A reagent substitution can begin as a purchasing problem and become a scientific ambiguity if the original and replacement materials are not clearly distinguished. Before the study starts, record what changed, why it changed and what evidence supports using the replacement for the intended question.
Keep the original requirement visible
eLife’s 2018 explanation of Key Resources Tables emphasises recording resource sources and identifiers to improve the handling of research-material information. Such identification provides a useful foundation for documenting a substitution, although it does not itself establish equivalence.eLife — Rigour and transparency with Key Resources Tables (opens in a new tab)
Start with the material specified in the study plan and retain that version. Record the replacement in a new entry rather than editing the original as though it had always been intended.
State the reason for the proposed change: availability, an unresolved specification, a different format or another concrete constraint. Keeping the reason separate from the scientific assessment prevents convenience from being mistaken for evidence.
If the original material was never fully defined, acknowledge that limitation. It may be impossible to establish an exact match to a requirement that omitted essential identity information.
Compare the fields that could change the question
| Field | Original and replacement comparison |
|---|---|
| Molecular identity | Sequence, termini, labels and other relevant structural features |
| Supplied form | Counterion, formulation and defined quantity basis |
| Evidence | Available identity, content and other relevant analytical information |
| Decision | Accepted differences, unresolved questions and responsible researcher |
A hypothetical replacement might preserve the residue sequence but change a terminal group. Record both facts. Describing it simply as “same peptide, different supplier” would conceal a potentially important identity difference.
A different catalogue number may instead reflect a pack-size change with no documented molecular change. That possibility still needs confirmation; an administrative difference and a chemical difference should not be conflated.
The comparison should state where information is missing. Blank cells are easily misread as “no difference”, so use explicit wording such as “not supplied for the proposed replacement”.
Decide what must be checked before proceeding
The responsible researcher should assess whether the substitution preserves the study’s intended comparison. Required checks depend on that comparison; there is no single test that proves all reagents interchangeable.
For an exploratory assay, the decision may involve a defined preliminary comparison. For an experiment intended to reproduce a published result, an unresolved molecular difference may limit the claim of replication even if the experiment proceeds.
Record the planned assessment before seeing the replacement’s results where possible. This reduces the temptation to define acceptability around whichever result appears most convenient.
Carry the decision into the study record
Update the working study plan to identify the material that will actually be used, while retaining the original plan and substitution record. Link the relevant correspondence and supporting documents rather than relying on a verbal agreement.
When writing the eventual methods, report the actual reagent and any difference relevant to interpretation. A reader should not have to infer the substitution from inconsistent product names across files.
A complete record does not make every substitution harmless. It makes the decision and its limits visible before they become entangled with the results the study is trying to explain.
Sources and further detail
- eLife — Rigour and transparency with Key Resources Tables (opens in a new tab)
Publisher explanation dated 9 April 2018, checked through its indexed text. Used for resource identification, not as evidence of reagent equivalence or a current universal submission rule.
Sources checked 20 September 2026. Request examples are original illustrations, not actual orders, supplier commitments or Novum product specifications. This article has not undergone independent scientific peer review.