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Exploring reaction pathways with transition path and umbrella sampling: application to methyl maltoside.
Richard J Dimelow1, Richard A Bryce, Andrew J Masters
1School of Chemistry, University of Manchester, Manchester M13 9PL, United Kingdom.
The Journal of Chemical Physics
|March 25, 2006
Summary
Transition path sampling (TPS) reveals subtle dynamics missed by potential of mean force (PMF) methods. This study compared TPS and PMF for a disaccharide conformational change, estimating a 160 ns transition time.
Area of Science:
- Computational Chemistry
- Molecular Dynamics
- Chemical Physics
Background:
- Transition path sampling (TPS) offers direct reaction rate calculation without predefined reaction coordinates.
- Potential of mean force (PMF) methods, while common, rely on accurate reaction coordinate selection.
- Understanding conformational changes in biomolecules is crucial for their function.
Purpose of the Study:
- To compare the efficacy of transition path sampling (TPS) and potential of mean force (PMF) methods.
- To investigate the conformational change of methyl beta-D-maltoside, a model disaccharide.
- To assess the ability of TPS to reveal reaction dynamics not apparent in PMF.
Main Methods:
- Comparison of transition path sampling (TPS) with weighted histogram analysis method (WHAM) for PMF calculation.
- Analysis of transition paths for methyl beta-D-maltoside's conformational change.
- Estimation of transition rates using transition state theory and TPS.
Main Results:
- TPS identified a reaction channel not visible through PMF analysis.
- The glycosidic torsional angles (phi, psi) were confirmed as suitable reaction coordinates for this isomerization.
- An approximate transition time of 160 ns was estimated for the rare isomerization event.
Conclusions:
- Transition path sampling provides deeper insights into molecular dynamics than PMF methods.
- While computationally more intensive (27.5x), TPS offers valuable information for complex systems.
- The study validates TPS as a powerful tool for studying rare events and conformational changes in carbohydrates.