changes in protein profiles in bortezomib applied multiple myeloma ...

The functions of the matrix are:
Absorb and accumulate the energy of the laser radiation,
Protect the analytes from destruction and fragmentation.
A good matrix material should be :
Adsorb strongly at the laser wavelength,
Chemically inert and stable in vacuum,
Be able to embed the analyte,
Pure et least 99%,
Promote co-desorption of the analyte upon laser irradiation as well as
ionisation of the analyte by donating protons.
3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid) (Beavis and Chait,
1989) and α-cyano-4-hydroxycinnamic acid (CHCA) (Beavis et al., 1992) are the most
preferred and popular matrices in proteomic researches.
In MALDI, process begins with the sample preparation. For the preparation,
matrix and our sample (analyte) mix in an eppendorf tube, and then this prepared
mixture spots to the MALDI Target and allows to dry. After it is dry, the target is
transferred in the vacuum chamber of the mass spectrometer. UV-Laser pulses are
directed at the sample plate, which carries the co-crystallized peptides and matrix
mixture, with a high energy (~10 6 W/cm 2 ). A large proportion of the laser beam is
efficiently absorbed by the matrix crystals inducing evaporation of the matrix, and this
energy is transferred to the analyte as heat in a controlled manner (it means that there is
no fragmentation). That is the most important stage in MALDI. If there is no problem,
analyte molecules are converted into gas-phase ions by gas phase proton-transfer
reactions. Finally they are directed into the mass analyzer by appropriate electric fields
(Figure 2.7).
MALDI permits the analysis of high molecular weight compounds with high
sensitivity. And also it has an ease of use while tolerating small amounts of
contaminants like salts and surfactants.
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