As a molecular modeler, have you ever struggled to filter, analyze, or organize residues effectively in your structural systems? Whether you’re handling complex protein datasets or nucleic acid structures, SAMSON’s Node Specification Language (NSL) provides a solution by enabling you to query and handle residue attributes with precision and efficiency. In this post, we’ll guide you through some key residue attributes that can simplify and enhance your modeling tasks.
What Are Residue Attributes?
Residue attributes in SAMSON are part of the NSL, offering a powerful way to query, analyze, and manipulate components of your molecular systems. These attributes are structured into various spaces, such as general node properties, structural group properties, and properties specific to residues. For residues in particular, SAMSON provides a range of attributes to identify residue-specific characteristics.
Key Residue Attributes You Can’t Ignore
Below are a few critical residue attributes worth exploring. These attributes are especially helpful when working with large protein structures, nucleic acids, or other macromolecular systems.
1. residue.secondaryStructure – Understand Protein Structures
The secondaryStructure attribute (r.ss) helps you identify specific secondary structure elements such as alpha helices (helix or h), beta sheets (strand or b), or loops/unstructured regions (loop or u).
Examples of usage:
residue.secondaryStructure helix(short version:r.ss h) – Matches residues in alpha helices.residue.secondaryStructure alpha, beta(short version:r.ss a, b) – Matches residues in alpha helices and beta sheets.
This allows modelers to highlight or isolate structural regions of interest directly in SAMSON.
2. residue.charge – Identify Charged Residues
The charge attribute (r.c) categorizes residues based on their side chain charge: negative (neg), neutral (neu), positive (pos), or undefined (un).
This is especially useful in tasks like identifying ionizable residues in a protein or configuring a system for molecular dynamics calculations.
Examples:
residue.charge neutral(short version:r.c neu) – Selects residues with neutral side chains.residue.charge negative, positive(short version:r.c neg, pos) – Matches all residues with negative or positive charges.
3. residue.type – Specify Amino Acid Types
When working with proteins, the type attribute (r.t) allows you to filter specific amino acids, such as alanine (ALA) or lysine (LYS).
Examples:
residue.type ALA(short version:r.t ALA) – Matches alanine residues.residue.type VAL, LYS(short version:r.t VAL, LYS) – Matches valine and lysine residues.
This attribute is ideal when you need to visualize certain residues selectively within large systems.
4. residue.aminoAcid – Quickly Isolate Amino Acids
For systems with mixed residue types (nucleic acids, water molecules, etc.), the aminoAcid attribute simplifies matching residues belonging to amino acids (true or false).
Example:
node.type atom in residue.aminoAcid(short version:n.t a in r.aa) – Selects atoms in amino acid residues.
Empower Your Molecular Modeling
Residue attributes like hydrophobicity, terminal status, and formal charges give modelers even more options to manipulate and explore their systems effectively. By combining these attributes, you can create precise queries for visualizations, analysis, or even simulations.
Want to dive even deeper? Please check out the full documentation about residue attributes in SAMSON by visiting this page.
SAMSON and all SAMSON Extensions are free for non-commercial use. Download SAMSON now at https://www.samson-connect.net and enhance your molecular modeling experience.