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

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ange of 600-2500 Da. This is the ideal prote<strong>in</strong> digestion for mass spectrometry.<br />

Actually, peptides hav<strong>in</strong>g 6-20 am<strong>in</strong>o acids are optimum for MS analysis and database<br />

searches. There are also different proteases exist and used for <strong>in</strong>-gel digestion process<br />

such as chymotryps<strong>in</strong>, peps<strong>in</strong> etc. The only difference is their cleavage characteristics.<br />

Figure 2.5. Schematic Representation of In-Gel Digestion<br />

(Source: Jiménez et al., 2001)<br />

2.1.4.4. ZipTip (C-18 Colon)<br />

Follow<strong>in</strong>g the <strong>in</strong>-gel digestion process, peptides are required to purify to<br />

elim<strong>in</strong>ate gel contam<strong>in</strong>ants such as salts, buffers, and detergents. To obta<strong>in</strong> good<br />

spectra, it is essential to keep the salt concentrations <strong>in</strong> buffers to a m<strong>in</strong>imum. If the gel<br />

contam<strong>in</strong>ants do not elim<strong>in</strong>ate from peptides, they can <strong>in</strong>terfere with mass spectrometry<br />

either <strong>in</strong>duc<strong>in</strong>g the poor quality mass signal or mask<strong>in</strong>g the peptide signals (Yates,<br />

1998). Thus, the obta<strong>in</strong>ed peptide mixtures should be purified with ZipTips (Millipore).<br />

36

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