Haemoglobin lyophilized with sucrose: the effect of residual moisture on storage

Sucrose is one of the most effective substances which protect haemoglobin from spontaneous methaemoglobin formation during lyophilization and subsequent storage. The dry haemoglobin-sucrose system was treated under different conditions of temperature (up to 85 degrees C), time of storage (up to 6 years) and residual moisture (less than 0.1-7.5% H2O), in order to reveal the main features of the hitherto unclear mechanisms of both spontaneous methaemoglobin formation and of the stabilizing effect of sucrose. In conclusion, a dry sucrose network was recognized as a significant support to the native ferrous structure of oxyhaemoglobin, while the presence of water molecules, of assumed peroxidic radicals and the action of thermal vibrations favour the oxidation and denaturation of haemoglobin.