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Melanotan II | CAS: 121062-08-6

CAS Number:
121062-08-6
Chemical Classification:
Research peptide

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Melanotan II (CAS 121062-08-6) is a cyclic lactam melanocortin agonist employed to study pigmentation biology and MC1R/MC4R pathway pharmacology in dermatological research settings. Melanogenic response magnitude varies with baseline skin type, UV co-exposure, and delivery route, factors that complicate cross-laboratory comparison of tanning endpoints. Experimental use spans melanocyte tyrosinase-activity assays, eumelanin quantification in UV-irradiated rodent skin, and receptor-selectivity panels in heterologous expression systems. Characterized by COA, LC-MS, HPLC, and NMR; not intended for cosmetic tanning outside research frameworks.

CAS
121062-08-6
Molecular Formula
C50H69N15O9
Molecular Weight
1024.2 g/mol
Purity
≥98%
Appearance
White lyophilized powder
Storage
Store at -20°C

Analytical Documentation

COA✓ Available
LC-MS✓ Available
HPLC✓ Available
NMR✓ Available

Research Inquiry

Overview

Melanotan II is a cyclic lactam-bridged heptapeptide analog of alpha-melanocyte stimulating hormone engineered for potent melanocortin receptor agonism across MC1R, MC3R, MC4R, and MC5R in research settings. Originally developed to study skin pigmentation pathways, melanotan II has become a standard pharmacological probe for melanocortin signaling in dermatological research, energy balance neuroscience, and receptor bias profiling. The Nle4-D-Phe7 substitutions and lactam bridge confer protease resistance and receptor selectivity shifts relative to native alpha-MSH. Melanotan II enables controlled investigation of eumelanin synthesis, hypothalamic satiety circuits, and sexual behavior endpoints in rodent research without human tanning product implications. Supplied at ≥98% purity (C50H69N15O9; 1024.2 g/mol), this material supports controlled laboratory investigation under research-use-only conditions.

Mechanism of Action

Melanotan II activates MC1R on melanocytes, stimulating adenylyl cyclase and MITF transcription leading to tyrosinase upregulation and eumelanin production in skin culture and animal pigmentation research. MC4R activation in hypothalamus reduces food intake and modifies energy expenditure in rodent metabolic studies. MC3R and MC5R engagement contributes to anti-inflammatory and autonomic phenotypes in specialized research protocols. Beta-arrestin recruitment profiles differ from alpha-MSH, supporting biased signaling studies. Melanotan II crosses the blood-brain barrier, centralizing both pigmentation and neuroendocrine research applications.

Receptor Binding & Signaling

Melanotan II binds MC1R, MC3R, MC4R, and MC5R with nanomolar potency in cAMP assays, with highest efficacy at MC1R for pigmentation research. Lower selectivity versus PT-141 makes it useful for pan-melanocortin activation experiments. Off-target GLP-1R or ghrelin receptor activation is negligible at research doses.

Research Applications

Melanogenesis and MC1R dermatology research

Primary melanocyte cultures and reconstructed skin models use melanotan II to quantify melanin content, tyrosinase activity, and MITF nuclear translocation. MC1R variant cell lines model receptor polymorphism effects on pigmentation signaling. Research supports cosmetic science and dermatological biology without human tanning guidance.

Energy balance and MC4R feeding studies

Rodent cumulative intake and meal pattern experiments administer melanotan II to test melanocortin satiety pathways compared with leptin and GLP-1 tools. MC4R antagonists reverse effects confirming mechanism. Metabolic neuroscience platforms benefit from defined melanocortin agonism.

Receptor bias and structural pharmacology

BRET and ERK versus cAMP biosensor cell lines profile melanotan II biased agonism relative to alpha-MSH. Cyclic peptide analogs map lactam bridge geometry to receptor conformational selection. Structure-activity research informs melanocortin medicinal chemistry.

Behavioral and autonomic research models

Specialized rodent protocols examine melanocortin effects on grooming, thermoregulation, and cardiovascular parameters in controlled experiments. c-Fos mapping identifies activated neural populations. Research confined to preclinical neuroendocrine science.

Molecular Information

Sequence & Chain Summary

Cyclic Nle4-D-Phe7-alpha-MSH analog with Asp5-Lys6 lactam bridge.

Modification Type

Lactam cyclization; Nle and D-Phe substitutions.

Structural Notes

Melanotan II mass 1024.2 g/mol with cyclic structure verified by MS/MS fragmentation patterns. Incorrect cyclization yields inactive linear contaminants resolved by HPLC. Hydrophobic character requires careful solubilization for uniform dosing in research. Batch-specific molecular characterization—including mass confirmation and purity profiling—is available through COA, LC-MS, HPLC, and NMR documentation supplied with Melanotan II.

Molecular Formula
C50H69N15O9
Molecular Weight
1024.2 g/mol
Purity Specification
≥98%

Experimental Notes

Stability

Store lyophilized at −20°C desiccated. Cyclic peptide stability superior to linear alpha-MSH yet sensitive to extreme pH ring opening. Light protection recommended for long-term archival storage. Lyophilized Melanotan II should be protected from repeated freeze-thaw cycles, moisture, and prolonged exposure to ambient light where applicable. Analytical integrity is best preserved when material is stored under the conditions specified on the certificate of analysis.

Storage Conditions

Store at -20°C. Melanotan II is supplied as white lyophilized powder. For long-term archival storage in research inventories, maintain sealed containers with desiccant where recommended and document lot numbers for traceability across experimental runs.

Laboratory Handling

Reconstitute with sterile water and optional dilute acetic acid. Vortex minimally to avoid foam. Dose calculations account for cyclic peptide molecular weight. Use MC1R functional assay for batch verification. Reconstitute only with appropriate research-grade solvents compatible with your assay format. Allow vials to reach equilibrium before opening, work under clean bench conditions, and label all working solutions with concentration, date, and researcher ID per institutional SOPs.

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Frequently Asked Questions

Research-focused answers about Melanotan II. For laboratory use only — not medical advice.

What is Melanotan II used for in research?
Melanotan II is for melanocortin receptor and pigmentation pathway research in laboratory models. Not for human tanning, cosmetic tanning products, or unregulated self-administration.
How does Melanotan II work biologically?
Melanotan II activates multiple melanocortin receptors, driving melanogenesis via MC1R and modulating feeding and autonomic pathways via MC4R and related receptors in research models.
What receptors does Melanotan II interact with?
Targets MC1R, MC3R, MC4R, and MC5R with potent agonism; MC1R primary for pigmentation research, MC4R for energy balance studies. Broader receptor profile than PT-141.
Is Melanotan II stable at room temperature?
Store lyophilized at −20°C desiccated. Cyclic peptide stability superior to linear alpha-MSH yet sensitive to extreme pH ring opening. Light protection recommended for long-term archival storage. For short-term laboratory workflows, minimize time at room temperature and return unused material to recommended storage promptly. Melanotan II is not formulated for ambient long-term storage.
What is the recommended storage condition for Melanotan II?
Store at -20°C. Store lyophilized material in a dedicated −20°C freezer, protect from moisture ingress, and avoid repeated temperature cycling. Reconstituted solutions should be aliquoted and frozen if not used within the validated window of your internal stability study.