Before the first peptide assay: define what your controls must show
A control is useful when it answers a defined question. Plan the comparison, the acceptance criteria and the follow-up before interpreting a peptide assay.
Before an assay produces a number, the team should agree on what would make that number interpretable. Which comparison represents the baseline? What shows that the assay responded as expected? What would cause the run to be investigated rather than reported as a finding?
Writing those answers down is often more valuable than adding controls by habit.
Define the purpose of each control
The Assay Guidance Manual is an NIH-supported resource for assay methods. Our worksheet below is an original planning aid: it asks the team to document the purpose of each comparison rather than prescribing a universal set of controls.
The precise implementation depends on the assay. A positive control is useful only if the team can explain the response it is expected to demonstrate. A baseline control is useful only if the comparison to the experimental condition is appropriate.
Use a planning worksheet
For an in-vitro study, complete a short worksheet before collecting the main dataset:
| Planning question | Decision to document |
|---|---|
| What is the endpoint? | The observation or measurement being interpreted |
| What establishes the baseline? | The comparison condition and why it is appropriate |
| What demonstrates an expected response? | The reference or positive control, if available |
| What could the vehicle contribute? | How the assay accounts for the sample's vehicle |
| How will a run be accepted? | Predefined criteria and who evaluates them |
| What happens when a control fails? | The investigation, repeat or exclusion process |
| What links the result to the material? | Lot, preparation and experimental record identifiers |
This is a discussion aid for the research team, not a validated protocol.
Make vehicle comparisons explicit
Vehicle conditions deserve their own line in the plan. The manual’s Assay Operations for SAR Support chapter emphasizes assessing DMSO compatibility for the particular assay. This supports asking about vehicle effects; it does not prescribe a solvent condition for every peptide experiment.
Do not turn that example into a universal solvent instruction. Identify the vehicle relevant to the actual assay, consult the method and document how its potential contribution will be assessed.
Decide how results will be compared over time
A reference result from one run is not automatically a substitute for a control in another. Ask what must stay consistent when changing a material lot, operator, instrument or procedure.
Keep a dated record of those changes alongside the control results. If a trend appears, the team should be able to see what changed without reconstructing the study from email.
Separate an observation from a product claim
An assay observation belongs to a defined material, method and set of conditions. Keep those details attached when communicating the result. A laboratory observation alone should not be presented as evidence of human benefit or as a general performance claim for a commercial product.
For the material side of that record, start with the relevant catalog documentation and Quality & COAs guidance.
This library discusses laboratory research and published methods. It does not provide medical advice or establish the suitability of any product for human or veterinary use.