Structural transitions and rheological properties of poly-d-lysine hydrobromide: effect of pH, salt, temperature, and shear rate

Abstract In this work, we analyzed the pH, temperature, and salt effects of the charged polypeptide and its size, poly- d -lysine (PDL) molecules while applying dynamic light scattering (DLS), Zeta potential, and rheology techniques to assess the most important characteristics of PDL. The experimental results showed that the structural transitions of PDL were a result of a competition between electrostatic interaction, which promotes an extended state, and the hydrophobic effect, which favors a compact state. Moreover, by exploiting the electrokinetic charge on the PDL molecules the zeta potential was determined. We tried to find an analogy between size, viscosity, and conformational changes of PDL so to serve as a guide for polypeptide aggregation in solution.