Ion Trap High-resolution Mass Spectrometry Research Articles

Simultaneous determination of three allergic proteins in rice and products by high performance liquid chromatography-tandem mass spectrometry combined with stable isotope-labeled peptides

基于稳定同位素标记特征肽段和液相色谱-质谱联用仪建立稻米及制品中3种过敏蛋白质的同时定量方法。稻米及制品样品经盐溶液提取,赖氨酰基内切酶(Lys-C)和胰蛋白酶依次水解,C18-SD柱净化后,采用纳升高效液相色谱-线性离子阱-静电场轨道阱(NanoLC-LTQ-Orbitrap)采集和Protein Discovery软件鉴定,NCBI和Uniprot数据库的基本局部搜索比对工具(BLAST)筛选验证,最终获得表征稻米及制品中α-淀粉酶/胰蛋白酶抑制剂类蛋白质(seed allergenic protein RAG2, RAG2)、乙二醛酶Ⅰ活性蛋白(glyoxalase Ⅰ)和α-球蛋白(19 kDa globulin)3种过敏蛋白质的特异性肽段。3个特异性肽段经液相色谱梯度洗脱,在Poroshell色谱柱上实现完全分离,由三重四极杆质谱仪分析。实验通过优化多反应监测(MRM)质谱参数,比较不同溶剂体系、水解酶种类和酶量等酶解条件,结合内标法定量,实现对稻米及制品中3种蛋白质的绝对定量。实验结果表明,当酶解溶剂中含1 g/L十二烷基硫酸钠,采用Lys-C和胰蛋白酶组合消化策略,可有效提高3种蛋白质的酶切效率至65.7%~97.3%。该方法在1~200 nmol/L范围内线性关系良好,相关系数均大于0.9972, 3种蛋白质的检出限和定量限分别为3 mg/kg和10 mg/kg。3种蛋白质在空白稻米制品基质中3个水平下的加标回收率为80.6%~103.7%,日间和日内精密度均小于11.5%。该方法稳定性好,检测灵敏度高,操作简便,在分析各类稻米及制品中3种过敏蛋白质含量具有广泛的应用前景。

Study of Nettle (Urtica dióica) Lignin by Atmospheric Pressure Photoionization Orbitrap Mass Spectrometry

Orbital ion trap high-resolution mass spectrometry with acetone doped atmospheric pressure photoionization is first used to characterize the structure of grass lignins using an example of nettle (Urtica dioica) dioxane lignin. The obtained mass spectrum contains about 3,000 peaks of deprotonated molecules of lignin oligomers in the molecular mass range up to 1.6 kDa. The study of tandem mass spectra and of a composition of monomers formed in the collision-induced dissociation of lignin macromolecules showed the special role of p-hydroxycinnamic acids in the formation of nettle lignin. Based on the results of tandem mass spectrometry, possible structures of nettle lignin oligomers formed by the addition of guaiacyl- and syringylpropane units followed by etherification by p-coumaric, ferulic, and dihydroferulic acids are proposed.

Multi-mycotoxin Analysis of Finished Grain and Nut Products Using Ultrahigh-Performance Liquid Chromatography and Positive Electrospray Ionization-Quadrupole Orbital Ion Trap High-Resolution Mass Spectrometry.

Ultrahigh-performance liquid chromatography using positive electrospray ionization and quadrupole orbital ion trap high-resolution mass spectrometry was evaluated for analyzing mycotoxins in finished cereal and nut products. Optimizing the orbital ion trap mass analyzer in full-scan mode using mycotoxin-fortified matrix extracts gave mass accuracies, δM, of < ± 2.0 ppm at 70,000 full width at half maximum (FWHM) mass resolution (RFWHM). The limits of quantitation were matrix- and mycotoxin-dependent, ranging from 0.02 to 11.6 μg/kg. Mean recoveries and standard deviations for mycotoxins from acetonitrile/water extraction at their relevant fortification levels were 91 ± 10, 94 ± 10, 98 ± 12, 91 ± 13, 99 ± 15, and 93 ± 17% for corn, rice, wheat, almond, peanut, and pistachio, respectively. Nineteen mycotoxins with concentrations ranging from 0.3 (aflatoxin B1 in peanut and almond) to 1175 μg/kg (fumonisin B1 in corn flour) were found in 35 of the 70 commercial grain and nut samples surveyed. Mycotoxins could be identified at δM < ± 5 ppm by identifying the precursor and product ions in full-scan MS and data-dependent MS/MS modes. This method demonstrates a new analytical approach for monitoring mycotoxins in finished grain and nut products.

A metabolomic strategy to screen the prototype components and metabolites of Qingkailing injection in rat urine by high-performance liquid chromatography with tandem mass spectrometry.

Xenobiotic metabolome identification of Chinese herbal formula in biological systems is a very challenging task. Qingkailing injection is a typical Chinese herbal injection, which is wildly used clinically in China. However, the holistic metabolic fate of the ingredient from Qingkailing injection remains unclear. In this work, a metabolomic strategy for comprehensively elucidating Qingkailing injection derived prototype components and metabolites in rat urine conducted by hybrid linear ion trap high-resolution mass spectrometry was developed. High-performance liquid chromatography coupled with hybrid linear ion trap high-resolution mass spectrometry was developed to obtain the urine profiling between the control group and Qingkailing injection treated group. Orthogonal partial least squares discriminate analysis was applied to distinguish the exogenous and the endogenous. In the S-plot, 37 xenobiotics derived from Qingkailing injection were found in urine, including 18 prototype compounds and 19 metabolites. The characterization of the prototype components and metabolites in rat's urine provided essential data for further pharmacological studies of Qingkailing injection. Our results indicated that the metabolomic approach was an effective tool to discover, screen, and analyze the multiple prototype components and their metabolites from complicated traditional Chinese preparations in vivo.

Liquid Chromatography–Hybrid Linear Ion Trap–High-Resolution Mass Spectrometry (LTQ-Orbitrap) Method for the Determination of Glycoalkaloids and Their Aglycons in Potato Samples

Potatoes produce biologically active secondary metabolites like glycoalkaloids and their aglycons, which may have both adverse and beneficial effects in the diet. A new analytical method that uses liquid chromatography–mass spectrometry (LTQ-Orbitrap) has been developed for the analysis of glycoalkaloids and their aglycons in potato samples. Two glycoalkaloids, α-solanine and α-chaconine, and two aglycons, demissidine and solasodine, were quantified in potato samples. Samples were extracted using methanol, purified on an SPE Strata C18 cartridge, and then analyzed in HPLC–mass spectrometry (LTQ-Orbitrap) with the FTMS operating in full scan at a resolving power of 30,000 (FWHM), enabling the detection and accurate mass measurement and with the ITMS mode operating in MRM (multiple reaction monitoring) for glycoalkaloids and their aglycons using the [M + H]+ ions and their optimized collision energies. After validation, the method was applied to screen different type of potatoes, and some cooking experiment were conducted.

Applicability of hybrid linear ion trap-high resolution mass spectrometry and quadrupole-linear ion trap-mass spectrometry for mycotoxin analysis in baby food

Recent developments in mass spectrometers have created a paradoxical situation; different mass spectrometers are available, each of them with their specific strengths and drawbacks. Hybrid instruments try to unify several advantages in one instrument. In this study two of wide-used hybrid instruments were compared: hybrid quadrupole-linear ion trap-mass spectrometry (QTRAP ®) and the hybrid linear ion trap-high resolution mass spectrometry (LTQ-Orbitrap ®). Both instruments were applied to detect the presence of 18 selected mycotoxins in baby food. Analytical parameters were validated according to 2002/657/CE. Limits of quantification (LOQs) obtained by QTRAP ® instrument ranged from 0.45 to 45 μg kg −1 while lower limits of quantification (LLOQs) values were obtained by LTQ-Orbitrap ®: 7–70 μg kg −1. The correlation coefficients ( r) in both cases were upper than 0.989. These values highlighted that both instruments were complementary for the analysis of mycotoxin in baby food; while QTRAP ® reached best sensitivity and selectivity, LTQ-Orbitrap ® allowed the identification of non-target and unknowns compounds.

Characterization of Sulfolipids of Mycobacterium tuberculosis H37Rv by Multiple-Stage Linear Ion-Trap High-Resolution Mass Spectrometry with Electrospray Ionization Reveals That the Family of Sulfolipid II Predominates

Mycobacterium tuberculosis, the causative agent of tuberculosis, is unique among bacterial pathogens in that it contains a wide array of complex lipids and lipoglycans on its cell wall. Among them, the sulfated glycolipid, termed the sulfolipid, is thought to mediate specific host-pathogen interactions during infection. Sulfolipids (SLs), including sulfolipid I (SL-I) and sulfolipid II (SL-II), are 2,3,6,6'-tetraacyltrehalose 2'-sulfates. SL-I was identified as a family of homologous 2-palmitoyl(stearoyl)-3-phthioceranoyl-6,6'-bis(hydroxyphthioceranoy1)trehalose 2'-sulfates and was believed to be the principal sulfolipid of M. tuberculosis strain H37Rv. We cultured and extracted sulfolipids using various conditions, including those originally described, and employed high-resolution multiple-stage linear ion-trap mass spectrometry with electrospray ionization to characterize the structure of the principal SL. We revealed that SL-II, a family of homologous 2-stearoyl(palmitoyl)-3,6,6'-tris(hydroxyphthioceranoy1)trehalose 2'-sulfates, rather than SL-I is the principal sulfolipid class. We identified a great number of isomers resulting from permutation of the various hydroxyphthioceranoyl substituents at positions 6 and 6' of the trehalose backbone for each of the SL-II species in the entire family. We redefined the structure of this important lipid family that was misassigned using the traditional methods 40 years ago.

Application of hybrid linear ion trap-high resolution mass spectrometry to the analysis of mycotoxins in beer

This paper reports the application of liquid chromatography electrospray ionization ion trap–orbitrap mass spectrometry for the determination of 18 mycotoxins (aflatoxins, fumonisins, trichothecenes, ochratoxin A, sterogmatocystin, beauvaricin, zearalenone and zearalenol) in beer. The extraction procedure was carried out by solid phase extraction (SPE): SPE columns were conditioned with acetonitrile/methanol and water. Beer was loaded onto the column which was washed with water. In these conditions, the recoveries were more than 65% and the relative standard deviation (RSD) were below 18%. The lowest limits of quantification (LLOQ) ranged from 9 to 155 ng ml−1. Matrix-matched calibration was performed for each beer and reliable results were obtained from selected mycotoxins. The method was applied to the analysis of 25 commercial beers. Taking advantage of the hybrid capabilities, the presence of other mycotoxins were checked; enniatins (A, A1, B and B1) and fusaproliferin were studied in all the tested samples. The survey detected the presence of zearalenone in one stout beer sample.