A Clear Guide to Segment Attributes in SAMSON

Molecular modeling involves managing and understanding vast amounts of structural data. One major challenge is efficiently selecting, filtering, and utilizing specific characteristics of molecular segments in your projects. This is where Segment Attributes in the Node Specification Language (NSL) within SAMSON come in handy.

In this blog post, we will dive into how to leverage Segment Attributes, saving you time and making molecular design more intuitive.

What are Segment Attributes?

Segment Attributes in NSL are used to define, select, and filter nodes representing segments in a molecular structure. In SAMSON’s NSL, the segment attribute space (short name: s) allows you to specify criteria for these segments, such as their visibility, residue counts, and more.

Why They’re Useful

Imagine you are working on a large molecular system and need to focus on specific structural groups or highlight a subset of nodes that meet certain criteria. With Segment Attributes, you can customize your queries precisely, selecting segments based on:

  • Visibility features (e.g., hidden or visible nodes)
  • Selected or flagged nodes
  • The number of residues, atoms, or specific elements (like carbons or hydrogens) in a segment.

This makes analyzing complex molecular systems significantly easier.

Exploring Key Attributes

Attributes Inherited from Node and Structural Groups

Here are some commonly inherited attributes:

  • Visibility: Use the visible (v) or hidden (h) attributes to filter visible or hidden nodes, for instance, with s.v or not s.h.
  • Selection: Use selected or selectionFlag (sf) to identify selected segments.
  • Structural Composition: Attributes like the numberOfAtoms (nat) or numberOfCarbons (nC) help you focus on specific structural details. For example, s.nat < 1000 identifies segments with fewer than 1000 atoms.

Segment-Specific Attributes

Two segment-specific attributes unlock new possibilities:

  1. Number of Residues (numberOfResidues): This attribute (short name: nr) lets you filter based on the number of residues in a segment. For example:

    • s.nr > 100 – matches segments with more than 100 residues.
    • s.nr 100:120 – selects only segments containing between 100 and 120 residues.
  2. Number of Structural Groups (numberOfStructuralGroups): The nsg attribute narrows down segments by structural groups. For example:

    • s.nsg > 10 filters segments with more than 10 groups.
    • s.nsg 10:12 focuses on segments with structural groups numbering between 10 and 12.

Making It Practical: An Example

Suppose you’re visualizing a protein complex and need to isolate segments with:

  1. More than 200 atoms.
  2. Specific visibility flags.

You can combine queries like:

or focus on hidden nodes:

These shortcuts are concise and powerful for managing molecular systems more effectively.

Start Leveraging Segment Attributes

The ability to customize queries with Segment Attributes transforms how molecular modelers explore and edit structures in SAMSON. To explore all Segment Attributes and examples, visit the official SAMSON documentation.

Note: SAMSON and all SAMSON Extensions are free for non-commercial use. Learn more and download SAMSON at https://www.samson-connect.net.

Comments are closed.