A study of isomeric diglycosyl flavonoids by SORI CID of Fourier transform ion cyclotron mass Spectrometry in negative ion mode

High-resolution Sustained off resonance irradiation (SORI) CID was employed to distinguish four pairs of isomeric diglycosyl flavonoids in the negative mode using the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR MS). All of these isomers can be distinguished via MS/MS data. For these diglycosyl flavones and flavanones, the deprotonated alpha 1-->6 linkage diglycosyl flavonoids produce fewer fragments than the alpha 1-->2 linkage type compounds and the Retro-Diels-Alder (RDA) reaction in MS/MS only takes place when the aglycone is a flavanone and glycosylated with an alpha 1-->2 intersaccharide linkage disaccharide. The deprotonation sites after collisional activation are discussed according to the high mass accuracy and high-resolution data of tandem spectrometry. Some of these high-resolution SORI CID product ions from alpha 1-->2 linkage diglycosyl flavonoids involve multibond cleavages; the possible mechanism is discussed based on the computer modeling using Gaussian 03 program package at the B3LYP/6-31G level of theory. Unambiguous elementary composition data provides fragmentation information that has not been reported previously.

MALDI-TOF-MS法对重组人内皮抑素蛋白分子质量测定

肿瘤的生长依赖于血管的生成,新生血管不仅为肿瘤生长提供必需的营养物质,而且为肿瘤细胞扩散提供了重要的途径[1].1997年哈佛大学的O'Reilly等[2]发现了一种内源性新血管生成抑制因子内皮抑素(Endostatin),显示出特异抑制激活的血管内皮细胞增殖和肿瘤新血管生成的生物学活性,其抗肿瘤作用具有高效、低毒、无耐药性的优点.

Multiple-stage tandem mass spectrometry for differentiation of isomeric saponins

Four isomers of steroidal saponins were differentiated using multiple-stage tandem mass spectrometry combined with electrospray ionization (ESI-MSn). With the addition of lithium salt, the [M+Li](+) ions of saponins were observed in the ESI spectra. MSn spectra of these [M+Li](+) ions provided detailed structural information and allowed differentiation of the four isomeric saponins. The cross-ring cleavage ions from the saccharide chains of the saponins could be used as diagnostic ions for information concerning the linkage of the sugar moieties of the saponins. The masses of the X, A, Y and C type fragment ions formed from [M+Li](+) ions of the isomeric saponins provided information defining the methyl group locations.

Studies on the flavones using liquid chromatography-electrospray ionization tandem mass spectrometry

Fragmentation pathways of nine flavone compounds have been studied by using electrospray ionization multi-stage tandem mass spectrometry (ESI-MSn). Analyzing the product ion spectra of flavonoids and aglycones, we observed some diagnostic neutral losses, such as *CH3, H2O, residue of glucose and gluconic acid, which are very useful for the identification of the functional groups in the structures. Furthermore, specific retro Diels-Alder (RDA) fragments for flavones with different hydroxyl substitution have also been discussed. The information is helpful for the rapid identification of the location site of hydroxyl substitution on flavones. Fragmentation pathways of C-glycosidic flavonoid have also been discussed using ESI-MSn, demonstrating ions [M-H-60](-), [M-H-90](-), [M-H-120](-) are characteristic ions of C-glycosidic flavonoid. According to the fragmentation mechanism of mass spectrometry and HPLC-MS data, the structures of seven flavones in Scutellaria baicalensis Georgi have been identified on-line without time-consuming isolation. The HPLC-ESI-MSn method for analyzing constituents in the Scutellaria baicalensis Georgi has been established.

Structural features of the L-argininamide-binding DNA aptamer studied with ESI-FTMS

The 24-mer DNA aptamer of Harada and Frankel ( Harada, K.; Frankel, A. D. EMBO J. 1995, 14, 5798-5811) that binds L-argininamide (L-Arm) was studied by electrospray ionization Fourier transform mass spectrometry (ESI-FTMS). This DNA folds into a stem and loop such that the loop is able to engulf L-Arm. As controls, two derivatives of the same base composition, one with the same stem but a scrambled loop and the other with no ability to form a secondary structure, were studied. The two DNAs that could fold into stem-loop structures showed a more negatively charged distribution of ions than the linear control. This tendency was preserved in the presence of ligand; complexes expected to have more secondary structure had ions with more negative charges. Distinct species corresponding to no, one, and two bound L-Arm molecules were observed for each DNA. The fractional peak intensities were fit to a straightforward binding model and binding constants were obtained. Thus, ESI-FTMS can provide both qualitative and quantitative data regarding the structure of DNA and its interactions with noncovalent ligands.

Analysis of strychnos alkaloids using electrospray ionization Fourier transform ion cyclotron resonance multi-stage tandem mass spectrometry

The fragmentations of four strychnos alkaloids have been investigated by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS) in the positive ion mode. Experiments using multi-stage tandem mass spectrometry (ESI-FT-ICR-MSn) allowed us to obtain precise elemental compositions of product ions at high mass resolution. The experimental data demonstrated that the nitrogen bridge and the coordinated oxygen atom on the nitrogen bridge in the alkaloid compounds were the active sites in the MS2 fragmentations. The loss of CH3 or the OCH3 group in those alkaloids, which have an OCH3 substituent, was the dominant fragmentation mode in the MS3 fragmentations. Logical fragmentation schemes for strychnos alkaloids have been proposed and these should be useful for the identification of these compounds.

Comparison of biochemical effects induced by Changle between male and female rats using NMR and ICP-MS techniques

Metabolic profiles caused by rare earth complex were investigated using NMR and ICP-MS techniques. Male and female Wistar rats were treated orally with Changle (A kind of rare earth complex applied in agriculture to raise the production of crops) at dose of 2, 5 and 20 mg (.) kg(-1) body weight/day respectively for 90 d. Urine and serum samples are collected on 90 d. The relative concentrations of important endogenous metabolites in urine and serum are determined from H-1 NMR spectra and the contents of the four rare earth elements ( La, Ce, Pr and Nd) constituting Changle in the serum samples are measured by ICP-MS technique. Changle-induced renal and liver damage in rats is found based on the increase in the amounts of the amino acids, trimethylamine N-oxide, N, N-dimethyglycine, dimethylamine, succinate, aketoglutarate and ethanol as well as rare earth concentrations. The similarities and differentiations are found in the alteration patterns of metabolites and rare earth concentrations in serum.

High-sensitivity molecular mass determination of lysozyme prior to MALDI-MS

Sodium dodecyl sulfate(SDS) is a powerful solubilizing detergent which is often used during the separation of highly complex protein mixtures by one- or two-dimensional (2D) gel electrophoresis. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is a widely used technique for mass spectrometric analysis of some protein molecules compared to other techniques. But the presence of SDS or some salts usually leads to signal deterioration when using MALDI-MS. A method for using nitrocellulose membrane as the solid-phase carrier combined with n-octyl-beta-D-glucopyranoside in the matrix highly enhances the sensitivity of the molecular mass determination of lysozyme. This technique has the advantage that the signal-to-noise of the molecular weight profile is improved compared with the mass spectrum and the profile is relatively easy to interpret.

Identification of the flavonoid constituents from leaves of Acanthopanax Senticosus Harms

Four flavonoids from leaves of Acanthopanax Senticosus Harms were observed in negative ion mode in the electrospray mass spectra. Two of them were further isolated and identified as quercitrin (quercetin-3-O-alpha-L-rhamnoside) and hyperin (quercetin-3-O-beta-D-galactoside) on the basis of MS' and NMR data. The other two compounds in the mixtures were tentatively established as quercetin and rutin (quercetin-3-O-rutinoside) in terms of their electrospray tandem mass spectrometry (ESI-MSn) data. Three of the four flavonoids (excluding hyperin) haven't been reported in this plant before.

Determination of rare and rare earth elements in soils and sediments by ICP-MS using Ti(OH)(4)-Fe(OH)(3) co-precipitation preconcentration

A method was developed for the determination of trace and ultratrace amounts of REE. Cd. In. Tl. Th. Nb, Ta. Zr and Hf in soils and sediments. With NaOH-Na2O2 as the flux. Ti(OH)(4)-Fe(OH)(3) co-precipitation as the preconcentration technique and inductively coupled plasma mass spectrometry (ICP-MS) for measurement, the whole procedure was concise and suitable for batch analysis of multi-element solutions. An investigation was carried out of the Ti(OH)(4)-Fe(OH)(3) co-precipitation system, and the results obtained showed that the natural situation of Ti tightly coexisting with Nb. Ta, Zr and Hf in geological samples plays a very important role in the complete co-precipitation of the four elements. The accuracy of this procedure was established using six Chinese soil and sediment certified reference materials (GSS and GSD). and the relative errors between the found and certified values were mostly below 10%.

提高MALDI-MS测量溶菌酶分子量灵敏度的研究

近 1 0年来 ,基质辅助激光解吸质谱 (MALDI- MS)作为一种新兴的“软电离”质谱技术 [1,2 ] ,已很快地应用于生物大分子特别是蛋白质研究领域 [3 ] .MALDI- MS可在 1 0 - 12 mol甚至 1 0 - 15mol的水平上 ,准确地测定分子量高达几万到几十万的生物大分子 ;还可通过改变基质、溶液条件和样品的制备方法等实现大分子蛋白质非共价复合物的质谱检测 [4 ] .MALDI- MS能够得到如此广泛的应用 ,在很大程度上要归功于基质的辅助效应 .基质的作用主要可以概括如下 [5～ 7] :(1 )削弱样品分子间的相互作用 ;(2 )与样品分子结合并使之快速结晶 ;(3 )帮助样品分子从激光脉冲中吸收能量 ,使其产生瞬间相变 ,当能量达到本体解吸临界值时便可得到离子信号 .Garozzo等 [8]曾报道了以羟基苯乙酮为基质可提高测量多种谷蛋白粘胶质分子量的灵敏度 .其中以 2 ,4,6 -三羟基苯乙酮 (2 ,4,6 - THAP)与 TFA混合作基质和 2 ,6 -二羟基苯乙酮 (2 ,6 - DHAP)与 H2 O,ACN混合作基质灵敏度最高 .表明这类基质在通过气相离子 ...

人参四逆汤抗休克作用的有效组分成分分析

分析人参四逆汤抗失血性休克作用的提取组分 S- 1和 S- 7的组成成分。方法　结合硅胶色谱柱分离 ,利用 ESI/MSn、MAL DI- TOF/MS等技术分析鉴定 S- 1和 S- 7的化学成分。结果　从人参四逆汤水煎液的抗休克作用的有效组分 S- 7中分析和鉴定了人参皂苷 - Ra1 、- Ra2 、- Rb1 、- Rb2 、- Rb3、- Rc、- Rd、- Re、- Rg1 、- Rg2 、- Rg3、- Rf等 12种人参皂苷 ;从有效组分 S- 1中检出下列二萜生物碱成分 :苯甲酰次乌头碱油酸酯 (14 - benzoylhypaconine- 8-linoleate,HAL )、苯甲酰去氧乌头碱油酸酯 (14 - benzoyldeoxyaconine- 8- oleate,HAO )、苯甲酰次乌头碱棕榈酸酯(14 - benzoylhypaconine- 8- palmitate,HAP)、苯甲酰中乌头碱 (benzoylmesaconitine,BM)、苯甲酰乌头碱 (benzoyla-conitine,BA)、苯甲酰次乌头碱 (benzoylhypaconitine,BH)。结论...