Concretely: survodutide · 2–8 °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.
Has anyone verified this independently?
Probably not at 2–8 °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 2–8 °C sits between or beyond the published points and what you will find is bracketing rather than a measurement. 2–8 °C is the condition the rule of thumb is anchored to, so it is the baseline rather than a multiplier: everything else in this thread is quoted relative to it. Whatever you find, check what was measured before you use it: a paper reporting purity at 2–8 °C has not measured content, and the two fail at different rates for different reasons.
Start with the sequence, because which pathways are available depends on which residues are present.
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.
| State | Condition | Usable window | Basis |
|---|---|---|---|
| Lyophilised solid | −20 °C, sealed, dry | 24–36 months | Supplier guidance |
| Lyophilised solid | 2–8 °C, sealed | 12–24 months | Supplier guidance |
| Lyophilised solid | 25 °C, sealed | 4–8 weeks | Extrapolated (Arrhenius) |
| Lyophilised solid | 40 °C, sealed | 1–2 weeks | Extrapolated |
| Solution, preserved | 2–8 °C | 28 days | USP microbiological convention |
| Solution, preserved | 25 °C | 3–7 days | Extrapolated |
| Solution, unpreserved | 2–8 °C | 24 hours | USP microbiological convention |
Windows for the solid state are chemical; windows for solution are microbiological and usually shorter than the chemical limit.
Aggregation is physical: peptides unfold at air-liquid interfaces and associate. Shaking maximises that interface, which is why swirling and shaking produce visibly different outcomes on the same vial.
Adsorption losses at low concentrations are quantified in formulation studies and are the reason carrier proteins are used in dilute preparations.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Swirl, never shake. Aggregation is a handling problem more than a time problem.
Analytical standards and reagents with traceable certificates. Every quantitative result you read inherits the accuracy of the standard behind it.
Shop standardsThe relevant point is that a mass shift of plus one dalton is deamidation and plus sixteen is oxidation, so degradation is often visible in a mass spectrum if anyone looks.
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.
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.
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.
Answering this needs the physical state, since a dry powder is protected from most of these and a solution is protected from none.
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.
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.
Deamidation via the succinimide intermediate is well characterised, with sequence-dependent rates highest for asparagine-glycine motifs.
Cold, dry, dark, still. Those four words cover most of the mitigation.
edited 8 Sept 2025 by Dr_Otto_Lindqvist — corrected a unit error in the worked example
Aggregation is a physical process and is the one most often caused by handling rather than by time.
Light exposure matters for tryptophan-containing sequences and for anything with a chromophore. Amber vials and a closed box are free mitigations.
Sequence decides which pathways are even available. Check the residues.
This is answerable from the chemistry rather than from anecdote, which is unusual and welcome.
Adsorption onto glass and plastic is significant at low concentrations — micrograms per millilitre — and negligible at milligrams per millilitre. It is the usual explanation for an apparent loss in a dilute preparation.
Metal-catalysed oxidation of methionine is documented across peptide and protein formulations and is why chelators appear in some formulations.
At dilute concentrations, suspect adsorption before you suspect chemistry.
edited 6 Nov 2025 by ten_mg_vial — fixed an arithmetic slip in the third paragraph
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.