User`s guide

Glossary-4 PerSeptive Biosystems
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Glossary
Matrix —Low-mass, UV-absorbing
substance used in MALDI technology to
enable sample ionization. Common
matrices include sinapinic acid,
dihydroxy benzoic acid, and
α
-cyano 4-
hydroxy cinnamic acid. See
Appendix C, Matrices, for more
information.
Metastable ion analysis —
See MS/MS analysis.
Mirror —A single plate at high
voltage. Commonly used to refer to the
reflector in a TOF instrument.
Mirror voltage ratio —Ratio of
the mirror high voltage supply to the
acceleration high voltage supply. Mirror
Voltage = ratio x accelerating voltage.
MS/MS analysis —Selection of
a precursor ion for fragmentation, and
the collection of the fragment ions.
MS/MS analysis can yield sequencing
information for a peptide.
By acquiring data using different mirror
voltages, you can focus on different
segments of the fragment population.
After acquisition, you can piece together
the segments to examine a composite
PSD spectrum.
Multiply charged ions —See
[M+2H]
2+
and [M+3H]
3+
.
m/z —Mass-to-charge ratio.
Parent ion —See Precursor ion.
Post-Source Decay
(PSD)
—Fragmentation of an ion
during flight, after it leaves the ion
source region.
Post-translational
modification
—Non-amino acid
modifications made to a peptide or
protein by chemical or enzymatic
means. Examples include deamidation,
acetylation, oxidation, glycosylation,
phosphorylation, and sulfation.
Pulsed Source —Ion source in a
Delayed Extraction system.
Precursor ion —Used in PSD
Analysis software. Original ion from
which fragments dissociate.
Precursor Ion Selector —
See Timed Ion Selector.
Product ion —Used in PSD
Analysis software. Fragment ion that
dissociates from precursor ion.
Sensitivity —Measure of the
amount of sample required to generate
an acceptable mass spectrum. Usually
expressed in terms of strength of signal
relative to noise.
Signal intensity —See Intensity.
Source —See Ion source.
Stitch —Segment of a PSD
composite spectrum.
Tandem mass
spectrometry
—See MS/MS
Analysis.