Characterization of SDF-1α present in the circulation. SDF-1 was affinity purified from aliquots (1 mL) of human serum and plasma (collected in heparin and PPACK) from the same individual using biotin-labeled goat anti-SDF-1 antibodies (BAF 310) immobilized onto beads. Aliquots of the purified material (20 μL) were immunoblotted with rabbit anti-SDF-1α antibodies that do not recognize SDF-1α missing the C-terminal lysine (aa 1-67), and reblotted with goat anti-SDF-1 antibodies that recognize SDF-1 lacking the C-terminal lysine. Lane 1: SDF-1α purified from serum; lane 2: SDF-1α purified from plasma; lane 3: recombinant SDF-1α, 3 ng; lane 4: recombinant SDF-1α, 1.5 ng. The experiment was carried out 3 times with similar results and a representative set of this data is shown.