Molecular modelers often need to sift through large datasets, identify specific residues, and extract meaningful insights efficiently. To address this, SAMSON’s Node Specification Language (NSL) offers a versatile tool: residue attributes. These attributes empower researchers to define, filter, and query molecular residues with precision, accelerating workflows and reducing errors. Whether you’re working on visualizing a subset of residues or identifying their chemical properties, residue attributes have you covered.
Why Are Residue Attributes Important?
Residue attributes help modelers analyze and manipulate molecular structures at the residue level. They enable targeted selection based on properties like secondary structure, polarity, hydrophobicity, or even unique types of residues like amino acids, nucleic acids, or terminal residues.
For example, you might want to find residues with a specific charge, identify terminal residues, or filter by secondary structure (e.g., alpha helices or beta strands). With NSL, such tasks become both intuitive and powerful. Below, we’ll explore some commonly used residue attributes and how they simplify molecular design.
Exploring Core Residue Attributes
Residues are rich in attributes, offering flexibility for a wide range of tasks. Here are some key attributes and how you can use them:
Residue Type
The residue.type (short name: r.t) attribute matches residues of specific types. Examples:
r.t ALA: Matches alanine residues.r.t LYS, PRO: Matches lysine and proline residues."CA" in r.t VAL: Matches alpha carbons in valines.
Secondary Structure
Use residue.secondaryStructure (r.ss) to target residues based on their secondary structure:
r.ss helix: Matches residues in alpha helices.r.ss a, b: Matches residues in alpha helices and beta sheets.
Aliases for secondary structures include alpha (a, helix, h), beta (b, strand, s), and unstructured (u, loop, l).
Polarity and Hydrophobicity
Residue polarity and hydrophobicity are essential for studying biochemical properties:
residue.polarity polar(short version:r.p polar): Matches residues with polar side chains.r.p acidic, basic: Matches acidic and basic residues.residue.hydrophobicity -60:-20: Matches residues with hydrophobicity in the range from -60 to -20.
Charge
Charge-based queries are straightforward using residue.charge (r.c):
r.c neg: Matches negatively charged residues.r.c neu, pos: Matches neutral or positively charged residues.
Aliases include negative (neg), neutral (neu), positive (pos), and undefined (un).
Residue Sequence
With residue.residueSequenceNumber (r.id), you can match residues by sequence number:
r.id == 42: Matches the residue with sequence number 42.r.id 1:10, 20:30: Matches residues in specified ranges.
Streamline Your Workflow
By leveraging these attributes, you can customize your molecular queries effortlessly. Whether pinpointing specific residues to analyze chemical properties, selecting atoms within residues, or filtering based on secondary structures—NSL empowers you to stay focused on your research.
Residue attributes are not just powerful but also easy to use. They save time, ensure precision, and enable researchers to ask complex questions directly within SAMSON.
Learn More
To explore the full documentation on residue attributes, visit the Residue Attributes Documentation. You’ll find detailed examples and explanations to optimize your molecular modeling workflows.
SAMSON and all SAMSON Extensions are free for non-commercial use. You can download SAMSON at this link.