Multiquanta Davydov solitons in proteins

Proteins are molecular nano-engines, which maintain living systems in far-from-equilibrium ordered states. To fuel bioprocesses, however, the energy in living systems needs to be transferred in minute quantities because higher energy densities are detrimental to the delicate and fragile structures. While the behavior of all molecules is fundamentally described by quantum mechanics, the highly efficient utilization of individual energy quanta by proteins suggests that characteristic quantum effects may be indispensable for properly describing and understanding life.

In our recent article published in Advances in Quantum Chemistry, we have analyzed the system of generalized Davydov equations that govern the quantum dynamics of multiple amide I exciton quanta propagating along the hydrogen-bonded peptide groups in α-helices. Computational simulations have confirmed the generation of moving Davydov solitons by applied pulses of amide I energy for protein α-helices of varying length. The stability and mobility of these solitons depended on the uniformity of dipole–dipole coupling between amide I oscillators, and the isotropy of the exciton–phonon interaction. Davydov solitons were also able to quantum tunnel through massive barriers, or to quantum interfere at collision sites. These computational results support a nontrivial role of quantum effects in biological systems that lies beyond the mechanistic support of covalent bonds as binding agents of macromolecular structures. Quantum tunneling and interference of Davydov solitons provide catalytically active macromolecular protein complexes with a physical mechanism allowing highly efficient transport, delivery, and utilization of free energy, besides the evolutionary mandate of biological order that supports the existence of such genuine quantum phenomena, and may indeed demarcate the quantum boundaries of life.

Collision of two Davydov solitons