MALDI TOF mass spectrum

The fact that only ethylene and tetramethylethylene are evolved from exp-[8]rotane 168 and permethyl-exp-[6]rotane 173 upon thermal decomposition leads to the conclusion that the spirocyclopropane moieties in these expanded [n]rotanes fragment only externally and leave carbene moieties behind. Indeed, the MALDI-TOF mass spectra of several exp-[ ]rotanes show fragment ions with M minus 28. Thus, if this fragmentation in an exp-[n]rotane were to continue n times, a cyclic C carbon cluster would be left over. So far, however, a fragment ion with m/z = 480 corresponding to 182 has not been recorded in the mass spectrum of exp-[8]rotane 168 and it remains to be seen whether a Cgo cluster 183 will be detected in the mass spectrum of exp-[12]rotane 171 (Scheme 35). 

The MALDI-TOF mass spectra of the Cso-fullerene-annelated [3]- and [4]rotanes 127 and 128 also demonstrated that these molecules fragment at the spirocyclopropane units with successive loss of the fullerene moieties. Unfortunately, however, the peaks for cyclo-Ci and cyclo-C2o carbon clusters were not observed [38]. 

Figure 6.4 Expanded portion of the MALDI-TOF mass spectra of two different clinical isolates (by region) of Vibrio parahaemolyticus obtained on a reflectron TOF/MS, showing a single change in mass of a protein from m/z 9479 to mtz 9587 giving rise to the strain and geography-related differences observed in Figure 6.3 and reported in Wilkes et al.54...

Figure 6.5 Expanded portions of the MALDI-TOF mass spectra of two clinical strains of Vibrio parahaemolyticus from the same outbreak (and region) obtained on a reflec-tron TOF/MS, showing consistent spectral features observed in all strains from this region/outbreak.

Williams,T. L. Andrzejewski, D. Lay, J. O., Jr. Musser, S. M. Experimental factors affecting the quality and reproducibility of MALDI TOF mass spectra obtained from whole bacteria cells. J. Am. Soc. Mass Spectrom. 2003,14, 342-351. 

C. L. Voorhees, K. J. Lay, J. O., Jr. Identification of bacterial proteins observed in MALDI TOF mass spectra from whole cells. Anal. Chem. 1999, 71, 3226-3230. 

Figure 9.5 Representative MALDI-TOF mass spectra from each of the eight MRSA isolates.

The 2 pi of the concentrated peptide solution was mixed with 4 pi of 2,5-dihydroxybenzoic acid [ 7 mg in 500 pi of the mixture of acetonitrile/0.1% trifluoroacetic acid, 1/2 (v/v)]. The resulting mixture was applied to the MALDI steel plate and left to crystallise. Afterwards, the MALDI-TOF mass spectra were measured by a BIFLEX IV instrument (Bruker, Germany) under appropriate conditions (potential 19 kV on the plate and 15.05 kV on the deflector, positive reflector mode potential 20 kV, laser intensity 50 or 60%). The range of detected masses was from 600 to 3000 Da. For the external calibration the standard mixture of peptides M-Pep was used. 

Fig.1.5 MALDI-TOF mass spectra of purified alfalfa-derived C5-1 using (a) h uman IgG or (b) protein A. (c) Hybridoma-derived C5-1 as control. Used with permission from Ref 18.

Fig. 10.1. MALDI-TOF mass spectra of (a) porcine cytochrome C from 2,5-dihydroxy-benzoic acid matrix at 337 nm and (b) a monoclonal antibody from nicotinic acid matrix at 266 nm. Reproduced fromRef. [15] by permission. John Wiley Sons, 1991.

MALDl-TOF mass spectrometry (MS) has also been used to characterize PAM AM dendrimer composition with and without added Cu + [98]. linear-mode MALDI-TOF mass spectra of G2 and G3, and their complexes with Cu + ions, are shown in Fig. 9. 

These carboxylate ions are weaker counterions than CP and Pp, so that the corresponding dendrimers tend to ionize more easily and to give clearer signals in MALDI-TOF mass spectra. As to the electrochemical properties, their cyclic voltammetries show a reversible metal centered oxidation and two reversible ligand-centered reduction processes at potential values very similar to those of the corresponding dendrimers with CP counterions. Therefore, the [Ru(tpy)2]2+ complexes are electrochemically equivalent and can efficiently store charges. 

NOTE Carotenoid solutions degrade rapidly at room temperature (within several hours) but can be stored for at least 1 month at or below -20°C and 3 months at or below -70°C in some cases. 1. Mix 20 pi carotenoid sample with 10 pi acetone saturated with 2,5-dihydroxybenzoic acid. 2. Using a microsyringe, load 5 to 10 pi carotenoid/matrix sample onto the target of a MALDI probe. 3. Let solvent evaporate (only a few seconds are required) and then insert probe through the vacuum interlock into the ion source of a MALDI-TOF mass spectrometer. 4. Record MALDI-TOF mass spectra in positive ion mode. Look for molecules ions and protonated molecules in the range m/z 300 to 1000. 

Abundant molecular ions, M+, will be observed as the base peaks in the MALDI-TOF mass spectra. Delayed extraction will enhance the abundance of the molecular ions relative to background noise, and the use of postsource decay will facilitate the detection of structurally... 

The automated process of producing genotype calls from MALDI-TOF mass spectra can be broken down into three stages (1) collection of good... 

The matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectra of 49a-d and macrocycle 50, using a-cyano-4-hydroxycinnamic acid (CCA) as a matrix, exhibited, besides [M+Na]+ as the main peak, [M+K]+ adducts and ions corresponding to protonated molecules [M+H]+ <1999RCM2359>. 

Figure 2. Peptide maps (A-C) and MALDI-TOF mass spectra (D-F) of PVDF-bound transferrin (53 pmol) digested with trypsin in the presence of 50 pi of 1% RTX-100/10% acetonitrile/100 mM Tris, pH 8.0 (A,D), 1% octylglucopyranoside/10% acetonitrile/100 mM Tris, pH 8.0 (B,E), and 1% decylglucopyranoside/10% acetonitrile/100 mM Tris, pH 8.0 (CJF) as described in Materials and Methods. Ninety percent of the digestion was analyzed by HPLC ( 29 pmol based on Table I) and 0.5% ( 150 fmol) was used for MALDI-TOF mass spectrometry. Peptides 1 and 2 in A-C were amino terminally sequenced (Table II) and analyzed by MALDI-TOF mass spectrometry (Figure 3).

Figure 4 MALDI-TOF mass spectra of functionalised PEG mixtures as prepared hy air-spraying with the compressed air applicator...

Fig. 20 MALDI-TOF mass spectra of T1 (compound 72) and the soluble part after 30 min of UV irradiation by a 125 W high-pressure mercury-arc light source. The arrows point towards the possible products with different masses (with 73-75 as defect sites). Used with permission [220]...

The [2-1-1] fragmentation of the precursors shown in Figure 6.2 also provides a potential route to monocyclic carbon clusters. Thus cyclic dehydro oligomers of diethynyl[4.4.1]propellatetraenes 6a,b incorporated in a fullerene structure have been prepared and their fragmentation was investigated by mass spectrometry [7]. MALDI TOF mass spectra of 6a,b exhibited peaks due to the stepwise loss of the fullerene fragments, leading to the formation of mono-fullerene adducts of C15 and C20. However, the... 

Fig. 9.15 MALDI-TOF mass spectra of HPL (I) or HPL incubated 1 h with orlistat (II) at a HPL orlistat molar ratio of 1 100. Adapted from [112],...

FIGURE 4.8 MALDI-TOF mass spectra of three proteins in a 10 mg/ml sinapinic acid and 0.1 to 0.3% acetic acid matrix (a) cytochrome-c (eqnine), =... 

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