A novel sample preparation method of matrix-assisted laser desorption/ionization time of flight mass spectrometry for polystyrene

A novel sample preparation method of matrix-assisted laser desorption/ionization mass spectrometry for polystyrene was reported. Compared to the conventional dried-droplet method, the efficiency of ionization and signal intensity of mass spectra were improved. The mechanism was also analyzed.

MicrobMatcher: a microbial comparison software based on matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry

Matrix-assisted Laser Desorption/Ionization with Time-of-flight Mass Spectrometry (MALDI-TOFMS) was investigated as a method for the rapid identifica-tion of species. Current demand in microbial identi-fication is how to compare unknown strains to the known one quickly, semi-automatically and accurately. In this paper, we present a software tool that allows flexibly microbial matching in a user-friendly way, by letting the users to customize comparison parameters including: in vitro transcription enzyme, mass tolerance,minimum fragment length, intensity threshold and corresponding weights. We provide three spectral scoring functions to compute the affin-ity between the species. Therefore, the precision of microbial comparison increases. To test and verify this tool, we employed experimental spectral data based on MALDI-TOFMS and the gene sequences of E.coli and Salmonella. This software is written in Java for cross-platform intention.

Two-dimensional gel electrophoresis and surface-enhanced laser desorption ionization-time of flight-mass spectrometry for detection of protein expression profiles in the hippocampus following closed brain injury

Gene expression profile changes in brain regions following traumatic brain injury at the gene level cannot sufficiently elucidate gene expression time, expression amount, protein post-translational processing or modification. Therefore, it is necessary to quantitatively analyze the gene expression profile using proteomic techniques. In the present study, we established a rat model of closed brain injury using Marmarou＇s weight-drop device, and investigated hippocampal differential protein expression using two-dimensional gel electrophoresis and surface-enhanced laser desorption ionization-time of flight-mass spectrometry. A total of 364 protein peaks were detected on weak cation exchange-2 protein chips, including 37 differential protein peaks. 345 protein peaks were detected on immobilized metal affinity capture arrays-Cu, including 12 differential protein peaks Further examination of these differential proteins revealed that glucose-regulated protein and proteasome subunit alpha type 3 expression were significantly upregulated post-injury. These results indicate that brain injury can alter protein expression in the hippocampus, and that glucose-regulated protein and proteasome subunit alpha type 3 are closely associated with the occurrence and development of traumatic brain injury.

The dissociation pathways of N_2^+ in intense femtosecond laser fields

Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mass spectra of N＋ fragment ions. The angular distributions of N^＋ and the laser power dependence of N^＋ yielded from different dissociation pathways show that the dissociation mechanisms mainly proceed through the couplings between the metastable states （A, B and C） and the upper excited states of N^＋.A coupling model of light-dressed potential energy curves of N2^＋ is used to interpret the kinetic energy release of N^＋.

A Time-of-flight Mass Spectrometric Study of the Laser Desorption Dissociation of C_(60) and C_(70)

1 Introduction C60 and other cage-like carbon molecules, or the fullerenes, have become one ofthe most interesting materials in physics, chemistry and materials science in recentyears. In 1985, C60+ ion was found to be prominent in the laser-ablation mass spec-trum of graphite and unusual stability was proposed for C60 later. The discovery byKratschmer and his co-workers of a method for producing macroscopic.quantities ofC60 and C70 in 1990 has stimulated great interest to investigate the properties of C60and other fullerenes. Many papers have been concerned with the dissociationand stability of C60 and its ions. Studies of C60+ dissociation by means

Studies on extracting solutions of endohedral rare-earth metallofullerenes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Thirteen extracting solutions of rare-earth metallofullerenes containing La,Ce,Pr,Nd Sm,Eu,Gd,Tb,Dy,Ho,Er,Tm and Yb respectively have been investigated by means of matrix-assisted laser desorpuon/ ionization time-of-flight mass spectrometry.The influences of the positive-ion/negative-ion mode,laser intensity,ma trix and mass discrimination to the analytical results are studied,based on which the optimal analytical conditions have been determined.The results show that the extracting solutions contain large quantities of rare-earth metallofullerenes besides empty fullerenes.On the basis of comparing their relative intensities,the different structure stabilities and solubilities of metallofullerenes with different rare-earth metals encapsulated into the fullerene cages,as well as some possible reasons to those differences,are discussed.

Detection of Sialylated N-Linked Glycans by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Native and methyl-esterified sialylated glycans were analyzed with 2,4,6-trihydroxyacetophenone（THAP）and 2,5-dihydroxybenzoic acid（DHB）as matrix by a matrix-assisted laser desorption/ionization time-of-flight mass spectrometer（MALDI-TOF MS）.High quality negative-ion spectra of commercial sialylated glycan were obtained with THAP as matrix.Detection limit of the glycan was less than 0.1 pmol.After methyl esterification of sialic acid（SA）residue,sialylated glycans were detected sensitively in the positive-ion mode using DHB as matrix.Neutral and sialylated glycans from the mixture of asialofetuin and fetuin were methylesterified and simultaneously recognized in one manipulation.Methyl esterification of SA residue offers a convenient and sensitive way to identify the structure of N-linked glycans for glycan profiling.

Mass spectrometry-based serum peptide profiling in hepatocellular carcinoma with bone metastasis

AIM: To investigate the potential of serum peptides as a diagnostic tool for hepatocellular carcinoma (HCC) with bone metastasis.

Identification of serum biomarkers for diagnosing stage Ⅰ lung adenocarcinoma by MALDI-TOF mass spectrometry

Objective To identify specific biomarkers that could improve early diagnosis of lung adenocarcinoma using matrix-assisted laser desorption/ionization (MALDI) technology. Methods Serum samples were isolated from 17 patients with stage Ⅰ lung adenocarcinoma and 17 age-and sex-matched healthy controls,and the serum proteomic profiles were obtained by matrix-assisted laser desorption ionization time of flight (MALDI-TOF) mass spectrometry. Results Compared with healthy control group,two highly expressed potential biomarkers were identified with the relative molecular weights of 6 631.64 Da and 4 964.21 Da. The two best novel protein peaks were automatically chosen for the system training and the development of the constructed model. The constructed model was then used to test an independent set of masked serum samples from 15 lung adenocarcinoma patients and 22 healthy individuals. The analysis yielded a sensitivity of 93.3%,and a specificity of 95.5%. Conclusion These results suggest that MALDI-TOF-MS ProteinChip technology is a quick,convenient,and high-output analyzing method that is capable of selecting several relatively potential biomarkers from the serum of lung adenocarcinoma patients and may have a clinical value in the future,and will provide clues to identifying new serologic biomarkers of lung adenocarcinoma.

Establishment and Preliminary Application of Two dimensional Electrophoresis and Mass Spectrometry in Ovary Study

Objective To apply two-dimensional electrophoresis and mass spectrometry in the ovary proteome researchMethods Protein extractions from mouse ovaries were run in IPGphor isoelectric focus system with 11 cm and 24 cm IPG strips respectively (pH 3～10, 0.3 mm thick), then the protein spots were identified by mass spectrometry.Results The ovary protein exactions separated by two-dimensional electrophoresis have got high resolution, and identifing protein by mass spectrometry was highly efficient and facilitly. These two techniques should facilitate further investigation of female reproduction proteome research.Conclusion These two rapid high resolutions and efficient techniques have a variety of applications foreground in female reproduction proteome pattern research.

Determination of persistent organic pollutants by gas chromatography/laser multiphoton ionization/time-of-flight mass spectrometry

An authentic mixture of polychlorinated biphenyls was measured using a short wide-bore capillary column for the group separation of major components present in an actual sample of Kanechlor. The limits of detection were improved by ca. 2 fold in comparison with those obtained using a conventional capillary column, since the retention time was reduced and the amount of analytes introduced into the mass spectrometer per unit time could be increased. On the other hand, surface-water and sediment samples containing polycyclic aromatic hydrocarbons （PAHs） were collected from the river located in the vicinity of a waste water treatment plant. Even acenaphthylene, a minor component of the mixture could be measured for the sediment sample, and the concentra- tions were determined for several heavy PAHs. As demonstrated, a technique involving laser multiphoton ionization/time-of-flight mass spectrometry was useful as a sensitive and selective analytical tool for the trace analysis of persistent organic pollutants in an environmental sample.

Xe-Kr laser induced collisional ionization system and experimental preparation of its initial state: Four-photon resonant excitation

This paper proposes a novel one-colour Xe-Kr laser induced collisional ionization system. Considering the level scheme of the system, it finds that the initial state of the reaction--the four 4f levels with even J of Xe-can be prepared through method of four-photon resonant excitation by dye laser with wavelength of -440 nm. Absorption of an additional photon （the transfer laser） of the same wavelength will complete the laser induced collisional ionization process. The resonance enhanced ionization spectrum of Xe by four laser photons at -440nm is measured through time-of-flight mass spectrometry, this aims at the preparation of the initial state of the system proposed. The Stark broadening of the measured spectrum is observed and consistent with the previous study. Analysis of the measured resonance ionization spectrum implies the feasibility of -440 nm four-photon resonant excitation of the initial 4f state of the Xe Kr system proposed in this paper, which prepares for a further experiment of laser induced collisional ionization.

磁性氮化碳复合材料的制备及其对磷酸化肽的富集

蛋白质的磷酸化在细胞信号传导和疾病发生发展中起着重要作用,但磷酸化的动态变化和低丰度的特点使得对其直接分析有着较大的困难。为了解决磷酸化肽难离子化、检测丰度低的瓶颈问题,本研究制备了一种磁性氮化碳复合材料,结合基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS),建立了一种对复杂样品中低丰度磷酸化肽富集与分析的方法。采用电子显微镜、红外光谱分析及X射线衍射分析等手段对合成的磁性氮化碳材料进行表征。以酪蛋白酶解产物为实验模型,发现磁性氮化碳材料能够实现对磷酸化肽的高选择性富集和高灵敏度检测,检出限为0.1 fmol。选择脱脂牛奶、人唾液和人血清为实际分析样品,发现磁性氮化碳材料对微量蛋白生物样品中磷酸化肽的分析具有较高的应用潜力。

建立一种适合本实验室快速检测产KPC酶肺炎克雷伯菌的方法

目的运用基质辅助激光解吸电离飞行时间质谱技术(MALDI-TOF MS)检测产肺炎克雷伯菌碳青霉烯酶(KPC)耐碳青霉烯类肺炎克雷伯菌(CRKP),筛选并验证其特征峰,建立一种适用于本实验室快速检测产KPC酶型CRKP的方法。方法收集临床耐碳青霉烯类肺炎克雷伯菌39株,运用PCR方法检测出其中23株产KPC酶,再采用MALDI-TOF MS技术检测KPC酶阳性CRKP菌株,得到质谱图后用Flex Analyst软件分析筛选出其中特征峰,并进行重复性实验和临床验证评估。结果综合筛选出产KPC酶CRKP最佳特征峰为m/z 6432,特征峰验证实验和重复性实验的特异性和敏感性分别为96.67%和100%。临床验证评估特异性和敏感性分别为92.31%和100%。结论利用MALDI-TOF MS技术可检出产KPC酶CRKP的最佳特征峰为m/z 6432,经实验证实该特征峰特异性和敏感性高,可为临床快速诊断和治疗产KPC酶CRKP提供理论基础。

核酸MALDI-TOF MS检测在肺结核诊断中的价值

目的探讨基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)在疑似肺结核(PTB)诊断中的应用价值及其阳性结果的影响因素,以期为临床治疗提供参考。方法选取甘肃省第二人民医院(西北民族大学附属医院)2022年8月—2023年3月收治的疑似PTB患者77例为研究对象。所有患者肺泡灌洗液(BALF)均接受MALDI-TOF MS检测和结核分枝杆菌(MTB)培养。根据MTB培养结果,对核酸MALDI-TOF MS检测进行诊断效能分析,并探讨核酸MALDI-TOF MS检测阳性的影响因素。结果核酸MALDI-TOF MS检测结果显示,MTB阳性共37例(48.1%,37/77),40例阴性(51.9%,40/77)。以培养结果为金标准,核酸MALDI-TOF MS的灵敏度、特异度、阳性预测值(PPV)、阴性预测值(NPV)和准确度分别为90.9%、84.1%、81.1%、92.5%和87.0%,采用Kappa检验法评价核酸MALDI-TOF MS检测和MTB培养法的一致性,结果显示Kappa值为0.739(P<0.05)。2组患者在是否有糖尿病、身体质量指数(BMI)及降钙素原(PCT)方面比较,差异均有统计学意义(P<0.05)。多因素Logistic回归分析结果显示:有糖尿病和PCT异常为核酸MALDITOF MS阳性的独立危险因素(P<0.05)。结论核酸MALDI-TOF MS检测对PTB的早期诊断具有重要价值,可为患者的规范用药提供更好的指导,即为患者的治疗制定更为精准、有效的治疗方案,从而提高治疗效果、改善患者生活质量。

基质辅助激光解吸电离飞行时间质谱在食源性致病菌鉴定中的应用

基质辅助激光解吸电离飞行时间质谱(matrix assisted laser desorption ionization time of flight mass spectrometry,MALDI-TOF MS)作为近年来发展的新型食源性致病菌鉴定技术,具有灵敏、准确、检测速度快等优点,该技术为食品病原微生物靶标性监测和食品安全事件应急检验提供了一种高效的鉴别技术参考,在保障民众生命健康和经济社会发展上发挥了重要作用。本文检索了近年来国内外MALDI-TOF MS技术在食源性致病菌检测中的相关研究案例,简要综述了MALDI-TOF MS检测原理、工作流程,影响鉴定结果的主要因素,介绍了MALDI-TOF MS技术应用于食源性致病菌检测中的实际案例,在此基础上分别从参考菌株数据库建设、标准化程序规范等方面对MALDI-TOF MS技术在食源性致病菌检测领域的未来研究方向进行展望,以期为后续食品安全检测及快速监管食源性致病菌污染提供技术支持。

血培养阳性样本快速菌种鉴定和药物敏感性分析

目的分析分离胶离心富集和5 h培养2种前处理方法在血培养阳性样本快速菌种鉴定和快速药物敏感性分析中的临床应用价值。方法收集2021年10月—2022年10月宁波大学附属第一医院报阳的血培养样本211例,分别采用分离胶离心富集和5 h培养(快速方法),以及12 h培养(标准方法)3种方法进行前处理。采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS,简称MS)对3种方法处理的血培养阳性样本进行快速菌种鉴定。采用自动化鉴定药敏仪对156例需氧瓶报阳血培养样本进行药物敏感性试验。以常规培养(18~24 h)+MS鉴定结果为标准,比较5 h培养+MS和分离胶离心富集+MS 2种快速方法菌株鉴定准确率。以培养24 h后仪器法药物敏感性试验结果为标准,判断5 h培养和分离胶离心富集后仪器法药物敏感性试验结果与标准方法的一致率。结果2种快速方法鉴定准确率最高的菌种为粪肠球菌,分别为100.00%、87.50%;5 h培养+MS对链球菌属的鉴定准确率较低(33.33%)。2种快速方法对肠杆菌科和非发酵菌的药物敏感性分析结果与标准培养+MS的药物敏感性分析结果一致性分别超过73.00%和85.00%;对葡萄球菌属和肠球菌属部分抗菌药物的药物敏感性分析结果一致性达100.00%;对万古霉素的药物敏感性分析结果一致性最低,为70.73%。结论5 h培养+MS和分离胶离心富集+MS可快速判断血培养阳性样本病原菌种类及其耐药性,准确率较高,适合在临床微生物实验室推广。

饮用水中高分子量消毒副产物的检测识别方法

消毒是饮用水处理过程中的重要步骤,但普遍采用的氯系消毒剂在杀灭细菌病毒的同时,能产生大量具有“三致”效应的卤代消毒副产物(DBPs),严重威胁了饮用水的化学安全.研究人员已在饮用水中陆续检测并识别出700多种DBPs,但这些已知DBPs均为分子量小于800 Da的低分子量DBPs,目前对高分子量DBPs的认识还较为有限.本研究建立了基于基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)的高分子量DBPs检测方法,发现在基质为2,5-二羟基苯甲酸,阳离子化试剂为三氟乙酸钠,使用三明治法点靶,反射-正离子模式,90%激光强度时,信噪比和信号重现性达到最优,信噪比之和达到了136.2,变异系数(CV)则为4.77%.利用上述方法,在模拟饮用水中检测到5种新的高分子量DBPs.在此基础上,通过同位素模式分析、TOF/TOF串联质谱和数据库验证,建立了针对未知高分子量DBPs的分子式/结构式识别方法,确定新的高分子量DBPs为寡糖羧酸类物质.

基质辅助激光解吸电离-飞行时间质谱法快速测定米饭和乳制品中蜡样芽孢杆菌呕吐毒素Cereulide

建立基质辅助激光解吸电离-飞行时间质谱(matrix-assisted laser desorption ionization time-of-flight mass spectrometry,MALDI-TOF MS)法分析蜡样芽孢杆菌呕吐毒素Cereulide的快速检测方法。分析了Cereulide标准物质的裂解规律,考察基质种类、点靶方式、基质溶剂和用量、激光强度等对Cereulide的质谱信号强度的影响,并进行方法学验证和实际样品检测。结果表明,选择以α-氰基-4-羟基肉桂酸为基质,均匀分散在50%乙腈-水(含0.1%三氟乙酸)中,采用先点基质再点样品的点样方式,反射线性正离子模式下选择激光强度70%进行食品中MALDI-TOF MS筛查时,可检测到Cereulide的[M+Na]^(+)和[M+K]^(+)目标离子峰,此质谱信号稳定、强度高、响应重复性好。方法学验证结果表明,Cereulide的[M+Na]^(+)和[M+K]^(+)目标离子峰在5~100 ng/mL范围内线性好,相关系数(r)>0.99;方法的检出限分别为3.0 ng/g和5.0 ng/g;对米饭和牛乳样品的加标回收率为73.3%~118.2%,相对标准偏差为0.3%~10.9%(n=6)。本方法分析速度快、准确性高、灵敏度好、抗干扰能力强、无需内标即可实现对米饭和乳制品中Cereulide的批量筛查和检测。

半夏炮制过程中毒性凝集素蛋白的基质辅助激光解吸电离飞行时间质谱分析

基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)受灵敏度和重复性的影响,对完整蛋白的定量分析存在困难。本研究采用纤维素纳米晶体(CNC)辅助MALDI-TOF MS,结合内标法定量分析半夏炮制过程中半夏凝集素(PTL),通过优化CNC辅助样本制备的时长和比例,以麦胚凝集素(TVL)为内标,直接分析不同炮制程度半夏各炮制品及其浸泡上清液中PTL含量。结果表明,CNC辅助MALDI样本制备有效提升了MALDI-TOF MS定量分析的线性和重复性。随着炮制时间的延长,姜半夏、清半夏和法半夏炮制品的PTL含量逐渐下降,浸泡上清液中PTL含量逐渐上升。其中,由于pH值的改变,法半夏炮制品浸泡上清液中PTL含量呈先上升后下降的趋势。此外,将该方法应用于不同饮片生产企业的多批次半夏炮制品饮片中,均未检出PTL。该方法操作简便,可有效分析半夏炮制过程中PTL含量的变化,为研究半夏炮制过程对PTL的影响提供了参考。