4.5. Protein Labeling with Cyanine Dyes

The proteins were labeled with 400 pmol of CyDye™ DIGE Fluor dyes (GE Healthcare, Buckinghamshire, UK) in 1 μL of DMF and mixed with 50 μg of protein. The mixtures were incubated on ice for 30 min in a dark place. Afterward, the labeling reaction was terminated by adding 1 μL of 10 mM lysine. Each technical duplicate of the sample was covalently labeled with a fluorophore, either Cy3 or Cy5. A mixture of equal amounts of protein isolated from each sample in the experiment was labeled with Cy2 and used as an internal standard (Table S2, Supplementary Materials).