> ## Documentation Index
> Fetch the complete documentation index at: https://docs.adaptyvbio.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Cell-Free Protein Expression

> High-throughput protein production using cell-free expression systems for rapid prototyping and functional studies

Cell-free protein expression uses the molecular machinery components of cells for protein synthesis without requiring living cells. This allows for rapid protein expression, significantly reducing the time from DNA to functional protein.

## How It Works

The cell-free system contains extracted cellular components—ribosomes, tRNAs, amino acids, and energy sources—reconstituted in a controlled environment. DNA templates are directly added to this system, which then transcribes and translates proteins within hours.

## Our System

We use an E. coli-based cell-free system that has been optimized to handle disulfide bond-containing proteins. Our system has successfully expressed a wide range of protein formats including:

* **scFvs** (single-chain variable fragments)
* **Nanobodies**
* **FABs** (antigen-binding fragments)
* **De novo designed proteins**
* **Various other protein formats**

## Key Benefits

<CardGroup cols={2}>
  <Card title="Rapid Expression" icon="clock">
    Protein production within hours instead of days, enabling faster design-build-test cycles.
  </Card>

  <Card title="Disulfide Bond Formation" icon="link">
    Optimized system components support proper folding of proteins requiring disulfide bonds.
  </Card>
</CardGroup>

## Applications

Cell-free expression enables rapid prototyping for:

* **Binding studies**: Direct use in BLI and SPR assays
* **Protein screening**: Quick evaluation of multiple variants
* **Functional characterization**: Immediate availability for downstream assays

## Integration with Other Technologies

Expressed proteins integrate seamlessly with our analytical workflow:

* **Affinity purification**: Direct capture using tagged proteins
* **Binding assays**: Immediate use in binding studies
* **Thermostability**: Direct input to nanoDSF analysis
* **Quality control**: Real-time monitoring capabilities

## Frequently Asked Questions

<AccordionGroup>
  <Accordion title="What is Cell-Free Expression at Adaptyv?">
    Adaptyv uses a **fully reconstituted, cell-free protein expression system** made from individually purified components of the *E. coli* transcription–translation machinery. This allows for **high control, low background**, and compatibility with sensitive or synthetic protein designs.

    Adaptyv bypasses the need for plasmid cloning by directly using **full-length double-stranded linear DNA (dsDNA)**, which is **ordered from external providers** and ready for immediate use in expression reactions. In some workflows, tag sequences may be appended in-house, and longer-term processes may involve assembling genes from fragments.

    **Our system includes:**

    * **Ribosomes**
    * **tRNAs and synthetases**
    * **Transcription and translation factors**
    * **T7 RNA polymerase** (for transcription)
    * **Nucleotides, amino acids, and energy sources**
    * **DsbC** (a disulfide bond isomerase)
    * **Oxidized and reduced glutathione**

    **Process:**

    * The DNA is transcribed into mRNA by T7 RNA polymerase
    * The mRNA is translated into protein by the ribosomes
    * Proteins are synthesized **within a few hours**

    Maximum yield is usually reached **within 4–6 hours**, though shorter reactions (e.g., 2–3 hours) are often sufficient for functional assays or screening purposes.

    **Typical yield:** 50-300 **µg/mL** for scFvs and 50-600 **µg/mL** for small de novo proteins. (Yield may vary based on sequence, folding, and template design).

    <Tip>
      By using full-length dsDNA with the PURE system, Adaptyv accelerates the design-test-learn loop, making protein expression faster, cleaner, and more programmable.
    </Tip>
  </Accordion>

  <Accordion title="Why do you express in Pure cell-free system instead of cell culture?">
    There are several advantages of cell-free systems in general, and "Pure"-type cell-free systems in particular:

    **1. Toxic protein expression**
    One can express proteins that are normally toxic to cells. In cell culture, if the protein damages cellular systems required for growth, cells die early and protein yield is very poor. In cell-free systems, as long as the protein doesn't interfere with the translation system, there's no problem.

    **2. Direct DNA addition**
    One can mix DNA directly with the translation mix - no need for cell transfection. Cell transfection requires cost, time, and has less than 100% efficiency.

    **3. No basal expression issues**
    No need for expression induction in cell-free systems. In cell culture, proteins take energy from cells, slowing growth. Therefore, expression must be heavily repressed during growth phase, then induced with inductor molecules.

    **4. Linear DNA compatibility**
    In "Pure" cell-free systems, linear DNA can be used instead of circular plasmids, since degrading enzymes are removed. This reduces cost and time for DNA preparation.

    **5. Consistent component ratios**
    In "Pure" systems, we mix purified components, so there's never component depletion, and ratios (energy sources, ribosomes) remain constant. This isn't true in live cell culture systems.
  </Accordion>

  <Accordion title="Why do some proteins express poorly or not at all?">
    Several factors can affect protein expression success:

    **1. Solubility issues**
    Some protein sequences tend to self-aggregate and precipitate out of solution, preventing sensor loading. This occurs when proteins have hydrophobic patches on the outside that cause them to stick together to avoid water exposure.

    **2. mRNA structure and interference**

    * **Secondary structures**: mRNA secondary structures can prevent proper translation by ribosomes
    * **Machinery interaction**: Some proteins may interact with cellular machinery, causing premature translation termination

    **Our optimization approach:**

    * Codon optimization software minimizes mRNA secondary structure stability
    * However, this may not be possible in all cases depending on amino acid sequence

    **Common problematic features:**

    * High hydrophobicity scores
    * Repetitive sequences
    * Unusual amino acid compositions
    * Large size (>50 kDa proteins may have lower success rates)

    <Note>
      Our team can provide sequence analysis and optimization recommendations to improve expression success rates for challenging proteins.
    </Note>
  </Accordion>

  <Accordion title="Does Adaptyv support non-standard amino acids or cyclic peptide synthesis?">
    **Non-standard amino acids:**

    * Our standard PURE system uses the 20 canonical amino acids
    * Non-canonical amino acid incorporation is possible but requires specialized protocols
    * Contact our team to discuss specific requirements for modified amino acids

    **Cyclic peptides:**

    * Traditional cyclic peptides require post-translational cyclization
    * Our cell-free system can potentially accommodate cyclization reactions
    * Requires custom development for specific cyclization chemistry

    **Alternative approaches:**

    * Disulfide-bonded peptides: Supported through DsbC and glutathione system
    * Split-intein mediated cyclization: Under development
    * Chemical cyclization post-expression: Possible with appropriate chemistry

    <Tip>
      For non-standard amino acids or cyclic peptides, we recommend discussing your specific requirements with our technical team to determine feasibility and develop custom protocols.
    </Tip>
  </Accordion>
</AccordionGroup>