Intersegment interactions and helix-coil transition within the generalized model of polypeptide chains approach

Area of Science:

• Biophysics
• Polymer Physics
• Computational Chemistry

Background:

• Understanding protein folding and stability is crucial in molecular biology.
• The helix-coil transition is a fundamental process in protein secondary structure formation.
• Modeling inter-chain interactions provides insights into complex biological systems.

Purpose of the Study:

• To extend a generalized model for polypeptide chains.
• To analyze the helix-coil transition in a system of two side-by-side interacting chains.
• To investigate the influence of different interaction energies on transition behavior.

Main Methods:

• Development of a theoretical model incorporating four types of inter-chain interactions (helix-helix, helix-coil, coil-helix, coil-coil).
• Analysis of the Hamiltonian to predict system behavior based on interaction energy dominance.
• Calculation of correlation length, number of junctions, and average helical segment length.

Main Results:

• When helix-helix and coil-coil interactions dominate, correlation length increases, narrowing the transition interval.
• When mixed interactions (helix-coil, coil-helix) dominate, a plateau appears on the denaturation curve.
• Rearrangement of helical segments occurs at the transition point under mixed interaction dominance.

Conclusions:

• The model provides a unified theoretical perspective on helix formation and intersegment interactions.
• Findings offer potential explanations for experimentally observed phenomena in protein folding.
• The study links theoretical predictions to existing experimental theories, enhancing understanding of polypeptide behavior.