> ## 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.

# scFv

> Minimal antibody fragment with variable domains linked by a peptide

scFv (single-chain variable fragment) is the smallest functional antibody fragment, consisting of VH and VL domains connected by a flexible peptide linker.

<CardGroup cols={2}>
  <Card title="Size" icon="ruler">
    \~25-30 kDa
  </Card>

  <Card title="Valency" icon="link">
    Monovalent (1 binding site)
  </Card>

  <Card title="Format" icon="dna">
    Single polypeptide chain
  </Card>

  <Card title="Production" icon="bacteria">
    Bacterial expression
  </Card>
</CardGroup>

## Structure

<Warning>
  Linker length (typically 15-20 amino acids) is critical for proper folding and stability.
</Warning>

* **VH domain** - Variable heavy
* **VL domain** - Variable light
* **Flexible linker** - Common: (Gly₄Ser)₃

## Key Applications

<Tabs>
  <Tab title="Phage Display">
    Easy library display and selection
  </Tab>

  <Tab title="Therapeutics">
    Good tissue penetration, low immunogenicity
  </Tab>

  <Tab title="Bispecifics">
    Building blocks for complex formats
  </Tab>
</Tabs>

<Tip>
  Ideal for applications requiring small size and single-gene expression.
</Tip>