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Chapter 6 Using Tools and Applications
6-6 Applied Biosystems
6
Hint: You can sort the results in a column by clicking the
column header.
Results include:
• Index—Sequential number assigned to each result.
• Input m/z—Entered m/z for each composition
calculation.
• Calculated Mass—Calculated mass for the entered m/z
and charge state for each theoretical composition.
• mDa Error and ppm Error—Error for each calculation.
• Double Bond Equivalents (DBE)—Value that
corresponds to the number of double bonds or rings that
the valence-bond theory requires to construct a molecule
from each calculated composition. If the target mass is a
protonated molecular ion, (M+H)
+
, the DBE value
includes 0.5 and corresponds to an even electron state.
To convert the reported DBE value to the actual number
of double bonds or rings, add 0.5. For example,
H
2
C=NH
2
+
has an (M+H)
+
total mass of 30.0344 and a
reported double bond equivalent of 0.5, with an actual
number of double bonds of 1.
• Formula—Elemental composition for each mass.
• Isotope Match Score—Number between 0 and 1.0 that
reflects how well the observed peak matches the
theoretical formula, based on mass and isotope pattern.
A higher number represents a better match.
NOTE: An Isotope Match Score of 0.00000 is always
reported for fragment ion calculations.
If no results are
displayed
If no results are displayed, it may indicate that the specified
Tolerance is too limiting and no matches were found.