How Do I Order Custom Peptides?
Quick answer
To order a custom peptide you provide the exact sequence, the quantity, the purity you need and any modifications or labels. The supplier reviews the sequence for synthesis risk, confirms the specification and price in a written quote, then proceeds to synthesis, purification, quality control and lyophilisation. Routine orders are typically delivered two to four weeks after the purchase order.
Key facts at a glance
| Minimum order | Typically 5 mg for a standard sequence |
|---|---|
| What to send | Sequence, scale, purity target, modifications, salt form |
| Purity options | Crude, 70%, 80%, 90%, 95% or 98%+ by HPLC |
| Standard turnaround | 2–4 weeks from purchase order, sequence dependent |
| Per-batch documents | Certificate of analysis, HPLC chromatogram and mass spectrum |
| Typical peptide content | 70–90% of net weight for purified peptides, stated on the COA |
What you need before you request a quote
A custom peptide order is only as clean as the specification behind it. Before contacting a supplier, write down the sequence in single-letter code, the N- and C-terminal forms you want, the quantity in milligrams or grams, the purity grade, and any modification such as acetylation, amidation, a fluorescent label, biotin, phosphorylation or a disulfide bridge. Each of these changes the synthetic route or the analytical work, so each one changes the price.
It also helps to state the intended application. A peptide for a cell-based assay may need to be sterile-filtered or supplied in a defined buffer; a peptide for antibody production may need a carrier-protein conjugation site; a peptide used as a mass spectrometry standard may need the highest available purity and a documented counter-ion. Suppliers cannot infer these requirements from a sequence alone, and assumptions discovered late in a project are the most common cause of re-quotes.
Order-specific information a supplier will ask for:
- Sequence and length: one-letter code, plus any non-natural residues written in full.
- Terminal chemistry: free amine or acetylated N-terminus, free acid or amidated C-terminus.
- Scale: the final quantity you need, not the crude synthesis size.
- Purity: the HPLC percentage that the release specification will be measured against.
- Salt form: usually trifluoroacetate or acetate; acetate is preferred where TFA interferes with a biological assay.
- Documentation: whether you need a COA only or also raw HPLC data, MS spectra and a sequence-confirmation report.
- Delivery details: destination country, import requirements and whether the material must ship at ambient temperature.
How a supplier turns your request into a written quote
A quote is not just a price for a sequence. It is a proposed specification, and the better ones list the assumptions explicitly. At MOL Changes a chemist checks residue count, aggregation-prone stretches, cysteine content, charge distribution and modification compatibility before pricing, because a 20-mer that is routine on paper can be difficult in the reactor.
Expect a quote to contain the fields below. If any field is missing, ask for it in writing before you approve the order, since verbal specifications are difficult to enforce at release.
| Quote field | What to check |
|---|---|
| Sequence | Every residue correct; non-standard residues named; disulfide pairing defined |
| Quantity | Net peptide weight versus gross vial weight; minimum deliverable after purification |
| Purity | Method stated (RP-HPLC, usually at 214 or 220 nm) and whether it is area percent |
| Counter-ion | TFA, acetate or hydrochloride, and whether residual TFA is measured |
| Analytics | HPLC and MS included by default, or optional; whether sequence is confirmed by MS/MS |
| Price and validity | Currency, Incoterms, quote expiry, payment terms |
| Lead time | Working days from purchase order, and what counts as day one |
The cost drivers behind a quote are worth understanding before you compare suppliers, because a low price often reflects a different purity method or a smaller delivered quantity rather than a more efficient factory.
What happens after you place the order
Once the specification is signed off, production follows a predictable sequence. The steps below are typical for solid-phase synthesis of a linear peptide; cyclic, labelled or long sequences add extra steps in the middle.
- Sequence entry and route selection: the sequence is loaded into the synthesis software and the resin, protecting-group strategy and coupling method are chosen.
- Chain assembly: amino acids are coupled one at a time from the C-terminus. Each coupling is monitored, and difficult stretches may need double coupling or a different coupling reagent.
- Cleavage and deprotection: the peptide is released from the resin and side-chain protecting groups are removed in a single acid step.
- Purification: preparative reversed-phase HPLC separates the target peptide from truncated and modified impurities.
- Quality control: analytical HPLC establishes purity, and mass spectrometry confirms the molecular weight. Additional tests cover counter-ion, water content and appearance where required.
- Lyophilisation and packing: the pooled fractions are freeze-dried, weighed, aliquoted and labelled with lot number, mass and storage instructions.
You should receive a dispatch notification with the lot number and the analytical documents, ideally before the parcel arrives so that the documents can be reviewed and stored alongside the material.
Choosing scale and purity without overpaying
Two specifications drive most of the price: how much peptide you need and how pure it must be. Both are easy to over-specify. If a peptide is used as an immunogen, 70–80% purity is often adequate because the immune system responds to the target sequence and minor truncations are a small fraction of the dose. If the peptide is a quantitative standard or is used in a sensitive functional assay, 95% or 98% removes ambiguity about what is causing the observed effect.
Quantity deserves the same scrutiny. Synthesis is quoted on the crude batch, but purification losses mean you should order the mass you need after purification, not before. A 95% purity target on a difficult sequence can lose a large share of the crude product, so a 10 mg request may need a 20 mg or 25 mg synthesis. Suppliers normally state the delivered net peptide content on the certificate of analysis, which lets you convert between gross weight and usable peptide.
Where the project allows, ordering one larger batch instead of several small ones is usually cheaper per milligram and gives you a single lot for the whole study. That consistency matters more than the unit price in assays that run for months.
Documentation, shipping and customs
Research peptides ship as lyophilised powder at ambient temperature in most cases, because the dry solid is stable enough for a normal courier journey. If you request a solution, or if the peptide is unusually labile, cold-chain shipping can be arranged. Ask for the shipping temperature to be stated in the quote so that receiving staff know what to expect.
International shipments need a commercial invoice, a packing list, a description of the goods and, in some destinations, an import permit or a statement of end use. Research-grade peptides are not medicines, and suppliers should not describe them as such on customs paperwork. Buyers are responsible for confirming that the material may lawfully be imported into their country; a supplier cannot do that on your behalf.
Documentation should travel with the goods and be available electronically. At minimum you want a certificate of analysis that names the lot, the sequence, the measured purity, the analytical methods and the storage recommendation, plus the chromatogram and mass spectrum for that lot. If the documents you receive reference a different lot number from the vial label, stop and query it before use.
Why an order can be re-quoted after sequence review
It is common for a first quote to be revised once the sequence has been examined properly. The usual reasons are technical rather than commercial: a run of hydrophobic residues that will aggregate on resin, several cysteines that require selective oxidation, an arginine-rich region that is prone to truncation, or a modification that is incompatible with the standard cleavage cocktail.
In those cases the supplier may propose a longer synthesis time, a different resin, a pseudoproline dipeptide to break up a difficult stretch, or a lower guaranteed yield. All of these are legitimate, and a supplier that flags them before production is more useful than one that discovers them halfway through. Treat a revised quote as technical information you can use, and ask what specifically changed and why.
When you are ready, the fastest route is to send the sequence and specification through the custom peptide synthesis service page or the contact form. For projects with unusual requirements, a short call with a chemist usually saves a round of emails.
Frequently asked questions
What do I need to provide to order a custom peptide?
You need the sequence in single-letter code, the quantity required, the purity target, the terminal chemistry, any modifications or labels, and the salt form you prefer. Also state the intended application and any documentation or shipping requirements, because these affect the route and the price.
What is the minimum quantity for a custom peptide order?
Most suppliers set a minimum in the region of 5 mg for a routine sequence, because setup, cleavage and QC dominate the cost of a very small batch. Very short peptides can sometimes be supplied below that, while difficult sequences may need a larger minimum to deliver the requested mass at high purity.
Can I order a peptide without knowing the sequence?
No. The sequence is the specification: it determines the molecular weight, the synthesis route, the impurities and the analytics. If you only know the target protein region, the supplier can help you choose an epitope or a fragment, but a defined sequence must be agreed before a quote is meaningful.
Do I need to pay for HPLC and mass spectrometry separately?
Usually not. Standard custom synthesis quotes include an HPLC chromatogram and a mass spectrum for the delivered lot, because purity and identity are part of the release specification. Extra work such as amino acid analysis, sequence confirmation by MS/MS, endotoxin testing or residual solvent testing is normally quoted as an add-on.
Can I change the order after synthesis has started?
Once chain assembly begins, the resin is committed to a specific sequence, so a sequence change means starting again and is treated as a new order. Quantity or documentation changes are sometimes possible if they do not affect the synthesis. Ask before production starts if you expect the specification to evolve.
Are custom peptides supplied for human use?
No. MOL Changes supplies research-grade peptides for laboratory and manufacturing use. They are not medicines, have not been evaluated for human safety or efficacy, and must not be represented as treatments. Any use in humans requires separate regulatory authorisation that a research supplier does not provide.
Sources and scope
This answer is based on peer-reviewed peptide chemistry and analytical literature, pharmacopoeial requirements (USP <503>, Ph. Eur. 2.2.29 and 2.2.46), FDA and EMA guidance on peptide drug substances, and MOL Changes in-house synthesis and testing data. Product statements describe research-grade peptides supplied for laboratory and manufacturing use. They are not medical advice and are not a substitute for clinical judgement.
