Structural transitions of the erythrocyte membrane: an ESR approach

The effect of temperature and ionic strength on the ESR spectrum of the fatty acid spin label I (10,3) in membranes of freshly drawn human red blood cells has been investigated. The results suggest that the microviscosity of the membrane is not strongly influenced by the ionic strength. Discontinuities at various temperatures could be observed, which disappear after cholesterol treatment. The possible role of membrane lipids and proteins on the thermotropic membrane behaviour observed is discussed. It is assumed that the spectra are averaged signals from different regions of the membrane.