Spin label study of erythrocyte membrane submitted to a bending stress

Red blood cells were submitted to a bending stress by incubation in hyperosmolar media and their membrane molecular structure studied by a fatty acid paramagnetic label which probes its hydrophobic part. Measurement of the apparent rotation frequency of the label, and numerical analysis of the spectrum shapes indicate that a high fluidity phase appears in the stressed membrane. The physiological implications of this finding are discussed in the light of the rheological properties of the circulating red blood cell.