DLK1, also known as protein delta homolog 1, belongs to the Notch/Delta/Serrate family of epidermal growth factor (EGF)-like repeat-containing proteins that act as ligands in the Notch signaling pathway. It has six well conserved epidermal-growth-factor motifs and contains up to ten O-glycosylation and N-glycosylation sites, six of which are differentially glycosylated. Recombinant human DLK1, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.