Molecular dynamics with helical periodic boundary conditions

Area of Science:

• Biophysics
• Computational Chemistry
• Structural Biology

Background:

• Helical symmetry is prevalent in biological molecules and frequently studied using molecular dynamics (MD) simulations.
• Standard periodic boundary conditions (PBC) are incompatible with infinite helical periodicity, limiting simulation efficiency and accuracy.
• Simulating helical structures like protein fibrils often requires specialized approaches due to limitations in conventional methods.

Purpose of the Study:

• To develop and validate a novel algorithm for simulating systems with helical symmetry in molecular dynamics.
• To enhance computational efficiency by approximating infinite helical periodicity.
• To enable the simulation of systems, such as protein fibrils, that are unstable under standard periodic boundary conditions.

Main Methods:

• An algorithm for infinitely propagated helicity was developed and integrated into MD software.
• Helical twist was implemented as a parametric geometry constraint.
• Translational PBC were modified to incorporate helical symmetry using a transitional solvent volume, creating helical periodic boundary conditions (HPBC).

Main Results:

• The HPBC algorithm was successfully implemented in the Tinker MD software.
• Test simulations of α-helical and polyproline II peptide structures validated the HPBC approach.
• HPBC enabled the simulation of a stable fibrillar structure for an insulin-based model, which was not achievable with standard PBC.

Conclusions:

• The proposed helical periodic boundary conditions (HPBC) offer a computationally efficient and compatible method for molecular dynamics simulations of helical systems.
• HPBC successfully addresses the limitations of standard PBC for simulating systems with inherent helical symmetry.
• This advancement facilitates the study of complex biological structures, including protein fibrils, enhancing our understanding of their dynamics and stability.