How to Qualify a Recombinant Protein Supplier for Your Lab

Updated 2026-09-28

Purity by HPLC/SDS-PAGE, endotoxin, lot-to-lot consistency, CoA and cold-chain shipping — the checklist university labs should run before reordering.

The checklist

Purity by HPLC and SDS-PAGE, endotoxin level, lot-to-lot consistency, expression system, tag and carrier status, and a CoA you can file for your institution. Then: shipping temperature, customs documentation and a supplier who answers technical questions quickly.

Why it matters more than price

In assay development a silent lot shift or endotoxin contamination can waste weeks of work. The cheapest protein without documentation is usually the most expensive decision in the lab.

Qualify once, reorder with confidence

Run a side-by-side evaluation against your current batch, record the tested lot number, then reorder the validated lot rather than re-qualifying from scratch.

Documentation is part of the product, not paperwork

It is tempting to treat the Certificate of Analysis as an administrative artefact that procurement files away. In practice it is the only evidence you will ever hold about the material in your freezer. A CoA that reports a purity figure without naming the method cannot be compared with another supplier's figure, because SDS-PAGE and HPLC answer different questions. A CoA that omits the expression system tells you nothing about glycosylation or host-cell protein carryover. A CoA without a lot number cannot be tied to your experiment at all. When a result stops replicating six months later, the CoA is what lets you ask whether the material changed rather than guessing that your technique did. Suppliers who understand this publish the method next to the number; suppliers who do not have left you a figure you cannot act on.

The questions that sort suppliers fastest

Three questions do most of the sorting. Ask for the Certificate of Analysis of the current lot before you order rather than after — a supplier who will not send it has already answered. Ask what varies between lots and how you would be told about a change to the manufacturing process; the answer reveals whether change control exists as a practice or only as a word. Then ask one technical question that is specific to your application: whether the material is glycosylated, or what the endotoxin level is, or whether a tag sits near a particular epitope. A supplier who routes that question to someone technical and answers it in a day is a different kind of organisation from one who replies with a catalogue link — and you have learned which one you are dealing with before any money changed hands.

Ask a technical question