Mass spectrometry MALDI source

The exception to this is the application of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In 1981, Barber and Liu and coworkers independently introduced the concept of employing MALDI where the absorption of the matrix is chosen to coincide with the wavelength of the employed laser to assist in the volatilization of materials. In 1988, Tanaka, Hillenkamp, and coworkers employed the laser as the energy source, giving birth to MALDI-MS. 

B. SPENGLER, D. KIRSCH and R. KAUFMANN obtain structural information with reflectron TOF mass spectrometry (MALDI post-source decay) [66],... 

In this study, we used matrix-assisted laser desorption ionization /Mass Spectrometry (MALDI/MS) to identify the peptides released from gastric parietal cell microsomes. MALDI, because of its sensitivity and relative tolerance to the presence of salts and buffers was examined for the analysis of unfractionated proteolytic digests (9, 10). MALDI with post-source decay (PSD) analysis was used to obtain sequence information on peptides even in crude digestion mixtures. Our strategy (Figure 1) consisted of proteolysis of intact vesicles, centrifugation at high speeds to separate membrane bound and soluble fractions and analysis of the mixture of released peptides by MALDI/MS. In addition, to increase the... 

Dissociation and ionization by means of one or several lasers. Sensitive detection of fragments and ions with resonance photoionization and mass spectrometric techniques (tunable lasers). Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) with pulsed ablating laser sources. High lateral resolution enables molecular microprobing of biological cell compounds... 

Of the two related techniques, FAB found far greater use in studies of enantioselective discrimination as compared to other desorption/ionization methods, such as MALDI and secondary ion mass spectrometry (SIMS). Chan and coworkers demonstrated enantiodiscrimina-tion of amino acids by a-, P-, and y-cyclodextrins using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) [28]. The observed levels of enantioselectivity were found to be dependent on the size of cyclodextrin cavities, as well as on the length and functionality of the amino acid side chain. Vairamani and coworkers demonstrated discrimination of amino acid methyl esters using various monosaccharide hosts by liquid secondary ion mass spectrometry (LSIMS) [29]. It is curious that more work has not been done using these sources. MALDI, in particular, is a simple and straightforward technique. Various researchers have demonstrated the observation of noncovalent complexes [30-32], for example, between peptides and proteins, but relatively little work has been performed that focuses on studying enantioselective noncovalent interactions by MALDI-MS. 

Niyompanich S, Jaresitthikunchai J, Srisanga K, Roytrakul S, Tungpradabkul S. Source-identifying biomarker ions between environmental and clinical Burkholderia pseudotnallei using whole-cell matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Flos ONE. 2014 9(6). 

Until about the 1990s, visible light played little intrinsic part in the development of mainstream mass spectrometry for analysis, but, more recently, lasers have become very important as ionization and ablation sources, particularly for polar organic substances (matrix-assisted laser desorption ionization, MALDI) and intractable solids (isotope analysis), respectively. 

When mass spectrometry was first used as a routine analytical tool, El was the only commercial ion source. As needs have increased, more ionization methods have appeared. Many different types of ionization source have been described, and several of these have been produced commercially. The present situation is such that there is now only a limited range of ion sources. For vacuum ion sources, El is still widely used, frequently in conjunction with Cl. For atmospheric pressure ion sources, the most frequently used are ES, APCI, MALDI (lasers), and plasma torches. 

TOF analyzers are especially compatible with MALDI ion sources and hence are frequently coupled in aMALDI-TOF configuration. Nevertheless, many commercial mass spectrometers combine ESI with TOF with great success. For proteomics applications, the quadrupole TOF (QqTOF) hybrid instruments with their superior mass accuracy, mass range, and mass resolution are of much greater utility than simple TOF instruments.21,22 Moreover, TOF instruments feature high sensitivity because they can generate full scan data without the necessity for scanning that causes ion loss and decreased sensitivity. Linear mode TOF instruments cannot perform tandem mass spectrometry. This problem is addressed by hybrid instruments that incorporate analyzers with mass selective capability (e.g., QqTOF) in front of a TOF instrument. 

J. J. Lennon and K. A. Walsh. Locating and Identifying Posttranslational Modifications by In-Source Decay During MALDI-TOF Mass Spectrometry. Protein Sci., 8(1999) 2487-2493. 

The development glycopeptide libraries obtained by the split-mix method is severely hampered by the lack of concurrent development of a general, facile separation and characterization technology. Some headway has been made with chemical coding of the libraries, but very few direct methods of analysis exist. One promising method that could be applied to the direct characterization of both types of libraries is mass spectrometry. More specifically, post-source-decay matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry (PSD-MALDI-TOF-MS) and CID-FAB/MS/MS have been used to characterize glycopeptides.53-55... 

Several original papers must be mentioned that deal with mass spectrometric techniques which the numerous reviews do not comprise. Kaufmann and coworkers268,288 studied the mass spectrometric analysis of carotenoids and some of their fatty acid esters using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry and its post-source-decay (PSD) variant. Some advantages concerning the thermal instability and limited solubility were discussed, but the fragmentation paths of the carotenoid cations were found to be essentially the same as those observed with conventional techniques. 

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