Controls for peptide experiments
The vehicle, scrambled and concentration controls that make a peptide result interpretable, plus compound-specific controls for copper and lipidated peptides.
The commonest reason a peptide experiment produces an uninterpretable result is not the peptide; it is the absence of the control that would have distinguished a real effect from the vehicle, the counter-ion, an impurity or an artefact of handling. This note lists the controls worth including in research peptide work, why each exists, and which of the catalogue compounds particularly need them. All Alphex products are for laboratory and in-vitro research only.
The essential controls
- Vehicle control. The diluent alone, at the same final concentration, prepared and stored identically. Non-negotiable when the stock contains benzyl alcohol (0.9% in bacteriostatic water), DMSO, or a buffer that differs from the assay medium. See benzyl alcohol explained.
- Scrambled-sequence peptide. The same residues in a randomised order, same length, same salt form, same purity. This controls for the counter-ion, for non-specific peptide effects (charge, surface activity) and for anything the vehicle control misses. It is the single most informative control in peptide work and the one most often omitted.
- Concentration series. A single concentration cannot distinguish a specific effect from a threshold artefact. A series also reveals non-monotonic behaviour, which often signals aggregation at the top end.
- Freshly prepared versus stored stock. Running the same concentration from a fresh vial and from the working stock detects degradation and adsorption losses. See recognising degradation.
- Batch control. Where a project spans batches, run an overlap experiment with both. Record batch numbers throughout. See record keeping.
Controls for specific compounds
- GHK-Cu: the copper is active in its own right in many systems. Include a copper-salt-only control at matched copper concentration, and ideally free GHK at matched peptide concentration, to attribute an effect to the complex rather than to either component. See GHK versus GHK-Cu.
- GLP-3 (RT) and other lipidated peptides: aggregation and plastic adsorption make the delivered concentration uncertain. Include a solubility check (clarity, and ideally a concentration measurement of the working solution) and use low-binding plastic throughout. See lipidated peptides.
- Ipamorelin and other D-amino-acid peptides: protease resistance means standard degradation controls behave differently; do not assume a peptide "will have degraded by" a given time. See D-amino acids.
- Any peptide in cell culture: an endotoxin control (polymyxin B, or a heat-inactivated comparison) where LPS-sensitive cells are used, since research peptides are not endotoxin-tested by default. See endotoxin testing.
Design points that prevent trouble
- Prepare all arms from the same stock on the same day where possible.
- Randomise and blind scoring for any subjective endpoint.
- Report concentration in molar units with the net-content assumption stated. See calculating concentration.
- Record purity, identity, supplier and batch for the peptide in the methods; increasingly, journals ask.
- Keep an aliquot of the batch used, frozen, in case a result later needs re-examination.
Frequently asked questions
Where do I get a scrambled control peptide?
Any custom peptide synthesis company will make one to a specified scrambled sequence; Alphex does not offer custom synthesis. See why the catalogue is small.
Is a "no treatment" arm enough?
No. It does not control for the vehicle or for non-specific peptide effects.
How do I control for impurities?
Buy to a tight purity specification, and compare batches with different impurity profiles if a result is critical. See 98% versus 99+%.
Alphex research peptides are supplied for laboratory and in-vitro research by qualified researchers only. They are not authorised for human or veterinary use.
Research use only. Alphex products are supplied exclusively for laboratory and in-vitro research by qualified researchers. They are not authorised for human or veterinary use, and nothing in this note is advice on any such use.
Published 18 March 2026. Alphex reviews research notes when the testing method, the catalogue or UK guidance changes.