Variability of HPLC and MS Laboratory Analysis Results
TL;DR: Laboratory analysis results can differ even for the same test material, because methods such…

Cyclic heptapeptide · alpha-MSH analog · CAS 121062-08-6
| Parameter | Value |
|---|---|
| Molecular formula | C₅₀H₆₉N₁₅O₉ |
| Molecular weight | 1024.2 Da |
| Amino acid count | 7 (cyclic heptapeptide) |
| Sequence | Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂ |
| CAS number | 121062-08-6 |
| PubChem CID | 92432 |
| Physical form | White lyophilized powder |
| Purity | ≥98% (RP-HPLC) |
| Solubility | Soluble in water, DMSO |
| Classification | Chemical reagent / research material |
| Intended use | For in vitro research use only, not for use in humans or animals |
Offered as a chemical reagent for in vitro laboratory use, within the framework of applicable European Union chemical substances regulations (REACH, CLP).
Reconstitution and storage conditions:
Typical analytical equipment:
All working parameters should be selected according to the research laboratory’s internal protocol. Product intended exclusively for in vitro and analytical use; not for human or animal use.
Melanotan II (MT-II) is a cyclic heptapeptide designed as a synthetic analog of alpha-melanotropin (alpha-MSH) at the University of Arizona laboratory. The cyclic lactam structure between Asp and Lys residues confers higher proteolytic stability than linear alpha-MSH. MT-II acts as a non-selective melanocortin receptor agonist at MC1R, MC3R, MC4R, and MC5R, without activity at MC2R.
In in vitro studies, MC1R activation stimulates the cAMP/PKA pathway in melanocytes, leading to CREB phosphorylation and transcription of melanogenesis-related genes (tyrosinase, TRP-1, TRP-2). Concurrent affinity for MC3R and MC4R in the central nervous system modulates neuroendocrine pathways studied in the context of energy homeostasis regulation.
Melanotan II and PT-141 are structurally related melanocortin peptides. PT-141 (Bremelanotide) is the active metabolite of Melanotan II, formed by removal of the C-terminal amide group.
| Feature | Melanotan II | PT-141 |
|---|---|---|
| Structure | Cyclic heptapeptide (lactam), C-amide | Cyclic heptapeptide (lactam), C-acid |
| Molecular weight | 1024.2 Da | 1025.2 Da |
| Target receptors | MC1R, MC3R, MC4R, MC5R | MC1R, MC3R, MC4R, MC5R |
| Primary research profile | MC1R (melanogenesis) + MC4R pathways | MC4R pathways in CNS |
| C-terminal group | -NH₂ (amide) | -OH (acid) |
| CAS number | 121062-08-6 | 189691-06-3 |
The key structural difference is the presence of an amide group at the C-terminus of Melanotan II (-NH₂), while PT-141 has a free carboxyl group (-OH). This modification affects the receptor affinity profile — Melanotan II shows stronger MC1R/melanogenesis pathway activation, while PT-141 is studied primarily in the context of MC4R pathways.
In lyophilized form, store Melanotan II at -20°C for long-term stability (at least 24 months). After reconstitution in sterile water, the solution remains stable for up to 30 days at 2-8°C. The cyclic lactam structure and absence of methionine residues in the sequence minimize the risk of oxidation and proteolytic degradation.
Melanotan II is structurally related to PT-141 (Bremelanotide) — its active metabolite differing in the C-terminal group. Both peptides belong to the family of synthetic alpha-MSH analogs with cyclic lactam structure.
Selected publications on Melanotan II and melanocortin peptides.
"Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization"
Peptides, 27(4):921-930
"Structure-activity relationships of the melanocortin peptides"
Current Topics in Medicinal Chemistry, 11(14):1729-1749
Produkt jest surowcem chemicznym przeznaczonym wyłącznie do zastosowań badawczych, naukowych i analitycznych in vitro. Nie jest przeznaczony do użytku ludzkiego ani weterynaryjnego, w tym w celach diagnostycznych, terapeutycznych, profilaktycznych lub żywieniowych.
Produkt nie jest sklasyfikowany jako substancja niebezpieczna zgodnie z rozporządzeniem CLP (WE) nr 1272/2008. Oferowany jest jako odczynnik chemiczny w ramach obowiązujących w Unii Europejskiej przepisów dotyczących substancji chemicznych (REACH, CLP). Nie stanowi produktu leczniczego, suplementu diety, wyrobu medycznego ani kosmetyku w rozumieniu obowiązujących przepisów prawa.
Substancję niewykorzystaną należy utylizować zgodnie z lokalnymi przepisami dotyczącymi odpadów chemicznych. W warunkach laboratoryjnych: neutralizować i utylizować wraz z odpadami laboratoryjnymi. Nie wylewać do kanalizacji.
Produkt oferowany jest zgodnie z obowiązującymi przepisami Unii Europejskiej dotyczącymi substancji chemicznych (REACH, CLP) oraz prawem polskim w zakresie obrotu odczynnikami chemicznymi i materiałami badawczymi. Pełne warunki sprzedaży oraz klasyfikacja produktu zawarte są w Regulaminie Sklepu.
Dokonując zakupu, Klient potwierdza zapoznanie się z powyższymi informacjami oraz akceptuje postanowienia Regulaminu.
Melanotan II is a non-selective agonist of melanocortin receptors (MC1R/MC3R/MC4R/MC5R). Research literature has documented adverse events associated with melanocortin activation, including effects on blood pressure, energy homeostasis, and melanocyte activity. Handling requires particular care in accordance with the internal laboratory protocol. Research substance — not intended for use in humans or animals.
W przypadku pytań dotyczących obchodzenia się z produktem lub informacji regulacyjnych: kontakt@peptydy-sklep.com.
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Melanotan II (MT-II) is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (alpha-MSH). It acts as a non-selective agonist at melanocortin receptors MC1R, MC3R, MC4R, and MC5R. CAS: 121062-08-6.
Melanotan II is a broader melanocortin agonist affecting MC1R/MC3R/MC4R/MC5R. PT-141 (Bremelanotide) is a metabolite of MT-II with greater selectivity for MC3R/MC4R. Both are cyclic heptapeptides.
Store lyophilized Melanotan II at -20°C to -80°C, protected from light. After reconstitution, store at 2-8°C and use within 30 days.
Melanotan II is available as a 10 mg lyophilized vial.
Every batch undergoes RP-HPLC analysis (≥98%) and mass spectrometry verification. Certificate of Analysis included.