[Lab] selectivity claims are usually receptor-panel marketing
selectivity claims are usually receptor-panel marketing. One vial, one service, one member paying, which is the only kind of result this board should treat as evidence.
On the thin testing history in this board, and what to do about it.
Most of the compounds discussed here have a handful of independent results across the entire site, and several have none. That is a fact about how few members have paid for testing, not a judgement about the material.
What follows: buy small, test identity first for anything unusual, and post the result even when it is unremarkable. The vendor source pages are built from exactly these submissions, and the compounds with the thinnest coverage are the ones where one more entry changes the picture most. Research material is not approved for human use, so what this board can usefully build is an analytical record.
Confirmed the lead time in writing before ordering a made-to-order line. It was longer than the site suggested and entirely reasonable once explained.
The three questions to ask before ordering anything from the long tail of a catalogue.
What exactly is it — catalogue number or sequence, not a common name, because several common names map to more than one molecule. How was identity established — mass against theoretical, ideally, rather than a bare purity figure. What are the storage conditions, stated specifically, with a state and a duration attached.
Then two commercial questions that save time: is this a stocked line or made to order, and what is the lead time in writing. All five are one email, and the shape of the reply tells you a great deal before any material moves.
Sceptical readings welcome. The confident ones are the ones I distrust.
best — the order this archive was captured in
Why purity and net content diverge, and why that is usually honest.
Purity by area percent is a relative measure of what the detector saw. Net peptide content subtracts counterion, water and residual solvent from the powder mass. For some compounds in this catalogue the gap between the two is large.
A vial can therefore be 99% pure and contain considerably less peptide by mass than the label weight suggests, with nothing wrong anywhere. The problem is not the chemistry; it is that people compare a purity figure from one supplier with a net content figure from another and conclude something about both. Ask which number you are being shown, every time.
Ordered under a name that turned out to cover two different molecules. Nobody’s fault but mine for not asking.
Same. Net peptide content is where the difference between the label and the vial actually shows up.
identity before purity, every time, for anything unusual
Disagree — that name refers to at least two different molecules depending on who is selling it. The thread needs to be specific.
lyophilised and stored cold is the default for a reason
Not convinced. A purity figure without a stated method is not comparable to one that has a method attached.