A study of intact human erythrocytes and their ghosts using stearic acid spin labels

Sendai virus-induced hemolysis: reduction in heterogeneity of erythrocyte lipid bilayer fluidity.

“…Interestingly, the fatty acid derivative spin labels, which may reflect an "average" fluidity of the membrane bilayer, are unaffected by hemolysis. The same pattern of fluidity changes is seen following osmotic hemolysis (6,16).…”

“…The complex effect on membrane bilayer fluidity by virus-induced hemolysis is similar to the effect of osmotic lysis, which also increases the fluidity of phosphatidylcholine spin labels, decreases that of phosphatidylethanolamine spin labels, and has no effect on fatty acid derivative spin labels (6,16). (21).…”

“…The region probed by PC12 exhibits the largest change in 2A'", while the PC5 and PC16 labels reflect less of a change. The shapes of ESR spectra of PC16-labeled intact and hemolyzed erythrocytes indicate that the spin labels are incorporated into the lipid bilayer and that no significant fraction of the spin label is tightly bound to protein (16).…”

“…Inelusion of an equal amount of egg lecithin in the PC12 vesicles does not alter the ESR spectrum. Erythrocytes were labeled with C5 and C12 by exchange from unfiltered spin label-bovine serum albumin complex (13,16 …”

Conformational changes at membranes of target cells induced by the peptide hormone angiotensin. A spin label study

“…This binding, observed with the hormone concentration needed for half maximum contraction in the intact ileum [8], could be displaced by native angiotensin. These findings are in agreement with previous work with angiotensin receptors in rabbit aorta [ 191. This, and results obtained with bovine and rat adrenal glands 1201, corroborate the current view that certain hormones interact first with the plasma membranes of target cells.…”