Concretely: semaglutide · 37 °C.
The claim is plausible, which is exactly why I want to check it.
I am able to read a paper if someone points me at one.
Is there data behind this, or is it received wisdom?
Probably not at 37 °C specifically, because that is not where stability programmes take their readings. Accelerated work is conventionally run at 25 °C and 40 °C, with the refrigerated condition as the control, so 37 °C sits between or beyond the published points and what you will find is bracketing rather than a measurement. 37 °C is 32 kelvin above the 5 °C middle of a 2–8 °C refrigerator. The ten-degree rule of thumb — degradation rate roughly doubling per 10 K — makes that about 9.2 times the refrigerated rate, which is an order-of-magnitude statement and not a shelf life. Whatever you find, check what was measured before you use it: a paper reporting purity at 37 °C has not measured content, and the two fail at different rates for different reasons.
Answering this needs the physical state, since a dry powder is protected from most of these and a solution is protected from none.
Oxidation targets methionine, cysteine and tryptophan, adding sixteen daltons per oxygen. It is catalysed by trace metals and promoted by dissolved oxygen and by light.
Hydrolysis cleaves the backbone, most readily at aspartate-proline and aspartate-glycine sequences, and is acid-catalysed. In a dry solid it barely proceeds at all.
Metal-catalysed oxidation of methionine is documented across peptide and protein formulations and is why chelators appear in some formulations.
Swirl, never shake. Aggregation is a handling problem more than a time problem.
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Browse resultsAnswer first: the degradation pathways worth knowing are hydrolysis, deamidation, oxidation, aggregation and adsorption, and each has a different trigger and a different mitigation.
Light exposure matters for tryptophan-containing sequences and for anything with a chromophore. Amber vials and a closed box are free mitigations.
Freeze-thaw cycling drives aggregation through concentration at the ice interface and pH shifts as buffer components crystallise out at different rates. Each cycle costs something.
Deamidation via the succinimide intermediate is well characterised, with sequence-dependent rates highest for asparagine-glycine motifs.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Cold, dry, dark, still. Those four words cover most of the mitigation.
Aggregation is a physical process and is the one most often caused by handling rather than by time.
Deamidation converts asparagine or glutamine to the corresponding acid via a succinimide intermediate, adding one dalton. It is base-catalysed, accelerates above neutral pH and is the dominant aqueous pathway for many peptides.
A mass spectrum resolves most of this: minus eighteen is dehydration or succinimide, plus one is deamidation, plus sixteen is oxidation, and an unchanged mass with a shifted retention time is an isomer.
Apparent loss in a dilute preparation is usually adsorption rather than degradation and is worth ruling out first.
A mass spectrum names the pathway. Plus one, plus sixteen, minus eighteen.
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