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451.
Jackson SN Ugarov M Post JD Egan T Langlais D Schultz JA Woods AS 《Journal of the American Society for Mass Spectrometry》2008,19(11):1655-1662
Combining matrix-assisted laser desorption/ionization (MALDI) mass spectrometry with ion mobility (IM) results in the fast
sorting of biomolecules in complex mixtures along trend lines. In this two-dimensional (2D) analysis of biological families,
lipids, peptides, and nucleotides are separated from each other by differences in their ion mobility drift times in a timescale
of hundreds of microseconds. Molecular ions of similar chemical type fall along trend lines when plotted in 2D plots of ion
mobility drift time as a function of m/z. In this study, MALDI-IM MS is used to analyze species from all of the major phospholipid classes. Complex samples, including
tissue extracts and sections, were probed to demonstrate the effects that radyl chain length, degree of unsaturation, and
class/head group have upon an ion’s cross section in the gas phase. We illustrate how these changes can be used to identify
individual lipid species in complex mixtures, as well as the effects of cationization on ion cross section and ionization
efficiency. 相似文献
452.
Wei H Nolkrantz K Powell DH Woods JH Ko MC Kennedy RT 《Rapid communications in mass spectrometry : RCM》2004,18(11):1193-1200
Electrospray sample deposition was explored for matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). In this method, nanoliter volumes of matrix/analyte mixture were electrosprayed from a high voltage biased (1-2 kV) fused-silica capillary onto a grounded MALDI plate mounted 100-500 microm from the capillary outlet. Electrospray deposition with these conditions produced sample spots 200-300 microm in diameter thus matching the laser spot size. Varying spray voltage and distance resulted in different crystal sizes and volatilization rates for alpha-cyano-4-hydroxycinnamic acid matrix. Best results were obtained when the sample was deposited as wet droplets as opposed to deposition as dried solid. Under 'wet-spray' conditions, 2-4 microm diameter crystals were formed and detection limits for several neuropeptides were 0.7-25 amol. Samples could be pre-concentrated on the plate by spraying continuously and allowing sample to evaporate in a small spot. Sample volumes as large as 580 nL were deposited yielding a detection limit of 35 pM for neurotensin 1-11. Electrospray sample deposition yielded similar results when using atmospheric pressure-MALDI coupled with a quadrupole ion trap mass spectrometer, except that the sensitivity was approximately seven-fold worse. 相似文献
453.
Zhang GP Callcott TA Woods GT Lin L Sales B Mandrus D He J 《Physical review letters》2002,88(7):077401
Element- and site-specific resonant inelastic x-ray scattering spectroscopy (RIXS) is employed to investigate electron correlation effects in NaV2O5. In contrast to single photon techniques, RIXS at the vanadium L3 edge is able to probe d-d* transitions between V d-bands. A sharp energy loss feature is observed at -1.56 eV, which is well reproduced by a model calculation including correlation effects. The calculation identifies the loss feature as excitation between the lower and upper Hubbard bands and permits an accurate determination of the Hubbard interaction term U = 3.0 +/- 0.2 eV. 相似文献