Improving All-Atom Force Field to Accurately Describe DNA G-Quadruplex Loops

Area of Science:

• Computational chemistry
• Molecular dynamics
• Structural biology

Background:

• DNA G-quadruplexes (GQs) exhibit structural diversity influenced by loop and flanking sequence interactions.
• All-atom molecular dynamics (MD) simulations of GQs are computationally intensive, facing challenges with slow folding times and force field (ff) inaccuracies.
• Previous simulations using the AMBER bsc1 ff (bsc1_vdW) showed limitations in accurately describing GQ loop structures, hindering studies of ligand binding.

Purpose of the Study:

• To enhance the prediction of DNA G-quadruplex loop structures using molecular dynamics simulations.
• To develop an improved force field by fine-tuning van der Waals parameters of the AMBER bsc1 ff for better GQ loop representation.
• To provide a more accurate simulation protocol for studying DNA G-quadruplex folding and ligand interactions.

Main Methods:

• Modification of the AMBER bsc1 force field by adjusting specific van der Waals parameters to create the bsc1_vdWL ff.
• All-atom molecular dynamics simulations of DNA G-quadruplex systems, including a three-layered antiparallel GQ (mHtel21).
• Testing the performance of the new bsc1_vdWL ff on various DNA G-quadruplex topologies (hybrid1, hybrid2, parallel propeller).

Main Results:

• The newly developed bsc1_vdWL force field demonstrated improved accuracy in predicting DNA G-quadruplex loop structures compared to the original bsc1_vdW ff.
• Simulations using bsc1_vdWL showed better representation of loop distributions across diverse GQ topologies.
• The enhanced force field shows promise for more reliable simulations of GQ folding and dynamics.

Conclusions:

• The bsc1_vdWL force field offers a significant improvement for simulating DNA G-quadruplexes, particularly their loop regions.
• Combining enhanced sampling MD simulation methods with bsc1_vdWL provides a robust protocol for addressing challenges in DNA GQ folding and GQ/ligand binding.
• This work facilitates a deeper understanding of GQ structural dynamics and their modulation by ligands at the all-atom level.