Frequently Asked Questions about Mass
Spectrometry
What is mass spectrometry?
Mass spectrometry, or MS, is the measurement of
molecular mass that is gained by determining the mass-to-charge
ratio (m/z) of ions generated from the target molecule. Mass
spectrometers are comprised of a source for generating the ions from
the sample and delivering them into the gas phase; an analyzer for
separating and sorting the ions; and a detector for sensing the ions
as they are sorted. An MS “run” generates a spectrum that displays
ion intensity as a function of m/z.
What are some uses for mass spectrometry (MS)?
According to the
American Society of
Mass Spectrometry’s Web site, MS can, among other things, detect
and identify the use of steroids in athletes, monitor a patient’s
breath during surgery, determine the composition of molecular
species found in space, and locate oil deposits by measuring
petroleum precursors in rock.
What can mass spectrometry do for you?
Mass spectrometry can be used to identify structures
of biomolecules, such as carbohydrates, nucleic acids and steroids.
It can also be used to sequence biopolymers such as proteins and
oligosaccharides.
What is MALDI and TOF?
MALDI, or Matrix-Assisted Laser
Desorption Ionization, is a solid-phase ionization
technique in which samples are dissolved in a solution containing a
chromophoric matrix. The matrix-sample mixture is dried on a target
plate and subjected to laser irradiation. As the matrix absorbs
energy from the laser, it desorbs (vaporizes) and ionizes, and
transfers charge to the sample that was desorbed with the matrix.
TOF, or time-of-flight, is mass analysis
technique in which ions are separated, based on the time it takes
for them to travel over a given distance. In a TOF MS ions of like
charge are simultaneously emitted from the source with the same
initial kinetic energy. Those with a lower mass will have a higher
velocity and reach the detector earlier than ions with a higher
mass.
What is peptide fingerprinting?
This is a process in which a protein sample is
digested with trypsin to produce fragments; the fragments are then
subjected to MALDI MS. The resulting peaks, which represent the
masses of every peptide fragment in the sample, constitute the
fingerprint that can be used to determine the identity of the
initial protein by comparing it to known patterns in a sequence
database.
What is one surprising MS application?
It can be used as an imaging technology. One
relatively new application is the imaging or mapping of proteins in
mammalian tissue samples using MALDI MS. Dr. Richard Caprioli of
Vanderbilt University has been applying this technique to explore
protein expression patterns in a variety of tissues including brain
and tumor.
For a more detailed tutorial on Mass
Spectrometry, please visit
http://ms.mc.vanderbilt.edu/tutorials/ms/ms.htm.
Procedure
/ Instrumentation / Accuracy
Sample Preparation / Protein
Identification /
Form / FAQ's
Analytical Services:
Protocols:
Fee Schedules: