Modeling Coil-Globule-Helix Transition in Polymers by Self-Interacting Random Walks

Area of Science:

• Statistical Physics
• Polymer Physics
• Computational Chemistry

Background:

• Random walks (RWs) are fundamental in statistical physics, modeling diverse physical, chemical, and biological systems.
• Understanding polymer conformational changes, like protein folding, is crucial in biological and material sciences.

Purpose of the Study:

• To propose and investigate a novel self-interacting random walk model in 3D space.
• To explore temperature-dependent structural transitions, including coil-to-globule and globule-to-helix transitions.
• To analyze the influence of Lennard-Jones potential parameters on polymer structure.

Main Methods:

• Development of a self-interacting random walk model in continuous 3D space.
• Simulation of walker interactions using a realistic Lennard-Jones potential.
• Systematic investigation of structural transitions across varying temperatures and equilibrium distances.

Main Results:

• Observed a novel globule-to-helix transition alongside the known coil-to-globule collapse.
• Identified diverse structural properties (globule-coil, helix-globule-coil, line-coil) based on equilibrium distance and temperature.
• Established a correlation form kBTc = λε for transition temperature (Tc) and potential well depth (ε), validated by simulations.

Conclusions:

• The self-interacting random walk model successfully captures complex polymer structural transitions.
• The findings provide a new framework for understanding helix formation in polymers, relevant to protein folding.
• The study highlights the interplay between temperature, molecular interactions, and polymer conformation.