Steered molecular dynamics

What is steered molecular dynamics?

Steered molecular dynamics is a simulation method that applies a time-dependent restraint or force along a selected coordinate to drive a molecular system through a transition. Common uses include ligand unbinding, domain separation, protein unfolding, and pathway generation. The observed response depends on pulling geometry, spring constant, velocity, environment, and starting state, so one forced trajectory is not an equilibrium mechanism or binding free energy.

Design the pulling coordinate around a concrete physical hypothesis. Define pulled and reference groups, periodic-boundary treatment, restraint direction, loading rate, equilibration, and independent starting conformations before simulation. Faster pulling improves throughput but usually increases nonequilibrium dissipation and can favor artificial pathways.

ProteinIQ does not currently execute the pulling protocol or calculate force–extension and work profiles. The connected workflow reviews a compatible trajectory with MDAnalysis-based structural metrics. Preserve the external engine inputs, pull output, force and work series, and replicate-level results alongside that review.

When to use steered molecular dynamics

• Best fit. Forced unbinding, unfolding, separation, and pathway hypotheses
• Required evidence. Externally generated topology and trajectory plus pull-coordinate, force, work, and replicate records

Benefits of steered molecular dynamics

• Drives otherwise slow transitions. Drives otherwise slow transitions for projects focused on forced unbinding, unfolding, separation, and pathway hypotheses.
• Tests explicit mechanical hypotheses. Tests explicit mechanical hypotheses for projects focused on forced unbinding, unfolding, separation, and pathway hypotheses.
• Generates candidate pathways. Generates candidate pathways for projects focused on forced unbinding, unfolding, separation, and pathway hypotheses.

Primary limitations

• Strongly protocol dependent. Strongly protocol dependent. Address this with externally generated topology and trajectory plus pull-coordinate, force, work, and replicate records.
• Nonequilibrium work needs careful treatment. Nonequilibrium work needs careful treatment. Address this with externally generated topology and trajectory plus pull-coordinate, force, work, and replicate records.
• One pathway is not a mechanism. One pathway is not a mechanism. Address this with externally generated topology and trajectory plus pull-coordinate, force, work, and replicate records.

Steered molecular dynamics methods

A moving harmonic restraint is often attached to a distance or projected coordinate. The pulling speed and spring constant set how abruptly the system is driven, while atom-group definitions and reference motion determine what the coordinate actually measures.

Jarzynski-type free-energy estimates require appropriate work definitions and an adequate ensemble of trajectories. A peak force from one fast pull should not be reported as an equilibrium binding affinity or directly compared across unmatched protocols.

Steered molecular dynamics applications

Steered molecular dynamics is best suited to forced unbinding, unfolding, separation, and pathway hypotheses. Match the modeled system, timescale, resolution, and ensemble to the observable rather than choosing a protocol because it produces a longer trajectory or more elaborate figure.

Use simulation as model-based evidence. Connect trajectory observations to experimental data, alternative parameterizations, independent starts, and uncertainty whenever the downstream claim concerns mechanism, affinity, kinetics, stability, or population.

How to run steered molecular dynamics online

The connected workflow is a post-run review workflow. Generate the scientific simulation externally, preserve its method-native records, then upload compatible files for complementary structural analysis.

1. Define pulling. Record pulled and reference groups, coordinate, direction, spring constant, velocity, and boundary handling.
2. Run externally. Equilibrate starting states and execute independent steered simulations in a suitable external engine.
3. Upload trajectory. Upload a compatible TPR topology and XTC trajectory to the review workflow.
4. Review response. Inspect structural response beside the external force, extension, and work traces.
5. Compare replicates. Compare pathways and summary statistics across replicates before drawing mechanistic conclusions.

How to interpret steered molecular dynamics results

Align structural events to the external force and extension traces: contact rupture, hydration changes, domain rotation, secondary-structure loss, and coordinate discontinuities may explain peaks. Check periodic boundaries and reference-group motion before assigning an event.

Report distributions across independent replicates, not only the smoothest trajectory. Distinguish reproducible intermediates from path-specific fluctuations and state how starting structures were selected.

How steered molecular dynamics works

Upload a compatible topology and trajectory from an external steered run for RMSD, RMSF, distance, and compactness review.

1. Define pulling. Record pulled and reference groups, coordinate, direction, spring constant, velocity, and boundary handling.
2. Run externally. Equilibrate starting states and execute independent steered simulations in a suitable external engine.
3. Upload trajectory. Upload a compatible TPR topology and XTC trajectory to the review workflow.
4. Review response. Inspect structural response beside the external force, extension, and work traces.
5. Compare replicates. Compare pathways and summary statistics across replicates before drawing mechanistic conclusions.

Inputs and outputs

Check formats before running, then inspect and download the result from every workflow step.

Inputs

• Simulation evidence. PDB mmCIF TPR GRO XTC A compatible TPR topology and XTC trajectory plus external pull-coordinate, force, work, and protocol files.

Outputs

• Simulation outputs. XTC PDB CSV JSON ZIP Structural trajectory metrics for review; pulling forces, work profiles, and free-energy treatment remain external.