Temperature-programmed Desorption Mass Spectrometry

Temperature-programmed desorption mass spectrometry (TPD MS) is discussed with reference to studies of modified pyrogenic oxides. Simple theoretical models are presented in order to allow an approximate analytical treatment of TPD MS data. The formulae for rate constant are presented for first-, second- and third-order reactions. Products of thermal decomposition of carbonized surface layer are observed and identified. The different pathways of uni- and bimolecular desorption were investigated by temperature-programmed desorption mass spectrometry. The rate constants of reactions were derived from TPD MS measurements. Applications of TPD MS to investigation of endocrine disruptors fate and formations on the solid aerosol surface are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Field Desorption Mass Spectrometry

Field desorption (FD) enables mass-spectrometric investigation of large organic molecules without their vaporization. The present state of our theoretical understanding of the ionization of these molecules in the adsorbed state on organic emitters is described. The special problems of the technique and prospective developments in the apparatus for future analytical problems are outlined. The present progress report concentrates on analytical studies of biochemical model compounds and degradation products from environmental chemicals and drugs. The method is particularly suitable for the detection and identification of submicrogram quantities of underivatized polar substances present in complex mixtures or pre-purified extracts from biological materials.     

膦桥过渡金属杂双核络合物场解吸质谱研究

本文报道了采用场解吸电离质谱（ＦＤＭＳ）技术获得的膦桥过渡金属杂双核络合物系列化合物的质谱图，讨论了该系列络合物的裂解规律和离子源条件下的稳定性。结果表明，ＦＤＭＳ技术对研究膦桥过渡金属杂双核络合物是有效的方法。     

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.     

场解吸质谱法对富勒烯的定量分析研究

首次报道了用场解吸质谱法（ＦＤＭＳ）对富勒烯Ｃ_（６０）和Ｃ_（７０）同时进行定量分析的方法，方法的相对偏差为±１％。与ＨＰＬＣ法比较，两者的偏差在±０．５％以内。特点是不需任何标准样品，并可同时对多种富勒烯的组分进行定性和定量分析。     

Desorption Mass Spectrometry for Nonvolatile Compounds Using an Ultrasonic Cutter

In this work, desorption of nonvolatile analytes induced by friction was studied. The nonvolatile compounds deposited on the perfluoroalkoxy substrate were gently touched by an ultrasonic cutter oscillating with a frequency of 40 kHz. The desorbed molecules were ionized by a dielectric barrier discharge (DBD) ion source. Efficient desorption of samples such as drugs, pharmaceuticals, amino acids, and explosives was observed. The limits of detection for these compounds were about 1 ng. Many compounds were detected in their protonated forms without undergoing significant fragmentation. When the DBD was off, no ions for the neutral samples could be detected, meaning that only desorption along with little ionization took place by the present technique.

多孔硅表面的激光解吸离子化质谱

多孔硅表面的解吸离子化质谱是一种新的生物质谱分析方法。克服了MALDI-TOF-MS中的基体干扰,适合进行了小分子分析。提出了新的样品制备方法,可以扩大测定范围,消除吸附杂质的干扰。发现该方法与多孔硅的光致光特性及表面疏水性无关。具有纳米结构的多孔硅作为该方法中能量的接收器。利用DIOS方法分析了氨基酸、肽、蛋白、糖等样品。此方法用于环糊精合成产物的分析,也得到了较好的结果。     

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。     

电喷雾-串联四极杆-飞行时间质谱法分析寡肽的一级结构

报道了 3种人工合成寡肽的电喷雾 串联四极杆 飞行时间 (ESI QqTOF)质谱的鉴定方法。采用TOFMS模式分别测定了 3种样品的分子量。再利用子离子模式 (ProductIon)对 [M +H]+ 或 [M +2H]2 + 进行CID分析 ,根据肽类分子的质谱碎裂规律推断寡肽的一级结构。结果表明 :ESI QqTOF质谱能测定出寡肽母离子与子离子的精确分子量 ,质量准确度小于 2 0× 10 - 6 ,能直接区分赖氨酸与谷氨酰氨残基 (Δm =0 .0 36Da) ,可为蛋白质的鉴定提供更准确的氨基酸序列信息 ,是蛋白质组学研究的理想工具。     

卟啉类化合物液相基体激光解吸质谱研究

本文叙述了使用液相基体帮助激光解吸质谱新方法对一系列卟啉类化合物分析研究工作。分别使用硝基苯辛醚和15-冠(醚)-5两种液相基体获得了一系列卟啉类化合物的激光解吸质谱,并对其特点进行了讨论所用方法绝对灵敏度优于0.5 ng。此外,还成功地对多至六个组分的卟啉类化合物进行直接解吸质谱分析。结果表明新的液相基体帮助激光解吸质谱法对卟啉类化合物分析有十分优异的“软”电离特性。     

High-Throughput Label-Free Enzymatic Assays Using Desorption Electrospray-Ionization Mass Spectrometry

High-throughput (HT) enzymatic assays, which typically rely on labeled compounds and plate readers, are important for drug discovery. Mass spectrometry (MS) provides an alternative method of performing HT label-free assays. Here we demonstrate the use of a HT platform based on desorption electrospray ionization (DESI) MS for the label-free study of enzymatic reactions directly from the bioassay matrix with an effective analysis time of 0.3 s per sample. This system allows for thorough analysis of the enzymatic process through monitoring of its substrate and product after an external calibration. We show the platform capabilities by an in-depth study of the acetylcholinesterase assay, including kinetic parameter determination, rapid inhibitor screening, and further characterization of positive hits (that is, IC₅₀ and K_i), as well as inhibition–reactivation assays. We anticipate that the expansion of this platform has high potential impact in label-free enzymology as well as in drug discovery.     

Comparison of Three Plasma Sources for Ambient Desorption/Ionization Mass Spectrometry

Plasma-based desorption/ionization sources are an important ionization technique for ambient surface analysis mass spectrometry. In this paper, we compare and contrast three competing plasma based desorption/ionization sources: a radio-frequency (rf) plasma needle, a dielectric barrier plasma jet, and a low-temperature plasma probe. The ambient composition of the three sources and their effectiveness at analyzing a range of pharmaceuticals and polymers were assessed. Results show that the background mass spectrum of each source was dominated by air species, with the rf needle producing a richer ion spectrum consisting mainly of ionized water clusters. It was also seen that each source produced different ion fragments of the analytes under investigation: this is thought to be due to different substrate heating, different ion transport mechanisms, and different electric field orientations. The rf needle was found to fragment the analytes least and as a result it was able to detect larger polymer ions than the other sources. Figure

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电喷雾解吸电离质谱法用于临床尿样的直接分析

将电喷雾解吸电离质谱(DESI-MS)用于临床尿样的分析, 优化了电喷雾溶剂流速、电喷雾电压和喷雾锥距离等重要参数. 采用普通滤纸作为样品载体, 在不需要样品预处理的前提下同时快速测定了临床尿样中的钾、钠、尿素、尿酸、丙酮酸和肌苷等多种成分, 并对各种成分的主要离子进行了串联质谱鉴定. DESI-MS在进行多组分同时测定时不需要进行样品预处理, 缩短了测定时间, 单个样品的分析时间不到1 min. 同时, 采用内标法对所测定组分进行了半定量分析.     

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。     

富勒醇的直接激光解吸飞行时间质谱分析

采用激光解吸电离飞行时间质谱对富勒醇样品进行研究,并与富勒烯标准品的质谱特征比较,以正负离子模式联合检测方法考察其特征结构。结果显示,正离子模式下,富勒醇碳笼易为规律性的碎裂峰,负离子模式下,则保留碳笼主体结构的特征峰,而富勒烯的碳笼结构在两种模式下不发生变化。表明该方法可以方便、快速地鉴别富勒醇的结构。采用该方法对富勒醇在二甲基亚砜(DMSO)中的稳定性进行分析,结果发现富勒醇可稳定存在于DMSO溶剂中,用于碱式反应条件下合成富勒醇的鉴别与条件筛选,选择反应碱的最佳浓度为1.0 g/mL。     

Desorption/Chemical Ionization Mass Spectrometry of Naturally Occurring Glycosides

Desorption/chemical ionization mass spectrometry (D/CI.-MS.) is a recently developed technique especially indicated for highly polar and non volatile compounds. Various naturally occurring glycosides such as saponins, iridoid and secoiridoid glycosides, cardenolides and flavone-O-glycosides have been investigated by this method. All the measurements were carried out on underivatized compounds. In addition to the structural informations generally furnished by field-desorption mass spectrometry (molecular ion and sugar sequence), the molecular ion and pertinent fragments of the aglycone could also be obtained.     

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。     

Fragmentation Analysis of Bradykinin by 252Cf-Plasma Desorption Mass Spectrometry

The ²⁵²Cf-plasma desorption (PO) mass spectrum of the nonapeptide bradykinin was studied in detail with particular emphasis on the fragmentation pattern resulting from fast metastable decay of the molecular ion. N-acetyl and O-methyl derivatives of bradykinin were used as mass shift species for assignment of N-terminal and C-terminal fragment ions. Thirty-seven sequence-specific fragment ions were identified, including those that are due to cleavage of peptide backbone as well as side chain bonds (i.e., d_n, v_n, w_n fragment ions). The degree of fragmentation correlates with what has been observed by fast atom bombardment tandem mass spectrometry using hi~h energy collisional activation. The high degree of excitation of bradykinin molecules in ²⁵²Cf-POMS is undoubtedly due to the special nature of excitation intrinsic to the ²⁵²Cf_PD process where electronic excitation occurs with a very high probability due to the high electron and photon flux surrounding the nuclear fission fragment track. These results offer further evidence that ²⁵²Cf_PDMS, in addition to providing molecular weight information, can be used to sequence peptides without the need for a second stage of molecular excitation.