# Phi-values in protein folding kinetics have energetic and structural components

Source: [Phi-values in protein folding kinetics have energetic and structural components](<https://www.sota2.com/research/paper/68fa1fd47a2b558e2932c8a4>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-23T19:53:56.736Z

Authors: Claudia Merlo, Ken A. Dill, Thomas R. Weikl

Published: 2005-07-14T15:26:57.000Z

## Abstract

Phi-values are experimental measures of how the kinetics of protein folding is changed by single-site mutations. Phi-values measure energetic quantities, but are often interpreted in terms of the structures of the transition state ensemble. Here we describe a simple analytical model of the folding kinetics in terms of the formation of protein substructures. The model shows that Phi-values have both structural and energetic components. In addition, it provides a natural and general interpretation of "nonclassical" Phi-values (i.e., less than zero, or greater than one). The model reproduces the Phi-values for 20 single-residue mutations in the alpha-helix of the protein CI2, including several nonclassical Phi-values, in good agreement with experiments.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/q-bio/0507025>)

[PDF](<https://arxiv.org/pdf/q-bio/0507025.pdf>)