Understanding Backbone Attributes in SAMSON’s Node Specification Language

For molecular modelers, handling complex structures with precision is paramount. SAMSON’s Node Specification Language (NSL) can assist in customizing model representations by utilizing backbone attributes effectively. In this post, we’ll dive into the specifics of backbone attributes and how they can facilitate molecular modeling tasks.

What are Backbone Attributes?

In SAMSON, backbone attributes are defined in the backbone attribute space (with its short name s). These attributes apply exclusively to backbone nodes and allow users to define properties or query specific structures precisely. Various attributes are either directly accessible or inherited from other attribute spaces, such as the node or the structuralGroup spaces.

Practical Attributes for Backbone Nodes

Here’s a glimpse at some useful backbone attributes and how molecular modelers can utilize them:

  • hasMaterial (hm): This attribute helps check if a backbone has a material attached. It can take values like true or false. For example, you can test if a backbone has material using bb.hm, or find backbones without material with not bb.hm.
  • numberOfAtoms (nat): This attribute works well for understanding molecular size by specifying the number of atoms in a backbone. Queries like bb.nat < 1000 or bb.nat 100:200 can help filter groups based on atom counts.
  • hidden (h): Use this attribute to determine the visual status of a backbone in the rendered model. For example, bb.h indicates that a backbone is hidden, while not bb.h shows visible backbones.
  • name (n): Modelers often need to filter structures based on naming conventions. With bb.n, users can specify names directly (e.g., bb.n "A") or search using wildcards like bb.n "L*".
  • formalCharge (fc): This attribute, inherited from the structuralGroup attribute space, allows querying backbones based on their formal charge values. For example, setting conditions like bb.fc > 1 or ranges like bb.fc 6:8 can be very useful when analyzing charged regions in molecules.
  • partialCharge (pc): Similar to formalCharge, this attribute accepts float values and can be employed for fine-grained queries, such as filtering by bb.pc 1.5:2.0.

Making the Most of Backbone Attributes

By effectively combining attributes, modelers can easily retrieve meaningful subsets of molecular data. For instance:

  • To identify backbones with a specific range of carbon atoms that are visible, you could query: bb.nC 10:20 and bb.v true.
  • To find all hidden backbones containing more than 50 atoms: bb.h true and bb.nat > 50.

These examples demonstrate how backbone attributes streamline molecular structure management, enabling modelers to focus on specific regions of interest effortlessly.

For a complete list of backbone attributes and their capabilities, check out the full documentation here.

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

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