2.5. Digestion of peptides with trypsin
In-gel digestion of protein spots showing changes in intensity
was performed. For this task, the spots (ca. 2 mm) were manually
cut from the gel and placed on a micro-SPE plate containing
peptide affinity resin using the Montage® In-Gel digestZP kit
(Millipore, Bedford, USA). The digestion and vacuum elution
protocols were performed according to the manufacturer's
recommendations. In brief, a dye removal step using acetonitrile
was first employed, followed by tryptic digestion (using ca.
166 ng of enzyme for each spot). Then, a clean-up step was
carried out using 130 μL of 0.2% (v/v) TFA solution. Finally,
purified peptides were eluted from the resin using 20 μL of 0.1%
(v/v) TFA in 50% (v/v) acetonitrile solution. For vacuum elution, a
Multiscreen® Vacuum Manifold (Millipore) was used