Competition among Li(+), Na(+), K(+), and Rb(+) monovalent ions for DNA in molecular dynamics simulations using the...

Area of Science:

• Computational Chemistry
• Biophysics
• Molecular Modeling

Background:

• Understanding monovalent ion interactions with DNA is crucial for biological processes.
• Accurate molecular dynamics (MD) force fields are needed to simulate these interactions.
• Previous models showed limitations in describing ion competition around DNA.

Purpose of the Study:

• To develop and validate parameters for monovalent cations (Li+, Na+, K+, Rb+) interacting with DNA.
• To compare the performance of the Drude polarizable and additive CHARMM36 force fields in simulating ion competition.
• To assess the impact of simulation system size on ion distribution accuracy.

Main Methods:

• Development and validation of ionic parameters for Drude and CHARMM36 force fields.
• Molecular dynamics (MD) simulations of DNA sequences with various monovalent ions.
• Optimization using gas-phase quantum mechanics (QM) energies and bulk electrolyte osmotic pressures.
• Validation against counterion condensation theory and experimental spectroscopy data.

Main Results:

• The Drude force field demonstrated an improved description of the ionic atmosphere around DNA compared to CHARMM36.
• MD simulations with the Drude FF showed closer agreement with experimental data on ion competition.
• Extended simulation systems (≥25 Å beyond DNA) are necessary for converged ion distributions.

Conclusions:

• The Drude polarizable force field offers a more accurate representation of monovalent ion behavior around DNA.
• Accurate force field parameters and adequate simulation system size are critical for reliable MD studies of ion-DNA interactions.
• This work provides improved tools for investigating the role of ions in DNA structure and function.