Frequently Asked Questions About Research Peptides (Lab-Focused)
This content is for laboratory research purposes only. Not for human or animal use.
New and experienced researchers often have similar questions about handling, storing, and using research peptides. This FAQ addresses the most common lab-focused questions.
What is the difference between a peptide and a protein?
Peptides are short chains of amino acids, typically fewer than 50 residues. Proteins are longer chains that fold into complex structures. Peptides are often used as signaling molecules, enzyme substrates, or antibody antigens in research.
How should I store lyophilized (freeze-dried) peptides?
Store lyophilized peptides at -20°C in a sealed container with desiccant. Allow the vial to reach room temperature (15–30 minutes) before opening to prevent condensation. Protect from light if the peptide is photosensitive (check COA).
How do I choose the right solvent for reconstitution?
- Most peptides: Sterile water or PBS (pH 7.0)
- Hydrophobic peptides: 0.1–1% acetic acid
- Very hydrophobic (for HPLC/MS): 10–30% acetonitrile
- Extremely hydrophobic (last resort): DMSO (dilute before use)
If the peptide does not dissolve in water, try dilute acetic acid. Do not vortex – swirl gently.
What purity do I need for my experiment?
- Western blot / ELISA: 90–95%
- Receptor binding / enzyme activity: 95–98%
- Cell culture: 98%+ with endotoxin testing
- Structural studies (NMR, crystallography): 99%+
Higher purity is safer but more expensive. Match purity to your application.
How do I read a Certificate of Analysis (COA)?
Look for three key things:
- HPLC purity (target ≥98% for most applications)
- MS observed mass (within ±1.0 Da of calculated)
- Lot number matching the vial label
Not every COA includes a printed chromatogram – that is fine. The numerical purity and MS data are the essentials.
How long do reconstituted peptides last?
- At 4°C (refrigerator): 1–2 weeks
- At -20°C: 1–3 months
- At -80°C: 6–12 months (with stabilizers like BSA)
Always aliquot into single-use volumes to avoid freeze-thaw cycles. Never refreeze a thawed aliquot.
Why does my peptide not dissolve?
Possible reasons:
- Wrong solvent (try acetic acid or acetonitrile)
- Peptide aggregated (sonicate briefly in a water bath)
- Peptide degraded (check COA date and storage)
If multiple solvents fail, contact the supplier – the product may be compromised.
Can I use peptides in cell culture?
Yes, but use peptides with:
- Purity ≥98%
- Endotoxin level <1.0 EU/mg (tested by LAL method)
- Sterile filtration (0.22 µm) before adding to cells
Some peptides are toxic at high concentrations – perform a dose-response pilot.
What is the difference between TFA salt and acetate salt?
TFA (trifluoroacetic acid) is the standard counter-ion from HPLC purification. For most assays, TFA is fine. For cell culture or sensitive MS/NMR, request acetate salt or TFA-free custom synthesis.
My peptide arrived clumped. Is it still usable?
Minor clumping can happen due to static or moisture. If the powder is not discolored and dissolves completely in the recommended solvent, it may still be usable. If it does not dissolve, or if it appears sticky or gel-like, contact the supplier for a replacement.
How do I know if my peptide has degraded?
Signs of degradation:
- Clumping or discoloration (lyophilized)
- Cloudiness or precipitate (reconstituted)
- Shifted retention time or new peaks on HPLC
- Loss of expected activity in control experiments
If degraded, discard and order fresh – using degraded peptide invalidates results.
Can I request a custom peptide sequence?
Yes. Most suppliers offer custom synthesis for sequences not available in standard catalogs. You will need to provide the amino acid sequence, desired purity, and quantity. Custom peptides typically take 2–4 weeks.
Research Peptides: Quick Summary
- Store at -20°C with desiccant, protect from light.
- Reconstitute in the correct solvent – do not vortex.
- Match purity to your application.
- Always review the COA before use.
- Aliquot reconstituted peptides – never refreeze.
Have a Question Not Listed Here?
Our research support team can answer specific questions about storage, reconstitution, purity, or custom orders. Contact us with your experiment details.
Optimus Labs supplies lab-tested research peptides, each provided with a downloadable Certificate of Analysis. Explore our Quality & Testing standards or browse the catalogue.
