Voyager DP-263-S Guía de usuario descargar pdf (Pagina 568)

100

101

Glossary-2 PerSeptive Biosystems

Glossary

Delay Time

—Used in Delayed

Extraction mode. Time in nanoseconds

(after the laser ionizes the sample) at

which full Accelerating Voltage is

applied, creating the potential gradient

that accelerates ions.

Digitizer

—A device that converts

an analog signal to a digital word and

stores the result in memory. This allows

the transfer of the digitized signal to a

computer for additional processing.

Dimer

—A species that results from a

association between two identical

molecules. Expressed as [2M+H]

Appears in a mass spectrum at 2 times

the protonated molecular ion mass,

minus one mass unit.

Edman degradation

technique

—An approach to

amino-end-group determination

involving the use of a reagent,

phenylisothiocyanate, that can be

applied to the liberation of a derivative

of the amino-terminal residue without

hydrolysis of the remainder of the

peptide chain.

Flight tube

—Vacuum chamber in

which ions drift from the source to the

detector.

Fore pump

—Rotary pump that

maintains vacuum in the sample loading

chamber, creates the low-vacuum

condition needed by the turbo pump,

and provides backing pressure to the

turbo pump.

Fragment

—Ion dissociated from

precursor ion.

FWHM

—Full width at half maximum.

GPMAW

—General Protein/Mass

Analysis for Windows software, a

software program used to identify

protein sequences.

Grid voltage

—Secondary voltage

used to fine

tune ion acceleration, on a

variable-voltage grid above the sample

plate.

Guide Wire voltage

—Voltage

applied to beam guide wire to focus ions

on detector. Particularly useful for

enhancing analysis of high mass ions.

Immonium ion

—In PSD, low

molecular weight fragment ions derived

from amino acids.

Initial velocity

—The velocity

associated with an ion when it is

released from the sample plate, before

acceleration. Voyager software allows

correction for matrix-dependent initial

velocities.

Intensity (signal or ion)

—

Amplitude of signal shown on

oscilloscope screen or spectrum

window.

Intensity (laser)

—Amount of

laser-generated light reaching the

sample spot. Controlled by adjusting the

laser attenuator using laser step setting.

Ion

—An isolated electron or proton or

an atom or molecule which, by loss or

gain of one or more electrons, has

acquired a net electric charge.

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