One of the most common frustrations in molecular modeling arises from accidental changes, experimental edits that don’t pan out, or simply wanting to compare different model states. For molecular modelers working on complex structures, reverting changes isn’t just a nice-to-have—it saves hours of work.
Thankfully, SAMSON provides a convenient way to Undo and Redo nearly all modeling operations. Whether you’re importing molecular data, modifying structures, or adjusting visualizations, SAMSON keeps track of your actions, allowing you to easily explore alternatives without fear of losing progress.
Per-Document Histories: Keeping Your Workflow Organized
Each document in SAMSON has its own history. That means any operations you perform—additions, deletions, transformations—are recorded within the document itself. This is especially useful if you work on multiple systems or simulations in parallel, allowing you to isolate and control actions in each case.
Accessing and Using the History View
If you’re not yet using the History view, it’s worth a look. You can open it by going to Interface > History in the menu bar, or simply by pressing:
- Ctrl + 3 on Windows and Linux
- Cmd + 3 on Mac
This opens a visual timeline of your recent operations, like this:
Clicking any item in the list reverts the state of your document to that point in time. It’s a powerful way to explore alternative workflows, test hypotheses without risk, and simply backtrack when needed.
Keyboard Shortcuts You’ll Use Daily
In addition to the visual history, SAMSON supports common Undo/Redo actions through shortcuts:
- Undo: Ctrl + Z (Windows/Linux) or Cmd + Z (Mac)
- Redo: Ctrl + Y (Windows/Linux) or Cmd + Y (Mac)
These make rolling back or reapplying changes immediate—even if you never open the History view at all.
One Limitation to Keep in Mind
It’s important to note that not all operations are undoable. Some complex or external operations might break the history chain. If you perform an untracked change between undoable ones, it could limit how far back you can go. For example:
Your history might look like:
- Add Atom
- Run External Simulation (not undoable)
- Add Bond
If you try to undo beyond the simulation step, SAMSON may not revert correctly due to partial state tracking.
Why This Matters in Real Work
Let’s say you’re optimizing a ligand-protein interface and you attempt several changes: moving a chain, modifying torsions, deleting overlapping atoms. With the history feature, you can test each strategy and roll back instantly if one doesn’t lead to better binding. This avoids having to save multiple versions manually—and makes the creative trial-and-error part of modeling less stressful.
To see an example of how you can scroll through history interactively, check this out:
Learn more in the official SAMSON documentation on Undo and Redo.
SAMSON and all SAMSON Extensions are free for non-commercial use. Get SAMSON at https://www.samson-connect.net