Moving specific parts of a molecule precisely can be an everyday hurdle in molecular modeling—especially when you want translational or rotational control along a molecule’s internal, principal directions. Manually adjusting positions or antibody orientations, for example, often feels like moving puzzle pieces without any guiding edges.
The Local Move Editor in SAMSON offers a practical and efficient solution to this issue, allowing you to translate and rotate molecular fragments using the object’s own internal coordinate system. This means you don’t have to align your transformations with the global axes manually—instead, you interact with each group or atom selection in its most intuitive way.
What Is the Local Move Editor?
The Local Move Editor (M shortcut) provides interactive widgets to translate and rotate selected molecular structures based on their principal axes. When you select a part of a molecule—say a side chain or a ligand—the move editor appears centered on it, enabling intuitive spatial manipulations.
Key Features
- Central Translation Widget: Move selection along the camera plane (very useful for 2D manipulations or aligning objects visually).
- Axis Translators: Translate along the molecule’s local X, Y, or Z axes using straight arrow widgets.
- Plane Translators: Glide the selection along planes defined by two of its principal axes.
- Rotational Arcs: Rotate around each of the three axes using curved arc widgets.
- Trackball (Sphere): Freely rotate the selection for more flexible adjustments.
- Snapping: Apply consistent grid-based translation or rotation for aligned setups (e.g., 10° steps).
Why This Matters
Let’s say you’re setting up an enzyme-substrate complex and need to modify a side chain orientation precisely to check for steric clashes. With the Local Move Editor, you don’t need to guess or repeatedly reselect and nudge coordinates; instead, you grab the widget and nudge the atoms interactively along the molecule’s own frame of reference.
You can even edit dihedral angles directly by clicking on the half of any bond and sweeping through torsion values in a hands-on way—minimizing guesswork.
Integrating Precision Moves with Real-Time Feedback
Another strong feature is the combination of visual manipulation with numerical input. By right-clicking any widget or pressing Ctrl/Cmd + click, you can input exact distance or angle values. Couple this with snapping options—like 0.5Å for translation or 10° for rotation—and you can replicate precise spatial configurations across molecular fragments.
Undo support ensures that mistakes are easy to correct, making experimentation risk-free.
When to Use It?
- Interactive docking or fragment positioning
- Fine-tuning torsion angles for conformational analyses
- Real-time simulation control during manipulation
- Teaching molecule orientation concepts interactively
Whether you are visualizing a conformation, setting up a system for simulation, or preparing publication figures, the Local Move Editor significantly streamlines small but crucial model adjustments.
To learn more about moving objects in SAMSON and working with move editors, visit the official documentation page.
SAMSON and all SAMSON Extensions are free for non-commercial use. You can get SAMSON at https://www.samson-connect.net.