Protein Photo-folding and Quantum Folding Theory

TL;DR

This paper develops a quantum folding theory to analyze protein photo-folding, revealing shared factors with nonradiative folding, and predicts temperature-dependent behaviors and spectral broadening effects in photo-folding processes.

Contribution

It introduces a quantum folding framework for protein photo-folding, linking it with nonradiative folding and predicting new spectral and temperature-dependent phenomena.

Findings

Stimulated photo-folding rates share temperature dependence with nonradiative folding.

Spectral lines broaden into bands with reduced width during photo-folding.

Resonance fluorescence cross section follows Luo-Lu's law with temperature.

Abstract

The rates of protein folding with photon absorption or emission and the cross section of photon -protein inelastic scattering are calculated from the quantum folding theory by use of standard field-theoretical method. All these protein photo-folding processes are compared with common protein folding without interaction of photons (nonradiative folding). It is demonstrated that there exists a common factor (thermo-averaged overlap integral of vibration wave function, TAOI) for protein folding and protein photo-folding. Based on this finding it is predicted that: 1) the stimulated photo-folding rates show the same temperature dependence as protein folding; 2) the spectral line of electronic transition is broadened to a band which includes abundant vibration spectrum without and with conformational transition and the width of the vibration spectral line is largely reduced; 3) the resonance fluorescence cross section changes with temperature obeying the same law (Luo-Lu's law). The particular form of the folding rate - temperature relation and the abundant spectral structure imply the existence of a set of quantum oscillators in the transition process and these oscillators are mainly of torsion type of low frequency, imply the quantum tunneling between protein conformations does exist in folding and photo-folding processes and the tunneling is rooted deeply in the coherent motion of the conformational-electronic system.