Plasma desorption mass spectrometry analysis

Plasma-desorption mass spectrometry is another technique that has been applied successfully to the detection of readily removable fatty acyl substituents in intact glycolipids and their acylated derivatives. The specific location of the fatty acyl substituents in the ring of the glycosyl residues, as in LOS antigens, is determined by methylation under nonbasic conditions (see Section II.lb), followed successively by O-deacylation, ethylation of the exposed hydroxyl groups, and GC-MS analysis of partially alkylated alditol acetates21 ethyl groups denote the sites of previous O-acylation. 

Karibian, D., Deprun, C., Carofif, M. Use of plasma desorption mass spectrometry in structural analysis of endotoxins effects on lipid A of different acid treatments. Prog Clin Biol Res 392 (1995) 103-111. 

Further characterization of the remaining fraction in the low-sulfur keratin group in the ethanol-treated animals included analysis of the trypsin-released peptides by plasma desorption mass spectrometry. These results indicated the... 

Concentration detection limits in CE-MS with the ESI interface are similar to those with UV detection. Sample sensitivity can be improved by using ion-trapping or time-of-flight (TOE) mass spectrometers. MS analysis can also be performed off-line, after appropriate sample collection, using plasma desorption-mass spectrometry (PD-MS) or matrix-assisted laser desorption-mass spectrometry (MALDI-MS). 

Latest results have been obtained by both Cf plasma desorption and FAB. The former is an ongoing study by Macfarlane on a decanucleotide (molecular mass — 4000) results on the sequence analysis are not yet available. The sequencing of a fully protected oligonucleotide, using 5 - and 3 -exonucleases has been proposed for one heptanucleotide, using Cf-plasma desorption mass spectrometry. For that type of work the negative ion mode was shown to be fast and reliable. 

One of the major problems in analytical chemistry is the detection and identification of non-volatile compounds at low concentration levels. Mass spectrometry is widely used in the analysis of such compounds, providing an exact mass, and hence species identification. However, successful and unequivocal identification, and quantitative detection, relies on volatilization of the compound into the gas phase prior to injection into the analyser. This constimtes a major problem for thermally labile samples, as they rapidly decompose upon heating. In order to circumvent this difficulty, a wide range of techniques have been developed and applied to the analysis of nonvolatile species, including fast atom bombardment (FAB), field desorption (FD), laser desorption (LD), plasma desorption mass spectrometry (PDMS) and secondary-ion mass spectrometry (SIMS). Separating the steps of desorption and ionization can provide an important advantage, as it allows both processes to be... 

Jespersen, S., Talbo, G., and Roepstorff, P. (1993) Optimization of sample recovery from the nitrocellulose support used in plasma desorption mass spectrometry and its use for multiple analysis of insulin. Biol. Mass Spectrom. 22, 77-83. 

Nielsen, P. F., and Roepstorff, P. (1989) Suppression effects in peptide mixture analysis by plasma desorption mass spectrometry. Biomed. Environm. Mass Spectrom. 18,131-137. 

Most early SIMS instruments (such as that described by Lehrle and co-workers) utilized primary-ion beams with fluxes in the l-pA/cm range or higher, which results in ablation of relatively large amounts of ions and neutrals from surface monolayers. These techniques, commonly refered to as sputtering, were used primarily for elemental analysis or for the analysis of relatively small organics. Following the introduction of plasma desorption mass spectrometry, which demonstrated the possibilities... 

In Chapter 4 we described a number of examples using plasma desorption mass spectrometry to map enzymatic digests. However, continuing an earlier example from this chapter, plasma desorption mass spectrometric analysis of amyloid peptides (PAi 4o and PAi 2) digested with pepsin resulted in peaks at m/z 561.1,613.1, 746.1, 1492.2, 1999.2, 2199.9, and 2315.2 that could be assigned to the peptide fragments ... 

Wood, K.V., Bonham, C., Hipskind, J., Nicholson, R.L., Analysis of anthocyanins and 3-deoxyanthocyanidins by plasma desorption mass spectrometry. Phytochemistry, 1994, 37, 557 560. 

Today, two-dimensional mass spectrometry analysis of biological tissues by means of a technique called mass imaging, mass spectrometry imaging (MSI), or imaging mass spectrometry has been used in mapping the distribution of elements or chemical groups in samples. Matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), secondary ion mass spectrometry (SIMS), and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) are three commonly used MSI techniques. 

Spectrometric Analysis. Remarkable developments ia mass spectrometry (ms) and nuclear magnetic resonance methods (nmr), eg, secondary ion mass spectrometry (sims), plasma desorption (pd), thermospray (tsp), two or three dimensional nmr, high resolution nmr of soHds, give useful stmcture analysis information (131). Because nmr analysis of or N-labeled amino acids enables determiaation of amino acids without isolation from organic samples, and without destroyiag the sample, amino acid metaboHsm can be dynamically analy2ed (132). Proteia metaboHsm and biosynthesis of many important metaboUtes have been studied by this method. Preparative methods for labeled compounds have been reviewed (133). 

Mass spectrometry is also used for nanoparticles investigations. Two ionization techniques often used with liquid and solid biological samples include electrospray ionization (ESI) and matrix-assisted laser desorption/ioiuzation (MALDI). Inductively coupled plasma (ICP) sources are mainly used for metal analysis. In general,... 

Ionization Methods/Processes. The recent development of several new ionization methods in mass spectrometry has significantly improved the capability for the analysis of nonvolatile and thermally labile molecules [18-23]. Several of these methods (e.g., field desorption (FD), Californiun-252 plasma desorption (PD), fast heavy ion induced desorption (FHIID), laser-desorption (LD), SIMS, and fast atom bombardment (FAB) or liquid SIMS) desorb and ionize molecules directly from the solid state, thereby reducing the chance of thermal degradation. Although these methods employ fundamentally different excitation sources, similarities in their mass spectra, such as, the appearance of protonated, deprotonated, and/or cationized molecular ions, suggest a related ionization process. 

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