why does nobody talk about identity
Genuine question, and the title is the question: why does nobody talk about identity.
Purity methods differ by compound class. A gradient and wavelength developed for one peptide will not necessarily resolve the relevant impurities of another.
Naming in this space is inconsistent. Several widely used names map to more than one molecule, so a catalogue number and a sequence beat a common name every time.
For any compound with a thin testing history, identity is the first question. Mass spectrometry against a theoretical mass answers it; an area-percent purity figure does not.
Ask me anything specific. Anything general I will probably get wrong.
best — the order this archive was captured in
Research-use-only material is not approved for human use. In this catalogue that covers essentially everything, which is why the board discusses material and analytics rather than outcomes.
Standing reminder: research-use-only material is not approved for human use, and no outcome claims without evidence.
Ordered under a name that turned out to cover two different molecules. Nobody’s fault but mine for not asking.
Net peptide content on the certificate was well below the purity figure and both were honest. Chemistry, not deception.
Bought small on anything without a testing history here. That rule has never once cost me anything.
Not convinced. A purity figure without a stated method is not comparable to one that has a method attached.
Not convinced.
This is the rule for anything unusual. Identity before anything else.
I would not treat catalogue breadth as a quality signal. It is a business decision, not an analytical one.
I would not treat catalogue breadth as a quality signal.
Disagreeing with this bit: handling for one compound does not transfer to another by default.
Storage guidance that names a temperature, a state and a duration reflects actual stability work. Generic guidance usually reflects a template.
Disagree — that name refers to at least two different molecules depending on who is selling it. The thread needs to be specific.
lead times on unusual lines are the thing to confirm up front
Net peptide content accounts for counterion, water and residual solvent. On some of these compounds the gap between purity and net content is substantial and entirely honest.
ask what the reference standard was
research-use-only material is not approved for human use
Stocked lines and made-to-order lines have different lead times and different storage histories. Both are ordinary; the difference is worth confirming before you commit.
Stocked line or made to order — did they say?
Right — HJ answered a handling question with actual storage conditions rather than a generic line, which is the standard.
Correcting my own comment: the storage condition I quoted was for the lyophilised powder, not for solution.
purity methods differ between compound classes
Yes. Naming conventions in this corner are loose enough that the same word covers several different molecules.
net peptide content is where the surprises live
a secretagogue and a fragment are not the same class of thing
the same name covers several different molecules in this space