In 1967 Baker reported the occurrence of a zone of dense material adjacent to the inner leaflet of the unit membrane of erythrocytes exposed to buffers with a pH 4.5. It was postulated that this arose because the haemoglobin, positively charged at that pH, was attracted to the negatively charged membrane.In an attempt to elucidate the mechanisms underlying the formation of the zone, fresh human erythrocytes were washed for 15 minutes at room temperature in citrate phosphate buffers in which the pH ranged from 4.0 - 7.4, or in a standard preservative solution, Acid Citrate Dextrose (ACD), pH 5.0. Paired samples were subsequently washed in buffer at pH 7.4 for 10 minutes to assess the possible reversibility of any changes produced. The cells were fixed in 2.5% glutaraldehyde in 0.1 m cacodylate buffer at the same pH as the washing buffer for one hour and then processed in two ways: Some were post-fixed in OSO4, The cells were stained with 0.5 - 1% Alcian Blue 8 G S in cacodylate buffer pH 7.0 for 15 - 30 minutes.
Lipid composition of freshly prepared and stored platelet concentrates