Recombinant human stromal cell-derived factor-1β (SDF1β), also known as CXCL12 or Pre-B cell growth-stimulating factor (PBSF), is a disulfide-linked monomeric protein consisting of 73 a.a. and migrates as an approximately 8 kDa protein under reducing and non-reducing conditions. Optimized DNA sequence encoding human SDF1β mature chain was expressed in E. coli.