When visualizing molecular simulations, being able to move forward through a trajectory is only one part of the story. Sometimes, depending on the system you’re modeling, watching a conformational change in reverse offers crucial insights. Whether you’re analyzing protein folding, ligand docking pathways, or mechanism reversibility, the ability to reverse-animate a trajectory can help uncover new patterns or validate hypotheses.
In SAMSON, this is exactly what the Play reverse path animation effect is built for. It allows you to play any path (or multiple paths) in reverse between two animation keyframes in the Animator panel. This makes it possible to examine molecular motions going backward in time, either for comparison or to highlight reversible processes.
When and Why to Play a Path in Reverse
Many modeling tasks benefit from viewing dynamics in reverse. Here are some example scenarios where this feature can be particularly enlightening:
- Protein Folding and Unfolding: Study the unfolding pathway to better understand stability and transitions.
- Ligand Dissociation: View binding site escape routes and potential energy barriers that may not be obvious in the forward path.
- Mechanism Validation: If a reaction mechanism is reversible, visualizing both directions helps assess symmetry or alternative routes.
How to Set Up a Reverse Path Animation
To use the Play reverse path animation in SAMSON, here’s what to do:
- Select a Path node in your model. This path contains the trajectory you’d like to reverse.
- Open the Animator panel and double-click Play reverse path from the list of effects.
- Move or adjust the animation keyframes in the timeline as needed. The path will be played backward between these two frames.
Tip: You can always modify the interpolation style between animation frames using the Easing curve setting in the Inspector. This gives you additional control over the pace and feeling of the reverse animation.
Smoothing and Synchronization
By default, SAMSON smooths path playback if the number of animation frames does not match the number of path frames. This helps achieve a continuous motion. However, if you need a precise step-by-step match, simply disable smoothing in the Inspector.
When you select and animate multiple paths, they are automatically synchronized. This is useful when comparing the behavior of different molecular fragments, or for visualizing cooperative processes such as protein domain movements or multi-molecule interactions in reverse.
Final Thoughts
Small changes in how a trajectory is presented can bring major perspective shifts. With Play reverse path, you gain a valuable tool for comparing, analyzing, and clearly presenting complex molecular motions — from a new and sometimes illuminating angle.
Learn more about this feature and how to use it in SAMSON’s documentation: https://documentation.samson-connect.net/users/latest/animations/play-reverse-path/
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON from https://www.samson-connect.net.