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.     

高电压辅助激光解吸附离子化质谱中盐效应的研究

通过与电喷雾质谱( Electrospray ionization mass spectrometry, ESI-MS)对比的方式,对高电压辅助激光解吸附离子化质谱( High-voltage-assisted laser desorption ionization mass spectrometry,HALDI-MS)中的盐效应进行了研究。在正、负离子模式下,分别以L-酪氨酸、β-环糊精、α-硫辛酸以及α-硫辛酸-β-环糊精复合体系为例,对比分析了加盐前后所得的ESI-MS和HALDI-MS谱图,发现HALDI-MS比ESI-MS具有更高的盐容忍度。本实验还发现在HALDI-MS中加入适量盐会引起α-硫辛酸与β-环糊精络合离子信号增强的特殊现象,并提出了产生这种信号增强作用的原因是溶液中盐类阳离子与α-硫辛酸-β-环糊精复合体系形成了三元复合物。     

基质辅助激光解吸电离质谱表征新型环状聚芳酯预聚体

应用基质辅助激光解吸电离质谱技术对新型环状聚芳酯预聚体进行了表征，从而确定了该环素聚合物不同聚合度（ｎ＝１，２……８）的存在，获得了满意的结果。实验证明本方法是测定环状聚合物不同聚合度快速、有效、准确的方法。     

基质辅助激光解析电离质谱和电喷雾质谱共同快速确证达托霉素结构

运用基质辅助激光解析电离-飞行时间串联质谱(MALDI-TOF/TOF MS)和电喷雾-四级杆-飞行时间质谱(ESI-Q-TOF MS)快速确证环脂肽达托霉素的结构。首先,ESI检测达托霉素相对分子量为1619.7107,与理论值偏差0.0007。选择其双电荷峰m/z 809.848作为母离子进行ESI串联质谱(MS/MS)测定,成功匹配了达托霉素环外氨基酸序列C9H19CO-Trp-Asn-Asp。其次,优化Li OH裂解达托霉素的实验条件,以MALDITOF/TOF MS监测开环效果,获得95%以上的开环样本后,分别运用MALDI和ESI进行MS/MS测定,达托霉素开环产物的b+和y+全部被匹配,达托霉素全部氨基酸序列得到确证。最后,对开环产物的ESI-MS/MS条件进一步优化,获得了丰富的低端碎片离子,解析了脂肪酸链结构,并绘制了脂肪酸链的裂解图。本方法快速、简便、准确,是确证环脂肽类化合物结构的可靠方法。     

Minimization of Fragmentation and Aggregation by Laser Desorption Laser Ionization Mass Spectrometry

Measuring average quantities in complex mixtures can be challenging for mass spectrometry, as it requires ionization and detection with nearly equivalent cross-section for all components, minimal matrix effect, and suppressed signal from fragments and aggregates. Fragments and aggregates are particularly troublesome for complex mixtures, where they can be incorrectly assigned as parent ions. Here we study fragmentation and aggregation in six aromatic model compounds as well as petroleum asphaltenes (a naturally occurring complex mixture) using two laser-based ionization techniques: surface assisted laser desorption ionization (SALDI), in which a single laser desorbs and ionizes solid analytes; and laser ionization laser desorption mass spectrometry (L²MS), in which desorption and ionization are separated spatially and temporally with independent lasers. Model compounds studied include molecules commonly used as matrices in single laser ionization techniques such as matrix assisted laser desorption ionization (MALDI). We find significant fragmentation and aggregation in SALDI, such that individual fragment and aggregate peaks are typically more intense than the parent peak. These fragment and aggregate peaks are expected in MALDI experiments employing these compounds as matrices. On the other hand, we observe no aggregation and only minimal fragmentation in L²MS. These results highlight some advantages of L²MS for analysis of complex mixtures such as asphaltenes.

Direct Analysis of Triacylglycerols from Crude Lipid Mixtures by Gold Nanoparticle-Assisted Laser Desorption/Ionization Mass Spectrometry

Triacylglycerols (TAGs), essential energy storage lipids, are easily detected by conventional MALDI MS when occurring on their own. However, their signals are easily overwhelmed by other lipids, mainly phosphatidylcholines (PCs) and, therefore, require purification. In order to profile TAGs from crude lipid mixtures without prefractionation, we investigated alternative matrixes that can suppress phospholipid ion signals and enhance cationization of TAGs. We found that an aqueous solution of citrate-capped gold nanoparticles (AuNPs) with a diameter of 12 nm is a superior matrix for the laser desorption/ionization mass spectrometry (LDI MS) of TAGs in crude lipid mixtures. The AuNP matrix effectively suppressed other lipid signals such as phospholipids and also provided 100 times lower detection limit for TAGs than 2,5-dihydroxybenzoic acid (DHB), the best conventional MALDI matrix for TAGs. The AuNP-assisted LDI MS enabled us to obtain detailed TAG profiles including minor species directly from crude beef lipid extracts without phospholipid interference. In addition, we could detect TAGs at a trace level from a total brain lipid extract.

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.     

基体辅助激光解吸电离飞行时间质谱法测定钙调素的分子量

近几年来，由于各种“软”电离技术的发展和应用「‘，’‘，为利用质谱分析生物大分子提供了一条十分有效的途径［‘j，其中基体辅助激光解吸电离飞行时间质谱法（MALDI－TOF－MS）是最有前途的技术之一D‘．钙调素（CaM）是动植物中普遍存在的多功能的胞内钙受体蛋白，参与调控许多生理反应［”．最近几年也在细胞外区域发现了钙调素及其功能［”．钙调素分子量的准确、快速测定是钙调素性质、结构和功能研究的首要问题．目前CaM分子量的测定大多采用SDS－PAGE、凝胶过滤和沉淀平衡等方法，例如对牛脑CaM分子量的SDS－PAGE测…     

激光解吸电离质谱新型液相基质研究

选用包括纳米粒子在内的多种基质化合物,构成了多种不同组成的液相基质.以多肽、蛋白、大环寡糖和有机小分子等数种类型化合物为样品,系统地考察了不同液相基质在基质辅助激光解吸电离飞行时间质谱(MALDI-TOF)分析中的应用情况,探讨了与固体制样方法的异同点.实验结果表明,有些液相基质对多类化合物具有较好的通用性,而有些液相基质对某些特定类型化合物的分析特别有效.     

双步激光解析/激光电离质谱法及其应用的新进展

激光光电离技术已广泛应用于质谱领域.基于单束激光的基质辅助激光解析(MALDI)质谱分析方法,已成为质谱分析生物大分子的标准方法之一.本文介绍的是另一种新的激光质谱分析方法:双步激光解析/激光电离质谱法(L2MS),与MALDI相比,该方法不需要加入与样品形成共结晶的基质,同时可通过独立地改变两束激光的光强和波长达到优...     

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.     

激光解吸电离飞行时间质谱下的银簇行为

近年来,对金属簇的研究已成为化学与物理学中最活跃的研究领域之一［１］．金属簇被认为是介于单个原子与固体之间的中间相［２］．深入地研究其结构、形成机理及物理与化学行为,对于寻找新的催化剂［３］,重新认识气相化学与凝聚相化学的关系［４］,都有非常重要的意...     

稠环齐聚物结构的激光解吸电离飞行时间质谱表征

应用激光解吸电离飞行时间质谱对几种不同结构的吡嗪稠环齐聚物进行了表征.样品溶解在二甲基亚砜中,以正离子方式记录谱图,结果发现除了产生目标化合物的质子化的分子离子峰外,还产生了少量的碎片分子离子峰.结果表明激光解吸电离飞行时间质谱能有效地、快速准确地给出这类化合物的分子离子峰,为吡嗪类稠环齐聚物的研究提供了有效的表征方法.     

基体辅助激光解吸电离飞行时间质谱用于寡糖的分析

将基体辅助激光解吸电离飞行时间质谱这种新兴的质谱方法用于植物中寡糖的分析。比较了不同的样品制备方法和检测方法对分析结果的影响,给出各寡糖样品的分子量分布,单体和端基基团的分子量。     

壳聚糖的基质辅助激光解吸电离飞行时间质谱分析

利用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)分析甲壳素脱乙酰化降解产物——壳聚糖,对基质、制样方法等影响MALDI-TOF-MS测定结果的因素进行了研究。实验发现,以2,5-二羟基苯甲酸(DHB)为基质,二次结晶法制样分析壳聚糖,既获得了壳聚糖的分子量信息,又可以推断壳聚糖的脱乙酰度,对壳聚糖的制备及其质量与性能控制有着十分重要的指导意义。     

基体辅助激光解吸—电离飞行时间质谱法分析衍生化的寡链糖

以２，５－二羟基苯甲酸（ＤＨＢ）＋间硝基苄醇（ＮＢＡ）混合基体辅助激光解吸电离飞行时间质谱法（ＭＡＬＤＩ）分析甲壳素降解并衍生化的寡链糖，获得了满意的结果。对比其它基体，如：芥子酸（ＳＡ）、α－氰基－４－羟基肉桂酸等（α＿ＣＨＣＡ），２，５＿ＤＨＢ＋ＮＢＡ混合基体解吸电离效果最好：信号强、信噪比高。甲壳素降解产物的质谱分析至今未见报道。     

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.     

单分散聚苯胺齐聚物的激光解吸电离质谱

采用基质辅助激光解吸电离飞行时间质谱（ＭＡＬＤＩ－ＴＯＦ－ＭＳ）技术分别对８个单分散的聚苯胺齐聚物进行了分析研究。实验结果表明,ＭＡＬＤＩ－ＴＯＦ－ＭＳ不但可以作为分析单分散聚苯胺齐聚物的直观、准确、快速的分析工具,而且可以为合成路线的确定提供有利的证据。     

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。     

Laser Desorption Ionization Versus Electrospray Ionization Mass Spectrometry: Applications in the Analysis of Cluster Anions

Mass spectra of transition metal carbonyl cluster anions were recorded using laser desorption ionization time-of-flight (LDI-TOF) and electrospray ionization (ESI) techniques. The LDI spectra generally contain peaks corresponding the intact cluster together with extensive CO loss fragments ions whereas the ESI spectra exhibit peaks corresponding the intact cluster together with few (if any) CO loss fragment ions. The parameters of both techniques can be modified to vary the extent of fragmentation. In all cases no fragmentation of the metal core is observed. Overall, ESI is a more informative method for the analysis of these types of cluster anions.