Abstract: Stroma-free deoxy mammalian tetrameric hemoglobin is crosslinked with certain bis diaspirin esters and modified with pyridoxyl-5'-phosphate followed by reduction to produce bis-diamide covalently crosslinked, pyridoxal-5'-phosphate covalently modified tetrameric hemoglobin wherein the crosslinking and modifying bonds occur in the beta cleft. The modified crosslinked stroma-free tetrameric hemoglobin of this invention is a disease-free, oxygen transporting discrete molecular species, free from cell surface antigens, having use as a substitute for transfusion of red blood cells. This modified crosslinked stroma-free hemoglobin is a stable oxygen carrying protein capable of oxygen delivery to perfused tissue and advantageously remaining in the intravascular space.

Abstract: A method for the production of stroma-free, non-heme protein-free hemoglo by use of zinc ion to promote precipitation of a zinc ion-bound insoluble hemoglobin complex, followed by membrane ultrafiltration of the zinc-hemoglobin complex from the filtrate fluid medium, preferably with a saline dialyzate.