Presented By- Anubhav Singh

M.pharm 1st Year IPR, GLA University

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

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.

Method where a laser is used to generate ions of high molecular weight samples, such as proteins and polymers.

The mechanism remains uncertain. It may involve absorption of light

by the matrix. Transfer of this energy to the

analyte- o 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

The MALDI technique combined with a MS detector (MALDI-MS) became an indispensable tool in analysis of biomolecules and organic macromolecules.

MALDI involves incorporation of the analyte into a matrix, absorption/desorption of laser radiation, and then ionization of the analyte.

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.

A typical sample preparation involves using 10-6 M solution of the analyte mixed with 0.1 M solution of the matrix.

The solvents are then evaporated in a vacuum of the MS, and the matrix crystallizes with the analyte incorporated.

According to Sigma Aldrich, the matrix must meet the following properties and requirements :o Be able to embed and isolate analyte (e.g. by co-

crystallization)o Be soluble in solvents compatible with analyteo Be vacuum stableo Absorb the laser wavelengtho Cause co-desorption of the analyte upon laser irradiationo Promote analyte ionization

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.

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 mass-to-charge ratio; therefore the heavier ions have shorter arrival times compared to lighter ions.

Applications of MALDI mass spectrometry in detection of-

o Synthetic polymerso Peptides and proteinso Oligonucleotideso Oligosaccharideso Lipidso Inorganicso Bacterial identification

MALDI-MS is a vital tool in mass analysis of biomolecules and organic macromolecules.

Detection limits of femtomole to attomole.

Reproducibility is relative.

Complimentary technique to ESI (electrospray ionization)

1. “Matrix Assisted Laser Desorption Ionization (MALDI).” http://www.tau.ac.il/lifesci/units/proteomics/voyager.html

2. (4/11/2013).

3. “MALDI-TOF Mass Analysis.” http://www.protein.iastate.edu/maldi.html (4/11/2013).

4. “Maldi Mass Spectrometry.” http://www.sigmaaldrich.com/img/assets/4242/fl_analytix6_2001_new.pdf (4/11/2013).

5. “MALDI Mass.” http://www.sigmaaldrich.com/analytical-chromatography/spectroscopy/maldi-mass.html (4/11/2013).