An analysis of the proton magnetic resonance (pmr) spectra of human erythrocyte membranes has been made in terms of the membrane components. The spectrum at 75° was assigned to 20% of the membrane proteins, 20% of the choline methyl groups of the phospholipids, and the acetamide groups of the sugars. Changes in the pmr spectra were noted when the membranes were altered by either protein solubilization or membrane fragmentation. The choline methyl signal was found to be particularly sensitive to the state of the membranes. Certain proteins were found to be released from the membranes at high temperatures and this phenomenon was dependent upon the pH and the solvent, as well as the presence of certain ions in solution. The amount of proteins solubilized, however, was significantly less than that observed by the high-resolution pmr method. The effect of certain divalent ions was particularly striking. The presence of more than 5 X 10-4m Mg2+for example, was sufficient to stabilize the proteins in the membrane and eliminate the high-resolution pmr signal.
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