SDF-1 (stromal cell-derived factor-1) is small cytokine belonging to the chemokine family that is officially designated Chemokine (C-X-C motif) ligand 12 (CXCL12).SDF-1 is produced in two forms, SDF-1α/CXCL12a and SDF-1β/CXCL12b, by alternate splicing of the same gene. SDF-1β is synthesized as a 93 amino acid (aa) precursor that contains a 21 aa signal sequence and a 72 aa mature region. The mature molecule exhibits a typical three antiparallel β-strand chemokine-like fold. There are no potential N-linked glycosylation sites. N-terminal aa ’s 1-8 form a receptor binding site, while aa’s 1 and 2 (Lys-Pro) are involved in receptor activation. The C-terminus is likely associated with heparin binding. SDF-1β circulates and undergoes proteolytic processing. SDF-1β are reported to be a monomers at neutral pH and physiologic ionic strength.