> For the complete documentation index, see [llms.txt](https://docs.rplpeptides.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rplpeptides.com/docs/guides/peptide-reconstitution-guide.md).

# Peptide Reconstitution Guide

## 1. Step-by-Step Reconstitution Protocol

**Step 1: Equilibration** Remove the lyophilized vial from -20°C storage. Allow to equilibrate to room temperature for **15–30 minutes** without opening. This prevents moisture condensation on the lyophilized cake.

**Step 2: Calculation** Calculate the required solvent volume:

```
Target Concentration (mg/mL) = Peptide Mass (mg) / Solvent Volume (mL)
Volume (mL) = Peptide Mass (mg) / Target Concentration (mg/mL)
```

For molarity:

```
Molarity (M) = Concentration (mg/mL) / Molecular Weight (g/mol)
```

**Step 3: Solvent Addition**

1. Sterilize vial septum with 70% ethanol wipe
2. Use a sterile syringe and needle
3. Add solvent **gently along the inner wall** of the vial
4. Do NOT inject directly onto the lyophilized cake
5. Remove needle and cap securely

**Step 4: Dissolution**

1. Gently swirl or invert the vial
2. Let stand for 5–10 minutes
3. Visually inspect — solution should be clear with no visible particles
4. If incomplete dissolution, gently warm to 25°C or sonicate briefly (30 sec water bath)

**Step 5: Aliquoting**

1. Prepare labeled, low-binding microcentrifuge tubes
2. Dispense single-use volumes (10–50 µL)
3. Snap-freeze in liquid nitrogen (optional, for >6 month storage)
4. Store at -20°C

## 2. Recommended Diluent Selection

| Diluent           |  pH | Best For                    | Notes                              |
| ----------------- | :-: | --------------------------- | ---------------------------------- |
| Sterile WFI       | 5–7 | Most peptides               | First choice; minimal interference |
| PBS (1×)          | 7.4 | Cell culture assays         | Physiological osmolarity           |
| 0.9% Saline       | 5.5 | In vivo injections          | Isotonic                           |
| 10 mM Acetic Acid | 3.5 | Basic/hydrophobic peptides  | Improves solubility                |
| 0.1% DMSO in PBS  |  —  | Hydrophobic stock solutions | Keep DMSO ≤0.1% final              |

## 3. Reconstitution Troubleshooting

| Problem                 | Likely Cause                          | Solution                                                              |
| ----------------------- | ------------------------------------- | --------------------------------------------------------------------- |
| **Cake won't dissolve** | Lyophilized cake too compact          | Add more solvent; increase incubation time; warm to 25°C              |
| **Solution cloudy**     | Aggregation or precipitation          | Dilute further; adjust pH; add co-solvent                             |
| **Gel formation**       | High concentration, β-sheet formation | Reduce concentration; add denaturant (6 M urea) compatible with assay |
| **Foaming**             | Surfactant-like peptide sequence      | Let settle before aliquoting; avoid pipetting air                     |
| **Loss of activity**    | Degradation or aggregation            | Verify storage; use fresh aliquot; check pH                           |

## 4. Important Notes

* Always record: batch number, date reconstituted, solvent used, final concentration, aliquoting volume
* Use low-binding tubes and pipette tips to minimize surface adsorption
* Do not vortex peptide solutions at any stage
* Do not subject to repeated freeze-thaw cycles (> 3×)
* For long-term storage of reconstituted peptides, snap-freeze aliquots in liquid nitrogen

***

*For reconstitution inquiries: <technical@rplpeptides.com>*


---

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