Exploring Structural Group Attributes in Molecular Models

Molecular modeling often involves working with complex systems composed of many structural groups. Understanding and managing these groups is key to achieving accurate modeling results. In SAMSON, structural groups have their own set of attributes that make it easier for users to query, filter, and manipulate data effectively. This blog post focuses on these attributes and explains how to leverage them to improve your molecular modeling workflows.

What Are Structural Groups?

In SAMSON, structural groups are special nodes that represent collections of atoms. These groups can have various attributes, inherited or specific, that help users tailor their queries and streamline their molecular studies. From visibility settings to atomic composition data, these attributes offer a rich framework to work with complex molecular systems.

Inherited Attributes: Filtering and Control

Some structural group attributes are inherited from broader node definitions. These inherited attributes include:

  • Visibility: Use visible (sg.v) and visibilityFlag (sg.vf) to match structural groups based on whether they are visible or hidden in the model.
  • Material Presence: The hasMaterial (sg.hm) and ownsMaterial (sg.om) attributes help you filter groups that have or own materials.
  • Selection State: Use selected (sg.selected) or selectionFlag (sg.sf) to match structural groups based on their highlighted state in SAMSON.
  • Name Matching: The name attribute (sg.n) lets you find groups with specific or wildcard-based names. For instance, sg.n "A*" matches all structural groups whose name starts with the letter ‘A’.

For a full breakdown of inherited attributes, visit the Node Attribute Space Documentation.

Specific Attributes for Structural Groups

Structural groups in SAMSON have additional attributes tailored for molecular analysis:

  • Atomic Composition: You can query groups based on their atomic composition. For example:
    • numberOfAtoms (sg.nat) matches groups with specific atom counts, such as sg.nat > 100.
    • Attributes like numberOfCarbons (sg.nC), numberOfHydrogens (sg.nH), and numberOfOxygens (sg.nO) allow you to focus on specific elements.
    • Need to query coarse-grained representations? Use numberOfCoarseGrainedAtoms (sg.ncga).
  • Charge States: The formalCharge (sg.fc) and partialCharge (sg.pc) attributes let you filter structural groups based on their charge values. For example, sg.pc 1.5:2.0 matches groups with partial charges between 1.5 and 2.0.
  • Structural IDs: Use structureID (sg.id) to work with specific groups, such as sg.id >= 10 or ranges like sg.id 5:10, 25:30.

Each attribute enhances your control over structural groups, making it easier to refine molecular analyses and achieve precise results.

Real-World Applications

By combining these attributes, you can solve various challenges, such as:

  • Identifying structural groups with a high number of hydrogen atoms for hydrogen bonding studies (sg.nH > 5).
  • Filtering visible structural groups by their partial charge to focus on highly polarized regions (sg.v and sg.pc > 1).
  • Locating coarse-grained representations of large assemblies (sg.ncga 100:200).

These examples highlight how powerful the structuralGroup attribute space can be when applied in practice.

Learn More

For a complete reference to the structuralGroup attribute space and its applications, visit the full documentation page: Structural Group Documentation.

SAMSON and all SAMSON Extensions are free for non-commercial use. You can get SAMSON at SAMSON Connect.

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