Comparative analysis of SDF-1α cleavage by human serum and plasma. Recombinant SDF-1α (1 μgin18 μL PBS) was incubated for 10 minutes at room temperature with PBS (2 μL; lane 1); normal human serum (2 μL; lane 2); normal human plasma collected in heparin (2 μL; lane 3); and normal human plasma collected in heparin and the thrombin inhibitor PPACK (2 μL; lane 4). Serum and plasma samples were from the same individual. At the end of incubation, 1 μL of the mixture was used for immunoblotting and the remainder was used for MALDI. (A) Western blot analysis of SDF-1α cleavage using rabbit and goat anti-SDF-1 antibodies. (B) MALDI analysis of SDF-1α cleavage by serum or plasma collected in heparin (hep). The experiment was carried out 4 times and a representative set of data is shown with similar results from each.