MALDI-MS spectra

Fig. 2 shows MALDI-MS spectra of the same three samples.The spectra usually show the mole peaks plus the molar mass of Na (23 Da) and K (39 Da). Unless they have been specifically added, the sodium and potassium ions come fi-om contaminants in the specimen and/or the matrix. Alternatively, another suitable salt may be added. The addition of lithium chloride suppresses sodium (and potassium) ions, so that the spectra can be more easily interpreted. Thus, the numbers in Fig. 2a refer to mole peaks M plus a (= M + 23 Da) and in Fig. 2b and 2c to M plus Li (= M + 7 Da). As can be seen, the resolution in the higher molecular mass range is more pronounced than in SFC. Components with more than 100 monomer units can be separated in the diol sample. 

We also used HPLC in connection with MALDI-MS. Our aim was to separate cyclic siloxanes, even larger ones not distinguishable by SFC, from linear ones quantitatively. Hexane and ethyl acetate were mixed in a ratio of 90 to 10 by volume and used as mobile phase in HPLC separations of mixtures of the cyclic siloxane sample with the diol sample. Cyclosiloxanes elute first, followed by the diols. Under these conditions only a small overlapping area is to be seen (Fig. 4a). The sample was fractionated and MALDI-MS spectra were taken from the fractions. 

MALDI-MS spectra of released fV-glycans before (panel A) and after (panel B) a-Galactosidase digestion. Monosaccharide symbols are shown in O Table 1... 

A) Protein separation, digestion and transfer Automated acquisition of MALDI-MS spectra B)... 

Figure 1.22. The MALDI-MS spectra of oligonucleotide obtained with traditional Dried Droplet deposition method (a) and obtained by spraying the matrix-analyte solution by a sieve-based device (b).

FIGURE 9.5 MALDI MS spectra of the peptides generated from the hydrolysis of 200 ng of bacteriorhodopsin under different conditions (a) 70% formic acid heated at 110 °C for 4 h, (b) 25% TFA heated at 110 °C for 4 h, and (c) 25% TFA digested by microwave irradiation for 10 min. I indicates peptides resulting from internal fragmentation. C and N indicate C- and N-terminal peptides, respectively. (Reproduced with permission from Zhong, H. Marcus, S. L. Li, L. J. Am. Soc. Mass Spectrom. 2005,16,471-481. Copyright Elsevier.)... 

Acquisition of an other MALDI-MS spectra with optimised parameters. 

DHB crystals, while the nonrinsed sample (right) is dominated by urea. MALDI-MS spectra of (b) rinsed and (c) control spots... 

Fig. 5 MALDI MS spectra of Au25(SCH2CH2Ph)ig using different matrices. The matrices are universal maldi matrix (UMM -1 1 mixture of dihydroxybenzoic acid and a-cyano-4-hydroxycinnamic acid), 4 -hydroxy-azobenzene-2-carboxylic acid (HABA), sinapinic acid (SA) and DCTB. Their structures are shown above the traces. ACS Publishing. Reproduced with permission. ...

Figure 6.2 MALDI-MS spectra of neutral oligosaccharides obtained by PNGase F digestion from lOOpg of glycoprotein, (a) IgGl (Herceptin), recorded on qQTOF instrument (b) Ovalbumin, recorded on...

Figure 6.5 MALDI-MS spectra (Bruker, Biflex-IV) acquired from an HPLC fraction (elution time 28 min) of polyclonal IgC. (a) After trypsin digestion, all ions are [M + Hf ...

Figure 10.1 MALDI-MS data preprocessing. A set of MALDI-MS spectra is preprocessed to obtain an N x P table of numerical values. Each entry in the table is the intensity value...

Figure 10.2 A data preprocessing workflow using MarkerView, DataExplorer, and oplAnalyzer for MALDI-MS spectra acquired on a 4800 MALDI-TOF/TOF mass spectrometer. The input is a set of spectra and the...

FIGURE 9.5 UTLC-MALDI-MS spectra of the three proteins myoglobin (a), cytochrome c (b), and lysozyme (c) separated on polyacrylamide modified nonporous silica particles and desorbed/ionized using sinapinic acid as matrix. (Reprinted from Zhang, Z., Ratnayaka, S.N., and Wirth, M.J., J. Chromatogr. A, 1218, 7196-7202, 2011. Copyright 2011, with permission from Elsevier.)... 

Fig. 19.2. (a-b) MALDI-MS spectra recorded on a rat brain tissue section after on tissue trypsin digestion (a) and on a tissue with trypsin digestion followed by derivatization with 3-SBA (b). (c-d) MALDI-MS/MS spectra of one of the peptides generated from digest (m/z 1,339.3) (c) and the same peptide after derivatization with 3-SBA (m/zl, 523.7) (d). 

Digital Microfluidics, Figure 7 (a) EWOD-driven sample purification and micrographs of dried spots. Insets the rinsed sample (lefi) appears to be primarily composed of DHB crystals, while the nonrinsed sample (right) is dominated by urea MALDI-MS spectra of (b) rinsed and (c) control spots... 

In MALDI-MS, impurities at low to intermediate concentrations form adducts with analyte molecules that can obscure the relevant data and reduce the overall signal intensity. Figures 7b and c contain representative EWOD-MALDI-MS spectra for rinsed and nonrinsed samples of angiotensin II prepared with 20 mM sodium phosphate. In the spectrum of the nonrinsed sample (Fig. 7b), peaks at M -H 23, A/ -f 45, and M - - 67 corresponded to the monosodium, disodium, and trisodium adducts of the parent molecule. These adduct peaks are barely visible in the spectmm of the rinsed sample. The intensities of the molecular-ion peaks in the rinsed spectra were about twice as great as those observed in the control spectra [ 10]. 

Figure 14.8. MALDI MS spectra of 1 pmol of protein bovine tranferrin obtained from the CHCA matrix (top) and the SA matrix (bottom). (Reproduced from Ref. 126 with permission.)...

Figure 4.1 Atmospheric pressure (AP)-MALDI-MS spectra of gramicidin obtained from a spiked urine sample with (a) conventional AP-MALDI-MS and (b) by using octadecanethiol-modified silver nanoparticles. (Reproduced with permission from Ref. [41]). 2008 ACS Publishing)...

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