Positive reflectron mode mass

Figure 2. MALDI-TOF positive reflectron mode mass spectra of the anthocyanm-polyflayan-3-ol oligomers of Hyred cranberry fruit and spray dried juice, (A) Anthocyanins [Mfr. (B) Anthocyanin linked to a single flavan-3-ol through a CH3-CH bridge [M]. (C) Anthocyanin linked to a polyflavan-3-ol of 2 degrees of polymerization through a CH3-CH bridge, containing either an A-type or a B-type interflavan bond [M]. ...

Figure 6.31. Positive-ion MALDI-TOF reflectron mode mass spectrum of grape seed extract (matrix 2,5-dihydroxybenzoic acid). (Reprinted from Journal of Agricultural and Food Chemistry, 48, Yang and Chien, Characterization of grape procyanidins using high-performance liquid chromatography/mass spectrometry and matrix-assisted laser desorption time-of-flight mass spectrometry, p. 3993, Copyright 2000, with permission from American Chemical Society.)...

Mass spectra were collected on a Bruker Reflex II-MALDI-TOF mass spectrometer (Billerica, MA) equipped with delayed extraction and a N2 laser (337 nm). In the positive reflectron mode, an accelerating voltage of 25.0 kV and a reflectron voltage of 26.5 kV were used. Spectra are the sum of 50-300 shots. Spectra were calibrated with bradykinin (1060.6 MW) and glucagon (3483.8 MW) as external standards. 

Fig. 23 The positive ion and reflectron mode MALDI-MS spectrum of 40 in ACC A (15 mg/mL 1 1 water-acetonitrile) MALDI matrix using nitrogen laser accumulated 50 laser shots. The inset spectrum shows the expanded molecular mass of 40 [47]...

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 samples were analyzed on the VG TofSpec-SE MALDI TOP mass spectrometer in the reflectron mode with positive ion detection. The samples were spotted on the sample plate in acetonitrile water (60 40) or chloroform methanohTFA (1 1 0.1) mixture plus ammonium suliate on alpha-C (a-cyano-4-hydroxycinnamic acid) matrix. The ionization of the samples was carried out with Nd YAG laser at 355 nm or nitrogen laser at 337 nm. Some of the fractions were analyzed by SIMS on a Kratos 890 mass spectrometer equipped with a Phrasor Scientific SIMS source. The mass spectral data were analyzed by the MSFIT program at the University of California, San Francisco. 

Figure 6. Peptide mass profiling of a silver stained protein spot from a narrow range, pH 4-7, 2DE separation of human heart (ventricle) proteins. A MALDI-TOF mass spectrum of tryptic peptides is shown, analyzed using a Micromass Tofspec 2E spectrometer (Manchester, UK) operated in the positive ion reflectron mode at 20 kV accelerating voltage with time-lag focusing enabled. The protein spot of interest was identified as human vimentin, (courtesy of J.A.Westbrook and R. Wait) (unpublished data). 2DE gels were silver stained using a modified Amersham Biosciences kit.

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