# Binding Characterization

> >

- **Type:** Skill
- **Install:** `agentstack add skill-adaptyvbio-protein-design-skills-binding-characterization`
- **Verified:** Yes — security-reviewed for prompt injection and unsafe behavior
- **Seller:** [adaptyvbio](https://agentstack.voostack.com/s/adaptyvbio)
- **Installs:** 0
- **Category:** [Agent Skills](https://agentstack.voostack.com/c/agent-skills)
- **Latest version:** 0.1.0
- **License:** MIT
- **Upstream author:** [adaptyvbio](https://github.com/adaptyvbio)
- **Source:** https://github.com/adaptyvbio/protein-design-skills/tree/main/skills/binding-characterization

## Install

```sh
agentstack add skill-adaptyvbio-protein-design-skills-binding-characterization
```

Requires the [AgentStack CLI](https://agentstack.voostack.com/docs/cli). Works with Claude Code, Cursor, and any MCP-compatible agent.

## About

# Binding Characterization: SPR and BLI

## SPR vs BLI Decision Matrix

| Factor | Choose SPR | Choose BLI |
|--------|------------|------------|
| **Sensitivity** | Small molecules, fragments (10μM)** | Fast dissociation in BLI dip | Increase analyte concentration |
| **Low expression** | Not enough signal | Increase biosensor loading |

---

## Mass transport considerations

Mass transport limitation occurs when analyte cannot diffuse to the surface fast enough to maintain equilibrium. This distorts kinetic parameters.

### Symptoms
- Observed kon appears slower than true kon
- Linear association phase (instead of exponential)
- kon varies with ligand density
- Rmax varies with flow rate

### When mass transport matters
- **High-affinity interactions** (kon >10^6 M^-1s^-1)
- **High ligand density** (>500 RU)
- **Slow flow rates** (9): Use slightly acidic buffer

### Reference subtraction
**Always include**:
- Blank reference channel (no ligand)
- Buffer-only injections
- Non-specific binding controls

---

## Regeneration conditions

### SPR regeneration scouting (try in order)

| Condition | Targets | Caution |
|-----------|---------|---------|
| 10 mM Glycine pH 2.0-2.5 | Most protein-protein | May denature ligand |
| 10 mM Glycine pH 1.5 | Strong interactions | Harsh, limit exposure |
| 1-2 M NaCl | Ionic interactions | Mild, try first |
| 10 mM NaOH | Very stable ligands | Can hydrolyze proteins |
| 10 mM Glycine pH 9-10 | Acid-stable proteins | Can aggregate |
| 10 mM EDTA | His-tag, metal-dependent | Strips Ni-NTA |
| 4 M MgCl2 | Hydrophobic interactions | Check ligand stability |

### Regeneration protocol
1. Start with mildest condition (high salt)
2. Test 30s contact time
3. Verify complete dissociation (return to baseline)
4. Verify retained ligand activity (repeat binding)
5. Use shortest effective contact time

### BLI tips
- Tips are often disposable (no regeneration needed)
- For reuse: Same conditions as SPR, but shorter exposure
- Anti-His tips: 10 mM Glycine pH 1.5, 30s
- Streptavidin tips: Generally not regenerable

---

## Common artifacts and solutions

### Biphasic binding
**Symptoms**: Two-rate association or dissociation
**Causes**:
- Sample heterogeneity (aggregates)
- Ligand heterogeneity (multiple conformations)
- Avidity effects (bivalent analyte)

**Solutions**:
- Filter/centrifuge sample
- Use monovalent Fab fragments
- Reduce ligand density
- Fit to heterogeneous model

### Negative dissociation
**Symptoms**: Signal increases during dissociation phase
**Causes**:
- Ligand leaching from surface
- Analyte aggregation on surface
- Reference channel drift

**Solutions**:
- Use capture antibody instead of direct immobilization
- Increase buffer stringency
- Better reference subtraction

### Hook effect
**Symptoms**: Signal decreases at high analyte concentrations
**Causes**:
- Surface saturation + rebinding suppression
- Crowding effects

**Solutions**:
- Reduce analyte concentration range
- Reduce ligand density
- Use smaller analyte fragments

---

## Kinetic data quality checklist

### Before analysis
- [ ] Reference-subtracted properly
- [ ] Buffer injection shows flat baseline
- [ ] Rmax consistent across concentrations
- [ ] No systematic drift during association
- [ ] Complete regeneration (return to baseline)
- [ ] Duplicate/triplicate injections consistent

### Fitting quality
- [ ] Residuals randomly distributed (no systematic deviation)
- [ ] Chi² 10^7 M^-1s^-1), where rates are unreliable
- koff too fast to sample (> 0.1 s^-1) or too slow to measure in the dissociation window (> theoretical maximum (aggregation or avidity)
- Large difference between kinetic and equilibrium KD

---

## References

### Platform comparisons
- [BLI vs SPR Comparison - Sartorius](https://www.sartorius.hr/en/news/blog/bli-vs-spr-choosing-the-ideal-method-for-analyzing-biomolecular-interactions/)
- [BLI vs SPR - Nicoya](https://nicoyalife.com/blog/biolayer-interferometry-vs-surface-plasmon-resonance/)

### SPR protocols
- [SPR Guidelines - van der Merwe, Oxford](https://www.path.ox.ac.uk/wp-content/uploads/2023/09/SPR-guidelines-1.pdf)
- [SPR Experiment Guide - Duke DHVI](https://dhvi.duke.edu/sites/default/files/2022-08/SPR%20Experiment%20Guide%20v1.3.pdf)

### Troubleshooting
- [4 Ways to Reduce NSB in SPR - Nicoya](https://nicoyalife.com/blog/4-ways-reduce-non-specific-binding-spr/)
- [3 Ways to Limit Mass Transfer Effects - Nicoya](https://nicoyalife.com/blog/3-ways-to-limit-mass-transfer-effects/)
- [Suppressing NSB in BLI - ACS Omega](https://pubs.acs.org/doi/10.1021/acsomega.1c05659)

### Regeneration
- [SPR Regeneration - SPRpages](https://www.sprpages.nl/kinetics/regeneration)
- [Mastering Regeneration - Nicoya](https://nicoyalife.com/blog/regeneration-buffer-spr-experiment/)

### Mass transport
- [Mass Transport Limitation in SPR - PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC4134667/)
- [Mass-Transfer Kinetics - SPRpages](https://www.sprpages.nl/data-fitting/kinetic-models/mass-transfer)

## Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

- **Author:** [adaptyvbio](https://github.com/adaptyvbio)
- **Source:** [adaptyvbio/protein-design-skills](https://github.com/adaptyvbio/protein-design-skills)
- **License:** MIT

Install and usage instructions live in the source repository linked above.

## Pricing

- **Free** — Free

## Security capabilities

Automated source analysis of v0.1.0 — what this tool can access:

- **Network access:** no
- **Filesystem access:** no
- **Shell / process execution:** no
- **Environment & secrets:** no
- **Dynamic code execution:** no

*"Yes" means the capability is present in the source — more access means more to trust, not that it is unsafe.*


## Versions

- **0.1.0** — security scan: passed — Imported from the upstream source.

## Links

- Listing page: https://agentstack.voostack.com/l/skill-adaptyvbio-protein-design-skills-binding-characterization
- Seller: https://agentstack.voostack.com/s/adaptyvbio
- Browse the marketplace: https://agentstack.voostack.com/browse

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