A strategy for the characterization of protein interaction networks by mass spectrometry.

Results with wild-type and iNOS knockout mouse osteoblasts DIGE was used to analyse protein extracts from mouse osteoblasts. iNOS knockout and wildtype mouse osteoblasts were compared using DIGE as described previously [4] except that the imaging system was upgraded to use a scientific grade 16-bit cooled charge-coupled device camera (Photometrics model 350). Figure 2 shows the result of superimposing fluorographs of the wildtype (Panel A) and knockout (Panel B) extracts in DIGE. Note that, as expected, the vast majority of the proteins comigrated and may be directly superimposed in the two images. The difference protein marked with double arrows has a posttranslational modification difference, indicated by the similarity of mass but differing isoelectric points, between wild-type and knockout spot profiles.