MALDI Technique of ionization

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Presented By- Anubhav Singh
M.pharm 1st Year
IPR, GLA University

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Introduction
Mechanism
Instrument
MALDI Matrix
MALDI Laser
Time Mass Detector
Application
Conclusion
References

3. 
Matrix-assisted laser desorption/ionization (MALDI) is a soft
ionization technique used in mass spectroscopy, allowing the
analysis of biomolecules (biopolymers such as DNA, Proteins,
peptide and sugars) and organic molecules (such as polymers,
dendrimers and other macromolecules), which tend to be fragile
and fragment when ionized by more conventional ionization
methods.
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Method where a laser is used to generate ions of high molecular
weight samples, such as proteins and polymers.

4. 
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The
mechanism
remains
uncertain.
It may involve absorption of
light by the matrix.
Transfer of this energy to the
analyteo which then ionizes into the
gas phase as a result of the
relatively large amount of
energy absorbed.
o To accelerate the resulting
ions into a flight-tube in the
mass spectrometer they are
subjected to a high electrical
field

5. 
The MALDI technique combined with a MS detector
(MALDI-MS) became an indispensable tool in analysis of
biomolecules and organic macromolecules.
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MALDI involves incorporation of the analyte into a matrix,
absorption/desorption of laser radiation, and then ionization of
the analyte.

7. 
The analyte incorporation in to a suitable matrix is the first
step of the MALDI process, and is an important feature of the
MALDI method.
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A typical sample preparation involves using 10-6 M solution of
the analyte mixed with 0.1 M solution of the matrix.
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The solvents are then evaporated in a vacuum of the MS, and
the matrix crystallizes with the analyte incorporated.

8. 
According to Sigma Aldrich, the matrix must meet the
following properties and requirements :
o Be able to embed and isolate analyte (e.g. by cocrystallization)
o Be soluble in solvents compatible with analyte
o Be vacuum stable
o Absorb the laser wavelength
o Cause co-desorption of the analyte upon laser irradiation
o Promote analyte ionization

10.  Numerous
gas and solid state lasers have been developed for
use in MALDI.
 Most MALDI devices use a pulsed UV laser
 N2 source at 337 nm.
 Neodymium-yttrium
aluminum garnet (Nd:YAG)
 Emits at 355 nm and gives a longer pulse time
 IR lasers are also used
 The most common IR laser is the erbium doped-yttrium
aluminum garnet (Er:YAG).
 Emits at 2.94 micrometer.
 It is “softer” than the UV, which is useful for certain
biomolecules.

12. 
The typical detector used with
MALDI is the time of flight mass
detector (TOF-MS)
o TOF is a method where the ions
are accelerated by an electric field,
resulting in ions of the same
strength to have the same kinetic
energy.
o The time it takes for each ion to
traverse the flight tube and arrive
at the detector is based on its massto-charge ratio; therefore the
heavier ions have shorter arrival
times compared to lighter ions.

13. 
Applications of MALDI mass spectrometry in detection ofo Synthetic polymers
o Peptides and proteins
o Oligonucleotides
o Oligosaccharides
o Lipids
o Inorganics
o Bacterial identification

14. 
MALDI-MS is a vital tool in mass analysis of biomolecules
and organic macromolecules.
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Detection limits of femtomole to attomole.
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Reproducibility is relative.
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Complimentary technique to ESI (electrospray ionization)

15. 1.
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5.
“Matrix Assisted Laser Desorption Ionization (MALDI).”
http://www.tau.ac.il/lifesci/units/proteomics/voyager.html
(4/11/2013).
“MALDI-TOF Mass Analysis.”
http://www.protein.iastate.edu/maldi.html (4/11/2013).
“Maldi Mass Spectrometry.”
http://www.sigmaaldrich.com/img/assets/4242/fl_analytix6_200
1_new.pdf (4/11/2013).
“MALDI Mass.” http://www.sigmaaldrich.com/analyticalchromatography/spectroscopy/maldi-mass.html (4/11/2013).