Dynamic light scattering from high molecular weight poly-l-lysine molecules

In this work, we experimentally determine the translational diffusion coefficient Dt of charged polypeptides, poly-l-lysine (PLL) molecules, that change conformation from random-coil to α-helix or β-sheet upon increasing the solvent pH and temperature, respectively. We measure the scattered light component having the same polarization direction as the incident light, to construct the field autocorrelation function and obtain Dt, further estimating the PLL dimensions in the random-coil and α-helix structures. We use a commercial high molecular weight PLL sample that is widely used in many practical applications.