SDF-1α peptide cleavage assay using RP-HPLC/MSD analysis. The 11-amino acid C-terminal peptide of SDF-1α corresponding to amino acids 58-68, IQEYLEKALNK, was incubated (100 μM) in PBS in the absence (A) or presence of (B) 1% human serum or (C) 10% human serum and incubated for 10 minutes at 37°C. Samples were stopped by acidification with TFA and analyzed by RP-HPLC/MSD. Representative elution profiles for the intact peptide and the -K peptide as measured at 205 nm are shown along with their respective molecular masses determined by electrospray mass spectrometry.