title: Effects of polymerization on the oxygen carrying and redox properties of diaspirin cross-linked hemoglobin.
abstract: Human hemoglobin site specifically cross-linked with bis(3,5-dibromosalicyl)fumarate results in a low oxygen affinity hemoglobin-based red cell substitute (alpha-DBBF). Polymerization of alpha-DBBF by bis(maleoylglycylamide) polyethylene glycol (BMAA-PEG) yields poly alpha-DBBF which offers the added benefits of reduced renal clearance and increased retention in the vascular circulation. Oxygen equilibrium curves for poly alpha-DBBF are slightly left-shifted (higher O2 affinity) compared to those of alpha-DBBF; with a diminished cooperativity and a reduced Bohr effect. In rapid mixing experiments (oxygen dissociation and carbon monoxide binding), poly alpha-DBBF exhibits a several fold increase in the overall rate of deoxygenation and carbon monoxide binding kinetics over its cross-linked counterpart. The rate of nitric oxide binding to the oxidized form of poly alpha-DBBF shows little or no change compared to the intramolecularly cross-linked derivative. The reduction of cyanomet poly alpha-DBBF by dithionite is several fold faster than that of HbA0 and alpha-DBBF whereas the slow subsequent cyanide dissociation from the ferrous iron remained unchanged among all proteins. The propensity of poly alpha-DBBF for auto-oxidation is slightly enhanced over alpha-DBBF whereas the extent of oxidative modification by hydrogen peroxide is very similar. Polymerization appears to selectively modify ligand interactions and redox kinetics of the tetrameric cross-linked form which reflects a possibly more open heme pocket. The data suggests that changes in oxygenation properties of hemoglobin brought about by a given modification are not necessarily predictive of other functional changes.
authors.affiliation: Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, MD 20892, USA.
authors.forename: M S
authors.initials: MS
authors.lastname: Rogers
authors.forename: B B
authors.initials: BB
authors.lastname: Ryan
authors.forename: R E
authors.initials: RE
authors.lastname: Cashon
authors.forename: A I
authors.initials: AI
authors.lastname: Alayash
mesh_terms: D001241:Aspirin / Q000031:analogs & derivatives* / Q000737:chemistry; D002248:Carbon Monoxide / Q000737:chemistry; D003432:Cross-Linking Reagents / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D011108:Polymers
chemical_list: D003432:Cross-Linking Reagents; D006454:Hemoglobins; D011108:Polymers; C021630:bis(3,5-dibromosalicyl)fumarate; D002248:Carbon Monoxide; C083478:diaspirin-cross-linked hemoglobin; D001241:Aspirin; D010100:Oxygen