Characterization of thermotropic structural transitions of the erythrocyte membrane: A biochemical and electron-paramagnetic resonance approach

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Abstract
The relationship between membrane structural properties and functions has been generally inferred from observed thermotropic phenomena. By the use of 16-dinyloxyl stearic acid spin probe we investigated the red blood cell membrane components involved in three characteristic thermotropic structural transitions occurring at 8, 20, and 40°C. The transition at 8°C is removed by chymotrypsin treatment at the cytoplasmic membrane layer. The 20°C phase transition is unmodified after chymotrypsin treatment and occurs at 15°C after complete proteolysis of intramembranc chymolrypsin insensitive peptides. Liposomes from the total lipid extract of RBC show only one thermotropic transition at 15°C. The 40°C phase transition is absent in vesicles free of skeletal proteins, in vesicles obtained after RBC storage, and in low-ionic-strength resealed ghosts. Transitions at 8°C and 40°C appear to be due to the interactions of cytoplasmic exposed proteins with membrane, whereas the 20°C transition is intrinsic to the lipid component.

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