bio-alignment-structural

A toolkit for aligning protein structures by comparing their three-dimensional shapes, not only their amino-acid sequences. It can superpose structures, score fold similarity, and search for remote structural matches.

In plain words
What is it for?
Use it to compare protein models, detect remote homology, search structural databases, create structural multiple alignments, and inspect superposed structures.
Why use it?
Proteins with related functions may have very different sequences, so sequence alignment alone can miss their relationship. Shape comparison can reveal deeper similarities.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/gptomics/bioskills/structural-alignment
Any agent
npx skills add GPTomics/bioSkills --skill structural-alignment
Clone the repo
git clone --depth 1 https://github.com/GPTomics/bioSkills

Made for: Claude Code, Codex.

Per session 102 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,081 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00102 $0.06081
Opus 5 $0.00051 $0.03040
Sonnet 5 $0.00020 $0.01216
Haiku 4.5 $0.00010 $0.00608

Measured 2d ago against content hash 5053d6163e1f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

bio-alignment-structural scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

The scan reads SKILL.md. This mod also ships 4 executable files (examples/biopython_superimposer.py, examples/foldmason_msa.py, examples/foldseek_search.py, …), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

1 near-identical copy found in the catalogue:

alignment/structural-alignment/SKILL.md · 331 lines

How it starts

The opening of the file, as written. The whole thing — 331 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Version Compatibility

Reference examples tested with: Foldseek 8+, TM-align 20220412+, US-align 20231222+, Foldmason 1+, BioPython 1.83+, pymol-open-source 3.0+

Before using code patterns, verify installed versions match. If versions differ:

  • CLI: foldseek --version, TMalign, USalign, foldmason --version
  • Python: pip show <package> then help(module.function) to check signatures

If code throws ImportError, AttributeError, or TypeError, introspect the installed package and adapt the example to match the actual API rather than retrying.

Structural Alignment

"Align two protein structures" -> Compute backbone-aware superposition and a fold-similarity score (TM-score, RMSD, or LDDT).

  • CLI pairwise: TMalign A.pdb B.pdb, USalign A.pdb B.pdb
  • CLI search at scale: foldseek easy-search query/ AFDB result.m8 tmp/
  • CLI structural MSA: foldmason easy-msa structures/*.pdb out tmp/
  • Python pairwise: Bio.PDB.Superimposer, or subprocess wrapping TMalign / USalign (see examples/tm_align_pairwise.py)
  • GUI / scripted molecular-graphics superposition: ChimeraX matchmaker, PyMOL super/cealign

"Find structural homologs of an AlphaFold model" -> Search a structure database by 3Di-encoded structural alphabet (Foldseek) or by full TM-align rotation (DALI, US-align).

When to Use Structural Alignment

Sequence identity Recommended approach
>= 40% Sequence DP (Bio.Align, BLASTP) is sufficient
25-40% Sensitive sequence (MMseqs2, jackhmmer, profile-profile HHsearch)
15-25% Profile-profile (HHsearch) OR Foldseek if structures available
< 15% (dark proteome / twilight zone) Foldseek (3Di), TM-align, US-align, pLM aligners

Sequence alignment below 15% identity is statistically indistinguishable from random pairings. The exact twilight-zone cutoff is length-dependent: Rost 1999 (Prot Eng) showed the curve drops to 25% at length 80, 20% at length 250 -- short alignments need higher identity for the same statistical signal, so a 15-25% rule of thumb is shorthand for "twilight zone for proteins of typical domain size (~150-300 residues)". If reasonable structural models exist (PDB, AlphaFoldDB, ESMFold), structural alignment is far more reliable in this regime.

Read the full file on GitHub · 331 lines

Files

What ships with it

5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 331 lines · 102 tokens per session scan A 5053d6163e1f

Subscribe to this mod's changes

bio-alignment-structural is a skill published in the GitHub repository GPTomics/bioSkills (1,198 stars, last pushed 17d ago), licensed MIT. It adds 102 tokens to every session and 6,081 once invoked, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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