Sodium trichloroacetate-induced helical conformation of poly(L-lysine).

Sodium trichloroacetate which has been reported previously to be an effective denaturation reagent for proteins was applied to poly(L-lysine) and poly(L-glutamic acid) to see its effects on a coil-to-helix transition and on the chemical reactivities of the xi-amino group of poly(L-lysine). Addition of sodium trichloroacetate to poly(L-lysine) induced a helical conformation even at neutral pH where the xi-amino group of the polymer was protonated. On the other hand, little effect was observed on the coil-to-helix transition of poly(L-glutamic acid). The xi-amino group of poly(L-lysine) has an anomalously high reactivity with naphthoquinone 4,6-disulfonate carrying a negative charge. Sodium trichloroacetate inhibited the reaction of the xi-amino group with this reagent, while sodium trichloroacetate enhanced slightly the reaction of the xi-amino group of poly(L-lysine) with diazonium-1-H-tetrazole carrying a positive charge.