CAD fragmentation

The sulfates as a class were fragmented by a single pathway, neutral loss of 80 mass units corresponding to loss of SO,. Consistent with its tendency toward dissociative electron capture (or solvolysis) in filament-on ISP Q ) and hydrolysis, 4-nitrophenol sulfate was most susceptible to S03 loss in CAD fragmentation (Table V). With a collision energy of only 14 eV, the parent ion was either absent or only a minor product ion. 

SRM provides additional selectivity in detecting an individual xenobiotic and its related metabolites. A moiety or substructure in the xenobiotic is tagged by its novel CAD fragmentation. In the case of 4-nitrophenol, the neutral loss of 30 mass units (NO) labels the nitrophenyl moiety (actually the NO, substituent). With Q. locked at m/z 138 and Q3 locked at m/z 108 we detect 4-nitrophenol and its glucuronide and sulfate conjugates (Figure 3). Presumably, other metabolite structures in which the nitrophenol moiety is retained would be detected similarly. 

For small molecules, the CAD fragmentation of the protonated molecules was usually performed to reduce or eliminate interference signals from the tissue or matrix [21,65-68], For example, one study that imaged a drug in tissue used a drug... 

Mass spectrometry-based protein identification protocols have propelled proteomics to the forefront of biomedical research. Provided with available genomic and/or protein sequence information in databases, protein identification by MALDl-based peptide mass fingerprint mapping and LC-MS/MS and MALDl-TOF/TOF peptide sequencing with CAD fragmentation is efficient. However, in situations in which sufficient genome and protein sequence data are unavailable, mass spectrometric methods can be used for de novo protein sequencing. The mass measurement accuracy of MS provides a unique capability to... 

Collision of normal ions from the first quadrupole with gas molecules in the second quadrupole increases fragmentation, a process known as either collisionally induced dissociation (CID) or collisionally activated decomposition (CAD). 

Figure 8. The m/z 137 ion was selected from the source and colli-sionally decomposed (N ) to give the CAD spectra. The top spectrum is the fragment arising from the isolated xenognosin and the bottom two spectra arise from the isomeric benzyl alcohols ((3).

An insight into the equilibria present in solutions of several complexes of the type (R3P)2HgX2 (X = C104, CF3COO) is provided by electrospray mass spectrometry (ES MS) (cf. Section 6.9.2.1.8). 39 In all cases the principal ions [(R3P)2HgX]+ are observed, even if these ions and other ionic constituents of the equilibria are known to be labile on the NMR timescale. In the presence of excess R3P the principal ions [(R3P)3HgX]+ appear. Also fragments of collisionally activated decomposition (CAD, can be influenced and controlled to some extent) are detected, e.g., [(R3P)HgX]+. 

The dissociation of gas-phase ions can be a guide to the structure of the ions. There are two ways to dissociate gas-phase ions, either by collision-induced dissociation (CID) sometimes termed collision-activation dissociation (CAD) or by photodissociation. In each method, a mass selected ion is dissociated and the fragment ion (often called a daughter ion) is measured the neutral fragment cannot be experimentally observed. 

CAD Domains present in proteins implicated in postmortem DNA fragmentation E(M) 0(0) 0(0) ... 

Figure 2. Top, APCI mass spectrum of rose oil vapors emanating from an open vial bottom, CAD/MS/MS fragment ion spectrum of m/z 193 ions from the rose oil vapors.

Figure 3. Top and middle, CAD MS/MS fragment ion library spectra of 0- and Qf-ionone, respectively bottom, CAD MS/MS fragment ion...

The TNF-a-induced DNA fragmentation may have been caused by caspase-activated deoxyribonuclease (CAD) in PC-12 cells. In non-apoptotic cells, CAD is present as an inactive complex with the inhibitor jOvd p3,24]. During apoptosis, caspase-3 inactivates ICAD, leaving CAD free to function as a nuclease [25]. Therefore, we used die fluorogenic substrate, Ac-DEVD-MCA, to determine whether the caspase-3 in PC-12 cells was activated by treatment with TNF-a and/or crocin. As shown in... 

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