基质辅助激光解吸电离飞行时间质谱法分析核糖核酸酶

应用基质辅助激光解吸电离飞行时间质谱法(MALD I-TOF-MS)成功地对核糖核酸酶相对分子量进行测定。探讨三种不同基质对其分析结果的影响,实验中发现α-氰基-4-羟基肉桂酸是适宜的基质,该方法是传统生物方法无法比拟的。     

大气压基体辅助激光解析离子源的研制及其与高分辨飞行时间质谱仪的联用

介绍了自制大气压基体辅助激光解析离子源的原理及结构.考察了该离子源与高分辨率垂直引入式飞行时间质谱仪联用后的性能.实验结果表明,仪器灵敏度、质量分辨率和精度等达到了较高水平.     

激光解吸电离飞行时间质谱技术及应用

本文简述了激光解吸电离飞行时间质谱(NALDI-TOF-MS)技术及其应用,同时介绍了MALDI-TOF-MS的构造、原理及特点。     

大气压离子源真空接口的研制及其在电喷雾电离飞行时间质谱仪上的应用

研制了一种大气压离子源真空接口,并已将其用于自制高分辨率垂直引入式电喷雾电离飞行时间质谱仪.初步研究了该接口的性能,包括射频四极杆、进样片对仪器灵敏度的影响.利用该接口检测了利血平样品.结果表明,接口能有效地提高离子的传输效率,使飞行时间质谱仪达到较高的灵敏度.     

Detection and registration of ion clots in laser time-of-flight mass spectrometers

A number of factors influencing the measurement errors of analytic signals detected with secondary electron multipliers (SEMs) and registered with fast ADCs are analyzed. Such signals are generated in laser time-of-flight mass spectrometry at the stage of ion detection and recording of mass spectra. In particular, the effect of statistical factors and sources of systematic errors during both measurements of isotope ratios and elemental analysis is considered. Such errors as the statistics of formation of ion clots, the limited range of ADC records, discrimination during detection of ions of different masses, and others are considered. It is shown that, without taking into account the features of operation of SEMs and ADCs, both the statistical and systematic errors of measuring isotope ratios may reach several percent. The proposed operating modes of the detector, with allowance for its features, the design of the recording system, and use of formulas for calculating and correcting errors, allow their reduction to ～0.10–0.01%     

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2007-2008

This review is the fifth update of the original review, published in 1999, on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2008. The first section of the review covers fundamental studies, fragmentation of carbohydrate ions, use of derivatives and new software developments for analysis of carbohydrate spectra. Among newer areas of method development are glycan arrays, MALDI imaging and the use of ion mobility spectrometry. The second section of the review discusses applications of MALDI MS to the analysis of different types of carbohydrate. Specific compound classes that are covered include carbohydrate polymers from plants, N- and O-linked glycans from glycoproteins, biopharmaceuticals, glycated proteins, glycolipids, glycosides and various other natural products. There is a short section on the use of MALDI mass spectrometry for the study of enzymes involved in glycan processing and a section on the use of MALDI MS to monitor products of the chemical synthesis of carbohydrates with emphasis on carbohydrate-protein complexes and glycodendrimers. Corresponding analyses by electrospray ionization now appear to outnumber those performed by MALDI and the amount of literature makes a comprehensive review on this technique impractical. However, most of the work relating to sample preparation and glycan synthesis is equally relevant to electrospray and, consequently, those proposing analyses by electrospray should also find material in this review of interest.     

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2003-2004

This review is the third update of the original review, published in 1999, on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings the topic to the end of 2004. Both fundamental studies and applications are covered. The main topics include methodological developments, matrices, fragmentation of carbohydrates and applications to large polymeric carbohydrates from plants, glycans from glycoproteins and those from various glycolipids. Other topics include the use of MALDI MS to study enzymes related to carbohydrate biosynthesis and degradation, its use in industrial processes, particularly biopharmaceuticals and its use to monitor products of chemical synthesis where glycodendrimers and carbohydrate-protein complexes are highlighted.     

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2017–2018

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2018. Also included are papers that describe methods appropriate to glycan and glycoprotein analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. Topics covered in the first part of the review include general aspects such as theory of the MALDI process, new methods, matrices, derivatization, MALDI imaging, fragmentation and the use of arrays. The second part of the review is devoted to applications to various structural types such as oligo- and poly-saccharides, glycoproteins, glycolipids, glycosides, and biopharmaceuticals. Most of the applications are presented in tabular form. The third part of the review covers medical and industrial applications of the technique, studies of enzyme reactions, and applications to chemical synthesis. The reported work shows increasing use of combined new techniques such as ion mobility and highlights the impact that MALDI imaging is having across a range of diciplines. MALDI is still an ideal technique for carbohydrate analysis and advancements in the technique and the range of applications continue steady progress.     

LTQ-Orbitrap Velos双分压线性阱和静电场轨道阱组合式高分辨质谱性能及应用

Orbitrap是近20多年来质量分析器的突破性技术,由静电场轨道阱方式提供高质量分辨能力和精确质量数。本文简述Orbitrap的基本工作原理和Orbitrap质谱仪的发展,重点讲述基于用线性离子阱或双分压线性阱和Orbitrap质量分析器组合的高分辨质谱仪LTQ Orbitrap Velos的结构、性能和功能,并和其它类型的高分辨质谱作比较。LTQ OrbitrapVelos由于其性能特点的优势,在前沿研究领域如蛋白组学、代谢组学、药物代谢和高通量筛选确证常规检测被广泛使用,因而对其在几个主要领域的应用特点进行讨论。     

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update covering the period 1999-2000

This review describes the use of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry for the analysis of carbohydrates and glycoconjugates and continues coverage of the field from the previous review published in 1999 (D. J. Harvey, Matrix-assisted laser desorption/ionization mass spectrometry of carbohydrates, 1999, Mass Spectrom Rev, 18:349-451) for the period 1999-2000. As MALDI mass spectrometry is acquiring the status of a mature technique in this field, there has been a greater emphasis on applications rather than to method development as opposed to the previous review. The present review covers applications to plant-derived carbohydrates, N- and O-linked glycans from glycoproteins, glycated proteins, mucins, glycosaminoglycans, bacterial glycolipids, glycosphingolipids, glycoglycerolipids and related compounds, and glycosides. Applications of MALDI mass spectrometry to the study of enzymes acting on carbohydrates (glycosyltransferases and glycosidases) and to the synthesis of carbohydrates, are also covered.     

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update covering the period 2001-2002

This review is the second update of the original review on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates that was published in 1999. It covers fundamental aspects of the technique as applied to carbohydrates, fragmentation of carbohydrates, studies of specific carbohydrate types such as those from plant cell walls and those attached to proteins and lipids, studies of glycosyl-transferases and glycosidases, and studies where MALDI has been used to monitor products of chemical synthesis. Use of the technique shows a steady annual increase at the expense of older techniques such as FAB. There is an increasing emphasis on its use for examination of biological systems rather than on studies of fundamental aspects and method development and this is reflected by much of the work on applications appearing in tabular form.     

Measurement of ion energy distributions using a combined energy and mass analyzer

A method is described for measuring ion energy distributions using a commercially available, combined energy analyzer/mass spectrometer. The distributions were measured at an electrode located adjacent to pulsed, electron beam-generated plasmas produced in argon. The method uses energy-dependent tuning and was tested for various plasma conditions. The results indicate an improved collection efficiency of low-energy ions when compared to conventional approaches in measuring ion energy distributions.     

Development of a low-temperature photoelectron spectroscopy instrument using an electrospray ion source and a cryogenically controlled ion trap

The ability to control ion temperatures is critical for gas phase spectroscopy and has been a challenge in chemical physics. A low-temperature photoelectron spectroscopy instrument has been developed for the investigation of complex anions in the gas phase, including multiply charged anions, solvated species, and biological molecules. The new apparatus consists of an electrospray ionization source, a three dimensional (3D) Paul trap for ion accumulation and cooling, a time-of-flight mass spectrometer, and a magnetic-bottle photoelectron analyzer. A key feature of the new instrument is the capability to cool and tune ion temperatures from 10 to 350 K in the 3D Paul trap, which is attached to the cold head of a closed cycle helium refrigerator. Ion cooling is accomplished in the Paul trap via collisions with a background gas and has been demonstrated by observation of complete elimination of vibrational hot bands in photoelectron spectra of various anions ranging from small molecules to complex species. Further evidence of ion cooling is shown by the observation of H2-physisorbed anions at low temperatures. Cold anions result in better resolved photoelectron spectra due to the elimination of vibrational hot bands and yield more accurate energetic and spectroscopic information. Temperature-dependent studies are made possible for weakly bonded molecular and solvated clusters, allowing thermodynamic information to be obtained.     

Airfoil sampling of a pulsed Laval beam with tunable vacuum ultraviolet synchrotron ionization quadrupole mass spectrometry: application to low-temperature kinetics and product detection

A new pulsed Laval nozzle apparatus with vacuum ultraviolet (VUV) synchrotron photoionization quadrupole mass spectrometry is constructed to study low-temperature radical-neutral chemical reactions of importance for modeling the atmosphere of Titan and the outer planets. A design for the sampling geometry of a pulsed Laval nozzle expansion has been developed that operates successfully for the determination of rate coefficients by time-resolved mass spectrometry. The new concept employs airfoil sampling of the collimated expansion with excellent sampling throughput. Time-resolved profiles of the high Mach number gas flow obtained by photoionization signals show that perturbation of the collimated expansion by the airfoil is negligible. The reaction of C(2)H with C(2)H(2) is studied at 70 K as a proof-of-principle result for both low-temperature rate coefficient measurements and product identification based on the photoionization spectrum of the reaction product versus VUV photon energy. This approach can be used to provide new insights into reaction mechanisms occurring at kinetic rates close to the collision-determined limit.     

The application of matrix-assisted laser desorption/lonisation time-of-flight mass spectrometry (MALDI-TOF MS) to the analysis of lubricants. part 1. polyol ester aviation turbine engine oils

In the present work, Matrix-Assisted Laser Desorption/lonisation Time-of-Flight Mass Spectrometry (MALDI-TOFMS) is demonstrated to be a valuable method for the analysis of synthetic polyol ester turbine engine oils. A softionisation technique, it generates, under adequate experimental conditions only, (quasi-)molecular ions and allows detection and identification of all components including di- and tripentaerythritol esters and oligomeric additives, without pre-separation.     

Combining high mass resolution and velocity imaging in a time-of-flight ion spectrometer using pulsed fields and an electrostatic lens

We describe a momentum resolving time-of-flight ion mass spectrometer that combines a high mass resolution, a velocity focusing condition for improved momentum resolution, and field-free conditions in the source region for high resolution electron detection. It is used in electron-ion coincidence experiments to record multiple ionic fragments produced in breakup reactions of small to medium sized molecules, such as F(3)SiCH(2)CH(2)Si(CH(3))(3). These breakup reactions are caused by soft x rays or intense laser fields. The ion spectrometer uses pulsed extraction fields, an electrostatic lens, and a delay line detector to resolve the position. Additionally, we describe a simple analytical method for calculating the momentum from the measured hit position and the time of flight of the ions.     

Surface analysis using a new plasma assisted desorption/ionisation source for mass spectrometry in ambient air

The authors report on a modified micro-plasma assisted desorption/ionisation (PADI) device which creates plasma through the breakdown of ambient air rather than utilising an independent noble gas flow. This new micro-PADI device is used as an ion source for ambient mass spectrometry to analyse species released from the surfaces of polytetrafluoroethylene, and generic ibuprofen and paracetamol tablets through remote activation of the surface by the plasma. The mass spectra from these surfaces compare favourably to those produced by a PADI device constructed using an earlier design and confirm that the new ion source is an effective device which can be used to achieve ambient mass spectrometry with improved spatial resolution.     

Wave frequency dependence of H- ion production and extraction in a transformer coupled plasma H- ion source at SNU

The effect of rf wave frequencies on the production of H(-) ion is investigated in a transformer coupled plasma H(-) ion source at Seoul National University. A Langmuir probe is installed to measure the plasma density and temperature, and these plasma parameters are correlated to the extracted H(-) beam currents at various frequencies. The Langmuir probe is also used to measure the density of H(-) ions at the ion source by generating photodetachment with an Nd:YAG laser. The extracted H(-) currents decrease to a minimum value until 13 MHz and then, increase as the driving frequency increases from 13 MHz while the relative H(-) population measured by photodetachment monotonically decreases as the driving rf frequency increases from 11 MHz to 15 MHz. A potential well formed at the extraction region at high frequencies of more than 13 MHz is considered responsible for the increased H(-) beam extraction even with a lower photodetachment signal. The variation in the driving rf frequency not only affects the density and temperature of the plasma but also modifies the plasma potential with the existence of a filtering magnetic field and consequently, influences the extracted H(-) current through the extraction as well as formation of H(-) ions.     

Design and performance evaluation of a novel square ion trap with mass analysis in the radial a axial directions

A novel three-dimensional square ion trap is reported as a mass analyzer or an ion transfer device. The square ion trap was constructed with six square planar electrodes while the electric field was optimized by changing their relative positions to arrange the strength of higher-order fields. Ion trajectory simulations demonstrate the square ion trap efficiently operates with radial and axial excitation. Additionally, ions ejected from the radial direction contained lower kinetic energies and their energy distribution were more centralized. These properties may improve the ion transfer efficiency.