When analyzing molecular simulations or transitions between conformations, understanding the complete trajectory—including its reverse—can offer essential insights. While most users typically examine forward motions, playing animations in reverse can reveal details such as intermediate conformations, relaxation events, or path symmetries that might be overlooked in the forward direction.
In SAMSON, a path node stores a trajectory: a sequence of structural variations or transitions of molecular systems over time. These paths are invaluable for visualizing and communicating conformational changes. But once you’ve examined a transition from Frame A to Frame B, what if you want to go back from B to A just as smoothly?
The Play reverse path animation in SAMSON helps you do just that. By reversing paths between two frames, you can:
- Visualize return transitions in molecular systems
- Inspect reversibility in a simulation
- Create smoother looping animations that cycle forward and backward
- Ensure clarity by examining alternate routes and dynamics
When Reverse Is the Right Direction
Consider a ligand unbinding simulation. Watching the forward motion might be inspiring—but reversing it can help you identify how the ligand re-enters the binding site, retracing contacts and movements. This helps in drug design, where predicting binding poses is critical.
In the same way, examining conformational rearrangements (e.g., in proteins or nucleic acids), using both directions of an animation helps detect symmetry or suggest possible relaxation mechanisms.
How to Apply the Reverse Animation
If you’ve already created or imported a path, applying the reverse animation is straightforward. Here’s how:
- Select the path node(s) you want to animate.
- Open the Animation panel in the Animator workspace.
- Double-click the Play reverse path animation effect.
This adds a new animation that plays the motion in reverse between two keyframes. You’re free to move those keyframes along the timeline, allowing full control over timing and placement.
Tuning Playback and Interpolation
Smoothing: If the animation has more frames than the selected path, SAMSON interpolates the frames between them for smoother playback. If needed, you can disable this smoothing option directly in the Inspector.
Timing and ramps: Just as in forward animations, reverse paths can use easing curves. These modify how the animation transitions between frames—slower start, sudden stop, etc.—making your animations more natural. Configure these in the animation’s properties panel.
Synchronizing Multiple Paths
If your system contains multiple trajectories (e.g., coupled domain motions or a protein-ligand complex), you can assign the reverse animation to multiple paths. SAMSON synchronizes these paths automatically, maintaining temporal consistency.
In summary, playing a path in reverse is a valuable tool to explore molecular mechanisms with more depth. Whether you are preparing a publication figure, an internal presentation, or just trying to better understand your system’s behavior, reverse animations can reveal what forward playback might miss.
To learn more, visit the complete documentation page here: Play reverse path animation in SAMSON.
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON at www.samson-connect.net.