Accepted answer
two weeks is 14 days at a temperature where the chemistry all but stops and the physics does not. minus 80 °C is 85 kelvin below a refrigerator, and below the glass transition of a lyophilised cake the ten-degree rule of thumb stops applying at all — solid-state chemistry is not slow liquid chemistry, it is a different regime, and the failure modes that survive it are mechanical rather than chemical. In a frozen solution the solute is excluded from the growing ice, so the unfrozen fraction concentrates and the buffer's pH moves as one salt crystallises before the other. The damage is done at the transitions, and 14 days of stable hold between them contributes very little. Reconstituted material has no certificate; the one in the box describes the powder.
Start with the sequence, because which pathways are available depends on which residues are present.
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.
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.
Aggregation at air-liquid interfaces is established from surface-tension and particle-count studies and is the basis for anti-agitation handling guidance.
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.
Does the same reasoning apply to material already in solution, or is that a different curve? – p_mkhize 6 months ago This should be linked from the help pages. – plate_count_9k 8 months ago add a comment