A SIMPLE METHOD FOR THE PREPARATION OF AN AMPHIPHILIC SEQUENTIAL POLYPEPTIDE

A monolayer of poly(γ-methyl L-glutamate) (PMG) was prepared by placing a solution of PMG dissolved in chloroform at an air-water interface. The area occupied by the monolayer decreased to form the solid condensed state of the PMG monolayer. An aqueous solution of potassium hydroxide was added in large excess to the aqueous phase beneath the solid condensed monolayer, and as a result, the γ- methyl L-glutamate side chains hydrated in the aqueous phase were saponified. However, the residual side chains oriented into the air could not be hydrolyzed, yielding poly [(γ-methyl L-glutamate)-co-(potassium L-glutamate)]. The resulting polymer was washed with hydrochloric acid to produce an amphiphilic helical copolypeptide, poly [(γ-methyl L-glutamate) -co- (L-glutamic acid)] (am.-MG/GA). Hydrolysis of am.- MG/GA by Staphylococcus aureus, Strain V8 protease, and gel filtration chromatographic analysis determined that the sequence of am.-MG/GA forms an amphiphilic helix that is hydrophilic on one face (which consists of L-glutamic acid side chains) and hydrophobic on the opposite face (which comprises γ-methyl L-glutamate side chains). The amphiphilic character of am.-MG/GA was evident from the high solubility of the copolypeptide in both polar and apolar solvents. © 1990, American Chemical Society. All rights reserved.