Source: Fibrinogen, purified from human plasma that has been shown by certified tests to be negative for HBsAg and for antibodies to HIV and HCV. ? MW: α chain isoform 1 (95 kDa), α chain isoform 2 (69.8 kDa), β chain (55.9 kDa) and isoform γ-B chain (51.5 kDa)