质量差为16, 每组中低质量峰为[M+Li]^+峰, 高质量为[M+Li]^+峰, 根据两峰已标出的质量数便可轻易地定出各成分的分子量来。谱图中出现的强峰组数就是糖苷混合物的成分数。     

细胞内游离离子及离子通道的核磁共振研究

生物细胞内游离离子及离：子通道(Ca^2 、Mg^2 、Na^ 、K^ 以及Na^ ／Ca^2 和Na^ ／Li^ 交换等)在生理病理过程中起着重要作用。用于这些方面研究的生物核磁共振方法主要包括有：^31PNMR、^19NMR、^7Li NMR及^23Na NMR等。^31P NMR主要用于对细胞内小分子代谢物、pH及游离Mg^2 的分析测定；^19F NMR是利用氟代指示剂间接地测定细胞内游离Mg^2 和Ca^2 的浓度，进而对钙镁离子通道进行分析研究；^7Li NMR、^23Na NMR等方法分别用于研究Li^ 、Na^ ／Li^ 交换、Mg^2 ／Li^ 交换、Na^ 及K^ 等。为了更好地理解和阐释细胞内离子的调控机制，本文对近几年核磁共振技术在这些方面的应用进行了综述。     

刺五加寡糖的电喷雾多级串联质谱研究

采用小柱层析法从刺五加中分离得到刺五加寡糖类系列化合物(刺五加二糖刺五加六糖).实验结果表明,在正离子模式下的ESI-MS谱中,此类化合物呈现出特征的加合离子峰簇[M+Na]⁺/[M+K]⁺或[M+H₂O+Na]⁺/[M+H₂O+K]⁺,可以确定其分子量;在负离子模式下的ESI-MS谱中,刺五加寡糖易形成[M-H]^-/[M+nH₂O-H]^-(n<3).还利用电喷雾多级串联质谱(ESI-MSⁿ)对刺五加三糖进行了系统的研究,推断出刺五加三糖的组成与结构.     

天然产物的质谱研究 Ⅴ.负离子快原子轰击及其碰撞活化质谱法在寡糖苷结构分析中的应用

本文研究了八种含1—3个糖基的糖苷的负离子快原子轰击(NFAB)质谱.NFAB质谱与相应的正离子谱(PFAB)比较,在高质量区示出较明显的准分子离子[M-H]~-峰而无加合离子峰,从而能较明确指示糖苷的分子量.在所试验的三种底物甘油、硫代甘油和聚乙二醇-200(PEG-200)中,以PEG-200给出的结果最佳.[M-H]~-离子的碰撞活化谱(NFAB-CA谱)产生的特征离子比[M+H]~+离子PFAB-CA谱中相应离子的丰度大,能更为明确地给出糖基连接顺序信息.     

天然产物的质谱研究V.负离子快原子轰击及其碰撞活化质谱法在寡糖苷结构分析中的应用

研究了八种含1一3个糖基的糖苷的负离子快原子轰击(NFAB)质谱,NFAB质谱与相应的正离子谱(PFAB)比较,在高质量区示出较明显的准分子离子[M-H][-]峰而无加合离子峰,从而能较明确指示糖苷的分子量, 在所试验的三种底物甘油、硫代甘油和聚乙二醇-200(PEG-200)中,以PEG-200给出的结果最佳,[M-H][-]离子的碰撞活化谱(NFAB-CA谱)产生的特征离子比[M+H][+]离子PFAB-CA谱中相应离子的丰度大,能更为明确地给出糖基连接顺序信息。     

C60与环己烷及环己烯离子体系的气相反应

在气相条件下研究了C60与环己烷及环己烯的离子-分子反应。C60可与上述体系中多种离子发生反应, 生成相应的加合离子, 表现出C60化学性质的活泼性和多样性。C60与C4H7^+和C5H7^+离子反应可能生成[2+4]环加成的加合离子。     

电喷雾质谱法中K^+加合离子受Cs^+影响及在牛膝多糖分子 量分布测定中的应用

以测定牛膝多糖的分子量分布为例,研究了在Cs^+存在情况下,电喷雾(ESI)/飞行时间质谱法(TOF-MS)中出现加合离子(adductions)的规律。实验中发现,牛膝多糖样品中加入适量的Cs^+,可影响其与Na^+,K^+加合离子的相对丰度,使K^+加合离子成为几乎唯一的加合离子形式,并获得了满意结果。另外讨论了Cs^+浓度、喷管电压(nozzlepotential)对这一现象的影响。     

中性载体ETH129推动金属离子在水/硝基苯界面的转移

本文用循环伏安法发现了中性载体ETH129(N, N, N', N'-四环己基-3-氧杂-戊二酰胺)在水/硝基苯界面推动H^+, Li^+, Na^+, Zn^2^+, Mg^2^+, Cu^2^+的离子转移,对推动离子转移过程的机理进行了探讨, 测定了相应离子的扩散系数和其配合物的稳定常数。     

天然有机化合物的质谱研究 黄酮和黄酮甙与碱金属离子K+和Na+的快原子轰击质谱

在作黄酮和黄酮甙的快原子轰击质谱时,如果同时加入氯化钠和氯化钾两种碱金属盐,就会在谱图中同时出现两个强峰,由于这两个峰相差１６个原子质量单位,很容量辨认,并且发现在其谱图中找不到明显的碎片离子和Ｎａ＾＋和Ｋ＾＋的加合离子,而只有其分子和Ｋ＾＋和Ｎａ＾＋的加合,所以很容易在ＦＡＢ谱中识别它们,因而就可以快速,准确地确定样品的分子量。     

寡糖快原子轰击质谱中碱金属加合离子应用技术的研究

生命科学的研究成果^[1～3]表明,糖蛋白和糖脂中的糖基可作为细胞的识别信号,能控制细胞的分裂和分化.快原子轰击(FAB)质谱是测定寡糖的重要手段^[4,5],但目前还存在不少问题.我们在对麦芽各糖的研究中.     

Studies on the mass spectrometry of natural products: V. Negative ion fast atom bombardment and collisional activation mass spectrometry in the structural analysis of oligoglycosides

The negative ion fast atom bombardment (NFAB) mass spectrometry of eight glycosides containing one to three sugar units have been studied. The mass spectra of NFAB exhibit more predominant quasi-molecular ions without adduct ions in the high mass region, which indicate more unambiguously the molecular weights of the glycosides, than the positive ion FAB (PFAB) spectra do. Among the three matrix substances tested, glycerol, thioglycerol and PEG-200, the last one was found to give the best results. The characteristic ions of NFAB collisional activation (NFAB-CA) spectra of [M-H]^? ions were more abundant and gave more definite information about sequences of the sugar units than the corresponding PFAB-CA spectra of [M + H]+ ions.     

Electrospray mass spectrometry and fragmentation of N-linked carbohydrates derivatized at the reducing terminus

Derivatives were prepared from N-linked glycans by reductive amination from 2-aminobenzamide, 2-aminopyridine, 3-aminoquinoline, 2-aminoacridone, 4-amino-N-(2-diethylaminoethyl)benzamide, and the methyl, ethyl, and butyl esters of 4-aminobenzoic acid. Their electrospray and collision-induced dissociation (CID) fragmentation spectra were examined with a Q-TOF mass spectrometer. The strongest signals were obtained from the [M + Na]+ ions for all derivatives except sugars derivatized with 4-amino-N-(2-diethylaminoethyl)benzamide which gave very strong doubly charged [M + H + Na]2+ ions. The strongest [M + Na]+ ion signals were obtained from the butyl ester of 4-aminobenzoic acid and the weakest from 2-aminopyridine. The most informative spectra were recorded from the [M + Li]+ or [M + Na]+ ions. These spectra were dominated by ions produced by sequence-revealing glycosidic cleavages and "internal" fragments. Linkage-revealing cross-ring cleavage ions were reasonably abundant, particularly from high-mannose glycans. Although the nature of the derivative was found to have little effect upon the fragmentation pattern, 3-aminoquinoline derivatives gave marginally more abundant cross-ring fragments than the other derivatives. [M + H]+ ions formed only glycosidic fragments with few, if any, cross-ring cleavage ions. Doubly charged molecular ions gave less informative spectra; singly charged fragments were weak, and molecular ions containing hydrogen ([M + 2H]2+ and [M + H + Na]2+) fragmented as the [M + H]+ singly charged ions with no significant cross-ring cleavages.     

Identification of flavone aglycones and glycosides in soybean pods by liquid chromatography-tandem mass spectrometry

High-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry was used to identify flavone aglycones and glycosides in soybean pods. Tandem mass spectrometry (MS-MS and MS-MS-MS) and photodiode array detection were also utilized in flavone characterization. A total of seven flavone aglycones and glycosides were identified. Among them three flavone aglycones--apigenin, 7,4'-dihydroxyflavone, and luteolin--and two flavone glycosides--apigenin-7-O-beta-D-glucoside, and luteolin-7-O-beta-D-glucoside--were unambiguously identified based on their abundant (M+H)+ ions, UV spectra, retention time, and tandem mass spectrometric analysis compared with authentic standards. The tentative identification of two flavone glycosides as 7,4'-dihydroxyflavone-7-O-beta-D-glucoside and apigenin-7-O-beta-D-glucoside-6"-O-malonate was based on UV spectra, (M+H)+ ions, and tandem mass spectrometry. This is the first report identifying flavone aglycones and glycosides in soybean pods.     

天然有机化合物的质谱研究 黄酮和黄酮甙与碱金属离子K+和Na+的快原子轰击质谱

在作黄酮和黄酮甙的快原子轰击质谱（ＦＡＢＭＳ）时,如果同时加入氯化钠和氯化钾两种碱金属盐,就会在谱图中同时出现［Ｍ＋Ｋ］＋和［Ｍ＋Ｎａ］＋两个强峰,由于这两个峰相差１６个原子质量单位（ａｍｕ）,很容易辨认,并且发现在其谱图中找不到明显的碎片离子和Ｎａ＋和Ｋ＋的加合离子,而只有其分子和Ｋ＋和Ｎａ＋的加合,所以很容易在ＦＡＢ谱中识别它们,因而就可以快速、准确地确定样品的分子量     

Formation and fragmentation of the [M + Na]+ ion of glycosides in fast atom bombardment mass spectrometry

Positive-ion fast atom bombardment (FAB) mass spectra of flavonol and steroid glycosides with sodium chloride added showed well known characteristic features; of the appearance of [M + Na]⁺ peaks, disappearance of [M + H]⁺ peaks and a significant decrease in the peak heights of fragment ions. Compared with the features in the FAB mass spectra of crown ethers with addition of salt, and above features suggest a complexation between Na⁺ and the glycosides in matrix solution. The B/E-constant linked scanning technique was used to obtain structural information of the [M + Na]⁺ ion of the glycosides. The B/E spectra gave the daughter-ion peaks, suggesting that coordination of Na⁺ with the biosides and triosides occurs at the sugar moiety, whereas the coordination with the monoglycosides occurs at the aglycone moiety, except for monoglycosides in which the aglycone moiety does not contain significant oxygen functional groups such as OH and CO.     

Evaluation of glycosylation and malonylation patterns in flavonoid glycosides during LC/MS/MS metabolite profiling

Flavonoid conjugates constitute several classes of plant phenolic secondary metabolites including many isomeric compounds differing in the hydroxylation pattern and substitution of their rings with different groups such as alkyls, acyls or sugars. These compounds occur in plant tissues mainly as glycosides and in many cases it is necessary to have reliable and detailed information concerning the structure of these natural products. Our results were obtained using leaf extracts of Arabidopsis thaliana and Lupinus angustifolius in which different glycosides of flavones, flavonols and isoflavones are present. Analysis of collision-induced dissociation (CID)/MS/MS spectra of protonated [M + H](+), sodiated [M + Na](+) or deprotonated [M - H](-) molecules recorded during HPLC runs may bring needed information in this respect. However, registration of mass spectra of [M + Na](+) ions with a good efficiency is possible only after post-column addition of a sodium acetate solution to the LC column eluate. The retention of sodium cation on the saccharidic parts of the molecule is observed after the CID fragmentation. In many cases, the location of this cation on the glycan attached to C-3 hydroxyl group of flavonol led to assignment of its structure. Additionally, the determination of the structure of the aglycone and of the sequence of the glycan part was made possible through the CID data obtained from the [M + H](+) and [M - H](-) ions. CID spectra show a different order of sugar elimination from hydroxyl groups at C-3 and C-7 in flavonol glycosides isolated from A. thaliana leaves and give sufficient information to discriminate flavonoid O-diglycosides from flavonoid di-O-glycosides.     

Fast atom bombardment (FAB) mass spectrometry of piperidine N-oxide derivatives and free radical quenching under FAB conditions

Mechanisms are proposed for the formation of M⁺, [M + 2H]⁺ and [M + 3H]⁺ ions in the fast atom bombardment (FAB) mass spectra of 4-(2,2,6,6-tetramethyl-1-oxyl)-piperidol and its carboxylates. Free radical quenching induced by the fast atom beam has been observed. The effects of temperature on the radical quenching and of acid on the FAB mass spectra are discussed. The experiment showed that the volatile liquid samples with vapour pressures higher than that for glycerol produced M⁺ even-electron molecular ions, and the FAB mass spectra were similar to the corresponding electron ionization mass spectra. For the solid samples, it was found that the free radicals were quenched during the FAB process so that the mononitroxide and dinitroxide compounds produced [M + 2H]⁺ and [M + 3H]⁺ ions, respectively. Further experiments showed that the intensities and stabilities of [M + 2H]⁺ and [M + 3H]⁺ ions could be improved by addition of acids.