Voyager DP-263-S Guía de usuario Pagina 569

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Glossary
Voyager
Biospectrometry
Workstation User’s Guide Glossary-3
G
O
S
S
L
A
R
Y
Ionization
—Conversion of sample
in solid, gaseous, or liquid phase to
ions.
Ion intensity
—See Intensity.
Ion source
—Device that produces
ions. In a TOF instrument, it refers to
the surface of the sample plate, the
variable-voltage grid above the plate,
and the grounded grid and aperture
above the variable-voltage grid.
Isomers
—Compounds that have
the same molecular weight but different
structures.
Isotopes
—One of two or more
atoms with the same atomic number but
a different mass. For example, carbon
isotopes
12
C,
13
C, and
14
C.
Laser
—Energy source for sample
ionization in MALDI technology. The
Voyager Biospectrometry Workstation
uses a Nitrogen laser at 337 nm that
provides 3-nanosecond
-
wide pulses.
Laser attenuator
—Device that
controls laser intensity. Controlled by
laser step setting.
Laser intensity
—See Intensity.
Laser step
—Unit of movement of
laser attenuator. The size of the laser
step is set in Laser Configuration. The
number of laser steps is controlled by
using the slider controls on the Manual
Laser Control page.
Low Mass Gate
—Mechanism
for suppressing low mass ions. The
voltage in the detector is not turned on
until ions below the specified starting
mass have passed.
Ladder sequencing
—Peptide
or DNA sequencing in which amino acid
sequence is read from one of the ends
of the peptide chain.
[M+H]
+
—Molecular ion.
[M+2H]
2+
—Doubly
-
charged ion.
Appears in spectrum at approximately
half the molecular weight of the ion.
[M+3H]
3+
—Triply-charged ion.
Appears in spectrum at approximately
one third the molecular weight of the
ion.
MALDI
—Matrix-assisted laser
desorption ionization. Described in
Section 1.3, MALDI-TOF MS
Technology Overview.
Mass accuracy
—The error
between the observed mass and the
calculated mass from atomic
composition. Can be expressed as
mass units or the ratio of mass
assignment error divided by ion mass in
percent terms.
Mass resolution
—Describes
the separation between adjacent mass
peaks. Expressed as the mass (
m)
of
the ion signal, divided by the width of
the peak at half-height (
m
).
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