In molecular modeling projects, there are scenarios where minimizing just a part of a molecule is essential. Whether you’re optimizing a specific region of a structure or focusing on a key functional group, understanding how to selectively minimize a part of a molecule can save time and improve results. SAMSON makes this task straightforward by allowing users to freeze parts of a molecule while minimizing others. This guide will walk you through the process, step by step.
Why Minimize Only Part of a Molecule?
Selective minimization is valuable when working on complex systems where applying energy minimization globally might alter regions of the molecule you want to keep static. For example, while refining the structure of a ligand in a binding site, you may prefer keeping certain other interactions intact.
Freezing Atoms for Partial Minimization
SAMSON allows you to freeze parts of your system, effectively fixing their positions during the minimization process. Here’s how the process works:
- Select the entire molecule you want to work with or leave the selection empty to include the whole document.
- Click Edit > Freeze to freeze the selected atoms (or the entire molecule/document if no selection is made). This prevents these atoms from moving during the minimization process.
- Next, use the selection feature again to select the specific part of the molecule you wish to minimize. This could be a functional group, a side chain, or any connected subset of the molecule.
- Click Edit > Unfreeze to unfreeze only the atoms in this new selection. These are the atoms that will now be active during the minimization process.
- Click Edit > Minimize to begin the interactive minimization process. Observe how the selected part of the molecule adjusts while the frozen atoms remain static.
- Once satisfied with the results, click Edit > Minimize again to stop the minimization.
- Finally, to restore full flexibility to the system, click Edit > Unfreeze while selecting the entire molecule, or leave the selection empty to unfreeze everything.
Visual Cues and Preferences
SAMSON provides clear indicators for frozen atoms—they appear with a dark blue overlay in the viewport, making it easy to track which parts of the molecule are fixed. Additionally, you can customize preferences for freezing and minimizing under Interface > Preferences > Editors > Minimize to tailor the workflow to suit your specific project needs.
What’s Next?
Once you’ve optimized the targeted portion of the molecule, you can proceed with additional steps in your workflow, such as building molecules or simulating interactions. Selective minimization provides the precision molecular modelers need for in-depth structural studies.
For a demonstration, refer to the following example video on minimizing a part of a molecule with frozen atoms:
To dive deeper into this process or explore additional workflows, check out the full documentation page at https://documentation.samson-connect.net/users/latest/minimizing/.
Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Download SAMSON today at https://www.samson-connect.net.