Custom peptide synthesis (revision 8)
Old revision·22:50, 5 Jan 2025·FreightFenna
| Custom peptide synthesis | |
|---|---|
| Input | A sequence and a specification |
| Priced by | Length, scale, purity grade, modifications |
| Contrast with | Catalogue supply of stocked compounds |
| Topic infobox · conventions | |
Custom peptide synthesis is the manufacture of a peptide to a sequence and specification supplied by the customer, as distinct from supply of a catalogue item held in stock. It is the ordinary route by which research peptides that are not commercially stocked are obtained.[1]
A custom order is defined by more than a sequence. Scale, purity grade, C-terminal functionality, any modifications such as acylation or cyclisation, salt form, and which determinations will appear on the certificate are all specification items, and a quotation that does not enumerate them is quoting for an underdetermined thing.[2]
Price scales with length, with target purity, and with the difficulty of the sequence — which is not predictable from length alone. A quotation therefore reflects an assessment of synthetic difficulty as much as a price list.[1]
What a specification should fix
[edit]| Item | Why it matters |
|---|---|
| Sequence and modifications | Defines the molecule; ambiguity here is fatal |
| C-terminal form | Acid or amide; set by linker choice |
| Purity grade | Determines purification effort and price |
| Salt form | Trifluoroacetate counterion or exchanged; affects Peptide content |
| Scale | Net peptide mass, not solid mass |
| Determinations on the certificate | What will actually be reported |
The distinction between net peptide mass and solid mass is the one most often left ambiguous. An order for "10 mg" may be filled as 10 mg of solid, which at typical content is rather less peptide, or as solid containing 10 mg of peptide. The two differ by the counterion and water fractions.[2]
Sequence ambiguity is the failure with the largest consequence. One-letter and three-letter codes, D-residue conventions, and non-standard abbreviations for modified residues all vary between houses, and a sequence should be unambiguous on its face. See Peptide.
What a quotation reveals
[edit]A quotation that names a delivery date, a purity grade and a determination set is a more informative document than one giving only a price. It says the supplier has assessed the sequence rather than applied a per-residue rate.[1]
Declining to quote is also informative and is not a negative signal. Some sequences are genuinely difficult, some require capability a given house does not have, and a house that declines rather than accepting and failing is behaving reasonably.