Asparagine, glycine, and the two residues that decide a shelf life
An isoaspartate rearrangement changes the molecule and not the mass. A method that confirms identity by molecular weight alone will report it as the parent compound.
Import & customs
Page 13 of 14 of this archive, newest first.
Twenty-eight days is a number from somebody else’s product
We set out what is known, what is inferred and what is simply assumed about the fortnight after a vial is opened.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
A supplier suspends shipping to Mexico after 23 consecutive customs detentions
The route did not close because of a rule about peptides.
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…
Oxidation, and the peroxide that came in with the surfactant
The sequence predicts the failure mode. A methionine predicts oxidation; an asparagine followed by a glycine predicts deamidation; a cysteine predicts disulphide scrambling.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
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.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
Collapse temperature, and the hour of the cycle where shelf life is lost
The physics of the drying cycle explains why some cakes are matte and full-volume and others are glassy discs, and why the difference is not cosmetic.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
A supplier suspends shipping to Norway after 12 consecutive customs detentions
The route did not close because of a rule about peptides.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
A supplier suspends shipping to South Korea after 17 consecutive customs detentions
The route did not close because of a rule about peptides.
A supplier suspends shipping to Australia after 19 consecutive customs detentions
The route did not close because of a rule about peptides.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.
A supplier suspends shipping to Switzerland after 17 consecutive customs detentions
The route did not close because of a rule about peptides.
Why summer is a documented quality problem in this trade
The route did not close because of a rule about peptides.