fragment ion

fragment ion

A term defined in the context of mass spectrometry as the charged product of an ion dissociation. A fragment ion may be stable or dissociate further to form other charged fragment ions and neutral species of successively lower mass. Molecular ions formed in the initial ionisation dissociate to fragment ions because of excess internal energy remaining after ionisation.
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Incorporation of an SIS peptide adds an additional level of confidence in peptide identification by providing a reference to which the fragment ion ratios can be compared, as well as providing a precise retention time standard for the analyte of interest that is independent of the chromatographic conditions used.
This is likely to be true in the MSZ event in the ion-trap, where only 1 major fragmentation pathway is followed (see the online Data Supplement), but when MS/MS is performed on both the tandem quadrupole and Q-TOF instruments, where fragmentation is dispersed over a wide range of fragment ions, it is to be expected that the 2 isomers will give different relative abundance for each fragment ion.
MS/MS usually offers high specificity, even in complex sample matrices, through selection of a specific precursor ion in the first mass analyzer and selection of a specific fragment ion formed during passage of the precursor ion through a collision cell.
With the ability to provide sequence information, to measure all detectable PTMs, and provide fragment ion information from MS/MS analyses, Byomap(TM) and Byologic[sup.
The system also allows for further identification of analytes on the isotopic pattern and high-resolution fragment ion spectra with the possibility of a library search.
A fragment ion at m/z 306 refers to the deprotonated glutathione (GSH) moiety and CNLs of 120 and 146, indicating the presence of a rhamnoside group.
Specificity: Selection of the precursor ion with the first quadrupole and the product fragment ion with the second quadrupole by the tandem mass spectrometer can exhibit highly specific detection for a given molecule.
Loss of a neutral carbon monoxide molecule from the base peak fragment ion gave a characteristic fragment ion at M/Z 135.
In the first step, the amino acid composition of an unknown peptide is determined on the basis of accurate mass values of the peptide precursor ion and of a small number of accurate fragment ion mass values.