MM/GBSA & MM/PBSA Binding Free Energy

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Overview

MM/GBSA and MM/PBSA occupy a useful middle ground: substantially more informative than docking scores, substantially cheaper than rigorous alchemical free energy. Calculated over molecular dynamics trajectories, they rank compounds within a congeneric series and, through per-residue decomposition, show which interactions carry the binding energy. We use them to triage tens of compounds down to the handful that merit FEP or synthesis, and we are explicit about where the approximation breaks down.

Schematic: replicate simulations are run and plotted together. A conclusion drawn from one trajectory cannot be distinguished from a sampling accident.

Key Advantages

Ensemble-Based, Not Single-Structure

Energies are averaged over trajectory snapshots rather than computed from one minimised pose, which is the main reason the method outperforms docking scores for ranking.

Per-Residue Decomposition

Binding energy is broken down by residue, identifying the interactions that matter and the ones that are merely decorative — directly useful for analogue design.

Entropy Treated Transparently

Entropy contributions are either included with a stated method or deliberately omitted, and the choice is documented, because inconsistent treatment is a common source of misleading numbers.

Benchmarked Against Your Data

Where measured affinities exist for part of the series, we report the observed correlation so you know how far to trust the ranking for the rest.

Where This Service Is Used

Ranking analogues in a lead optimisation series before committing synthesis effort

Rescoring virtual screening hits to improve on docking-score ordering

Identifying which interactions dominate binding for a given chemotype

Comparing binding across wild-type and mutant forms of a target

Selecting the small subset of compounds that justify the cost of FEP calculations

Methods and Techniques Applied

Molecular dynamics production runs for each complex with consistent protocol across the series

Snapshot extraction with a sampling interval chosen to limit correlation between frames

MM/GBSA and MM/PBSA calculation with solvation model and parameter choices documented

Per-residue energy decomposition and identification of the dominant contributions

Optional entropy estimation by normal mode or interaction entropy approaches

Correlation analysis against measured data where available, with the error range reported

What We Need From You

Target structure and the binding poses for all compounds to be compared

The compound series, ideally congeneric, since cross-series comparison is unreliable

Measured affinity data for any subset, used to benchmark the ranking

The decision the ranking must support, which sets how many compounds need treating

What You Receive

Binding energy table with component breakdown for every compound

Per-residue decomposition identifying the interaction hot spots

Correlation plot and statistics against measured data where such data exists

Ranked compound list with an explicit statement of which differences are within noise

Full protocol record: force field, solvation model, sampling and entropy treatment

What We Compute and Report

Estimated binding energy per compound with its component breakdown and statistical spread

Per-residue energy decomposition identifying which interactions carry the binding

Rank order across the series with an explicit statement of which gaps are within noise

Correlation statistics against your measured affinities where a calibration set exists

Sampling and convergence metrics for every complex analysed

Interpretation and Limitations

Computational predictions prioritise hypotheses; they do not independently establish binding, biological activity, therapeutic efficacy, safety or clinical validity. Performance depends on input quality, target class, the structural evidence available and the applicability domain of the selected methods. Scores used for ranking are comparative devices and should not be read as measured quantities. All deliverables are for research use only and are not intended for diagnostic or therapeutic use.

Specifications

Item	Specification	Notes
Compounds per study	5–100	Congeneric series give the most reliable ranking
Typical turnaround	2–4 weeks	Including the underlying MD sampling
Sampling per compound	20–100 ns	Extended where convergence requires it
Methods	MM/GBSA and MM/PBSA	Both reported where they disagree meaningfully

Service Workflow

Step 01

Scientific Consultation

We discuss the objective, the decision it supports and the data you hold. Nothing is quoted before we understand what the result has to answer.

Step 02

Feasibility Review

We check that the data, target class and available structural evidence can support the proposed approach, and say plainly where they cannot.

Step 03

Technical Proposal

Scope, methods, deliverables, timeline and price are confirmed in writing, together with the limitations we expect to report.

Step 04

Computation and QC

The analysis runs on pinned tool versions in a containerised environment, with quality checkpoints and method comparison where that is informative.

Step 05

Report and Follow-Up

You receive the ranked results, the documented methods, the limitations and a proposed validation plan, plus support in interpreting them.

Is This the Right Service for You?

Choose this service when

Tens of analogues in one series need ordering before synthesis

Virtual screening hits need rescoring beyond docking-score ordering

You need to know which specific interactions carry the binding energy

Consider another service when

A small number of decisions justify the most accurate method available

Free Energy Perturbation

The binding mode itself is still uncertain

Molecular Docking

What Goes Wrong, and How We Handle It

The failure modes that produce confident-looking results which do not survive the next experiment. Each one is designed against rather than discovered afterwards.

Systematic errors cancel within a congeneric series and do not cancel across them; cross-series comparisons are declined or heavily caveated.

Case Studies

The situation

A chemistry team could make eight compounds in the next cycle and had twenty-eight candidates on paper.

What the work involved

All complexes were simulated under one protocol, end-point energies were computed with per-residue decomposition, and the calculation was benchmarked against nine compounds already measured.

What came back

Correlation against the measured set was reported up front, six candidates were separated clearly from the rest, and two contributing interactions were identified that the team had not been optimising.

Illustrative of the shape this work takes. Details are generalised, no client or target is identified, and scope and outcome vary with the system in question.

Questions We Are Asked Before Scoping

Note: ICDMO delivers computational (in silico) services. Results prioritise hypotheses for testing; they do not by themselves establish binding, biological activity, efficacy or safety. All deliverables are for research use only and are not intended for diagnostic or therapeutic use. Downstream experimental work is scoped separately and executed through qualified partners.

Get in Touch
about MM/GBSA & MM/PBSA Binding Free Energy

Tell us about the target, the data you hold and the decision the result needs to support. A scientist reviews every enquiry and replies within one business day.

Feasibility reviewed before any scope or price is fixed

Methods, parameters, confidence and limitations in every report

Confidentiality agreement available before data is shared