> ## 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.

# Biolayer Interferometry (BLI)

> Label-free optical technique for real-time protein binding measurements

BLI measures real-time protein binding by detecting changes in light interference patterns when molecules bind to a sensor surface.

<CardGroup cols={2}>
  <Card title="Method" icon="eye">
    Label-free optical detection
  </Card>

  <Card title="Data" icon="chart-line">
    Real-time kinetics
  </Card>

  <Card title="Sensitivity" icon="magnifying-glass">
    Sub-nanomolar detection
  </Card>
</CardGroup>

<Steps>
  <Step title="Ligand Immobilization">
    Designed proteins immobilized on biosensor tip using Twin-Strep-Tag
  </Step>

  <Step title="Analyte Binding">
    [Target protein](/docs/experiment-setup/target-proteins) flows over sensor surface
  </Step>

  <Step title="Signal Detection">
    Binding causes detectable light interference shift
  </Step>

  <Step title="Kinetic Analysis">
    Association and dissociation rates calculated
  </Step>
</Steps>

## Key Parameters

<Tip>
  BLI provides three critical binding parameters: k\_on (association), k\_off (dissociation), and K\_D (equilibrium constant).
</Tip>

* **k\_on** - Association rate constant
* **k\_off** - Dissociation rate constant
* **K\_D** - Equilibrium dissociation constant (k\_off/k\_on)

## How we use BLI at Adaptyv

We use the **Gator Bio Pro** for BLI measurements. Our typical workflow involves:

* **Protein immobilization**: User-designed proteins are expressed with a linker and Twin-Strep-Tag
* **Target protein binding**: Biosensor is moved into solutions of the target protein at different concentrations
* **Kinetic analysis**: Real-time binding measurements to determine association and dissociation kinetics

This approach enables efficient characterization of binding interactions for designed proteins with high sensitivity.

## Related pages

* [Binding](/docs/experiment-types/binding)
* [Binding Data Package](/docs/experiment-setup/binding-data-package)