Custom peptide synthesis (revision 23)

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]

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.

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.

Quotations for sequences corresponding to compounds under patent, or to controlled substances, raise separate questions that are legal rather than technical. This wiki does not advise on them; see Regulatory status by jurisdiction and Patent expiry and biosimilars.^[3]

Custom work more often carries fuller documentation than catalogue supply, because the specification was negotiated. Certificates from custom orders in submissions to this wiki more often include mass confirmation, amino acid analysis and an itemised related-substances table than catalogue certificates do.^[4]

That is an observation about a self-selected set of submitted documents rather than a general finding about the market, and it should not be read as a comparison between named organisations.

The single most useful field remains the same as for any peptide: whether the document reports enough to let a reader work out how much peptide is in the container. See Peptide content and Underfilling.^[2]

• Peptide synthesis
• Contract development and manufacturing organisation
• Certificate of analysis
• Peptide content
• Solid-phase peptide synthesis