Characterization of synthetic G-CSF 1–174 (22) and G-CSF (2a). (A) Silver-stained SDS-PAGE, NuPage 4–12% Bis-Tris gel: lanes 1 and 10, benchmark protein ladder (MW marker); lanes 2, 5, and 9, blank; lane 3, synthetic G-CSF 1–174 22; lane 4, synthetic G-CSF 2a; lanes 6–8, recombinant G-CSF 2b gradient. (B) High-resolution mass spectrometry: top, synthetic G-CSF 1–174 (22) and bottom, synthetic G-CSF 1–174 (2a).