What Information Do I Need for a Peptide Quote?

The nine details that turn an inquiry into a quote

Most first inquiries are one line long: a sequence and the words "please quote". That is enough to start a conversation and not enough to price a project, so the reply is a question list and a week disappears. Sending the nine details below in the first message usually produces a usable quote within a day or two.

1. Sequence in single-letter code. Include non-natural residues in full and identify disulfide pairs by residue number.
2. N- and C-terminal forms. Free amine or acetylated; free acid or amidated.
3. Modifications. Label, PEG, biotin, phosphate, lipid or cyclization, each with its position.
4. Counter-ion. Trifluoroacetate or acetate, and whether residual TFA must be measured.
5. Quantity. The mass you need after purification, plus any overage for testing.
6. Purity target. A percentage and the analytical method that will verify it.
7. Analytical package. COA only, or also raw chromatograms, spectra and sequence confirmation.
8. Destination and date. Country, Incoterms and the date the material must be in hand.
9. Confidentiality. Whether a CDA is needed before the sequence is shared in full.

Sequence details that move the price

Not all residues cost the same. Each coupling is a reaction with a yield, and some residues couple slowly or incompletely. A sequence with a run of hydrophobic residues may aggregate on the resin, a stretch of beta-sheet-forming residues can be difficult to solvate, and multiple arginines are prone to truncation. Any of these can require double coupling, a different solvent, a pseudoproline dipeptide or a longer synthesis cycle.

Cysteines deserve special attention. A peptide with two cysteines that must form a specific disulfide needs selective deprotection and controlled oxidation, which is additional chemistry and additional analytics. A peptide with four or more cysteines may need several oxidation steps and a folding check. State the intended disulfide pattern; do not assume the supplier will guess it from the sequence.

Length is the other obvious driver, but complexity matters more than raw residue count. A 15-mer with two modifications can be harder than a 30-mer of ordinary residues. If the quote is much lower than expected, ask what was assumed about the difficult motifs.

Purity, counter-ion and the analytical package

Purity is a specification with a method attached. "95%" means little until it is defined as area percent by reverse-phase HPLC at a stated wavelength, with a stated gradient and integration threshold. Say whether you need crude, 70%, 80%, 90%, 95% or 98%+, and say what the peptide will be used for, because that decides whether the number is adequate.

The counter-ion is part of the specification. Trifluoroacetate is the default from HPLC purification, but residual TFA can interfere with cell assays and with some analytical methods. Acetate is a common alternative. If the assay is sensitive, ask whether the counter-ion content is measured and stated on the certificate of analysis.

Analytics can be quoted as a package or itemized. Standard release is a COA with an HPLC chromatogram and a mass spectrum. Additional work might include amino acid analysis, sequence confirmation by tandem mass spectrometry, endotoxin testing, water content by Karl Fischer or residual solvent testing. Tell the supplier which of these your quality system requires, because retrofitting them after the batch is released is expensive.

Quantity, scale and delivered net peptide

Quote the quantity you need to use, not the quantity you want to buy. Purification loses material, and a difficult sequence at high purity can lose a large share of the crude product. If you need 10 mg of usable peptide, the synthesis may need to start at 20 mg or more. Suppliers normally quote the synthesis scale and guarantee a delivered mass, and the certificate states the net peptide content so you can convert between gross weight and usable material.

Think about the whole study before choosing a size. Running three separate small batches creates three lots, three sets of data and three chances of a specification miss. One larger batch costs less per milligram and gives a single lot for the entire study, which matters more than unit price when an assay runs for months. The trade-off is storage: a large batch must be aliquoted and stored properly.

Ask whether the quoted mass is the minimum guaranteed or the expected yield. A quote that guarantees 10 mg with a note that the actual may be 15 mg is more useful than one that promises 15 mg and delivers 9 mg against a specification that allows it.

Destination, date and commercial terms

A peptide quote is not complete without logistics. State the destination country and city, because freight, insurance and any import permit requirement depend on it. State the date the material must be in hand, not the date you would like it shipped, and ask whether that date is realistic given the sequence and the analytical work.

Ask for the Incoterms 2020 term in the quote. DAP and CIP are common for first orders; EXW shifts all freight and risk to you, and DDP may not be offered for research materials. Confirm the currency, the quote validity and the payment terms, including whether a deposit is required and what triggers the balance.

Finally, ask what happens if the lot misses the specification. A replacement or credit clause belongs in the quotation or the quality agreement, not in a later email. The cost drivers article explains which line items should appear in a detailed quote.

Confidentiality before you send a sequence

A sequence can be the most sensitive information in a discovery project, especially if it is novel or patentable. Most suppliers will sign a mutual confidentiality agreement before receiving it, and a serious supplier expects the request. Ask early rather than after the first email, and keep the agreement separate from the purchase order.

You do not need to disclose the target protein or the therapeutic program to get a quote. The chemistry depends on the sequence and the specification, not on the biology. Send the minimum technical information needed: sequence, modifications, quantity, purity and analytics. If a supplier insists on knowing the application before quoting, that is a sales process rather than a technical one.

For a first contact, a partial sequence with the terminal regions obscured can still support a feasibility opinion. Once the CDA is signed, send the full sequence and ask for a written route assessment.

A copy-ready RFQ template

The list below can be pasted into an email. It takes two minutes to fill and saves a round of questions.

• Sequence: single-letter code, disulfide pairs, non-natural residues.
• Termini: N-terminal form and C-terminal form.
• Modifications: type, position and number per molecule.
• Counter-ion: TFA, acetate or no preference.
• Quantity: delivered mass required, plus testing overage.
• Purity: target percentage and method.
• Analytics: COA, HPLC, MS and any additional tests.
• Destination: country, city, Incoterms and required date.
• Confidentiality: CDA required before full sequence disclosure.

MOL Changes reviews each request with a chemist before quoting, and standard projects run from 5 mg to kilogram scale with a typical lead time of two to four weeks. Send the template through the custom synthesis page or the contact form.