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At Profacgen, our molecular dynamics simulation services deliver time-resolved, atomic-level characterization of protein conformational changes, ligand binding thermodynamics, and molecular interactions under physiologically relevant conditions, complementing static structural methods with dynamic insights inaccessible to current experimental approaches.
Molecular dynamics (MD) simulation is a computer simulation technique that predicts the time-dependent evolution of a system of interacting particles using laws of physics. Studying the dynamic development of a biological system with consideration of protein flexibility is of vital importance, since many biological phenomena involving proteins are dynamic processes, including transport, molecular recognition, enzyme catalysis, and allosteric regulation. Static models produced by NMR, X-ray crystallography, and homology modeling offer valuable structural insights, while MD simulation provides atomic-level information about protein conformational changes and binding thermodynamics under predefined physiological conditions (temperature, pressure), enabling study at timescales inaccessible to current experimental methods.
Profacgen studies molecular dynamics of protein systems using state-of-the-art software tools. Our general workflow follows: first, a model system is selected, missing segments are fixed, and protonation states determined. The system is then energy-minimized and equilibrated by solving Newton's equations of motion until system properties no longer change with time. After equilibration, a production run is performed for an appropriate period to output trajectories, which are analyzed for properties of interest.
Our molecular dynamics simulation platform delivers time-resolved insights across the critical dimensions of protein biology and drug discovery:
Protein flexibility: Quantification of backbone and side-chain motions, loop dynamics, and domain movements across multiple timescales (femtoseconds to microseconds). MD simulation reveals how intrinsic flexibility governs substrate binding, allosteric communication, and signal transduction, providing information masked by static structural snapshots
Conformational dynamics: Characterization of structural transitions between functional states, population shifts upon ligand binding, and induced-fit versus conformational selection mechanisms. We monitor protein folding processes and identify cryptic or allosteric binding sites that emerge only during dynamic fluctuations
Molecular interactions: Detailed mapping of hydrogen-bonding networks, hydrophobic interactions, electrostatic complementarity, and van der Waals contacts between proteins and ligands, nucleic acids, lipids, or other proteins. Free energy calculations quantify binding affinity and specificity with enhanced accuracy over static docking methods
Stability assessment: Evaluation of protein folding energy, thermal stability, and denaturation pathways through replica-exchange and enhanced sampling simulations. We predict the impact of mutations on stability and identify aggregation-prone regions to guide protein engineering and formulation development
Figure 1. Molecular dynamics simulation process.
Our Simulation Services
Profacgen offers specialized molecular dynamics simulation services tailored to diverse biological systems and analytical objectives:
Protein Dynamics Analysis
Comprehensive characterization of protein motions, flexibility, and conformational landscapes.
Equilibrium simulations: root-mean-square deviation/fluctuation analysis, radius of gyration, and solvent accessible surface area monitoring
Enhanced sampling: replica-exchange MD, metadynamics, and umbrella sampling for rare event characterization and free energy landscape mapping
Principal component analysis and essential dynamics to identify dominant collective motions
Protein-Ligand Simulations
Quantitative assessment of binding thermodynamics, kinetics, and interaction mechanisms.
Binding free energy calculation: MM/PBSA, MM/GBSA, and alchemical free energy perturbation (FEP) for affinity ranking and mutation impact assessment
Steered molecular dynamics for unbinding pathway characterization and mechanical stability assessment
Cryptic and allosteric pocket identification through dynamic surface mapping
Mutation Impact Studies
Computational prediction of how amino acid substitutions affect protein structure, stability, and function.
Free energy perturbation and thermodynamic integration for quantitative ΔΔG estimation
Local structure perturbation analysis: hydrogen-bond disruption, hydrophobic core destabilization, and electrostatic surface alteration
Long-range allosteric effect propagation through dynamic network analysis
Stability Evaluation
Assessment of protein thermal and colloidal stability under diverse environmental conditions.
Temperature-dependent replica-exchange simulations for melting profile prediction
Chemical denaturation simulation: urea and guanidinium chloride effects on unfolding pathways
Aggregation propensity assessment through oligomeric assembly simulations and interface analysis
Simulation Workflow
Our molecular dynamics simulations follow a rigorous, validated workflow ensuring reproducibility and biological relevance:
Model Preparation: Starting structures are retrieved from the Protein Data Bank or generated by homology modeling. Missing segments are reconstructed, protonation states are assigned based on pH, and cofactors, ions, and post-translational modifications are incorporated to generate a biologically realistic starting model.
System Setup: The protein is solvated in an explicit water box (aqueous or organic solvents) with appropriate counterions to ensure system neutrality. Lipid bilayers, membranes, or other cofactors are embedded as required. Periodic boundary conditions are applied to eliminate edge effects and mimic an infinite system.
Energy Minimization and Equilibration: The system is subjected to steepest descent and conjugate gradient-based energy minimization to eliminate steric clashes. Equilibration is performed in stages: first with restrained protein heavy atoms, then with progressively reduced restraints, solving Newton's equations of motion until system properties (temperature, pressure, density, energy) no longer change with time.
Production MD Simulation: After equilibration, a production run is performed for an appropriate period (nanoseconds to microseconds) to generate trajectories. GPU-accelerated high-performance programs enable long-timescale simulations, capturing biologically relevant events including conformational transitions, ligand binding, and allosteric signaling.
Trajectory Analysis and Biological Interpretation: Trajectories are analyzed for structural, dynamic, and thermodynamic properties of interest. Visualization programs display, animate, and analyze biomolecular systems. Results are interpreted in the context of experimental data and biological knowledge to generate actionable hypotheses for follow-up studies.
Applications
Our molecular dynamics simulation services support diverse therapeutic and research applications:
Drug Discovery: Identification of cryptic and allosteric binding sites through dynamic surface mapping; enhancement of traditional virtual screening methodologies by incorporating receptor flexibility; direct prediction of small-molecule binding energies through alchemical free energy calculations. MD simulation refines docking poses and ranks compounds by predicted affinity with improved accuracy
Protein Engineering: Stability optimization through mutation impact prediction; activity enhancement by characterizing catalytic loop dynamics; developability assessment by evaluating aggregation propensity and colloidal behavior. Structure refinement of experimentally determined models corrects local errors and improves overall quality
Binding Mechanism Studies: Elucidation of induced-fit and conformational selection mechanisms; mapping of allosteric communication pathways; quantification of enthalpic and entropic contributions to binding. Steered molecular dynamics reveals unbinding pathways and mechanical stability of protein-ligand complexes
Structure Optimization: Refinement of homology models and low-resolution experimental structures; loop reconstruction and side-chain repacking; validation of predicted models against experimental observables. MD simulation optimizes protein structures for downstream molecular docking and virtual screening campaigns
Deliverables
Profacgen provides structured documentation and data outputs aligned with your simulation objectives:
Parameter
Description
Simulation Trajectories
Raw and processed trajectory files with associated topology, coordinate, and parameter files. Trajectories include atomic coordinates, velocities, and energies at defined time intervals for full reproducibility
Stability Analysis
Time-series plots of RMSD, RMSF, radius of gyration, and secondary structure content. Thermal and chemical stability predictions with melting profiles and denaturation pathway characterization
Interaction Profiles
Protein-ligand interaction fingerprints, hydrogen-bond occupancy matrices, hydrophobic contact maps, and electrostatic complementarity scores. Binding free energy decomposition by residue and energy component
Free Energy Calculations
Binding, solvation, and interaction free energy estimates with statistical uncertainty quantification. Mutation ΔΔG predictions and relative affinity rankings for compound optimization
Comprehensive Study Report
Detailed project report with simulation parameters, system setup, analysis methods, statistical results, and biological interpretation suitable for publication, patent filing, or regulatory submission
Broad System Compatibility: Simulation of macromolecular systems containing proteins, nucleic acids, lipids, and small ligands. Support for aqueous and organic solvents to match diverse biological and chemical environments.
Multiple Force Field Support: We support various force fields including CHARMM, AMBER, and OPLS, enabling selection of the optimal parameter set for your specific system and ensuring compatibility with established simulation protocols.
High-Performance Computing: GPU-accelerated programs capable of long-timescale simulations, enabling capture of biologically relevant events on timescales from nanoseconds to microseconds with efficient computational throughput.
Advanced Sampling Methods: Periodic boundary conditions, steepest descent and conjugate gradient-based energy minimization, replica-exchange, metadynamics, and steered molecular dynamics for enhanced conformational sampling and free energy calculation.
Customizable Service: We provide the service in a customizable fashion to suit our customers' specific research goals, from standard equilibrium simulations to complex free energy calculations and interactive molecular dynamics.
Representative Program Scenarios
Scenario 1: Allosteric Pocket Identification for GPCR Drug Discovery
Program Context:
A drug discovery program targeting a G-protein-coupled receptor required identification of allosteric modulation sites distinct from the orthosteric ligand-binding pocket. Crystal structures revealed only the inactive-state conformation, and no allosteric ligands were known.
Objective:
To use molecular dynamics simulation to identify cryptic pockets and allosteric pathways in the GPCR, characterize their dynamic opening-closing behavior, and guide virtual screening for allosteric modulators.
Approach:
Profacgen performed three independent 1-microsecond replica-exchange molecular dynamics simulations of the receptor in a lipid bilayer. Trajectory analysis using pocket detection algorithms identified three transient pockets on the intracellular face with opening frequencies >15%. Principal component analysis revealed correlated motions linking the extracellular ligand-binding site to the intracellular G-protein interface. Free energy calculations estimated pocket druggability scores.
Outcome:
Two cryptic pockets with favorable druggability profiles were selected for virtual screening. A library of 50,000 compounds was docked against dynamic pocket ensembles, yielding 12 hits with predicted allosteric activity. Experimental validation confirmed 3 compounds with EC50 < 10 µM for receptor modulation without orthosteric competition. The MD-guided approach identified targets invisible to static structural methods.
Scenario 2: Antibody Aggregation Propensity Assessment by Temperature-Dependent MD
Program Context:
A therapeutic antibody program required early assessment of long-term stability and aggregation risk prior to formulation development. Experimental stability data were limited to accelerated aging studies, and molecular mechanisms of aggregation were poorly understood.
Objective:
To predict antibody thermal stability and identify aggregation-prone regions through temperature-dependent molecular dynamics simulations, guiding formulation and engineering strategies to improve shelf-life.
Approach:
Profacgen performed replica-exchange molecular dynamics simulations of the antibody Fc region across a temperature range of 280-450 K. Melting profiles were derived from heat capacity curves, and unfolding pathways were characterized by secondary structure loss and solvent exposure trajectories. Hydrophobic patch analysis and oligomeric assembly simulations identified self-association interfaces.
Outcome:
The predicted melting temperature (Tm = 72°C) agreed within 3°C of differential scanning calorimetry data. A hydrophobic patch in the CH2 domain was identified as the primary nucleation site for aggregation. Structure-guided mutagenesis of two surface residues reduced aggregation propensity by 60% in accelerated stability studies while maintaining effector function. The computational assessment saved 4 months of experimental screening.
Q: What systems can be simulated by molecular dynamics?
A: We simulate macromolecular systems containing proteins, DNAs, RNAs, lipids, and other small ligands. Simulations can be performed in aqueous or organic solvents. Our capabilities include membrane-embedded proteins, protein-nucleic acid complexes, protein-ligand systems, and multi-protein assemblies. We support various force fields including CHARMM, AMBER, and OPLS to match your system requirements.
Q: How long should a molecular dynamics simulation run?
A: Simulation length depends on the biological question and system size. Standard equilibrium simulations typically run 100-500 nanoseconds. Enhanced sampling methods (replica-exchange, metadynamics) may require shorter individual runs but multiple replicas. Long-timescale events such as protein folding or large conformational transitions may require microseconds. Our GPU-accelerated infrastructure enables efficient long-timescale simulations.
Q: What is the difference between MD simulation and docking?
A: Molecular docking generates static poses of ligands within a fixed receptor structure, providing rapid but approximate binding mode predictions. MD simulation captures time-dependent motions of both protein and ligand, enabling quantification of binding free energy, identification of cryptic pockets, and characterization of induced-fit mechanisms. MD provides dynamic information inaccessible to docking and is essential for accurate affinity prediction and mechanism elucidation.
Q: Can MD simulation predict binding affinity accurately?
A: Yes, with appropriate methods. Alchemical free energy perturbation (FEP) and thermodynamic integration (TI) can predict binding free energies with errors approaching 1 kcal/mol for closely related compounds. MM/PBSA and MM/GBSA provide faster but less precise estimates suitable for ranking large compound libraries. Accuracy depends on force field quality, simulation length, and proper treatment of entropy. We select the optimal method based on your precision requirements and timeline.
Q: What are periodic boundary conditions and why are they used?
A: Periodic boundary conditions replicate the simulation box infinitely in all directions, eliminating edge effects and approximating an infinite bulk system. This is essential for accurate calculation of thermodynamic properties and prevents artificial interactions between a molecule and its own image. We apply periodic boundary conditions in all production simulations to ensure biologically relevant behavior and proper treatment of long-range electrostatics.
Q: Can you perform customized simulations outside standard protocols?
A: Yes. We provide the service in a customizable fashion to suit our customers' specific research goals. Our capabilities include steered molecular dynamics, interactive molecular dynamics, custom force field development, and specialized analysis protocols. Please contact us to discuss your specific requirements and we will design a tailored simulation strategy.
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Figure 1. Molecular dynamics simulation process.