Melanotan 1

Research Overview

Melanotan I serves as a valuable research tool for investigating MC1R-mediated melanogenesis and pigmentation mechanisms. This synthetic peptide analog was developed as a more stable, longer-acting version of natural α-MSH with enhanced MC1R selectivity compared to broader-spectrum melanocortin agonists. Research applications focus primarily on melanocyte biology, pigmentation pathways, and photoprotection mechanisms. For anti-inflammatory skin research, the tripeptide KPV provides a complementary melanocortin-derived research tool.

The peptide’s designation as Afamelanotide in clinical research contexts reflects its development for investigating photoprotection and pigmentation disorders. Melanotan I is a potent agonist across the melanocortin receptor family (MC1R, MC3R, MC4R, MC5R), with MC1R being its most extensively studied target in melanocyte and pigmentation research models. It is most potent at MC1R but is not receptor-selective.

Melanotan I research has contributed significantly to understanding melanocortin receptor biology, particularly MC1R signaling pathways in melanocytes, photoprotection mechanisms, and pigmentation regulation. The peptide’s linear structure distinguishes it from cyclic analogs like Melanotan II, providing complementary research tools for melanocortin system investigation.

Molecular Characteristics

Complete Specifications:

• CAS Registry Number: 75921-69-6
• Molecular Weight: 1,646.84 Da
• Molecular Formula: C₇₈H₁₁₁N₂₁O₁₉
• Amino Acid Sequence: Ac-Ser-Tyr-Ser-Nle-Glu-His-D-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH₂
• PubChem CID: 16132268
• Peptide Classification: Synthetic linear tridecapeptide, non-selective melanocortin agonist (predominant MC1R potency)
• Appearance: White to off-white lyophilized powder
• Solubility: Water, bacteriostatic water, phosphate buffered saline

The peptide’s 13-amino acid linear structure closely resembles natural α-MSH (Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH₂) with two critical modifications: norleucine (Nle) substitution at position 4 replacing methionine, and D-phenylalanine at position 7 replacing L-phenylalanine. The Nle substitution prevents methionine oxidation, while D-Phe provides enzymatic resistance and enhanced stability.

Pharmacokinetic Profile in Research Models

Melanotan I pharmacokinetic characterization in preclinical research reveals important properties for experimental design:

Absorption and Bioavailability:

• Subcutaneous administration provides sustained absorption profile
• Enhanced stability against peptidase degradation compared to native α-MSH
• Multiple administration routes investigated: SC, IV, intradermal
• Depot effect observed with SC administration in research models

Distribution and Elimination:

• Plasma half-life: Approximately 30-45 minutes in rodent models
• Extended biological activity (12-72 hours) despite relatively short plasma presence
• Tissue distribution primarily to skin and melanocytes
• Gradual clearance allows for less frequent administration in research protocols

Pharmacodynamic Characteristics:

• Duration of melanogenic effects: 24-72 hours post-administration
• concentration-dependent MC1R activation and melanin synthesis
• MC1R binding affinity: Nanomolar range
• Sustained pigmentation effects in research models

These pharmacokinetic properties inform research protocol design, particularly regarding administration intervals and timing of pigmentation measurements in experimental studies.

Research Applications

Melanogenesis and Pigmentation Biology Research

Melanotan I serves as the primary research tool for investigating MC1R-mediated melanogenesis:

• Melanin Synthesis Studies: Investigation of eumelanin production pathways, tyrosinase activation, and melanogenic enzyme regulation
• MC1R Signaling Research: Analysis of cAMP/PKA pathway activation, MITF (microphthalmia-associated transcription factor) regulation, and melanogenic gene expression
• Melanocyte Biology: Studies on melanocyte proliferation, dendricity, melanosome maturation, and melanosome transfer to keratinocytes
• Pigmentation Kinetics: Investigation of pigmentation development time course, concentration-response relationships, and pigmentation maintenance
• Skin Phototype Research: Examination of pigmentation responses across different genetic backgrounds and baseline pigmentation levels

Research protocols employ cultured melanocytes, reconstructed skin models, and animal pigmentation models to characterize Melanotan I’s melanogenic effects.

Photoprotection Mechanism Studies

Research investigates Melanotan I’s effects on UV protection:

• UV-Independent Pigmentation: Studies on melanin production without UV exposure requirement
• DNA Damage Protection: Investigation of melanin-mediated protection against UV-induced DNA damage, thymine dimer formation, and oxidative stress
• Photoprotection Quantification: Research on SPF (sun protection factor) enhancement, minimal erythema dose (MED) changes, and UV tolerance
• Melanin Distribution Studies: Examination of supranuclear melanin cap formation and nuclear DNA protection
• Antioxidant Effects: Investigation of melanin’s free radical scavenging and oxidative damage prevention

Laboratory studies utilize UV irradiation models, DNA damage assays, and photoprotection measurement techniques to examine Melanotan I’s protective mechanisms.

MC1R Receptor Pharmacology

Melanotan I enables melanocortin-receptor (predominantly MC1R) research:

• Receptor Selectivity Studies: Investigation of MC1R vs. other melanocortin receptor binding and activation
• Structure-Activity Relationships: Comparative studies with α-MSH variants to understand MC1R binding requirements
• Receptor Signaling Pathways: Analysis of cAMP generation, MAPK activation, and downstream signaling cascades specific to MC1R
• Receptor Regulation: Studies on MC1R expression, internalization, desensitization, and recycling
• Genetic Variant Research: Investigation of MC1R polymorphisms and their effects on peptide responsiveness

Research protocols include receptor binding assays, functional cAMP assays, receptor transfection studies, and signaling pathway investigations.

Dermatological Research Applications

Research extends to various skin biology areas:

• Pigmentation Disorder Models: Investigation of pigmentation mechanisms relevant to conditions like vitiligo, albinism, and pigmentation abnormalities
• Skin Cancer Prevention Research: Studies on melanin-mediated photoprotection and UV-induced carcinogenesis prevention
• Photosensitivity Disorder Models: Research relevant to porphyria and other photosensitivity conditions
• Keratinocyte-Melanocyte Interactions: Investigation of cell-cell communication, melanosome transfer, and paracrine signaling
• Skin Aging Research: Studies on photoaging mechanisms and pigmentation changes

Laboratory models include organotypic skin cultures, co-culture systems, and various dermatological disease models.

Comparative Melanocortin Research

Melanotan I serves as comparison tool for melanocortin pharmacology:

• Receptor Subtype Selectivity: Comparative studies with non-selective agonists (MT-2) and other selective agonists
• Metabolic vs. Pigmentary Effects: Research distinguishing MC1R pigmentary effects from MC4R metabolic effects (investigated by MC4R-preferring compounds such as PT-141)
• Structure-Function Studies: Comparison of linear vs. cyclic melanocortin peptides
• Safety Profile Research: Investigation of receptor-specific vs. pleiotropic effects
• Therapeutic Window Studies: Research on efficacy vs. off-target effect concentrations

Laboratory Handling and Storage Protocols

Lyophilized Powder Storage:

• Store at -20°C to -80°C in original sealed vial
• Protect from light exposure (peptide is photosensitive)
• Desiccated storage environment required
• Stability data available for 24+ months at -20°C

Photosensitivity Considerations:
Melanotan I demonstrates light sensitivity. Store in amber vials or protect from light exposure. During experimental procedures, minimize light exposure and use light-protected containers.

Quality Assurance and Analytical Testing

Each Melanotan I batch undergoes comprehensive analytical characterization:

Purity Analysis:

• High-Performance Liquid Chromatography (HPLC): ≥99% purity
• Analytical method: Reversed-phase HPLC with UV detection at 280nm
• Multiple peak integration to ensure accurate purity determination

Structural Verification:

• Electrospray Ionization Mass Spectrometry (ESI-MS): Confirms molecular weight 1,646.84 Da
• Amino acid analysis: Verifies sequence composition
• Peptide content determination: Quantifies actual peptide content by weight

Contaminant Testing:

• Bacterial endotoxin: <5 EU/mg (LAL method)
• Heavy metals: Below detection limits per USP standards
• Residual solvents: TFA and acetonitrile within acceptable limits
• Water content: Karl Fischer titration (<8%)
• Oxidation products: Monitored for methionine oxidation (should be absent with Nle substitution)

Documentation:

• Certificate of Analysis (COA) provided with each batch
• Third-party analytical verification available upon request
• Stability data documented for recommended storage conditions
• Batch-specific QC results traceable by lot number

Research Considerations

Experimental Design Factors:

Researchers should consider several factors when designing Melanotan I experiments:

1. MC1R Selectivity: Melanotan I’s strong MC1R potency makes it a widely used tool for studying melanogenic signaling in melanocyte models, where MC1R is the predominant melanocortin receptor.

2. Concentration Selection: Determine appropriate concentrations based on MC1R binding affinity (nanomolar range) and experimental model. Typical research concentrations range from 1nM to 10μM depending on application.

3. Temporal Considerations: Pigmentation development requires time (hours to days). Design experiments with appropriate timing for melanin synthesis and measurement.

4. Baseline Pigmentation: Research outcomes may vary based on baseline melanin content and MC1R genotype. Consider genetic background in experimental design.

5. Light Protection: Implement light protection protocols throughout experimental procedures due to peptide photosensitivity.

Mechanism Investigation:

Melanotan I’s primary mechanism involves MC1R activation and downstream signaling:

• MC1R binding and activation
• Gs protein coupling and adenylyl cyclase activation
• cAMP generation and PKA activation
• CREB phosphorylation and MITF expression
• Melanogenic enzyme upregulation (tyrosinase, TRP-1, TRP-2)
• Eumelanin synthesis and melanosome maturation

Secondary effects include:

• Dendrite formation and melanosome transfer
• Melanocyte proliferation
• Antioxidant and DNA protective mechanisms

Compliance and Safety Information

Regulatory Status:
Melanotan I (Afamelanotide) is provided as a research chemical for in-vitro laboratory studies and preclinical research only. While clinical research has been conducted with this compound, this product is supplied for research purposes and has not been approved by the FDA for general therapeutic use, cosmetic applications, or over-the-counter use.

Intended Use:

• In-vitro cell culture studies
• In-vivo preclinical research in approved animal models
• Laboratory investigation of MC1R pharmacology and melanogenesis
• Academic and institutional research applications

NOT Intended For:

• Human consumption or administration
• Cosmetic or tanning applications
• Therapeutic treatment or diagnosis
• Dietary supplementation
• Veterinary therapeutic applications without appropriate oversight

Safety Protocols:
Researchers should follow standard laboratory safety practices when handling Melanotan I:

• Use appropriate personal protective equipment (lab coat, gloves, safety glasses)
• Handle in well-ventilated areas or fume hood
• Protect from light exposure during handling
• Follow institutional biosafety guidelines
• Dispose of waste according to local regulations for biological/chemical waste
• Consult material safety data sheet (MSDS) for additional safety information

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