Solution conformation of poly(L-lysyl-L-glutamic acid) and poly(L-lysyl-L-glutamine)

Solution conformation of poly(L-lysyl-L-glutamic acid) (PLGU) and poly(L-lysyl-L-glutamine) (PLGN) was studied in water as a function of pH, added salt, detergents, methanol and trifluoroethanol (TFE). Both the polypeptides exhibit no ordered conformation in the pH range 1.5-12.5; salts and detergents did not have any marked effect. Replacement of side chain carboxyl by an amide group did not help in inducing PLGN to adopt a helical conformation even at pH as high as 12.0, unlike poly(L-lysine). The helicogenic solvents, methanol and TFE, induce formation of weak helices in PLGU as well as in PLGN. It is not unlikely that H-bonding between the side chains leads to stabilizing an unordered conformations.