Poly-L-Arginine Molecule Properties in Simple Electrolytes: Molecular Dynamic Modeling and Experiments

Area of Science:

• Polymer Science
• Biophysics
• Computational Chemistry

Background:

• Poly-L-arginine (P-Arg) is a cationic polypeptide with potential applications in drug delivery and gene therapy.
• Understanding its physicochemical properties in solution is crucial for optimizing its use.
• Previous studies have often lacked a comprehensive approach combining theoretical and experimental methods.

Purpose of the Study:

• To determine the physicochemical properties of poly-L-arginine (P-Arg) in NaCl solutions.
• To correlate theoretical predictions with experimental data for P-Arg behavior.
• To develop a robust method for characterizing P-Arg samples.

Main Methods:

• Molecular dynamics (MD) modeling to predict molecule conformations, monomer length, and chain diameter.
• Experimental techniques including secondary structure analysis, diffusion coefficient, hydrodynamic diameter, and electrophoretic mobility measurements.
• Dynamic viscosity measurements to determine intrinsic viscosity.

Main Results:

• MD modeling provided theoretical calculations for P-Arg conformations and dimensions.
• Experimental data at various ionic strengths and pHs were interpreted using MD results.
• Intrinsic viscosity measurements confirmed extended P-Arg conformations at low ionic strength.
• Effective ionization degree and electrokinetic charge were determined.
• Experimental and theoretical dimensions of P-Arg molecules showed agreement.

Conclusions:

• A combined MD modeling and experimental approach successfully characterized P-Arg physicochemical properties.
• P-Arg exhibits extended conformations in dilute solutions, especially at low ionic strength.
• A robust method was proposed for determining key parameters like molar mass and hydrodynamic diameter of P-Arg samples.