Lipid analysis of several glycerol teichoic acid preparations strongly indicated that covalently bound lipid is not required for spontaneous adsorption of glycerol teichoic acid to erythrocyte membranes. Although fatty acids were detected in each of four batches, none were covalently bound. Chloroform-ether-extracted antigens retained potent erythrocyte membrane-binding activity as measured by passive hemagglutination, even though they were shown to contain less than one fatty acid residue per 4,869 teichoic acid chains. Mild ammonolysis abolished erythrocyte-sensitizing activity in passive hemagglutination, but further studies indicated the loss of activity was due to partial destruction of the polyglycerophosphate backbone and not to the removal of esterified lipid. The amount of hydrolyzed antigen required to produce 100% passive hemagglutination inhibition was between 170 and 330 times the amount required to produce the same result using unhydrolyzed glycerol teichoic acid. The average chain length was reduced from 19.1 to 9.7, 7.4, and 5.1 glycerophosphate residues for antigen samples hydrolyzed for 1, 5, and 16 h, respectively.
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