Aerosol Matrix-Assisted Laser Desorption Ionization Mass Spectrometry

A new method of liquid sample introduction for a time-of-flight mass spectrometer (TOF-MS) has been developed by applying the method of matrix-assisted laser desorption ionization to aerosols. Analyte biomolecules are dissolved in a methanol solvent along with a UVabsorbing matrix and formed into an aerosol with a pneumatic nebulizer. The aerosol particles are dried in a heated skimmer tube before ionization by pulsed 355-nm UV laser radiation. Mass analysis is achieved in a linear TOF-MS. Results for the ionization of bovine insulin (5733.5 Mw) are reported.     

Infrared Matrix-Assisted Laser Desorption Electrospray Ionization (IR-MALDESI) Imaging Source Coupled to a FT-ICR Mass Spectrometer

Mass spectrometry imaging (MSI) allows for the direct monitoring of the abundance and spatial distribution of chemical compounds over the surface of a tissue sample. This technology has opened the field of mass spectrometry to numerous innovative applications over the past 15 years. First used with SIMS and MALDI MS that operate under vacuum, interest has grown for mass spectrometry ionization sources that allow for effective imaging but where the analysis can be performed at ambient pressure with minimal or no sample preparation. We introduce here a versatile source for MALDESI imaging analysis coupled to a hybrid LTQ-FT-ICR mass spectrometer. The imaging source offers single shot or multi-shot capability per pixel with full control over the laser repetition rate and mass spectrometer scanning cycle. Scanning rates can be as fast as 1 pixel/second and a spatial resolution of 45 μm was achieved with oversampling.

应用基质辅助激光解吸电离飞行时间质谱法测定牛甲状腺球蛋白的分子量

应用基质辅助激光解吸电离飞行时间质谱法测定了牛甲状腺球蛋白的纯度与相对分子量.选择芥子酸为适宜的基质,并对所得的结果进行了讨论.实验结果表明分析方法具有灵敏度高、重现性好、信息直观等特点,明显优于其他传统测定蛋白质的方法.     

基质辅助激光解吸电离质谱成像在指纹分析中的研究进展

基质辅助激光解吸电离质谱(MALDI-MS)是一种高灵敏度、高通量、多组分同时分析的软电离质谱技术,可通过对物质分析实现分子结构的确认及物质分布信息的获取,因此在指纹分析中获得越来越多的关注。 本文从条件优化入手,讲述基质优化过程。 接着介绍了MALDI-MS成像(MALDI-MSI)在指纹分析领域具体的应用,在形态分析研究方面,总结其与常规显现方法联用对成像效果的影响、对疑难指纹的图像处理;在化学信息分析研究方面,分别从根据质谱信息分析生活习惯/案前活动、指纹遗留时间和个体同一认定对各研究的优点及局限性进行评述,最后为MALDI-MSI在指纹领域未来发展提出展望。     

Online Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry with In situ Mixing

Online matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is reported with in situ matrix/analyte aerosol mixing. The analyte and matrix were dissolved in separate solvents and pneumatically atomized into particles. Continuous flows of analyte particles and matrix droplets in nitrogen were mixed in a tee. The resulting particles were sampled using a nozzle, focused into a beam with an aerodynamic lens system, and vertically deposited continuously on a movable target. The matrix/analyte mixture was desorbed/ionized using a 266 nanometers pulsed laser at an incident angle of 45°. The nascent ions were analyzed using reflectron TOF MS. The performance of online MALDI-TOF MS was evaluated by the analysis of palmityl palmitate with the lithium salt of 2, 4-dihydroxybenzoic acid as the matrix. Strong and stable MALDI signals of palmityl palmitate were obtained. The matrix solvent mixture and the analyte concentration were optimized and the results demonstrate the development of an alternative for online MALDI analysis.     

Interrogation of Microporous Silica by Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry

Microporous sol-gels prepared from a tetramethyl orthosilicate precursor with 5-hydroxytryptophan, 5-HTPP, as a dopant were investigated by matrix-assisted laser desorption/ionization mass spectrometry (MALDI). Spectra of 5-HTPP and its oxidation products were obtained when (a) the matrix, -hydroxycinnamic acid, was included in the sol, (b) thin wafers of silica were used, and (c) the surface of the gel was abraded after mounting the sol-gel on the MALDI sample puck so that laser reflection was minimized. The methodology permitted elucidation of the 5-HTPP oxidation pathway. In microporous silica a low molecular product, the dione, was obtained whereas in a mesoporous matrix, dimeric products were formed.     

Analysis of Hanford-Related Organics Using Matrix-Assisted Laser Desorption Ionization Time-Of-Flight Mass Spectrometry

Matrix-assisted laser desorption/ionization coupled with time-of-flight mass spectrometry (MALDI/TOF-MS) was used for the analysis of low-molecular phosphate compounds found in Hanford tank wastes. The mass spectra of these compounds indicate protonated peaks as well as sodium adducts. Analytical methods presently utilized for the analysis of the phosphate-related organics are both time consuming and labor intensive. A promising alternative is MALDI/TOFMS. The MALDI process produces both positive and negative ions directly and very little sample is required. In addition, there is limited sample preparation and minimal hazardous waste production.     

聚芳醚砜环状低聚物的基质辅助激光解吸电离质谱分析

采用基质辅助激光解吸电离飞行时间质谱技术分别对两种合成的聚芳醚砜环状低聚物进行了分析研究，并讨论了低聚物中不同聚合度离子组份的分布规律。     

OmniSpect: An Open MATLAB-Based Tool for Visualization and Analysis of Matrix-Assisted Laser Desorption/Ionization and Desorption Electrospray Ionization Mass Spectrometry Images

We present omniSpect, an open source web- and MATLAB-based software tool for both desorption electrospray ionization (DESI) and matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) that performs computationally intensive functions on a remote server. These functions include converting data from a variety of file formats into a common format easily manipulated in MATLAB, transforming time-series mass spectra into mass spectrometry images based on a probe spatial raster path, and multivariate analysis. OmniSpect provides an extensible suite of tools to meet the computational requirements needed for visualizing open and proprietary format MSI data.      

Negative Ion In-Source Decay Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry for Sequencing Acidic Peptides

Matrix-assisted laser desorption/ionization (MALDI) in-source decay was studied in the negative ion mode on deprotonated peptides to determine its usefulness for obtaining extensive sequence information for acidic peptides. Eight biological acidic peptides, ranging in size from 11 to 33 residues, were studied by negative ion mode ISD (nISD). The matrices 2,5-dihydroxybenzoic acid, 2-aminobenzoic acid, 2-aminobenzamide, 1,5-diaminonaphthalene, 5-amino-1-naphthol, 3-aminoquinoline, and 9-aminoacridine were used with each peptide. Optimal fragmentation was produced with 1,5-diaminonphthalene (DAN), and extensive sequence informative fragmentation was observed for every peptide except hirudin(54–65). Cleavage at the N–Cα bond of the peptide backbone, producing c′ and z′ ions, was dominant for all peptides. Cleavage of the N–Cα bond N-terminal to proline residues was not observed. The formation of c and z ions is also found in electron transfer dissociation (ETD), electron capture dissociation (ECD), and positive ion mode ISD, which are considered to be radical-driven techniques. Oxidized insulin chain A, which has four highly acidic oxidized cysteine residues, had less extensive fragmentation. This peptide also exhibited the only charged localized fragmentation, with more pronounced product ion formation adjacent to the highly acidic residues. In addition, spectra were obtained by positive ion mode ISD for each protonated peptide; more sequence informative fragmentation was observed via nISD for all peptides. Three of the peptides studied had no product ion formation in ISD, but extensive sequence informative fragmentation was found in their nISD spectra. The results of this study indicate that nISD can be used to readily obtain sequence information for acidic peptides.

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Advanced Mass Calibration and Visualization for FT-ICR Mass Spectrometry Imaging

Mass spectrometry imaging by Fourier transform ion cyclotron resonance (FT-ICR) yields hundreds of unique peaks, many of which cannot be resolved by lower performance mass spectrometers. The high mass accuracy and high mass resolving power allow confident identification of small molecules and lipids directly from biological tissue sections. Here, calibration strategies for FT-ICR MS imaging were investigated. Sub-parts-per-million mass accuracy is demonstrated over an entire tissue section. Ion abundance fluctuations are corrected by addition of total and relative ion abundances for a root-mean-square error of 0.158?ppm on 16,764 peaks. A new approach for visualization of FT-ICR MS imaging data at high resolution is presented. The ??Mosaic Datacube?? provides a flexible means to visualize the entire mass range at a mass spectral bin width of 0.001?Da. The high resolution Mosaic Datacube resolves spectral features not visible at lower bin widths, while retaining the high mass accuracy from the calibration methods discussed.     

基质辅助激光解吸电离质谱分析糖类物质

基质辅助激光解吸电离质谱（MALDI-MS）是一种样品无需衍生、图谱解析简单、灵敏度高、快速便捷的分析生物样品结构的方法,已被广泛用于糖类物质的结构分析。此技术与HPLC、糖苷酶外切技术以及各种串联质谱等技术结合使用,可给出糖类物质详细的结构信息。本文介绍了基质辅助激光解吸（MALDI）离子化技术的原理、特点、与飞行时间质量分析器（TOF）联用时的相关技术和裂解方式,以及MALDI-MS在分析糖类物质时选用的基质、样品的制备、糖链碎片分析的方法和在不同糖型分析中的应用,展示了它的发展前景。随着MALDI对糖类物质分析时基质的改进、质谱分辨率的提高、质量检测范围的扩大,MALDI-MS技术必将成为糖类物质分析中强有力的工具。     

表面活性剂的基体辅助激光解吸电离/质谱分析表征

利用基体辅助激光解吸电离／质谱（MALDI－MS）技术对表面活性剂的分析表征进行了详细研究。以2，5－二羟基苯甲酸作为基体，考察MALDI样品制备方法如液滴干燥法、快速干燥法及三明治法对测定结果的影响，发现三明治方法更适合表面活性剂的分析。MALDI可以准确测定离子型表面活性剂的分子量，同时对于非离子型表面活性剂，还可以测定其平均聚合度和分子量的分布。     

基质辅助激光解析电离飞行时间质谱分析合成聚合物样品制备的研究进展

基质辅助激光解析电离飞行时间质谱（MALDI-TOF-MS）在合成聚合物的表征手段中具有不可替代的优点,可以提供聚合物的质量分布、嵌段长度、端基等信息.但由于合成聚合物的离子化效率通常不佳,因此样品制备是分析成功的关键.从基质、基质添加剂以及混样方式3个方面综述了MALDI-TOF质谱分析合成聚合物样品制备的研究进展.     

MALDI－TOF－MS法分析人血清白蛋白

用基质辅助激光解吸附飞行时间质谱（ＭＡＬＤＩ－ＴＯＦ－ＭＳ）法分析测定了人血清白蛋白。结果表明，全军血液制品研究中心应用Ｒｉｖａｎｏｌ和Ｃｏｈｎ＇ｓ两种方法分离提取的人血清白蛋白，其分子量与理论计算值相吻合，其纯度与市售标准人血清白蛋白相一致，用ＭＡＬＤＩ－ＴＯＦ－ＭＳ法分析鉴定人血清白蛋白，准确、简便和灵敏（仅需ＰＭ浓度样品），且重复性好，日内和日间差的变异系数均小于０．０３％，是ＳＤＳ－ＰＡＧＥ电泳法所无法比拟的。     

基质辅助激光解吸电离飞行时间质谱表征双二氮杂萘酮化合物

采用基质辅助激光解吸电离飞行时间质谱(MAIDI-TOF MS)，以2，5-二羟基苯甲酸(DHB)为基体对10种合成的新型双二氮杂萘酮化合物进行了质谱分析，得到了较强的样品准分子离子信号；对校正标样进行了筛选并讨论了标样对测定准确度的影响；研究了样品与金属离子形成加成物的性质。     

基质辅助光解吸电离飞行时间质谱测定双二氮杂萘酮苯醚芳香聚合物

基质辅助光解吸电离飞行时间质谱测定双二氮杂萘酮苯醚芳香聚合物;MALDI-TOF MS     

Large-Area Graphene Films as Target Surfaces for Highly Reproducible Matrix-Assisted Laser Desorption Ionization Suitable for Quantitative Mass Spectrometry

Due to the known sweet-spot issues that intrinsically arise from inhomogeneous formation of matrix-analyte crystals utilized as samples in matrix-assisted laser desorption ionization (MALDI) mass spectrometry, its reproducibility and thus its applications for quantification have been somewhat limited. In this paper, we report a simple strategy to improve the uniformity of matrix-analyte crystal spots, which we realized by adapting large-area graphene films, i.e., non-inert, interacting surfaces, as target surfaces. In this example, the graphitic surfaces of the graphene films interact with excess matrix molecules during the sample drying process, which induces spontaneous formation of optically uniform MALDI sample crystal layers on the film surfaces. Further, mass spectrometric imaging reveals that the visible uniformity is indeed accompanied by reproducible MALDI ionization over an entire sample spot, which greatly suppresses the appearance of sweet spots. The results of this study confirm that the proposed method achieves good linear responses of ion intensity to the analyte concentration (R² > 0.99) with small relative standard deviations (σ < 10%), which is a range applicable for quantitative measurements using MALDI mass spectrometry.

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Characterization of Potential Protein Biomarkers for Major Depressive Disorder Using Matrix-Assisted Laser Desorption Ionization/Time-of-Flight Mass Spectrometry

Matrix-assisted laser desorption ionization/time-of-flight (MALDI-TOF) mass spectrometry is a sensitive analytical tool for characterizing various biomolecules in biofluids. In this study, MALDI-TOF was used to characterize potential plasma biomarkers for distinguishing patients with major depressive disorder (MDD) from patients with schizophrenia and healthy controls. To avoid interference from albumin—the predominant protein in plasma—the plasma samples were pretreated using acid hydrolysis. The results obtained by MALDI-TOF were also validated by electrospray ionization-quadrupole time-of-flight (ESI-QTOF) mass spectrometry. The analytical results were further treated with principal component analysis (PCA), hierarchical clustering analysis (HCA), and receiver operating characteristic (ROC) curve analysis. The statistical analyses showed that MDD patients could be distinguished from schizophrenia patients and healthy controls by the lack of apolipoprotein C1 (Apo C1), which, in fact, was detected in healthy controls and schizophrenia patients. This protein is suggested to be a potential plasma biomarker for distinguishing MDD patients from healthy controls and schizophrenia patients. Since sample preparation for MALDI-TOF is very simple, high-throughput plasma apolipoprotein analysis for clinical purposes is feasible.