# Melanotan II Spray

> Research use only. Not for human or veterinary use. Supplied by Veracue Labs.

- Page: https://veracuelabs.com/product/melanotan-ii-spray
- Category: Nasal Sprays
- Sizes and prices in USD: 10 mg at $65.99
- Certificate of analysis: none posted on the page. Request one for a specific lot at https://veracuelabs.com/contact-us.
- Prices are a snapshot from 2026-10-17. The product page shows the current price.

## Overview

Melanotan II Spray is a spray-dispensed research bottle of Melanotan II, a seven-residue synthetic analogue of alpha-MSH written Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2. The ring is a lactam, an amide bond between the Asp and Lys side chains, and the chain ends in an amide. For the free peptide the formula is C50H69N15O9, the average mass is about 1024.2 g/mol and the CAS number is 121062-08-6.

## Product Details

### Melanotan II Spray Specifications

Product name: Melanotan II Spray (the peptide is also written Melanotan 2, MT-II or MT2)
Packaging: Spray-dispensed bottle
Sprays per bottle: 45 sprays per bottle
Size offered: 10 mg
Compound class: Synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone
Sequence: Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Ring closure: Lactam, an amide bond between the Asp and Lys side chains
C-terminus: Amide (-NH2)
Molecular formula (free peptide): C50H69N15O9
Average molecular weight: About 1024.2 g/mol
Monoisotopic mass: About 1023.5403 Da
CAS Registry Number: 121062-08-6
PubChem CID: 92432
UNII: UPF5CJ93X7
ChEMBL ID: CHEMBL430239
Research designation: Research Use Only

The identity rows describe the free peptide as a reference molecule and are not measurements of a Veracue lot. Salt or counterion form, purity, fill volume and concentration belong to lot-level paperwork, and documentation can be requested through the contact page.

### The Peptide in the Bottle

The material in Melanotan II Spray is Melanotan II, a seven-residue peptide that keeps the His, Phe, Arg and Trp core of alpha-melanocyte-stimulating hormone (alpha-MSH) and holds it in a ring. Norleucine sits at position 4 of the parent numbering, the phenylalanine at position 7 is the D-isomer, and a lactam bond between aspartic acid and lysine closes the structure. The bottle contains 45 sprays and is supplied for laboratory research only.

Four labels circulate for this one molecule: Melanotan 2, Melanotan II, MT-II and MT2. Each resolves to CAS 121062-08-6, which makes the CAS number the quickest way to match a supplier label to a literature record.

### Look-Alikes and Exclusions

- Melanotan 1 (Melanotan I) is a linear 13-residue peptide with the formula C78H111N21O19, CAS 75921-69-6 and a mass of roughly 1,647 g/mol. It has no ring.
- PT-141 carries the same ring and the same first residue but ends in a free carboxylic acid. Its formula is C50H68N14O10 and its CAS number is 189691-06-3.
- Melatonin shares only part of a name. It is a small indoleamine and not a peptide.
- Not sold as a dietary, cosmetic or veterinary product.

## Research Focus & Mechanism Overview

### Residue-by-Residue Layout

Literature on this peptide keeps the numbering of the parent hormone, which is why a chain of seven residues is described with positions 4 through 10.

Position: Residue: Structural note

Ac-: N-terminal acetyl cap: Blocks the free amine at the start of the chain.
4: Nle (norleucine): A straight-chain relative of methionine that carries no sulfur.
5: Asp: Its side-chain carboxyl forms one end of the lactam.
6: His: Part of the His, Phe, Arg, Trp core.
7: D-Phe: The mirror-image form of phenylalanine.
8: Arg: Basic side chain.
9: Trp: Indole side chain.
10: Lys: Its side-chain amine forms the other end of the lactam.
-NH2: C-terminal amide: Stands where a free carboxylic acid would otherwise end the chain.

### Melanotan II, PT-141 and Melanotan 1 Compared

Attribute: Melanotan II: PT-141: Melanotan 1

Shape: Cyclic, lactam ring: Cyclic, lactam ring: Linear
Length: 7 residues: 7 residues: 13 residues
C-terminus: Amide: Free acid: Amide
Formula (free peptide): C50H69N15O9: C50H68N14O10: C78H111N21O19
Average mass: About 1024.2 g/mol: About 1025.2 g/mol: About 1,647 g/mol
CAS: 121062-08-6: 189691-06-3: 75921-69-6

Melanotan II and PT-141 differ by a single atom swap at the end of the chain: an amide nitrogen in Melanotan II sits where PT-141 has a hydroxyl oxygen. The result is about one mass unit between them, while Melanotan 1 is separated by more than 600 Da.

### Receptor Context at Assay Level

Five G protein-coupled receptors make up the melanocortin family, MC1R through MC5R, and cyclic AMP formation is the usual readout in cell-based work. Reference pharmacology groups Melanotan II with ligands that engage MC1R, MC3R, MC4R and MC5R without a strong preference among them. MC2R is the odd one out, since it is the receptor for ACTH.

A ligand with a broad receptor profile is convenient as a pharmacological tool and harder to interpret in a mixed system, so selective compounds or defined cell lines are used to assign a signal to one subtype. Published affinity and potency values shift between laboratories and assay formats, so a single figure is best read as a single measurement. This is molecular reference context only, and Veracue provides no dosing, administration or usage guidance of any kind.

### What the Lactam Ring Means for Analysis

Melanotan II holds no cysteine and its formula contains no sulfur, so there is no disulfide bond to reduce. Method notes that mention a reduction step or a disulfide-linked mass change were probably written for a different peptide. The ring is an ordinary amide bond, which does not respond to thiol reducing agents.

Norleucine replaces methionine, so the usual methionine oxidation site is absent, although tryptophan remains in the chain.

## Quality & Purity Standards

### What a Mass Spectrum of This Peptide Should Show

At about 1 kDa the peptide appears mostly as singly and doubly protonated ions. These are the calculated monoisotopic values for the free peptide:
Species: Calculated value

Neutral monoisotopic mass: 1023.5403 Da
[M+H]+: m/z 1024.548
[M+2H]2+: m/z 512.777
[M+Na]+: m/z 1046.530

Instruments that report average mass place the neutral molecule near 1024.2 g/mol, so check which convention a report uses before comparing numbers.

### Telling It Apart From PT-141 by Mass

Melanotan II and PT-141 sit about 0.98 Da apart in monoisotopic mass, 1023.5403 against 1024.5243. That gap is close to the spacing between isotope peaks, so the first isotope peak of Melanotan II lands almost on top of the main peak of PT-141, and a low-resolution scan can blur the two. High-resolution mass or fragment data, together with the formula printed in the report (C50H69N15O9 against C50H68N14O10), settles the question.

### Reading a Lot Document for a Spray Bottle

Documentation can be requested through the contact page. When a lot document is supplied, match its lot number to the label on the bottle first. Then look for the chemical form, because the formula and mass above describe the free peptide and a salt weighs more. Also look for an identity result stated as observed against expected mass, the method behind any purity figure, the test date and the testing laboratory.

For a spray bottle, fill volume and concentration are lot-level facts. The count of 45 sprays is a packaging figure and not a measure of peptide content per spray.

### Quick Checks

### Can an HPLC trace alone confirm which peptide is in the bottle?

No. A chromatogram shows how much of the detected material elutes together, and a clean trace of PT-141 would look just as tidy. Identity comes from mass and, where needed, fragment data.

### What does a formula with 14 nitrogens indicate?

C50H68N14O10 matches PT-141 and not Melanotan II. Melanotan II carries 15 nitrogens, one more than PT-141, because its terminus is an amide.

### Why record the chemical form?

Mass-based calculations should use the formula weight of the form actually present. Applying the free-peptide weight of about 1024.2 g/mol to a salt gives a silent error.

### Ask Before You Order

- Ask about documentation
- Browse the research catalog

## Compliance Notice

### Laboratory Use Notice

Melanotan II Spray is a laboratory reagent, sold for research and analytical work by qualified researchers and institutions. It is not a drug, dietary supplement, cosmetic or food, and it is not meant for people or animals in any manner, including ingestion, injection or any other form of administration. Veracue provides no dosing, administration or usage guidance of any kind, and buyers are responsible for lawful handling. Sitewide terms are set out in the Medical Disclaimer and the Terms and Conditions.

## Questions and answers

### What does Melanotan II Spray contain?

A single synthetic peptide, Melanotan II: seven residues, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam ring and a C-terminal amide. The free-peptide formula is C50H69N15O9 and the CAS number is 121062-08-6.

### How many sprays does a bottle hold, and what size is offered?

Each bottle holds 45 sprays, and the size offered is 10 mg. The spray count is a packaging fact, while fill volume and concentration are lot-level details.

### Which names and abbreviations refer to this peptide?

Melanotan 2, Melanotan II, MT-II and MT2 are four labels for the same molecule. Matching CAS 121062-08-6 confirms it whichever label a supplier or paper uses.

### Which identifiers should be matched against a lot record?

The sequence, the formula C50H69N15O9, an average mass near 1024.2 g/mol and CAS 121062-08-6. PubChem CID 92432 is the matching database record.

### How does Melanotan II differ from PT-141?

Both are seven-residue lactam-ringed peptides, but PT-141 ends in a free carboxylic acid and Melanotan II ends in an amide. That gives PT-141 the formula C50H68N14O10 and CAS 189691-06-3, about one mass unit above Melanotan II.

### How does Melanotan II differ from Melanotan 1?

Melanotan 1 is a linear 13-residue chain of roughly 1,647 g/mol with formula C78H111N21O19 and CAS 75921-69-6. Melanotan II is a ring of seven residues at about 1024.2 g/mol.

### Why do the residues in Melanotan II run from position 4 to 10?

The literature keeps the numbering of the parent hormone, alpha-MSH, so norleucine is position 4 and the final lysine is position 10. It is still a seven-residue peptide.

### What m/z values should the free peptide give in electrospray?

Calculated monoisotopic values are about 1024.548 for [M+H]+ and 512.777 for [M+2H]2+. A sodium adduct, [M+Na]+, appears near 1046.530.

### Why can a mass scan confuse Melanotan II with PT-141?

They are only about 0.98 Da apart, roughly the spacing between isotope peaks. High-resolution mass, fragment data or the printed formula separates them.

### Is Melanotan II related to melatonin?

Only by a similar-sounding name. Melatonin is a small indoleamine, while Melanotan II is a cyclic peptide.

### Why should the chemical form appear in the paperwork?

The formula and mass quoted here describe the free peptide, and a salt form weighs more. Without the stated form, a mass-based calculation can carry an unnoticed error.

### How can documentation for a lot be requested?

Documentation can be requested through the contact page. When a document is supplied, check that its lot number matches the bottle label.

### What does the research-use-only label mean for this bottle?

The contents are a laboratory reagent for research and analysis. They are not for people or animals, and not for ingestion, injection or any other form of administration.

### Is there any guidance on using the spray?

No. Veracue provides no dosing, administration or usage guidance of any kind, because the bottle is sold as a laboratory research item.

More from Veracue Labs: https://veracuelabs.com/llms.txt