PT-141 | 20mg | 3ml
PT‑141 (also known as bremelanotide) is a synthetic cyclic heptapeptide melanocortin‑receptor agonist derived structurally from Melanotan II. It is produced by modifying the C‑terminus of the MT‑II scaffold — replacing the terminal amide with a hydroxyl group — yielding a related cyclic peptide with a distinct receptor‑selectivity profile while retaining the lactam‑bridged, enzymatically stable architecture of its parent compound. These properties make PT‑141 a well‑defined reference peptide for studying melanocortin signalling under controlled laboratory conditions.\n\nIn biochemical and cellular research systems, PT‑141 acts as an agonist at the centrally expressed melanocortin receptors MC3R and MC4R, with comparatively higher potency at MC4R and substantially reduced activity at MC1R relative to Melanotan II. This shift toward MC4R selectivity makes PT‑141 a useful tool for isolating MC4R‑mediated signalling — including G‑protein‑coupled cAMP and phospholipase‑C cascades, intracellular calcium flux, and ERK/MAPK pathway activation — within neuronal and receptor‑expressing model systems. The molecular responses observed vary with receptor subtype, concentration, exposure time, and experimental model, and PT‑141 is used to characterise melanocortin‑receptor signalling rather than to infer defined biological or physiological outcomes.
Strength
20mg
Concentration
6.67 mg/ml
Purity
≥99% HPLC
COA
Included
Free Reusable auto-injector pen, worth $50
A reusable pen is added free to your order, automatically.
- Same-day dispatch on orders placed before the daily cut-off.
- Free shipping within the United States over $100, tracked.
- Cold-chain packed: sealed foil pouch, ice packs, plain outer box.
- Batch-specific Certificate of Analysis included.
| Designation | Cyclic melanocortin heptapeptide (bremelanotide) |
| CAS Number | 189691-06-3 |
| Molecular Formula | C₅₀H₆₈N₁₄O₁₀ |
| Molecular Weight | 1025.2 g/mol |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH |
| Strength | 20mg |
| Concentration | 6.67 mg/ml |
| Presentation | 3ml Vial , Pen and Needles |
| Purity | ≥99% (HPLC) |
| Storage | Must be kept in a refrigerator at 2°C–8°C for optimal potency. |
| Certificate of Analysis | Batch-specific COA included |
How we ship it
Every pre-mixed vial ships cold from the warehouse serving your region and arrives in a plain box. Refrigerate on arrival at 2–8 °C.
Chilled
Vials travel with frozen gel packs inside a sealed foil pouch, which holds temperature for roughly seven days — far longer than the journey needs, so the cold chain has room to spare.
Insulated
The pouch sits inside a wool-lined envelope, so the cold chain survives a normal courier journey.
Discreet
Plain outer box with no branding and nothing on the label that names the contents.
Same-day dispatch
Order before the daily cut-off, Monday to Friday.
Free over $100
Within the US: tracked, next business day.
2–8 °C on arrival
Refrigerate as soon as the parcel lands.
PT-141
$200.00 · Qty 1
PT-141 (bremelanotide): structure, format and buying criteria for US research laboratories
PT-141 (bremelanotide) is a synthetic seven-residue peptide closed into a macrocycle by a side-chain lactam bridge, supplied here as a pre-mixed solution in a 20mg vial for in-vitro laboratory research.
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Two things about this listing differ from a lyophilized vial of the same compound: the material arrives already in solution, and the molecule sits one small chemical edit away from a close structural relative, which makes identity verification less trivial than it first appears. Both are worth understanding before you compare suppliers.
Structural identity
| Field | Value |
|---|---|
| Common name | PT-141 |
| Synonym | Bremelanotide |
| Class | Synthetic cyclic heptapeptide; melanocortin-receptor agonist |
| CAS | 189691-06-3 |
| Molecular formula | C50H68N14O10 |
| Average molecular mass | ~1025.2 g/mol |
| Sequence | Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-OH |
| Ring | Side-chain lactam, Asp to Lys |
| Format supplied | Pre-mixed solution, 20mg vial |
| Documentation | Certificate of Analysis — see /coa |
A single terminal group separates it from the parent scaffold
PT-141 is built on the same cyclic backbone as Melanotan II, its structural parent and, for the purposes of this page, nothing more. The distinguishing edit sits at the C-terminus: where the parent carries a primary carboxamide, PT-141 carries a free carboxylic acid — a nitrogen-for-oxygen exchange with the loss of a hydrogen. That is the whole structural difference, and it has three analytical consequences a receiving lab should care about.
Mass. Swapping an amide for an acid changes the average mass by roughly one dalton — about 1025.2 for PT-141 against about 1024.2 for the amide form. On a low-resolution instrument, or on a report quoting mass only to the nearest unit, those two isotope envelopes overlap badly. A COA line reading "MS confirms ~1025" is not, on its own, a confirmation of identity. Ask for theoretical and observed masses printed side by side, at resolution sufficient to separate them.
Charge. The free acid is deprotonated at neutral pH, so the molecule carries one more negative charge than the amide form. That shows up in ion-exchange behavior and in the isoelectric point, and typically shifts retention slightly under identical reversed-phase conditions. Retention time alone is weak evidence; retention time against a reference standard run in the same sequence is much stronger.
Ring integrity. The lactam is formed by condensing the aspartate side-chain carboxyl with the lysine side-chain amine, so the cyclic peptide is 18 daltons lighter than its linear precursor. Uncyclized linear material is the impurity to look for, visible both as a distinct chromatographic peak and as a +18 mass; cyclodimers appear at approximately twice the monomer mass. Separately, the phenylalanine residue is in the D-configuration, and epimerization to the L-configuration produces a diastereomer of identical mass that mass spectrometry cannot resolve at all. Only chromatography, or dedicated chiral analysis, separates it — the single strongest argument for insisting on a full chromatogram rather than a summary purity number.
Receptor selectivity as a research subject
The melanocortin family comprises five G-protein-coupled receptors, MC1R through MC5R. Published work on melanocortin ligands is a body of in-vitro and animal laboratory research under examination, and this page draws no conclusions from it. The methodological point is the transferable one: in-vitro reports of how a ligand distributes its binding affinity across those subtypes depend heavily on assay format, cell line, receptor expression level and readout, and the values are not portable between systems. Treat subtype numbers as properties of a particular assay, not of the molecule in the abstract.
Pre-mixed solution against lyophilized powder
| Consideration | Lyophilized vial | Pre-mixed solution |
|---|---|---|
| Preparation at the bench | Requires reconstitution and a diluent decision per lab | Arrives ready as supplied |
| Sources of variance | Weighing, transfer and reconstitution error sit with the buyer | Fixed at fill; consistent across draws from one vial |
| Shelf stability | Generally the more robust long-term form | Shorter practical life; degradation pathways stay active |
| Moisture and stopper entry | Repeated entry admits moisture into dry cake | Not applicable, but headspace and septum integrity matter |
| Transit sensitivity | Tolerant of ambient excursions | Temperature and light exposure in transit are real variables |
| Freeze–thaw | Not a factor before reconstitution | Repeated cycling is the main avoidable stressor |
| Surface adsorption | Begins only after reconstitution | Ongoing from fill onward; container chemistry matters |
Neither format is universally better. The trade is that a solution removes a step where a lab introduces its own error, and accepts in exchange a shorter stability window and real sensitivity to how the package travelled. Ask any overseas supplier what packaging and temperature control it uses, and inspect on arrival.
What a Certificate of Analysis should contain
Documentation for this catalogue is published at /coa. Whoever you buy from, a COA is only worth reading if it carries all of the following.
- A lot or batch number matching the vial in your hand, plus an analysis date. A document with no lot linkage is a marketing asset, not a record.
- A reversed-phase HPLC chromatogram, not just a percentage. Note the detection wavelength: 214 nm reports the peptide bond and sees far more than 280 nm, which reports only aromatic residues.
- Purity stated with its definition: area percent, at which wavelength, integrated over what window.
- Mass confirmation with theoretical and observed values, and enough resolution to be meaningful given the one-dalton issue above.
- The identity of the testing laboratory. An unnamed lab, or one document reused verbatim across lots, is a red flag.
- For solutions: appearance, container and closure description, and any statement on filtration.
- Where applicable, residual solvent, counterion content and bioburden or endotoxin results.
Ask for that document before ordering rather than after, and ask whether the raw chromatograms behind it can be produced. A supplier that answers plainly is a better bet than one quoting a higher purity figure with nothing behind it.
Checks on receipt, storage and handling
Record the condition of the package on arrival before anything else: external temperature indicator if present, seal and septum integrity, clarity and color of the solution, and any visible particulate or haze. Keep the vial cold and dark; both tryptophan and histidine are oxidation-sensitive, and light exposure is a slow, cumulative and entirely avoidable stressor. Minimize freeze–thaw cycling, and let a chilled vial equilibrate before opening so condensation does not form inside the closure. Log lot numbers against your own analytical results, so a future anomaly can be traced to a batch rather than argued about.
Origin and testing
This material is synthesized in the UK and verified in US laboratories. The split is the point: synthesis and independent analysis are not performed by the same party, which is what makes the analysis worth anything. The Certificate of Analysis for this product is available at /coa.
PT-141 (bremelanotide): research FAQs
- What is PT-141?
- PT-141 is the development code for bremelanotide, the international nonproprietary name of a synthetic cyclic heptapeptide, a melanocortin-receptor agonist analog. Of its seven residues, six form a ring closed by a lactam bridge between an aspartate side chain and a lysine side chain. Ours is supplied pre-mixed as a solution for in-vitro laboratory research only and is not for human or veterinary use.
- What is the structure of PT-141?
- The sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-OH: an acetylated norleucine, then a six-residue ring closed by an amide bond between the aspartate and lysine side chains, ending in a free carboxylic acid. The molecular formula is C50H68N14O10, the average molecular mass is about 1,025.2 g/mol, and the CAS registry number is 189691-06-3.
- Is PT-141 the same molecule as Melanotan II?
- No, though only one group separates them. Both are built on the same cyclic backbone. Melanotan II ends in a primary amide, whereas PT-141 ends in a free carboxylic acid, so the two differ in mass by roughly one dalton and in net charge at neutral pH. That small gap is why identity testing has to be precise enough to tell them apart.
- How can a lab confirm it has PT-141 and not a close relative?
- Mass alone is weak evidence, because the amide and acid forms sit about 1 Da apart and their mass envelopes overlap on low-resolution instruments. Look for theoretical and observed masses side by side at adequate resolution, plus a full HPLC chromatogram. Watch for linear, uncyclized material at +18 Da, and note that the D-Phe epimer has identical mass, so only chromatography can separate it.
- Is the PT-141 sold here an FDA-approved drug?
- No. Bremelanotide is the active ingredient of an FDA-approved prescription medicine, but that finished pharmaceutical product and research-grade PT-141 are not interchangeable. The material sold here is not that product, has not been evaluated by the FDA, and is supplied for in-vitro laboratory research only. It is not for human or veterinary use.
- Is PT-141 supplied as a powder or a solution?
- As a solution. It arrives pre-mixed in a sealed vial, so there is no lyophilized cake to reconstitute at the bench and no weighing step where error can enter. In exchange, a solution has a shorter practical life than a dry powder and is more sensitive to temperature and light in transit, which is why it travels cold-packed and should be refrigerated on arrival.
- How should PT-141 be stored?
- Refrigerate at 2 to 8°C, keep the vial dark and sealed, and avoid freeze-thaw cycling. Tryptophan and histidine are both oxidation-sensitive, and light exposure is a slow, cumulative stressor. Let a chilled vial reach room temperature before opening so condensation does not form inside the closure, and log the lot number against its Certificate of Analysis.
- How does PT-141 ship in the US, and is there a certificate?
- Orders are packed cold at the warehouse that serves the United States and sent tracked, arriving across the US the next business day. Prices are in US dollars, and Visa, Mastercard and Apple Pay are accepted. Each batch has a Certificate of Analysis reporting its HPLC purity, published in the COA library on this site for review before you order.
Research guides
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