When working in molecular modeling, achieving the lowest energy conformation for your structures is often crucial. Minimizing structures helps refine molecular geometries, making your models more realistic and computationally efficient. SAMSON, the integrative molecular design platform, offers an easy and interactive way to minimize molecular structures in real-time. Let’s explore how interactive minimization works in SAMSON and how you can use it effectively to solve some common pain points.
What is Interactive Minimization?
Interactive minimization allows you to visually and immediately observe how your molecular structure adjusts to achieve a low-energy conformation. This feature is powered by the Universal Force Field (UFF), ensuring quick and efficient calculations. It’s particularly useful for refining structures while keeping control over the modeling workspace.
Getting Started
To minimize your molecules interactively in SAMSON, follow these steps:
- Go to Edit > Minimize or use the handy shortcut Z to start and stop the minimization process.
- You can move molecules and atoms using Move editors, or even add atoms during the minimization with the Add editor.
Minimizing a Single Molecule
If you only want to optimize one molecule in a system (or a single connected component):
- Uncheck the Include all atoms in the document option in Interface > Preferences > Editors > Minimize.
- Select the molecule you wish to minimize.
- Start the minimization by choosing Edit > Minimize.
Note: When minimizing a selection, the whole connected component of the selected part is considered. For instance, selecting one atom in a molecule will minimize the entire molecule that the atom belongs to.
Refining a Part of a Molecule
Minimizing an entire molecule isn’t always necessary—sometimes, only specific regions need optimization. You can freeze atoms to keep parts of a molecule fixed while minimizing the rest:
- Select the whole molecule, or leave the selection empty if you want to freeze everything.
- Freeze the atoms by clicking Edit > Freeze.
- Select the part of the molecule you want to minimize.
- Unfreeze the selected atoms by choosing Edit > Unfreeze.
- Begin the interactive minimization with Edit > Minimize.
- When finished, stop minimization and unfreeze all atoms by clicking Edit > Unfreeze with nothing selected.
Frozen atoms are not adjusted during minimization and retain their positions. These atoms are displayed with a dark blue overlay in SAMSON’s viewport, so you can clearly see which parts are fixed.
Adjusting Interactive Minimizer Options
You can customize the behavior of the interactive minimizer in the Preferences panel under the Minimize section. For instance, you can choose whether to minimize all molecules or focus on specific components. Refer to the image below to identify the options:
Conclusion
Interactive minimization in SAMSON is a powerful tool that lets you fine-tune molecular structures while granting you full control over the process. It simplifies geometry adjustments, reduces modeling challenges, and dynamically evolves your workspace. To dive deeper into these features and discover more, visit the official documentation page.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON from https://www.samson-connect.net.