Agent skill

Cell Free Expression

by adaptyvbio in adaptyvbio/protein-design-skills

Guidance for cell-free protein synthesis (CFPS) optimization.

MITAuto-check passedResearch & Science

Install Cell Free Expression

skills CLI
$ npx skills add adaptyvbio/protein-design-skills --skill cell-free-expression -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install adaptyvbio/protein-design-skills cell-free-expression --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/adaptyvbio/protein-design-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/cell-free-expression .claude/skills/cell-free-expression && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
cell-free-expression
GitHub stars
163
Used in
3 other repos
Token cost
~2.8k tokens
SKILL.md length
1,015 words
Files
1
Skills in repo
24
Repo updated
First seen
Licence
MIT

At a glance

Guidance for cell-free protein synthesis (CFPS) optimization.

  • Works in 6 steps: First 30 codons: Most critical - use… → Rare codon clusters: Avoid 2+ rare… → Rare codon content: Keep overall <5% of… → …
  • Planning CFPS experiments
  • SKILL.md covers System Selection Guide, CFPS Troubleshooting Matrix, Codon Optimization for CFPS and mRNA Template Design, plus 7 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Cell Free Expression is an agent skill from adaptyvbio/protein-design-skills. Guidance for cell-free protein synthesis (CFPS) optimization. Use when: (1) Planning CFPS experiments, (2) Troubleshooting low yield or aggregation, (3) Optimizing DNA template design for CFPS, (4) Expressing difficult proteins (disulfide-rich, toxic, membrane).

Its SKILL.md is about 2.8k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Research & Science, covering Protein structure and design. The repository describes itself as: Claude Code skills for protein design. The licence is MIT.

When your agent uses it

  • Planning CFPS experiments
  • Troubleshooting low yield
  • Optimizing DNA template design for CFPS
  • Expressing difficult proteins (disulfide-rich

Example prompts

  • “/cell-free-expression”

Workflow steps

6 steps, taken from the first numbered list in SKILL.md.

  1. First 30 codons: Most critical - use only high-frequency codons
  2. Rare codon clusters: Avoid 2+ rare codons within 10 nt
  3. Rare codon content: Keep overall <5% of coding sequence
  4. GC content: Target 40-60% for balanced expression
  5. Avoid runs: No >6 consecutive G or C residues (secondary structure)
  6. Strategic slow codons: Place rare codons between domains (aids folding!)

What it can do on your machine

Read from SKILL.md and the folder at commit 59dd633. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    Links to these hosts (documentation or services it may open):

    • pmc.ncbi.nlm.nih.gov
    • nature.com
    • ncbi.nlm.nih.gov
    • mdpi.com
    • journals.plos.org
    • febs.onlinelibrary.wiley.com
    • pnas.org
    • frontiersin.org

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Cell Free Expression loads about 2.8k tokens when it runs. Until then it costs about 71 tokens; SKILL.md has 1,015 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~71
When it runs · the whole SKILL.md, loaded when a task matches
~2.8k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from adaptyvbio/protein-design-skills at commit 59dd633, republished under its MIT licence (© adaptyvbio). 1,015 words, ~2,790 tokens.

Download SKILL.mdSave it as .claude/skills/cell-free-expression/SKILL.md (or your agent's skills folder).
name
cell-free-expression
description
Guidance for cell-free protein synthesis (CFPS) optimization. Use when: (1) Planning CFPS experiments, (2) Troubleshooting low yield or aggregation, (3) Optimizing DNA template design for CFPS, (4) Expressing difficult proteins (disulfide-rich, toxic, membrane).
license
MIT
category
experimental
tags
expression, cfps, validation

Cell-Free Protein Synthesis (CFPS)

System Selection Guide

SystemBest ForYieldPTMsDisulfidesCost
E. coli extractRapid prototyping, prokaryotic proteinsHigh (100-400 μg/mL)NonePoor (reducing)Low
E. coli PUREDefined conditions, unnatural AAsMedium (50-150 μg/mL)NoneControllableHigh
Wheat germEukaryotic proteins, membrane proteinsHigh (100-500 μg/mL)LimitedModerateMedium
Rabbit reticulocyteMammalian proteins, post-translational studiesLow (10-50 μg/mL)SomePoorHigh
Insect (Sf21)Glycoproteins, complex foldsMedium (50-100 μg/mL)GlycosylationGoodHigh
HeLa/CHONative mammalian proteinsLow (10-50 μg/mL)Full mammalianGoodVery High

CFPS Troubleshooting Matrix

ProblemLikely CausesDesign FixReagent Fix
No expressionRare codons at N-terminus, poor RBSCodon optimize first 30 codonsUse BL21-CodonPlus extract
Low yieldStrong mRNA secondary structure, template issuesOptimize 5' UTR (ΔG > -5 kcal/mol)Increase Mg²⁺ (10-18 mM), ATP
AggregationHydrophobic protein, fast translationAdd solubility tags (MBP, SUMO)Add 0.1% Tween-20, chaperones
Inactive proteinMisfolding, missing cofactorsSlow translation (use rare codons!)Add GroEL/ES, DnaK/J
TruncationRare codon clusters, mRNA instabilityRemove AGG/AGA/CUA clustersSupplement rare tRNAs
DegradationProteolysisN-terminal Met-AlaAdd protease inhibitors

Codon Optimization for CFPS

Codons to Avoid in E. coli CFPS
CodonAmino AcidIssuetRNA Abundance
AGGArgVery rare, stalling0.2%
AGAArgVery rare, stalling0.4%
CUALeuLow abundance0.4%
AUAIleRare0.5%
CGAArgInefficient decoding0.6%
CCCProCan cause pausing0.5%
GGAGlyModerate1.1%
Design Rules
  1. First 30 codons: Most critical - use only high-frequency codons
  2. Rare codon clusters: Avoid 2+ rare codons within 10 nt
  3. Rare codon content: Keep overall <5% of coding sequence
  4. GC content: Target 40-60% for balanced expression
  5. Avoid runs: No >6 consecutive G or C residues (secondary structure)
  6. Strategic slow codons: Place rare codons between domains (aids folding!)
When to Use Rare Codons
  • Domain boundaries (allow cotranslational folding)
  • Before complex structural elements
  • When protein is prone to misfolding

mRNA Template Design

5' UTR Optimization
ElementOptimal DesignImpact
RBS (SD sequence)AGGAGG, 7-9 nt from startRibosome binding
Spacing7 nt between SD and AUGTranslation initiation
Secondary structureΔG > -5 kcal/molAccessibility
Upstream AUGAvoid (causes false starts)Reduces truncations
Secondary Structure Targets
RegionIdeal ΔGImpact
-30 to +30 around AUG> -5 kcal/molTranslation initiation
Full 5' UTR> -10 kcal/molRibosome loading
RBS accessibilityUnpairedCritical
Template Format
FormatAdvantagesDisadvantages
PlasmidStable, high yieldRequires cloning
Linear PCRFast, no cloningMay need stabilization
mRNADirect translationUnstable, expensive

Disulfide Bond Formation

System Capabilities
SystemNative Disulfide SupportAdditives Needed
Standard E. coli extractPoor (DTT present)IAM, PDI, GSSG/GSH
Oxidizing E. coli extractGoodPre-oxidized glutathione
Wheat germModerateLower DTT, add PDI
PURE systemMinimalFull oxidative system
Insect/MammalianGoodMicrosome membranes
Oxidative Folding Protocol (E. coli extract)
1. Deplete DTT from extract (dialysis or treatment with IAM 5 mM)
2. Add oxidized/reduced glutathione: 4 mM GSSG, 1 mM GSH (4:1 ratio)
3. Add 10 μM PDI (protein disulfide isomerase)
4. Optional: Add 5 μM DsbC (disulfide isomerase)
5. Express at 25°C (not 37°C) for better folding
6. Incubation time: 4-6 hours
Disulfide-Rich Protein Tips
  • Start with wheat germ or oxidizing extract
  • Use PURE system for precise control
  • Consider co-expression of PDI/DsbC
  • Verify by non-reducing SDS-PAGE

Expression Prediction from Sequence

FeatureGoodMarginalBad
Rare codon content<3%3-8%>10%
First 30 codons rare01-2>2
GC content45-55%35-45% or 55-65%<30% or >70%
5' UTR ΔG> -3 kcal/mol-3 to -8< -10 kcal/mol
Hydrophobic stretches<5 consecutive5-7>8 consecutive
N-terminal residueMet-Ala, Met-Ser, Met-GlyMet-Val, Met-ThrMet-Arg, Met-Lys
Cysteine pairsPaired (even number)MixedOdd number (free thiols)

Solubility Enhancement Strategies

Fusion Tags (ranked by effectiveness)
TagSizeSolubility EnhancementCleavageNotes
MBP40 kDaExcellentTEV, Factor XaBest overall
SUMO11 kDaVery GoodSUMO proteaseNative N-terminus after cleavage
NusA55 kDaExcellent-Large size
Trx12 kDaGoodEnterokinaseFor disulfide proteins
GST26 kDaModerate-Dimeric
His₆1 kDaMinimal-Mainly for purification
Show full SKILL.md (404 more words)Show less
Buffer Additives for Solubility
AdditiveConcentrationMechanism
Trehalose50-100 mMChemical chaperone
Glycerol5-10%Reduces hydrophobic aggregation
L-Arginine50-100 mMSuppresses aggregation
Tween-200.05-0.1%Prevents surface adsorption
Proline50 mMOsmolyte stabilization
Chaperone Supplementation
Chaperone SystemTarget ProblemConcentration
GroEL/GroESGeneral folding1-2 μM
DnaK/DnaJ/GrpEAggregation-prone1 μM each
Trigger FactorNascent chain1-2 μM
ClpBAggregate resolubilization0.5 μM

Temperature Optimization

TemperatureUse CaseTrade-offs
37°CFast expression, stable proteinsHigher aggregation risk
30°CBalanced (default)Good compromise
25°CDisulfide proteins, complex foldsSlower, better folding
18-20°CAggregation-prone proteinsMuch slower, best folding
16°CCold-shock proteinsVery slow, specialized

E. coli Extract Preparation (Key Variables)

VariableImpactOptimal Range
Cell density at harvestRibosome contentOD₆₀₀ 2.5-3.5
Lysis methodExtract activitySonication, bead beating
Run-off reactionRemoves endogenous mRNA20-80 min at 37°C
Mg²⁺ concentrationTranslation fidelity10-18 mM
K⁺ concentrationTranslation rate150-200 mM
Energy systemSustained synthesisATP/GTP, creatine phosphate

PURE System Specifics

Advantages
  • Defined composition (no proteases/nucleases)
  • Linear DNA templates work well
  • Unnatural amino acid incorporation
  • Reproducible between batches
Limitations
  • No chaperones (add separately)
  • No post-translational modifications
  • Lower yields than crude extracts
  • Higher cost
When to Use PURE
  • Unnatural amino acid incorporation
  • Studying translation mechanisms
  • "Clean" proteins needed
  • Protease-sensitive targets
  • Linear template expression

Common Artifacts and Solutions

Low Molecular Weight Bands

Causes: Premature termination, proteolysis, internal initiation Solutions:

  • Optimize rare codon clusters
  • Add protease inhibitors
  • Check for internal AUG codons
  • Use PURE system
Higher MW Bands

Causes: Incomplete termination, read-through, aggregation Solutions:

  • Ensure strong stop codon (UAA preferred)
  • Check template 3' end
  • Add release factors (RF1/RF2)
  • Reduce protein concentration
No Soluble Protein

Causes: Aggregation during synthesis Solutions:

  • Lower temperature (25°C → 18°C)
  • Add chaperones
  • Use solubility tag
  • Optimize translation rate

References

CFPS Overview
Extract Preparation
PURE System
Wheat Germ
Codon Optimization
Disulfide Formation
Solubility Tags
Temperature Effects

© adaptyvbio, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/cell-free-expression of adaptyvbio/protein-design-skills.

Open the folder on GitHubat commit 59dd633

Used in 3 other repositories

We found 3 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 3 other GitHub owners. This page covers the copy in adaptyvbio/protein-design-skills, which our catalogue first saw on October 7, 2026.

Compare with similar skills

Cell Free Expression next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

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DiffDock Molecular DockingK-Dense-AI/scientific-agent-skills48k1 repos~3kAutomated safety check: NotesMIT
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Questions about Cell Free Expression

What does Cell Free Expression do?

Guidance for cell-free protein synthesis (CFPS) optimization. Cell Free Expression is an agent skill from adaptyvbio/protein-design-skills. Guidance for cell-free protein synthesis (CFPS) optimization.

When should I use Cell Free Expression?

Cell Free Expression fits situations like: planning CFPS experiments; troubleshooting low yield; optimizing DNA template design for CFPS; expressing difficult proteins (disulfide-rich.

How do I install Cell Free Expression in Claude Code?

Run `npx skills add adaptyvbio/protein-design-skills --skill cell-free-expression -a claude-code`. Or copy the skill folder (skills/cell-free-expression in adaptyvbio/protein-design-skills) into .claude/skills/cell-free-expression in your project. Claude Code loads it when a task matches its description.

How do I install Cell Free Expression in Codex?

Run `npx skills add adaptyvbio/protein-design-skills --skill cell-free-expression -a codex`. Or copy the skill folder (skills/cell-free-expression in adaptyvbio/protein-design-skills) into .agents/skills/cell-free-expression in your project. Codex loads it when a task matches its description.

Can I use Cell Free Expression in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add adaptyvbio/protein-design-skills --skill cell-free-expression -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/cell-free-expression, .gemini/skills/cell-free-expression, .github/skills/cell-free-expression and .opencode/skills/cell-free-expression in your project.

What does Cell Free Expression need to run?

SKILL.md names no scripts, command-line tools or credentials: Cell Free Expression is instructions for the agent only.

Does Cell Free Expression access the network?

SKILL.md names 8 domains. As links in the text: pmc.ncbi.nlm.nih.gov, nature.com, ncbi.nlm.nih.gov, mdpi.com, journals.plos.org, febs.onlinelibrary.wiley.com, pnas.org and frontiersin.org. This is read from the text; nothing was executed.

Is Cell Free Expression safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Cell Free Expression use?

Cell Free Expression is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Cell Free Expression use?

About 2.8k tokens (SKILL.md is roughly 11k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Cell Free Expression?

Skills that share tags, products or a category with Cell Free Expression: Alphafold Database Fetch And Analyze (google-deepmind/science-skills, 3.2k stars), Pymol Visualization (ChatMol/ChatMol, 372 stars), Complexa Binder Design (NVIDIA-BioNeMo/bionemo-agent-toolkit, 478 stars) and DiffDock Molecular Docking (K-Dense-AI/scientific-agent-skills, 48k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Cell Free Expression?

adaptyvbio (a GitHub organization) maintains it in adaptyvbio/protein-design-skills, which has 163 GitHub stars. The repository holds 24 skills in this directory. The repository was last updated on June 11, 2026.

Source: adaptyvbio/protein-design-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.