Seven checks that separate a supplier who tests every lot from one who copies a certificate: lot-matched COAs, a named lab, LC-MS identity, net peptide content, endotoxin, a real address, and how they talk about use. With a worksheet, an example support exchange, and the FDA's own test for intended use.
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Any researcher can send a sealed vial to an independent analytical lab and get purity by HPLC, identity by mass spectrometry and the milligrams actually in the vial back within about a week. What it costs, what to send, how to read the result against the supplier's certificate, and what to do when they disagree.
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A reviewer should be able to reconstruct exactly what was in the vial and what reached the assay. That takes eleven facts: supplier, product, lot, purity with method, identity with method, net peptide content, salt form, endotoxin, storage, reconstitution and vehicle. What each one is for, a template paragraph, and what NIH expects for key chemical resources.
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A research peptide label carries seven fields that matter: compound name, net amount, lot number, purity claim, storage instruction, the research-use statement and the supplier. What each one should say, how to check it against the certificate, a worked label-to-certificate comparison, and the three things a label cannot tell you.
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Almost every research peptide is built by solid-phase synthesis, one residue at a time on a resin bead, then cleaved, purified by HPLC and freeze-dried. Each step leaves a characteristic impurity, and each impurity shows up on a specific line of the certificate. The six steps, the yield arithmetic, what a crude chromatogram looks like, and the map between the two.
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Endotoxin is a bacterial residue that survives filtration and freeze-drying and can trigger immune and inflammatory responses in cultured cells on its own. The certificate reports it in endotoxin units per milligram. How the test works, a dilution table for every catalog vial, which cell types care, and when the number matters.
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Every vial in the catalog reconstituted at 1, 2 and 3 mL, with the resulting mg/mL, micrograms per insulin-syringe unit, and the draw for a 250 mcg aliquot. Plus the molar concentration from PubChem weights, and the two vials that need a different approach.
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Two different compounds are sold under the name CJC-1295. One carries a Drug Affinity Complex that binds albumin and acts for days; the other is the bare 29-residue GRF analogue that acts for minutes. What the difference is, how the literature describes each, and how the certificate tells them apart.
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Bacteriostatic water is sterile water with 0.9% benzyl alcohol added to stop microbial growth in a vial drawn from repeatedly. Benzyl alcohol is not inert to cultured cells. What the preservative is for, how much of it reaches a culture at each dilution, when to use sterile water or buffer instead, and how to control for it.
Read the post →The blog covers buying, handling and research-design questions as they come up. The evergreen material lives in the guides: reconstitution, reading a certificate of analysis, storage and stability, one research guide per compound and the glossary.
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