Human secreted Programmed Cell Death 1 Ligａnd 1 (PD-L1)-Fc fusion protein, also known as CD274 and B7 homolog 1 (B7-H1) with a I54A mutation, GenBank Accession No. NM_014143, amino acids 19-239, fused at the Cterminus with the Fc portion of human IgG1, with C-terminal Avi-tag™ expressed in a HEK293 cell expression system and enzymatically biotin-labeled using Avi-tag™ technology. MW = 54 kDa.