PT-141 Canada

PT-141 is the shortest route into melanocortin receptor work that a Canadian lab can order domestically, and it is also the compound most often confused with its two relatives, Melanotan 1 and Melanotan 2. This page explains what is actually in a PT-141 vial, how it differs from the melanotans on a certificate, and what ordering it inside Canada involves.

What PT-141 is

PT-141, also catalogued as bremelanotide, is a cyclic heptapeptide: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH. The ring is closed by a lactam bridge between the aspartate side chain and the lysine side chain, and the calculated monoisotopic mass is close to 1,025 Da. It is a metabolite of Melanotan 2, from which it differs by the loss of the C-terminal amide: Melanotan 2 ends in a carboxamide, PT-141 ends in a free carboxylic acid.

That single difference is 1 Da on a mass spectrum, which is small but resolvable on any instrument that produces a certificate. Our article on the lactam bridge and melanocortin selectivity covers why the ring matters to receptor work.

PT-141 against Melanotan 1 and Melanotan 2

• Melanotan 1 (afamelanotide): a linear 13-residue analog of alpha-MSH with Nle4 and D-Phe7 substitutions, mass near 1,646 Da. Stocked as Melanotan 1 10 mg.
• Melanotan 2: the cyclic heptapeptide amide, mass near 1,024 Da. Stocked as Melanotan 2 10 mg.
• PT-141: the cyclic heptapeptide acid, mass near 1,025 Da. Stocked as PT-141 10 mg.

Melanotan 1 is easy to tell apart by mass. Melanotan 2 and PT-141 are not, at least not at a glance, so a certificate for either should report the observed mass to at least one decimal place and ideally show retention time against a reference standard. Our comparison of the three melanocortin peptides sets the structures side by side.

What to look for on the certificate

Cyclic peptides bring one impurity class that linear ones do not: the uncyclised linear precursor, which has the same mass plus 18 Da (one water) and a different retention time. A chromatogram with a secondary peak eluting earlier than the main peak, and a mass trace showing +18, is reporting incomplete cyclisation. At 99%+ purity that peak is small, but it is worth confirming it is small rather than absent from the report.

The tryptophan residue gives PT-141 a usable absorbance at 280 nm, so a certificate run at 220 nm and 280 nm should agree on the main peak. Where the two wavelengths disagree, something without a chromophore is co-eluting. The HPLC area percentage guide explains what each figure can and cannot tell you.

Storage and solution behaviour

As a lyophilised powder PT-141 is stable at minus 20 °C and tolerates short periods at room temperature in transit. In solution the tryptophan is susceptible to oxidation under light, so stock solutions belong in amber or foil-wrapped tubes. The peptide is soluble in water and dilute acetic acid; it is less soluble at neutral pH near its isoelectric point, which is one reason reconstitution in plain phosphate buffer sometimes produces haze. Aliquot after reconstitution and avoid repeated freeze-thaw.

Buying PT-141 in Canada

Our stock is held in Canada and ships domestically. There is no customs clearance on a domestic parcel, so there is no duty, no brokerage fee and no hold at the border. Orders placed before the daily cut-off usually leave within one business day, with tracked Canada Post, Purolator, FedEx or UPS service chosen at checkout. Tracked shipping is free over $200, and GST or HST is charged at the delivery province’s rate.

Volume pricing counts every vial in the order toward the break, so a PT-141 vial ordered alongside Melanotan 1 and Melanotan 2 for a receptor panel moves the whole cart down the ladder. Larger quantities are covered on the bulk orders page.

Certificates and guarantee

Published certificates for PT-141 are on the certificates page, reproduced as issued by the laboratory. If an independent laboratory finds a vial below its stated purity, the purity guarantee refunds the product and the cost of the test.

Research use only

PT-141 is supplied as a laboratory reference material for in vitro and analytical work. It is not a drug and not for human or veterinary use. We do not provide dosing or administration information.