Non-Markovian Electron Transfer in Ligand-Receptor Complexes: Insights from Non-Gaussian Anharmonic Baths

Area of Science:

• Biophysics
• Quantum Chemistry
• Computational Biology

Background:

• Electron transfer (ET) is fundamental in biological processes.
• Environmental factors like structure, memory, and fluctuation statistics govern ET dynamics.
• Protein receptor-ligand complexes present complex biomolecular environments.

Purpose of the Study:

• To investigate electron transfer dynamics in protein environments.
• To contrast harmonic (Gaussian) bath approximations with anharmonic, non-Gaussian models.
• To determine the conditions under which anharmonic models are necessary for accurate ET dynamics.

Main Methods:

• Utilized a non-Markovian open-quantum-systems framework.
• Employed a non-Markovian stochastic Schrödinger equation (NMSSE).
• Modeled anharmonic environments using discrete Poisson (shot-noise) events and ensemble-averaged trajectory simulations.

Main Results:

• Identified three regimes: weakly, intermediate, and strongly anharmonic.
• Demonstrated that anharmonic effects enhance ET and reshape dynamics, especially at weak electronic coupling.
• Showcased significant deviations from harmonic-bath behavior in the strongly anharmonic regime.

Conclusions:

• Harmonic approximations are sufficient only in weakly anharmonic regimes.
• Explicit anharmonic, non-Gaussian bath models are required for faithful ET dynamics in many biomolecular environments.
• The study delineates the applicability limits of harmonic approximations in ET studies.