Conformations of Poly-l-lysine Molecules in Electrolyte Solutions: Modeling and Experimental Measurements

Abstract

Physicochemical properties of poly-l-lysine (PLL) hydrobromide were determined by molecular dynamics (MD) modeling and a variety of experimental techniques. Primarily, the density, the chain diameter, the monomer length, and the PLL molecule conformations were theoretically calculated. These results were applied for the interpretation of experimental data acquired for the PLL sample of average molar mass equal to 122 kg/mol. They comprised the diffusion coefficient, the hydrodynamic diameter, and the electrophoretic mobility of molecules determined for the ionic strength ranging from 2 × 10–5 to 0.15 M and pH 5.6. Using these data, the electrokinetic charge and the effective ionization degree of PLL molecules were determined as a function of ionic strength. Additionally, precise dynamic viscosity measurements for dilute PLL solutions were performed yielding the intrinsic viscosity, which decreased from 2420 to 120 for ionic strengths of 2 × 10–5 and 0.15 M, respectively. This confirmed that PLL molecules ...