Concentration- and dehydration-dependent structural transitions in poly-l-lysine

The structural changes in poly-l-lysine (PLL), investigated as a function of simultaneous changes in concentration and pH, revealed a transition from right handed α-helical to left handed poly-l-proline II (PP II)-type helical structure. The PPII-type structure of PLL in solution state was not influenced by the addition of sugars (trehalose or sucrose). The structure of PLL changes from PPII-type in solution state to β-sheet in the dehydrated film state. In the presence of trehalose at PLL–trehalose mass ratio of 1:0.5, the structure of PLL changes from PPII-type in solution to a mixture of α-helix + β-sheet in the dehydrated film state. In the presence of trehalose at PLL–trehalose mass ratio of 1:1, the PPII-type structure of PLL in solution is maintained in the dehydrated film state.