Molecular modelers frequently work with complex systems, and one recurring challenge is efficiently selecting or filtering residues based on specific properties. The Node Specification Language (NSL) in SAMSON offers a set of tools tailored for residue attribute management, simplifying the modeling process. Let’s dive into how residue attributes can make your modeling tasks more precise and effective.
Why Use Residue Attributes?
Residue attributes allow you to define, filter, and manipulate residues based on their chemical and structural properties. These attributes include both inherited properties from broader node classifications and residue-specific criteria. By leveraging these attributes, you can:
- Identify residues with specific visibility or selection states.
- Filter residues based on atomic composition, polarity, or hydrophobicity.
- Target residues by sequence number or secondary structure type.
Key Residue Attribute Examples
Here are a few practical applications:
Filter By Residue Charge
The residue.charge attribute (short name: r.c) allows you to selectively match residues with specific side chain charges. Supported values include:
negative(neg)neutral(neu)positive(pos)undefined(un)
For instance:
residue.charge negative(short version:r.c neg): Matches residues with negatively charged side chains.residue.charge neutral, positive(short version:r.c neu, pos): Matches residues that are neutral or positively charged.
This is particularly useful for designing charge-based interactions in protein-ligand systems.
Explore Secondary Structures
If you’re analyzing or designing structures based on secondary folding patterns, the residue.secondaryStructure attribute (short name: r.ss) can help you:
| Attribute Name | Aliases | Meaning |
|---|---|---|
alpha |
a, helix, h |
Matches alpha helices. |
beta |
b, strand, s |
Matches beta strands. |
unstructured |
u, loop, l |
Matches unstructured regions (loops). |
Practical examples include:
residue.secondaryStructure helix(short version:r.ss h): Matches residues in helices.residue.secondaryStructure alpha, beta(short version:r.ss a, b): Matches residues in helices or sheets.
Use Residue Type for Precision
Planning on targeting a specific residue like alanine or lysine? The residue.type attribute (short name: r.t) provides detailed filtering options to match residues such as:
- Standard amino acids: e.g.,
ALA,LYS,GLU. - Nucleic acids (RNA/DNA): e.g.,
A,C,U. - Modified residues:
SEC(selenocysteine),PYL(pyrrolysine).
Examples:
residue.type ALA(short version:r.t ALA): Matches alanines."CA" in residue.type LYS(short version:"CA" in r.t LYS): Matches only alpha carbons in lysines.
Better Selection, Smarter Modeling
Residue attributes provide flexibility and control, enabling modelers to fine-tune their workflows using NSL’s query capabilities. Whether you’re working on protein folding, drug design, or system optimization, these attributes offer a robust toolkit for precise residue targeting.
To see the full details and examples for residue attributes in SAMSON’s NSL, visit the Residue Attribute Documentation.
SAMSON and all SAMSON Extensions are free for non-commercial use. Get started today by downloading SAMSON at samson-connect.net.