
Chapter 7 PSD Analysis
7-6 PerSeptive Biosystems
7
7.1.2 Segments and Composite Spectra
Overview
To obtain the most information about an ion, collect fragment
ion spectra across a molecular weight range from the mass of
the original precursor ion down to 50 Da (determined by the
desire to see immonium ions that indicate the presence of
individual amino acids).
Each fragment ion spectrum is referred to as a segment, and
is collected with a discrete focusing region (controlled by the
Mirror Ratio setting). Segments are combined to generate a
composite spectrum.
Number of
segments
The number of PSD segments you must collect depends on
the quality of data needed. The PSD software allows you to
collect any number of segments. A larger number of fragment
spectra generally yield better resolution in the composite
spectrum. For more information, see Section 7.3.2,
Determining the Number of Segments to Acquire
for a Complete Composite Spectrum.
Composite
spectrum
When you view the PSD data in the Data Explorer software,
the software automatically assembles or “stitches” together
the best portions of fragment ion spectra (referred to as PSD
segments) to generate the full composite PSD spectrum. For
information, see the
Data Explorer Software User’s Guide
,
Chapter 8, Viewing Voyager PSD Data.
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