How Much Does Custom Peptide Synthesis Cost?

Why there is no honest list price per amino acid

Buyers often ask for a price per residue and then multiply by the sequence length. That arithmetic ignores where the cost actually sits. A synthesis run consumes reagents in proportion to the number of couplings, but it also consumes a fixed amount of setup time, resin, cleavage cocktail, purification runs and QC regardless of length. A five-residue peptide and a fifteen-residue peptide may need the same number of HPLC runs to purify, so the shorter one costs far more per residue.

The other problem is that per-residue averages hide sequence effects. One arginine-rich 12-mer can be harder to make than a well-behaved 30-mer, because repeated guanidinium side chains cause incomplete coupling and truncated impurities that are difficult to separate. Suppliers who publish a flat per-residue rate usually apply a difficulty surcharge later, or set the rate high enough to cover the hard cases.

For budgeting, ask for a quote on your actual sequence at two or three scales. That gives you a real curve for your project instead of a generic average, and it usually takes less time than debating rates.

The variables that set the price of a custom peptide

None of these variables acts alone. A long, cysteine-rich peptide ordered at 98% purity in a 5 mg batch combines the four most expensive factors at once, and the quote will look nothing like a short linear peptide at 80%. That is why comparing two suppliers on a single number without comparing specifications is misleading.

How the purity target changes the price

Purity is measured by reversed-phase HPLC and reported as area percent of the main peak. Moving from crude to 95% typically means multiple preparative runs, fraction analysis and re-purification of overlapping pools. Recovery falls at every step, so the crude synthesis must be larger to deliver the same final mass. The practical consequence is that the price gap between 80% and 95% is often larger than the gap between 95% and 98% on an easy sequence, and much larger on a difficult one.

Choose the lowest grade that satisfies the assay. Crude peptide is appropriate for screening libraries and for some immunisations, where a mixture is acceptable. 70–80% suits routine ELISA coating and many cell-culture experiments. 90–95% is the usual working grade for receptor studies and for anything that will be quantified. 98% or better is reserved for standards, structural work, clinical-adjacent studies and cases where a minor impurity could plausibly explain the result.

Ask how purity is measured as well as what it is. A 95% figure by analytical HPLC at 214 nm is not the same as 95% by UV at 280 nm, which only sees aromatic residues. The certificate of analysis should name the column, gradient and wavelength. The purity testing guide explains the methods in more detail.

Why difficult sequences cost more to make

Solid-phase synthesis proceeds one residue at a time, and each coupling is rarely complete. A small percentage of unreacted chains at every step becomes a large population of truncated sequences by the end of a long synthesis. Difficult motifs make that worse: beta-sheet-prone stretches stack on the resin and hide reactive sites, poly-arginine sequences suffer from steric crowding and premature chain termination, and multiple cysteines require orthogonal protecting groups and controlled oxidation.

Chemists respond with double couplings, longer coupling times, microwave assistance, pseudoproline dipeptides, switched solvents or a different resin. Every one of those consumes more reagent, more machine time and more operator attention, and the resulting crude product is usually dirtier, so purification is harder too. A sequence that needs three of these interventions can cost several times what a routine peptide of the same length costs.

This is also why a supplier may decline to guarantee a yield on a difficult sequence, or quote a larger synthesis to deliver the requested mass. For a fuller explanation of what makes a sequence hard, see peptide length and sequence complexity.

How scale affects the price per milligram

Doubling the batch does not double the price. Setup, route development, QC and documentation are largely fixed, so they are spread over more material. Reagent costs rise with scale but usually sublinearly, because bulk reagents are cheaper per mole and larger reactors are more efficient per gram. The result is the familiar curve: price per milligram falls steeply from 5 mg to 50 mg, flattens between 100 mg and 1 g, and then depends more on reactor availability and scheduling than on chemistry.

The curve also depends on purification yield. At high purity, larger batches can lose a greater absolute mass to chromatography, and a very large batch may need to be split into several purification runs. Very large orders, in the hundreds of grams or kilogram range, are usually re-quoted after a route review because the manufacturing approach may change.

If your study will consume the peptide over months, a single larger lot is usually better value and better science than repeated small lots, since lot-to-lot variation is one more variable you do not need.

What a quoted price should include, and what it often does not

A complete quote covers synthesis, cleavage, purification to the agreed specification, release testing by HPLC and mass spectrometry, lyophilisation, vialling and a certificate of analysis. Shipping, insurance, customs duties and any special packaging are frequently excluded, and expedited scheduling is almost always priced separately.

Watch for quantity definitions. A price for 10 mg may refer to gross powder weight, which at 80% peptide content and a residual counter-ion gives you noticeably less than 10 mg of peptide. The certificate should state peptide content, net weight and the method used to determine them. If a quote is silent on this, ask, because it changes the effective cost per usable milligram.

Also confirm what happens if the batch fails release. Reputable suppliers re-run at their own cost when the failure is theirs, but the definition of failure belongs in the quote. When you compare suppliers, compare the specification line by line rather than the headline total; a quotation for custom peptide synthesis is a technical document as much as a commercial one.

How to compare quotes from different suppliers

Normalise before you compare. Convert every price to cost per milligram of peptide content at a stated purity, then check that the analytical package, documentation and shipping terms match. A quote that includes MS/MS sequencing and lot-specific chromatograms is not the same product as one that includes a single HPLC trace.

Then check the schedule. A lower price with a six-week lead time may cost more in project delay than a higher price delivered in three weeks. Ask what the supplier does when a sequence proves harder than expected: do they absorb the extra work, re-quote, or deliver a lower mass? The answer tells you how the price will behave in practice.

Finally, ask for a representative certificate of analysis from a comparable project. It is the best single predictor of what your documentation will look like, and it shows whether the supplier measures peptide content, counter-ion and water content or simply reports a purity percentage.