Low viscosity of densely and highly polymerized human hemoglobin in aqueous solution--the problem of stability

The viscosity of highly and densely polymerized human hemoglobin is low enough in reasonable concentrations to serve as an effective oxygen carrying blood substitute. But polymerisation with glutardialdehyde leads to instable polymers. In contrast polymerisation with diisocyanate gives stable polymers which can be fractionated. Fractionation reduces viscosity. The viscosity of the fractionated polymers is at 5 g/dl as low as the viscosity of plasma.