Molecular modifications of hemoglobin.

Abstract

There are two major limitations on the use of acellular hemoglobin solutions in vivo: rapid renal clearance and increased oxygen affinity. A series of chemical modifications of hemoglobin are presented in an attempt to address these problems. Reactions of hemoglobin with phosphorylated sugars and gluteraldehyde under a number of conditions, resulted in either hemoglobin denaturation or production of multiple hemoglobin polymers. In contrast, phosphorylated cyclic nucleotides upon ring opening with sodium periodate resulted in high-yield crosslinking of hemoglobin to exclusively form species with a molecular weight of 68,000. Because yield of modified hemoglobin increased with degree of phosphorylation of the cyclic nucleotide, this reaction is most consistent with formation of a crosslinked product within the 2,3-diphosphoglycerate pocket. Resultant oxygen affinities of such modified hemoglobins were variable and believed to be due to residual nonspecific sodium periodate oxidation. Affinity difunctional crosslinking agents like the phosphorylated dialdehydes seem useful in overcoming the major limitations of unmodified hemoglobin while maintaining basic hemoglobin structure.