Matrix-assisted laser desorption/ionisation mass spectrometry

Fast atom bombardment (FAB) Plasma desorption (PD) Liquid secondary-ion mass spectrometry (LSIMS) Thermospray (TSP)/plasmaspray (PSP) Electrohydrodynamic ionisation (EHI) Multiphoton ionisation (MPI) Atmospheric pressure chemical ionisation (APCI) Electrospray ionisation (ESI) Ion spray (ISP) Matrix-assisted laser desorption/ionisation (MALDI) Atmospheric pressure photoionisation (APPI) Triple quadrupole (QQQ) Four sector (EBEB) Hybrid (EBQQ) Hybrid (EB-ToF, Q-ToF) Tandem ToF-ToF Photomultiplier... 

Saenz, A. J. Petersen, C. E. Valentine, N. Gantt, S. L. Karman, K. H. Kingsley, M. T. Wahl, K. L. Reproducibility of matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry for replicate bacterial culture analysis. Rapid Comm. Mass Spectrom. 1999,13,1585-1585. 

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. 

Domin, M. A. Welham, K. J. Ashton, D. S. The effect of solvent and matrix combinations on the analysis of bacteria by matrix-assisted laser desorption/ ionisation time-of-flight mass spectrometry. Rapid Comm. Mass Spectrom. 1999, 13, 222-226. 

Experimental considerations Sample preparation and data evaluation are similar to membrane osmometry. Since there is no lower cut-off as in membrane osmometry, the method is very sensitive to low molar mass impurities like residual solvent and monomers. As a consequence, the method is more suitable for oligomers and short polymers with molar masses up to (M)n 50kg/mol. Today, vapour pressure osmometry faces strong competition from mass spectrometry techniques such as matrix-assisted laser desorption ionisation mass spectrometry (MALDI-MS) [20,21]. Nevertheless, vapour pressure osmometry still has advantages in cases where fragmentation issues or molar mass-dependent desorption and ionization probabilities come into play. 

Mass spectrometry is used to identify unknown compounds by means of their fragmentation pattern after electron impact. This pattern provides structural information. Mixtures of compounds must be separated by chromatography beforehand, e.g. gas chromatography/mass spectrometry (GC-MS) because fragments of different compounds may be superposed, thus making spectral interpretation complicated or impossible. To obtain complementary information about complex mixtures as a whole, it may be advantageous to have only one peak for each compound that corresponds to its molecular mass ([M]+). Even for thermally labile, nonvolatile compounds, this can be achieved by so-called soft desorption/ionisation techniques that evaporate and ionise the analytes without fragmentation, e.g. matrix-assisted laser desorption/ionisation mass spectrometry (MALDI-MS). 

Ferret, C., Pezet, R., and Tabacchi, R., Fractionation of grape tannins and analysis by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, Phytochem. Anal, 14, 202,... 

Below we report methodological studies based upon HPLC, GC/FID, GC-MS, LC-MS, matrix-assisted laser desorption ionisation coupled with time-of-flight mass spectrometry (MALDI-ToF/MS), CE, proton nuclear magnetic resonance ( I INMR), RIA and enzymatic colorimetric techniques. 

Bunch, J., Clench, M. R., and Richards, D. S. (2004). Determination of pharmaceutical compounds in skin by imaging matrix-assisted laser desorption/ionisation mass spectrometry. Rapid Commun. Mass Spectrom. 18 3051-3060. 

Prideaux, B., Clench, M. R., Carolan, V. A., Morton, J., and Rajan-Sithamparanadarajah, B. (2005). Imaging matrix assisted laser desorption ionisation—mass spectrometry for the investigation of dermal absorption of chlorpyrifos. In Proceedings of the 53rd ASMS Conference on Mass Spectrometry and Allied Topics, San Antonio, TX. 

C. S. Creaser, J. C. Reynolds, and D. J. Harvey, Structural analysis of oligosaccharides by atmospheric pressure matrix-assisted laser desorption/ionisation quadrupole ion trap mass spectrometry, Rapid Commun. Mass Spectrom., 16 (2002) 176-194. 

D. S. Ashton, C. R. Beddell, D. J. Cooper, and A. C. Lines, Determination of carbohydrate heterogeneity in the humanised antibody CAMPATH 1H by liquid chromatography and matrix-assisted laser desorption ionisation mass spectrometry, Anal. Chim. Acta, 306 (1995) 43 18. 

S. G. Penn, M. T. Cancilla, M. K. Green, and C. B. Lebrilla, Direct comparison of matrix-assisted laser desorption/ionisation and electrospray ionisation in the analysis of gangliosides by Fourier transform mass spectrometry, Euro. J. Mass Spectrom., 3 (1997) 67-79. 

B.L.M. van Baar, A.G. Hulst, A.L. de Jong and E.R.J. Wils, Characterisation of botulinum toxins type A and B, by matrix-assisted laser desorption ionisation and electrospray mass spectrometry, 7. Chromatogr., A, 970, 95-115 (2002). 

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. 

MALDI-MS Matrix-assisted laser desorption/ionisation mass spectrometry... 

The two additives have heen identified hy matrix assisted laser desorption ionisation mass spectrometry (MALDI-MS) and attenuated total reflection infrared spectroscopy (ATR). 

Schrader, M., Jurgens, M., Hess, R., Schuiz-Knappe, P., Raida, M., Foessmann, W. G. (1997). Matrix-assisted laser desorption/ionisation mass spectrometry guided purification of human guanylin from blood ultrafiltrate. J. Chromatogr. A 776, 139-145. 

Kolarich D, Altmann F N-glycan analysis by matrix assisted laser desorption/ionisation mass spectrometry of electrophoretically separated non-mammalian proteins. Application to peanut allergen Ara h 1 and olive pollen alleigen Ole e 1. Anal Biochem 2000 285 64-75. 

Mass spectrometry has assumed great importance in determinations of the molar masses of biological macromolecules, even quite large ones. This is due to developments such as electrospray ionisation (ESI) and matrix assisted laser desorption/ ionisation (MALDI), which have made it possible to determine the molar masses of biopolymers up to several 100 kDa (Pitt 1996 Kellner et al. 1999 Snyder 2000). The combination of MALDI techniques with time-of-flight mass spectrometers (MALDI-TOF) is of particular significance for determination of the molar masses of proteins with high sensitivity (typically pmol quantities, although exceptionally fmol) and precision (proteins up to 100 kDa with precision of about 0.01 %). Mass spectrometry can provide very accurate measurements of protein molar mass that can yield information about even minor structural modifications not readily accessible by other means. 

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. 

Orsnes, H. andZenobi, R. (2001) Interfaces for on-line sample delivery for matrix-assisted laser desorption ionisation mass spectrometry. Chem. Soc. Rev. 30, 104-112. 

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. 

Weiss, K.C., Yip, T.T., Hutchens, T.W. and Bisson, L.F. (1998) Rapid and sensitive fingerprinting of wine proteins by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry, Am. J. Enol. Vitic., 49(3), 231-239. 

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]. 

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