Matrix-assisted laser desorption ionisation matrices used

Bright, J. J. Claydon, M. A. Soufian, M. Gordon, D. B. Rapid typing of bacteria using matrix-assisted laser desorption ionisation time-of-flight mass spectrometry and pattern recognition software. J. Microbiol. Meth. 2002, 48,127-138. 

S.T. Hsiao, M.C. Tseng, Y.R. Chen and G.R. Her, Analysis of polymer additives by matrix-assisted laser desorption ionisation/time of flight mass spectrometer using delayed extraction and collision induced dissociation, J. Chinese Chem. Soc., 48 (2001) 1017-1027. 

Matrix assisted laser desorption ionisation (MALDI) and ESI-MS spectra of non-ionic surfactant blends of AE obtained after positive ionisation were compared [28]. Both the ionisation procedures, which produce [M + Na]+ ion clusters, were very useful for this purpose, but the ESI spectra generated were more complex, whereas MALDI ionisation led to simpler spectra that can be interpreted more easily [28]. 

For the characterisation of the biodegradation intermediates of C12-LAS, metabolised in pure culture by an a-proteobacterium, Cook and co-workers [23] used matrix-assisted laser desorption/ionisation (MALDI)-time of flight (TOF)-MS as a complementary tool to HPLC with diode array detection and 1H-nuclear magnetic resonance. The dominating signal in the spectrum at m/z 271 and 293 were assigned to the ions [M - H] and [M - 2H + Na]- of C6-SPC. Of minor intensity were the ions with m/z 285 and 299, interpreted to be the deprotonated molecular ions of C7- and C8-SPC, respectively. 

Martin, R. L. Branda, E. L. Analysis of high mass peptides using a novel matrix-assisted laser desorption/ ionisation quadrupole ion trap time-of-flight mass spectrometer. Rapid Commun. Mass Spectrom. 2003, 17, 1358-1365. 

Owen, S. J., Meier, F. S., Brombacher, S., and Volmer, D. A. (2003). Increasing sensitivity and decreasing spot size using an inexpensive, removable hydrophobic coating for matrix-assisted laser desorption/ionisation plates. Rapid Commun. Mass Spectrom. 17 2439-2449. 

The mass spectrometry analysis was performed by the matrix assisted laser desorption/ionisation time-of-flight (S8-MALDI) technique using a Voyager-DE PRO Biospectrometry Workstation (Applied Biosystems, USA). Radiation pulses of 0.5 ns and 3 Hz frequency from N2 laser operating at 337 nm were used to desorb the species and negative/positive ions formed were detected in reflectron mode. Sulfur used as a matrix material was also dissolved in toluene and mixed with the samples solution prior to deposition onto a target. 

The classical area of application of mass spectrometry has been with small volatile compounds, although non-volatile samples could be analysed if they were suitably derivatised. The application of mass spectrometry to large complex molecules like proteins has been made possible by the development of novel ionisation techniques which enable large molecules (> 200 kDa) to be introduced into the mass spectrometer in an intact form suitable for analysis (Siuzdak 1996 Dass 2000). Of the various techniques that have been developed, electrospray ionisation (ESI) and matrix-assisted laser desorption ionisation (MALDI) are the ones best suited for use with macromolecules and macromolecular complexes. 

Larhrib, H. Wells, M.H. Rubinstein, M.H., et al. Characterization of PEGs using matrix-assisted laser desorption/ ionisation mass spectrometry and other related techniques. Int. J. Pharm. 1997, 14, 187-198. 

Recently, MALDI-TOF (matrix-assisted laser desorption/ionisation-reflection time-of-flight) mass spectrometry was introduced as a new approach for the investigation of pellicle composition [39], Using mass spectrometry for compositional analysis, it was found that more intact salivary protein species were present in an in vitro-formed pellicle compared to an in vivo-formed pellicle [39], This finding suggests that the in vivo pellicle is an entity formed with components undergoing more extensive enzymatic (proteolytic) processing than in the in vitro pellicle. Therefore, in vitro-formed pellicle layers cannot completely mirror what occurs within the oral cavity [39], This difference may be due to differences in the proteolytic capacity of the saliva supernatant used for in vitro pellicle formation and that of the oral environment. In addition, a particular saliva sample used for in vitro pellicle formation is a closed system, whereas the oral environment is an open system with continuous influx and clearance of oral fluids [39]. 

Bright, J.J. Claydon, M.A. Soufian, M. Gordon, D.B. "Rapid Typing of Bacteria Using Matrix-assisted Laser Desorption Ionisation Time-of-flight Mass Spectrometry and Pattern Recognition Software, J. Microbiol. Methods 48(2-3), 127-138 (2002). 

Matrix assisted laser desorption ionisation (MALDI) is an important technique for characterisation and fingerprinting of large molecules. However, solvents used at sample preparation have a negative effect on the quahty of the fingerprint. Work is therefore performed on development of solvent free sample preparation methods for characterisation of synthetic polymers [61]. 

Three soft ionisation methods are in use for earbohydrates, fast atom bombardment (FAB), eleetrospray ionisation (ESI) and matrix-assisted laser desorption/ionisation (MALDI). FAB is the oldest and involves directing a high-energy beam of Cs" ions or Xe atoms at the sample dissolved in a nonvolatile solvent such as m-nitrobenzyl alcohol. The atoms sputter the sample and matrix [M + H] or [M + Na]" ions are commonly observed. With an upper limit of M of about 2000, FAB is not that soft, and is usually used for small oligosaccharides it has the further disadvantage that the sample is prepared and then directly introduced into the mass spectrometer, so that it cannot be combined with liquid chromatography. 

Kaufmann, R., Spengler, B., and Lutzenkirchen, F. (1993). Mass spectrometric sequencing of linear peptides by product-ion analysis in a reflectron time-of-flight mass spectrometer using matrix-assisted laser desorption ionisation, Rapid Commun. Mass Spectrom., 7,902. 

A reliable analysis of multicomponent mixtures is particularly difficult and the situation becomes more complicated and less meaningful with increasing mixture size. Nevertheless, the analysis of peptide libraries is possible by mass spectroscopic means.366-572 mixture size increases, the main aim of any analysis is to ensure that the vast majority of expected library members are represented in the mixture. The use of MS in conjunction with other analytical techniques (HPLC-MS, GC-MS, MS-MS) have been used successfully in library characterisation. 3.425.573 Electronspray-MS is a particularly mild method for ionisation. s Matrix-assisted Laser Desorption Ionisation - time-of-flight (MALDI-TOF) mass spectrometry is a tool of increasing importance in multicomponent analysis. Its reduced tendency to preferential ionisation results in an increased likelihood of observing ions from all components.5 575... 

Chromatographic methods, such as reverse phase HPLC (RP-HPLC) and size exclusion chromatography, were used for identity and purity control, and also for quantitative measurement. The major impurity, which can be detected by RP-HPLC after the two first purification steps (Fig. 3), was isolated and analysed by mass spectrometiy. The mass measured by Matrix Assisted Laser Desorption Ionisation Time Of Flight (MALDI-TOF) mass spectrometry for this impurity was around twice the mass of the monomer (78265 Da), and was interpreted to be a dimer of BBG2Na. 

Matrix assisted laser desorption/ionisation (MALDI) For laser desorption methods a pulsed laser is used to desorb species from a target surface. Therefore, a mass analyser compatible with pulsed ionisation methods has to be used. Typically, time-offlight (TOF) analysers are employed, but several hybrid systems (Q-TOF) and, recently, high resolution Fourier transform ion cyclotron resonance (FT-ICR) analysers have been successfully adapted (see Section 10.2.4). Direct laser desorption rehes on the very rapid heating of the sample or sample substrate to vapourise molecules without decomposition. The more recent development of MALDI relies on the absorption of laser energy by a solid, microcrystalline matrix compound such as a-cyano-4-hydroxy ciimamic acid or sinapinic acid [8, 34]. MALDI has become an extremely popular method for the rapid and sensitive analysis of high-molecular-weight compounds [4]. 

A time of flight (TOP) mass spectrometer measures the mass-dependent time it takes ions of different masses to move from the ion source to the detector. This requires that the starting time (the time at which the ions leave the ion source) is well-defined. Therefore, ions are either formed by a pulsed ionisation method (usually matrix-assisted laser desorption ionisation, or MALDI), or various kinds of rapid electric field switching are used as a gate to release the ions from the ion source in a very short time. 

Mahon, A., Kemp, T. J., Varney J. E., and Derrick, P. J., Ions Derived from Linear Polysulfide Oligomers Using Matrix-assisted Laser Desorption/Ionisation Time-of-flight Mass Spectrometry Polymer, 39, 6213. 1998. 

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