Introduction
Melanotan II is a synthetic cyclic heptapeptide analogue of the endogenous melanocortin hormone α‑melanocyte‑stimulating hormone (α‑MSH). In the research supply chain, highly purified raw material is sought by academic laboratories, pharmaceutical researchers, and specialty distributors who require a defined, fully characterized peptide for controlled in vitro and preclinical investigations. Because the peptide’s sequence and conformation target multiple melanocortin receptor subtypes, it serves as a versatile tool in receptor‑pharmacology studies, photobiology assays, and metabolic‑pathway analysis. All material discussed here is intended exclusively for laboratory research use; no therapeutic, diagnostic, or in‑vivo human application is implied, and the product is not for veterinary or clinical use. The following sections detail the chemical identity, quality‑assurance parameters, research applications, and logistical aspects that inform sourcing decisions for this raw material.
Chemical Properties of Melanotan II
The chemical identity of Melanotan II is thoroughly documented in the scientific literature. Its primary structural features are:
- CAS Registry Number: 121062‑08‑6
- Molecular Formula: C₅₀H₆₉N₁₅O₉ (free base form)
- Molecular Mass: 1024.2 g·mol⁻¹ (monoisotopic mass of the neutral peptide)
- Amino Acid Sequence: Ac‑Nle‑Asp‑His‑D‑Phe‑Arg‑Trp‑Lys‑NH₂
- Cyclization: Lactam bridge between the β‑carboxyl group of the aspartic acid residue and the ε‑amino group of the lysine residue, forming a cyclic heptapeptide core.
The acetylated N‑terminus (Ac‑Nle) and amidated C‑terminus contribute to metabolic stability under laboratory conditions. Commercial raw material is typically supplied as the trifluoroacetate (TFA) salt, a lyophilized powder that is readily soluble in aqueous buffers. The counter‑ion content (TFA) is determined during quality‑control analysis and reported on the Certificate of Analysis. The peptide’s conformational constraint—imposed by the lactam bridge—mimics key structural features of α‑MSH and has been shown to confer high affinity for melanocortin receptors, especially MC1R and MC4R, in competitive binding studies described in peer‑reviewed journals.
Research Applications
Because Melanotan II interacts with several melanocortin receptor subtypes, it is widely employed in mechanistic investigations across multiple fields of preclinical science. All applications described below are restricted to laboratory research models; no clinical or therapeutic inference is permitted.
Melanocortin Receptor Pharmacology
The peptide is a well‑characterized agonist of MC1R, MC3R, MC4R, and MC5R in cell‑based reporter assays. Researchers use it to probe differential G‑protein coupling, receptor internalization kinetics, and signal transduction. Radioligand displacement studies routinely include Melanotan II as a reference compound because its binding profile has been mapped across all five human melanocortin receptors in heterologous expression systems.
Pigmentation and Photoprotection Research
In melanocyte cell culture and reconstructed skin models, Melanotan II stimulates tyrosinase activity and melanogenesis, leading to increased eumelanin synthesis. These effects are exploited to investigate UV‑induced DNA damage responses, antioxidant properties of melanin, and the molecular regulation of pigmentation. Such studies contribute to fundamental understanding of skin physiology and photoprotection, without implying any cosmetic or sun‑protection claim for the peptide itself.
Appetite Regulation and Energy Homeostasis
A substantial volume of published work has examined the role of central MC4R signaling in energy balance. In rodent models, intracerebroventricular or peripheral administration of Melanotan II acutely reduces food intake and increases resting energy expenditure. These observations have made the peptide a standard pharmacological tool for dissecting hypothalamic appetite circuits and for validating MC4R‑targeting strategies in obesity research. All such studies are conducted under institutional animal care protocols and remain purely investigative.
Additional Investigational Areas
Exploratory research has also utilized Melanotan II in models related to sexual arousal, cardiovascular regulation, and inflammation. For example, the peptide’s pro‑erectile effects in anaesthetised rats are mediated by MC4R in the central nervous system, providing a model to study neurogenic erectile pathways. Such work expands the repertoire of melanocortin‑related physiology but does not support any therapeutic application.
Quality Specifications
Raw‑material purity and identity are critical parameters for reproducibility in research. Reputable suppliers of Melanotan II raw material adhere to the following minimum specifications, confirmed by a comprehensive Certificate of Analysis (CoA) issued for each manufactured lot.
- Purity (HPLC): ≥ 99.0 % as determined by reverse‑phase high‑performance liquid chromatography (RP‑HPLC) at 220 nm. The CoA includes a representative chromatogram with retention time and peak area integration.
- Endotoxin Level: < 1.0 EU/mg, measured by the Limulus Amebocyte Lysate (LAL) method. This specification ensures suitability for sensitive cell‑based assays where bacterial lipopolysaccharide could confound results.
- Peptide Content: Typically 80–85 % net peptide content after correction for counter‑ions and water; the absolute peptide amount is quantified by amino acid analysis and nitrogen determination.
- Identity Confirmation: Mass spectrometry (ESI‑MS or MALDI‑TOF) provides the observed molecular ion, which must match the theoretical mass within accepted tolerance. Amino acid analysis verifies the correct molar ratio of constituent amino acids.
- Physical Appearance: White to off‑white lyophilized powder, free of visible particulates.
- Residual TFA: Counter‑ion content is controlled (e.g., < 15 % w/w) for studies where TFA interference must be minimised; specific values are reported on the CoA.
In addition to these core tests, some manufacturers offer supplementary analyses such as residual solvent determination (by GC) or peptide content by elemental analysis upon request. Documentation typically includes a Material Safety Data Sheet (MSDS) covering safe handling, transport, and disposal.
Handling and Storage
Maintaining the integrity of the lyophilized powder and its reconstituted solutions requires adherence to controlled laboratory practices. The following recommendations are derived from common industry and supplier guidelines:
- Storage Temperature: Store the unopened vial or bulk container at –20 °C in a frost‑free freezer. For long‑term storage (> 1 month), –80 °C is advisable, although –20 °C is sufficient for the typical 24‑month shelf life.
- Protection from Light: Keep the container in its original light‑resistant packaging or wrap in aluminium foil, as the tryptophan residue is susceptible to photo‑oxidation.
- Moisture and Air Exposure: The lyophilized powder is hygroscopic. Allow the container to reach room temperature before opening to avoid condensation. After use, purge with dry nitrogen or argon, seal tightly, and return to the freezer immediately.
- Reconstitution: For research use, the peptide is often dissolved in sterile, deionized water or physiological saline at a concentration of 1 mg/mL. Vortex gently; avoid vigorous shaking. Once reconstituted, the solution should be aliquoted into single‑use portions and stored at –20 °C to –80 °C.
- Freeze‑Thaw Cycles: Repeated freeze‑thaw cycles can degrade the peptide; consume thawed aliquots quickly and discard any unused portion.
- Weighing and Handling: Use a glove box, fume hood, or ventilated balance enclosure when weighing the dry powder. Wear appropriate personal protective equipment (gloves, lab coat, safety glasses). Avoid inhalation or skin contact.
Under these conditions, the stability of Melanotan II raw material is maintained for up to 24 months from the date of manufacture, as confirmed by periodic quality‑control re‑testing.
Purchasing Considerations
For institutions and distributors sourcing Melanotan II raw material, several factors influence the procurement process:
- Bulk Quantities: Material is typically offered in gram, multi‑gram, or kilogram lots. Bulk pricing is structured around total quantity, with reduced per‑gram costs at higher volumes. Custom aliquoting (e.g., 10 mg, 100 mg, 1 g containers) is often available upon request.
- Custom Packaging: Beyond standard amber glass vials with rubber septa, suppliers can provide sealed foil pouches, PTFE‑lined caps, or larger laboratory bottles for kilo‑scale orders. Packaging is tailored to preserve product integrity under the intended storage conditions.
- International Shipping: Temperature‑controlled logistics are employed for trans‑border deliveries. Lyophilized powder is typically shipped with cold packs or, for long‑distance transit in warm climates, with dry ice to maintain < 25 °C. The exact method is selected based on destination, customs requirements, and shipping duration.
- Documentation and Compliance: Every shipment includes a Certificate of Analysis, Safety Data Sheet, and, when required, a Certificate of Origin. Buyers should verify that the material meets their regulatory import requirements.
- Research Use Statement: All purchase agreements explicitly state that the product is for laboratory research purposes only and is not intended for human or veterinary use. This contractual clause is mandatory.
Buyers are encouraged to request a sample lot (typically a few hundred micrograms) for in‑house analytical verification before committing to a large‑scale order. Pre‑established relationships with certified manufacturers that operate under Good Manufacturing Practice (GMP)-like principles for research‑grade peptides can further reduce supply‑chain risk.
Frequently Asked Questions
What is the solubility of Melanotan II?
The lyophilized powder is freely soluble in deionized water or 0.9 % sodium chloride solution (normal saline) at a concentration of 1 mg/mL. For in vitro experiments, gentle vortexing achieves full dissolution. If necessary, small amounts of dilute acetic acid or basic buffer can aid solubilisation, but routine laboratory use rarely requires such additives. Always verify solution clarity and pH before use in cell‑based assays.
How should the raw material be handled in the laboratory?
Weighing and aliquoting operations should be performed inside a fume hood or a glove box that is classed for handling fine powders. An analytical balance with anti‑static device is recommended. Personnel must wear nitrile gloves, a laboratory coat, and safety goggles. The work area should be wiped down after handling, and any spills must be cleaned immediately according to the MSDS. Direct inhalation of aerosolized powder must be avoided.
Is a Certificate of Analysis provided with every order?
Yes. A batch‑specific Certificate of Analysis accompanies each shipment. The CoA documents HPLC purity, endotoxin level, mass spectrometry identity data, net peptide content, residual TFA, and physical appearance. Traceable lot numbers link the CoA to the original manufacturing record and retention samples. Additional characterization (e.g., amino acid analysis, circular dichroism) can be included by arrangement.
Can I obtain a small sample before bulk purchase?
Most reputable suppliers provide a sample quantity, often 1–5 mg, for quality assessment. The sample is shipped under the same temperature‑controlled conditions and with its own CoA. This practice allows the buyer’s quality‑control laboratory to independently confirm the material’s suitability for ongoing research projects.
Conclusion
Melanotan II raw material, offered with a purity of ≥ 99 % and supported by rigorous analytical documentation, is an essential research tool for laboratories studying melanocortin receptor biology, pigmentation mechanisms, and energy homeostasis pathways. Its bulk availability, custom packaging options, and temperature‑stable international shipping infrastructure make it accessible to academic core facilities, pharmaceutical R&D programmes, and qualified distributors worldwide. The emphasis on endotoxin control, accurate identity confirmation, and transparent lot‑specific reporting ensures that researchers receive a product consistent with the demands of reproducible, high‑quality science.
As emphasised throughout this article, all Melanotan II material is sold strictly for laboratory research applications. It is not for diagnostic purposes, direct clinical use, or any form of human or veterinary administration. Handling and use must comply with the recipient institution’s safety and ethics guidelines. For detailed quotations, technical data sheets, or to discuss bulk purchase agreements, please direct inquiries to your peptide raw‑material supplier.
Research use only: This product is intended exclusively for in vitro and preclinical laboratory research. It is not a drug, medicine, cosmetic, or dietary supplement, and must not be administered to humans or animals outside of controlled research protocols. No statements in this document should be interpreted as promoting therapeutic benefit or diagnostic application.
For research use only. Not for human or veterinary use.
