Dependence of amino-acid dielectric relaxation on solute-water interaction: Molecular dynamics study

Computational molecular methods represent an ultimate microscope to visualize and quantify dynamics of biomolecules and nanostructures on the atomic scale and also a tool to link this dynamics to macroscopic observables. However, these potentially powerful computational methods have been so far poorly explored to gain a deeper knowledge of broadband biomolecular dielectric properties which are essential for novel non-invasive electromagnetic methods in biomedical diagnostics and treatment. To fill in this gap, we explore here a broad range of parameter space of molecular dynamics simulation (two common water models, four force fields, eight types of amino acids) and demonstrate their effects on dielectric increment and relaxation time. We found that the force field and water parameters influence the extracted dielectric increment and relaxation time of the biomolecule-water solution dielectric spectra significantly. To understand this observation, we dissected the effect of individual parameters of molecular force field on the dielectric spectra. For the first time, we showed the charges on the atoms, and the bond length of amino acids are the determining factors of both their dielectric increment and relaxation time in molecular dynamics simulations. Hence, our results leverage atomic resolution-based computational methods for a deeper understanding of biomolecular microwave dielectric properties with potential biological, medical and nanotechnological applications. •Force field and water molecule models affect dielectric parameters of amino acids in solutions.•Charges on atomic groups of amino acids affect dielectric increment and relaxation time.•Dielectric increment and relaxation time of amino acids are also affected by bond length.•Threonine, leucine, glutamine, histidine, and tyrosine can exhibit two conformations with different dipole moments.