For molecular modelers working with complex structures, understanding the attributes of segments can be critical for efficient organization, visualization, and analysis. In this post, we dive into the segment attributes in SAMSON’s Node Specification Language (NSL), offering an insightful guide to this powerful tool.
Segments in NSL are defined in the segment attribute space with the short name s. These attributes allow you to match and manipulate specific portions of your molecular models in an intuitive way. Here’s an overview of the key segment-specific attributes and how you can use them to solve key modeling challenges.
Inherited Attributes from Node and StructuralGroup
The segment attribute space inherits several useful properties from both the node and structuralGroup spaces. These inherited attributes include:
- Node Attributes: Examples include
hasMaterial(s.hm),visible(s.v), andselected(s.selected). - StructuralGroup Attributes: Examples include
formalCharge(s.fc),numberOfAtoms(s.nat), andpartialCharge(s.pc).
These attributes let you filter segments based on their visibility, charge, selection state, or atom count, among other criteria. For instance:
s.hm: Matches segments with material attached (e.g.,s.hm true).s.nat > 500: Matches segments that contain more than 500 atoms.
Segment-Specific Attributes
What’s particularly exciting about working with segments is the availability of attributes tailored specifically to them. Let’s explore two key attributes:
numberOfResidues (s.nr)
If your work involves proteins or other biomolecular structures, numberOfResidues is a crucial attribute. This property lets you match segments with a defined number of residues:
s.nr > 100: Matches segments with more than 100 residues.s.nr 50:70: Matches segments with 50 to 70 residues.
Such filtering can help you focus on specific chains or regions of interest in large macromolecular assemblies.
numberOfStructuralGroups (s.nsg)
Another powerful attribute is numberOfStructuralGroups, which matches segments containing structural groups like ligands or domains:
s.nsg > 5: Matches segments with more than 5 structural groups.s.nsg 3:7: Matches segments with 3 to 7 structural groups.
Using s.nsg, you can systematically isolate the functional groups in your structure or identify regions of interest.
Why Segment Attributes Matter
Working with segment attributes reduces manual work while improving accuracy in molecular modeling projects. Whether you’re identifying parts of a protein based on residue count or isolating key structural units, leveraging these attributes simplifies workflows and enhances data interpretation.
For the full list of attributes, their short names, values, and examples, consult SAMSON’s comprehensive documentation: Segment Attributes Documentation.
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