Folding Funnel 2D: Exploring Free-Energy Landscapes in Molecular Biology

What is Free-Energy Landscape Theory

Free-energy landscape theory provides a framework for understanding the conformational changes in biomolecules such as proteins. It represents the free energy of each possible conformation of a molecule as a function G(Q), where Q denotes the degree of folding or the extent to which the molecule adopts its native structure.

The landscape is visualized as a surface, with valleys representing stable conformations and peaks indicating less stable ones. The lowest point on this surface corresponds to the most stable, folded state of the molecule.

G(Q) Function in Folding Funnel 2D

The G(Q) function in the simulation is a mathematical expression that encapsulates the thermodynamic properties of protein folding. It includes terms for configurational entropy (S0), thermal energy (T), and ruggedness (frustration amplitude). The term -D*Q represents the enthalpic driving force towards folding, while T*S0*(1-Q) accounts for the loss of configurational entropy upon folding.

The roughness term adds a stochastic element to the landscape, simulating the presence of local energy minima that can trap conformations and contribute to the ruggedness observed in real protein folding landscapes.

Temperature and Folding Transition

Temperature plays a crucial role in determining the stability and dynamics of molecular structures. In the context of free-energy landscape theory, it affects the balance between enthalpic (favoring folding) and entropic (disfavored by increased disorder) contributions to G(Q). The transition temperature Tf is defined as the point where the free energy barrier for unfolding equals thermal energy at that temperature.

By adjusting the temperature in Folding Funnel 2D, one can observe how the landscape changes, leading to different folding behaviors and transition temperatures.

Ruggedness and Configurational Entropy

Ruggedness or frustration amplitude is a measure of the complexity and irregularity in the free-energy landscape. It reflects the presence of multiple local minima, which can trap conformations and make folding pathways less predictable.

Configurational entropy S0 quantifies the disorder associated with different molecular conformations. A higher configurational entropy indicates greater flexibility and fewer constraints on the molecule’s shape.

Frequently asked questions

Try it live

Everything above runs in your browser — open Folding Funnel 2D: Free-Energy Landscape and change the parameters while it is running. Nothing is installed, nothing is uploaded, the whole model lives in one tab.