Laser desorption time-of-flight

Vestal, M. L. Juhasz, R Martin, S. A. Delayed extraction matrix-assisted laser desorption time-of-flight mass spectrometry. Rapid Comm. Mass Spectrom. 1995, 9, 1044-1050. 

MALDI-TOF-MS Matrix-assisted laser desorption time-of-flight mass spectrometry... 

M.L. Vestal, P. Juhasz, and S.A. Martin, Delayed Extraction Matrix assisted Laser Desorption Time of flight Mass Spectrometry, Rapid Commun. Mass Spectrom., 9, 1044 1050 (1995). 

R. S. Annan and S. A. Carr. Phosphopeptide Analysis by Matrix-Assisted Laser Desorption Time-of-Flight Mass Spectrometry. Anal. Chem., 68(1996) 3413-3421. 

Mass spectral data were obtained either on electrospray infusion (EDI) Model TSQ 700 mass spectrometer (Finnigan MAT) or a Matrix Assisted Laser Desorption Time-of-Flight (MALDI-TOF) (Finnigan, Model 2000). 

Fig. 3. Schematics of a matrix-assisted laser desorption time-of-flight mass spectrometer. Ions are desorbed from the target, accelerated into the machine, and left to drift freely in the flight tube. Heavy ions are slower than light ions and reach the detector later. The flight time is converted into mass using an appropriate calibration.

Fig. 6. Protein identification using a peptide map measured with a matrix-assisted laser desorption time-of-flight mass spectrometer. All the peptide extracted from the gel is measured and the set of masses is used in the database search. The mass resolution is in the order of 10,000. Individual isotopes of a 2.5 kDa peptide are clearly resolved.

Foret et al.98 collected fractions of model proteins and variants of human hemoglobins after fractionation by CIEF, and then analyzed them by matrix-assisted laser desorption-time-of-flight-mass spectrometry (MALDI-TOF-MS). As the authors point out, MS is an orthogonal method to CIEF because it separates according to molecular mass. 

Normally, the isolation of various metallofullerenes is confirmed by laser-desorption time-of-flight mass spectrometry. For ESR-active metallofullerenes, the observation of the corresponding h) erfine structures can further confirm the identification and isolation. 

Often soft ionization techniqnes such as fast-atom bombardment (FAB) and matrix-assisted laser desorption (MALDI) greatly increase the utility of mass spectrometry in the analysis of fluorinated compounds. Using a commercial matrix-assisted laser desorption time-of-flight mass spectrometer, molecular ions of a polyelectrolyte,... 

Blakley, C.R., Vestal, M.L., Verentchikov, A. and Wang, Y.P. (1994) Liquid Chromatograph and Capillary Electrophoresis Interfaces for Matrix Assisted Laser Desorption Time-of-flight Mass Spectrometry. Proceedings of the 42nd ASMS Conference on Mass Spectrometry and Allied Topics, Chicago, IL, p. 1045. 

Peptide ladder samples were analyzed on a matrix-assisted laser desorption time-of-flight mass spectrometer constructed at The Rockefeller University and described elsewhere (8,9). The individual peptides (9 residues to 18 residues in one vial and 19 to 32 residues in another vial) were mixed in approximately equal amounts and dissolved in water. The ladder mixtures were added to the matrix material (4-hydroxy-a-cyano-cinnamic acid (4HCCA) in formic acid/water/isopropanol 1 3 2) to a final concentration of 1-5 pM for each peptide component. The complete peptide ladder, which ranged from the 9 mer to the 32 mer (except 16 mer and 28 mer) was measured from 4HCCA in water/acetonitrile 2 1. The final concentration of each peptide component was in the range of 0.2-1 pM. Bovine insulin emd substance P were used as internal calibrants. 

Mass spectrometry is another detection technique widely used in neuropeptide analysis. Concentration sensitivities in CE-MS do not reach those obtained by CE-LIF nevertheless, tedious derivatization procedures are avoided. In addition, CE-MS has proven to be a powerful tool for structure elucidation as illustrated by the investigation of the in vivo metabolic fate of peptide E by Caprioli s group [12]. After microdialysis and in-line SPE, neuropeptides migrating out of the electrophoresis capillary were deposited directly onto a precoated cellulose target used in matrix-assisted laser desorption-time of flight (MALDI-TOF) MS subsequently. Structural information is then obtained along with the mass of the peptide(s). 

Figure 3. Laser-desorption time-of-flight mass spectra of molecular carbon samples, (a, left) Pure Cm and Cw samples. The ions are produced by SO mJ pulses (over a I-mm area) of 266 nm radiation. Small peaks at lower masses are due to fragmentation occurring during desorption, (b, center) Enriched samples of the larger fullerenes. (c, right) Effect of desorbing laser pulse fluence on the mass spectrum of pure samples (pulse energies indicated in pJ per pulse).

We isolated C7g, Cg2 and Cg4 by high-performance liquid chromatography (the preparation is described in detail elsewhere ). Laser-desorption time-of-flight mass spectra were obtained to confirm the purity of the isolated samples. We used an ArF (193 nm) laser as the desorption light source . Mass spectra for the samples of C78, Cg2 and Cg4 are shown as inserts to Fig. la-c. We measured C NMR spectra of the higher fuiierenes using CS2 as the solvent with Cr(C5H702)3 as a relaxant. 

A. Laser desorption time-of-flight mass spectrometric analysis of transferrin precipitated with antiserum a unique simple method to identify molecular weight variants. Biol Mass Spectrom. 1994 Apr 23 4) 230-3. 

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