The cholesterol-to-protein ratio of the DRM-containing fraction is high for samples extracted in 0.5% and 1% Tx-100. As expected, no cholesterol was detected in fraction 2 of samples extracted in 2% Tx-100. The cholesterol-to-protein ratio equals the percentage of cholesterol in a given fraction relative to the total cholesterol obtained for fractions 1 to 6 divided by the percentage of protein in a given fraction relative to the total protein obtained for fractions 1 to 6. A high cholesterol-to-protein ratio reflects enrichment in cholesterol or loss of protein relative to the membrane profile as a whole.