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An energetic model for macromolecules unfolding in stretching experiments.

D De Tommasi¹, N Millardi, G Puglisi

¹Dipartimento di Scienze dell' Ingegneria Civile e Architettura, Politecnico di Bari, Bari, Italy.

Journal of the Royal Society, Interface

|September 20, 2013

Summary

We present a simple analytical model for macromolecule unfolding, focusing on entropic and unfolding energies. This approach accurately reproduces experimental data, like titin unfolding, and simplifies complex force-elongation curves.

Keywords:

biopolymers macromolecule mechanics macromolecules unfolding protein stability titin

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Area of Science:

Biophysics
Polymer Science
Materials Science

Background:

Macromolecule unfolding is crucial in biological and material contexts.
Understanding the energetic factors governing unfolding is essential for predicting material properties and biological function.
Existing models may lack analytical simplicity or broad applicability across different macromolecule types.

Purpose of the Study:

To develop a simple, analytical model for describing the unfolding of multi-domain macromolecules.
To elucidate the contributions of entropic and unfolding energies to the unfolding process.
To validate the model's predictive power using experimental data.

Main Methods:

Minimization of the total energy (entropic plus unfolding) of a two-state system.
Development of a fully analytical theoretical framework.
Comparison of model predictions with atomic force microscopy (AFM) unfolding experiments of titin.

Main Results:

The model provides an analytical description of macromolecule unfolding.
It highlights the distinct roles of entropic and unfolding energies in the process.
The model quantitatively reproduces experimental force-elongation curves from titin unfolding experiments.
In the thermodynamic limit, the characteristic sawtooth force-elongation curve simplifies to a constant force plateau.

Conclusions:

The proposed simple energy minimization approach effectively models multi-domain macromolecule unfolding.
The analytical model offers insights into the energetic regulation of unfolding dynamics.
The model's ability to match experimental data demonstrates its utility for proteins and potentially other macromolecules.