Quantum Effects In Terahertz Electromagnetic Wave Interaction With Biomolecules

The fusion of quantum mechanics and biology has given rise to the field of quantum biology,while the intersection of terahertz（THz）science and biophysics has led to the emergence of THz biophysics.Quantum biology seeks to elucidate biological phenomena through the lens of quantum physics,while THz biophysics investigates the mechanisms underlying the interaction between electromagnetic（EM）waves and biomolecules.Both disciplines share a common focus on the microscopic processes at the molecular level.The convergence of these two interdisciplinary fields promises to deepen our understanding of the structure and function of biomolecules.This dissertation,based on quantum theories of the interaction between THz waves and biomolecules,employs multi-level dynamical simulation methods to study the quantum effects in biological membrane-water systems,hydrogen bonds in base pairs,and the interaction mechanisms between THz waves and these molecular systems.This dissertation comprehensively explores theoretical and simulation methods for the interaction between THz waves and biomolecules.Classical simulation methods encompass non-equilibrium molecular dynamics（MD）simulations under external fields.At the quantum level,this dissertation establishes the Hamiltonian for resonant interactions based on the quantum optics and presents a quantum theory for simulating the interaction between intense THz radiation（ITR）and molecules under non-resonant conditions.These tools provide a comprehensive theoretical toolbox for studying the interaction of THz waves with molecular systems.Since the vibrational modes of molecules form the basis for their resonant interaction with EM waves,this dissertation analyzes the vibrational modes of water nanoclusters and phospholipid molecules.It discovers quantized THz vibrational modes in the hydrophobic tails of phospholipids and identifies quasi-one-dimensional THz phonon band gaps distinct from the water environment.Hydrogen bonds are essential for the structure and function of molecules like water,proteins,and deoxyribonucleic acid（DNA）.However,the microscopic interaction mechanisms between hydrogen bonds and THz waves remain elusive.This dissertation reveals the quantum mechanical basis for the periodic tunneling and resonant interaction of protons in the fundamental unit of water,the Zundel cation（H₅O₂⁺）,through potential energy surface scans.Additionally,it elucidates the non-resonant interaction of ITR with Zundel cations,including oscillatory proton transfer and overall vibrational excitation within the THz frequency range,based on first-principles calculations.Ionizing radiation such as ultraviolet light can disrupt base-pairing structures formed by hydrogen bonds,causing DNA damage.The potential mechanisms of action of non-ionizing radiation,such as THz waves,on DNA remain unclear.To address this,the dissertation calculates the vibrational energy levels of protons in base pair hydrogen bonds and simulates the effects of ITR on base pair hydrogen bonds using time-dependent Schr?dinger equations.The results indicate that sub-picosecond directional electric fields can induce proton oscillations and transient transfer processes within hydrogen bonds.Potassium ion channel proteins were the first ion channel proteins whose molecular structures were resolved.However,electrophysiological MD simulations of these proteins often require unrealistically high transmembrane voltages or ion concentration gradients.Furthermore,the debate continues regarding whether ion permeation through these channels occurs through a"soft-knock"or"direct-knock"mechanism.This dissertation introduces a THz trapped ion model for potassium ion channel proteins,providing a unified theoretical framework for understanding channel selectivity and the ultrafast spectroscopic detection of ion permeation dynamics.Within this model,the distinct features of potential energy surfaces for different ions explain channel selectivity,while the zero-point energy and weak tunneling effects account for deviations in parameters observed in electrophysiological MD simulations.Finally,the model directly leads to an unmarked THz spectroscopic detection scheme capable of distinguishing between the two proposed permeation mechanisms,potentially resolving the controversy surrounding ion conduction mechanisms.In conclusion,this doctoral dissertation employs a multi-level approach to elucidate the quantum mechanisms underlying the interaction between THz waves and biological molecular systems.It unveils THz quantum effects within several important biological molecular systems,demonstrating the significant value of THz waves in probing and controlling microscopic MD processes.This work also shows the importance of the convergence of THz biophysics with quantum physics.