Thermal stability of solitons in protein $\alpha$-helices

TL;DR

This study computationally demonstrates that protein alpha-helices can sustain long-lived solitons at body temperature, enabling efficient energy transport, especially in full protein structures with multiple excitons, which could be vital for biological functions.

Contribution

It provides the first detailed computational analysis of thermal effects on protein solitons, showing their stability in full alpha-helices at physiological temperature, highlighting their potential biological relevance.

Findings

Single alpha-helix spines have short soliton lifetimes under thermal noise.

Full protein alpha-helices with three excitons maintain solitons over 30 ps.

Solitons can facilitate energy transport along 18-nm-long alpha-helices.

Abstract

Protein$\alpha$-helices provide an ordered biological environment that is conducive to soliton-assisted energy transport. The nonlinear interaction between amide I excitons and phonon deformations induced in the hydrogen-bonded lattice of peptide groups leads to self-trapping of the amide I energy, thereby creating a localized quasiparticle (soliton) that persists at zero temperature. The presence of thermal noise, however, could destabilize the protein soliton and dissipate its energy within a finite lifetime. In this work, we have computationally solved the system of stochastic differential equations that govern the quantum dynamics of protein solitons at physiological temperature, T=310 K, for either a single isolated $\alpha$-helix spine of hydrogen bonded peptide groups or the full protein $\alpha$-helix comprised of three parallel $\alpha$-helix spines. The simulated stochastic dynamics revealed that although the thermal noise is detrimental for the single isolated $\alpha$-helix spine, the cooperative action of three amide I exciton quanta in the full protein $\alpha$-helix ensures soliton lifetime of over 30 ps, during which the amide I energy could be transported along the entire extent of an 18-nm-long $\alpha$-helix. Thus, macromolecular protein complexes, which are built up of protein $\alpha$-helices could harness soliton-assisted energy transport at physiological temperature. Because the hydrolysis of a single adenosine triphosphate molecule is able to initiate three amide I exciton quanta, it is feasible that multiquantal protein solitons subserve a variety of specialized physiological functions in living systems.