Stabilizing effect of water/alcohol solvents towards autoxidation of glutaraldehyde-modified haemoglobin

Glutaraldehyde-cross-linked haemoglobin is potentially very attractive as a useful oxygen carrier for biomedical and technological purposes. However, its oxygen-binding ability is restricted by the autoxidation of the iron which is faster than for native haemoglobin. We have studied the stabilization effect of ethanol, butan-1-ol, ethylene glycol and glycerol on the autoxidation of glutaraldehyde-cross-linked oxyhaemoglobin. We have shown that, in the presence of water/alcohol mixtures, cross-linked haemoglobin became more stable towards autoxidation than native oxyhaemoglobin in an aqueous environment. From a structural point of view, an e.p.r. study showed that alcohols and cross-linking had opposite effects on the haem environment. In contrast with the cross-linking, alcohols stabilize oxyhaemoglobin by decreasing the charge transfer from the iron to the oxygen, decreasing the O-O length and increasing the total distance (F8 His)-N-F-O2.