What the sequence tells you about how a peptide will fail
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
Certificates of analysis
Page 47 of 51 of this archive, newest first.
VendorInvestigate result on a Changsha dulaglutide lot lands 3.5 points above the supplier’s stated figure
A reminder that a purity figure is the output of a method, and that methods differ.
Equal area is not equal mass: the response factor problem
Peptide bonds absorb strongly near 214 nm; aromatic side chains absorb near 280 nm. A method reading at 280 is blind to any fragment lacking an aromatic residue.
BCH names the synthesis and fill sites behind its catalogue
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
Independent analysis puts a SWB dulaglutide lot at 96.2%, against 95.6% on the certificate
The report states the gradient, the wavelength and the integration threshold, which is more than most.
Holograms, QR codes and other things that are not verification
Reported from the analysis, not from a warning notice.
What changed at QYB in March, and what the company says prompted it
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
MKM names the synthesis and fill sites behind its catalogue
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
The impurity hiding underneath the parent peak
The most useful single addition to any purity determination is a second separation under a different pH or on a different stationary phase, and the second-most useful is a…
Holograms, QR codes and other things that are not verification
Reported from the analysis, not from a warning notice.
Holograms, QR codes and other things that are not verification
Reported from the analysis, not from a warning notice.
Denmark health authority warns on falsified semaglutide pens
Reported from the analysis, not from a warning notice.
Four ways a peptide comes apart
Deamidation, oxidation, aggregation and hydrolysis account for nearly all of what happens to a peptide over time. Each has a characteristic residue, a characteristic…
Australia health authority warns on falsified tirzepatide pens
Reported from the analysis, not from a warning notice.
What changed at HJ in March, and what the company says prompted it
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
VendorInvestigate result on a Hong Kong mazdutide lot lands 2.6 points above the supplier’s stated figure
The result is unremarkable. What the report states alongside it is not.
The badge is about a sample. The listing is about a product.
The Journal does not treat a badge as evidence and states so wherever it reports one.
MKM names the synthesis and fill sites behind its catalogue
Documentation practice is the only part of vendor quality a buyer can assess before purchase.
Independent analysis puts a BCH cagrilintide lot at 96.1%, against 95.2% on the certificate
The Journal submitted the sample and paid for the analysis. The vendor was told in advance.
Aggregation: the impurity your chromatogram dissolved before it looked
We describe each pathway in enough chemical detail to explain why it is invisible to the method the trade uses, because that is the part which has practical consequences.