Figure 2

SDS electrophoresis of milk fractions for GeLC analysis. A total of 30 μg of each pooled milk fraction from the uninfected (lanes 1, 3, and 5) or mastitis (lanes 2, 4, and 6) milk samples was subjected to SDS electrophoresis and stained with Coomassie blue G250. A series of 10 slices were excised from each lane as indicated and each slice was subjected to in situ digestion, extraction of peptides followed by tandem mass spectrometry as described in the Methods section. The lesser intensity of lane 2 is most likely due to difference in protein/peptide composition between the infected and non-infected whey.