Last Updated: April 19, 2026

Research Use Only: This content is for laboratory and in vitro research purposes only. Not approved by the FDA for human or veterinary use. Nothing constitutes medical advice.

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The Palmetto Peptides Complete Guide to the Research Peptide MT-2 (Melanotan II)

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What Is MT-2 Research Peptide?

MT-2, formally known as Melanotan II, is a synthetic cyclic heptapeptide analog of alpha-melanocyte-stimulating hormone (α-MSH) — a naturally occurring signaling peptide produced in the pituitary gland. In laboratory research, MT-2 is classified as a broad-spectrum melanocortin receptor agonist, meaning it binds to and activates multiple receptors within the melanocortin system: specifically MC1R, MC3R, MC4R, and MC5R.

Researchers use MT-2 as a reference compound in receptor pharmacology studies, melanocyte cell culture experiments, structure-activity relationship (SAR) research, and assay development. Its well-characterized binding profile, decades of published characterization data, and commercial availability at research-grade purity have made it one of the most studied synthetic peptides in melanocortin receptor biology.

MT-2 is not approved for any human or veterinary application. All research use is strictly in vitro and laboratory-based.

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Quick Reference: MT-2 at a Glance

Property	Value
Full Name	Melanotan II
Abbreviation	MT-2
Type	Synthetic cyclic heptapeptide
Sequence	Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂
Molecular Formula	C₅₀H₆₉N₁₅O₉
Molecular Weight	1024.18 g/mol
CAS Number	121062-08-6
Receptor Targets	MC1R, MC3R, MC4R, MC5R
Research Purity Standard	≥98% by RP-HPLC
Appearance	White to off-white lyophilized powder
Recommended Storage	-20°C, sealed, protected from light
Reconstitution Solvent	0.1% acetic acid in sterile water
Regulatory Status	Research use only; not FDA-approved for human or veterinary use

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The Origin of MT-2: A Brief History

MT-2 was developed as part of a systematic melanocortin peptide research program at the University of Arizona, initiated in the late 1970s and producing MT-2's synthesis in the late 1980s and early 1990s. Led by Dr. Victor Hruby and collaborators, the program's original goal was to create synthetic analogs of α-MSH that would be more potent and more metabolically stable than the native hormone — primarily for basic receptor biology research.

The earlier compound Melanotan I (MT-1, or afamelanotide) preceded MT-2 and was a linear analog with selectivity for MC1R. MT-2 followed as a second-generation compound featuring a cyclic backbone, key non-natural amino acid substitutions, and significantly broader receptor activity across the melanocortin family.

Over the 1990s and 2000s, MT-2 became a standard reference compound in the expanding field of melanocortin receptor pharmacology — particularly as research into MC4R and its role in central nervous system signaling grew substantially.

For a detailed timeline of MT-2's scientific development, see our supporting article: History and Development of MT-2 Research Peptide: From Discovery to Modern Laboratory Use.

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Chemical Structure of MT-2: Why It Looks the Way It Does

MT-2's structure was deliberately engineered to outperform its parent molecule in laboratory conditions. Understanding a few key features explains why it behaves the way it does in receptor assays.

The Cyclic Backbone

MT-2 contains a lactam bridge — a covalent bond formed between the side chain of Aspartic acid (position 2) and the side chain of Lysine (position 7) in its sequence. This bridge creates a ring structure that locks the peptide into a fixed three-dimensional conformation.

Think of it this way: a linear peptide is like a flexible chain that can wiggle into many different shapes. A cyclic peptide is more like a rigid ring — it presents the same shape to a receptor every time. That consistency reduces the energetic cost of fitting into the receptor's binding pocket, which is a big part of why MT-2 binds melanocortin receptors with substantially higher affinity than native α-MSH.

Key Non-Natural Amino Acid Substitutions

Two deliberate modifications distinguish MT-2 from anything that occurs in biology:

Norleucine (Nle) replacing Methionine: Methionine is oxidation-prone. Norleucine is the structurally similar but oxidation-resistant replacement, preserving the steric properties while eliminating a degradation liability.

D-Phenylalanine (D-Phe) replacing L-Phenylalanine: D-amino acids are mirror images of the naturally occurring L-amino acids. This single inversion causes the peptide backbone to fold in a way that positions MT-2's receptor-binding core — the His-D-Phe-Arg-Trp pharmacophore — in an optimal orientation for melanocortin receptor engagement. This is the primary reason MT-2 is dramatically more potent at receptor binding than native α-MSH.

Terminal Modifications

The N-terminus of MT-2 is capped with an acetyl group and the C-terminus carries an amide group. Both modifications block the peptide's ends from enzymatic cleavage, contributing further to MT-2's stability in aqueous research conditions.

For the full structural breakdown, see: Chemical Structure and Synthesis of Melanotan II (MT-2) Research Peptide Explained.

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The Melanocortin System: Context for Understanding MT-2 Research

To understand why MT-2 matters as a research tool, it helps to know what the melanocortin system is and why scientists study it.

Five Receptors, Many Research Areas

The melanocortin system is a family of five G protein-coupled receptors (GPCRs) that respond to melanocortin peptides — a group that includes α-MSH, β-MSH, γ-MSH, and ACTH (adrenocorticotropic hormone). These receptors are found in different tissues and are involved in a variety of physiological signaling pathways studied at the basic science level.

Receptor	Primary Location	Research Interest
MC1R	Melanocytes, skin	Pigmentation biology, melanogenesis
MC2R	Adrenal cortex	ACTH/cortisol signaling (MT-2 does NOT bind MC2R)
MC3R	Hypothalamus, limbic system	Energy homeostasis signaling
MC4R	Central nervous system (hypothalamus)	Neurological signaling, feeding behavior research
MC5R	Exocrine glands, peripheral tissues	Exocrine and peripheral signaling

MT-2 is a valuable research tool precisely because it activates MC1R, MC3R, MC4R, and MC5R — four of the five receptors in the family — with high affinity. This broad profile makes it useful both as a pan-agonist reference and, in combination with selective antagonists, as a tool for dissecting individual receptor contributions.

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How MT-2 Works in Laboratory Studies: The Mechanism of Action

When MT-2 is applied in a cell-based or receptor binding assay, the sequence of molecular events follows a well-characterized pathway:

Step 1: Receptor Binding

MT-2 occupies the orthosteric binding site on melanocortin receptors. The pharmacophore sequence — His-D-Phe-Arg-Trp — makes the key contacts with the receptor's binding pocket. The cyclic conformation presents these contacts in a pre-organized geometry that improves binding affinity relative to linear analogs.

Step 2: G Protein Activation

Melanocortin receptors (MC1R, MC3R, MC4R, MC5R) couple primarily to Gs proteins — stimulatory G proteins. When MT-2 occupies the receptor, it drives a conformational change that activates the associated Gs alpha subunit.

Step 3: cAMP Elevation (The Primary Measurable Signal)

The activated Gs alpha subunit stimulates adenylyl cyclase, which converts ATP to cyclic AMP (cAMP) — the primary intracellular second messenger of the melanocortin signaling cascade. In virtually every cell-based MT-2 study, intracellular cAMP elevation is the key downstream readout.

Step 4: PKA Activation and Cell-Type-Specific Downstream Effects

Elevated cAMP activates Protein Kinase A (PKA), which phosphorylates targets that vary by cell type. In melanocytes, this leads ultimately to MITF transcription factor upregulation and activation of melanin synthesis genes. In neurons expressing MC4R, it affects ion channel activity and neuropeptide signaling networks. The specific downstream effects depend on which receptor is activated and in which cellular context.

MT-2 binds melanocortin receptor
         ↓
Gs protein activation
         ↓
Adenylyl cyclase stimulated
         ↓
ATP → cAMP (rises intracellularly)
         ↓
PKA activation
         ↓
Cell-specific downstream effects
(melanocytes: MITF/tyrosinase | neurons: ion channels/neuropeptides)

For a complete mechanistic breakdown, see: Mechanism of Action of MT-2 Research Peptide in Melanocortin Receptor Studies.

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MT-2 vs Melanotan I: Key Differences for Researchers

Melanotan I (MT-1) and MT-2 are both synthetic melanocortin agonists derived from the same research program, but they are meaningfully different compounds. Choosing the wrong one for your experiment can introduce significant receptor-selectivity confounds.

The Short Version

MT-1 is a longer, linear peptide with strong selectivity for MC1R. Researchers who want clean MC1R pharmacology in a melanocyte cell line often prefer MT-1 because its activity is more confined to that single subtype.

MT-2 is shorter, cyclic, and activates MC1R, MC3R, MC4R, and MC5R with comparable high affinity. Researchers studying MC4R, conducting pan-melanocortin activation studies, or using MT-2 as a reference compound in SAR work choose MT-2 for its broader profile and its much larger published literature base.

Feature	MT-1 (Melanotan I)	MT-2 (Melanotan II)
Length	13 amino acids (linear)	7 amino acids (cyclic)
Receptor selectivity	MC1R preferred	MC1R, MC3R, MC4R, MC5R
Best for	Isolated MC1R studies	MC4R, pan-agonist, SAR reference
Stability in solution	Moderate	High (cyclic backbone)

For the full comparison, see: MT-2 vs Melanotan I Research Peptides: Key Differences for Laboratory Applications.

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Current Research Applications of MT-2

MT-2 serves several distinct functions in the scientific literature. Here is a summary of where it is actively used:

Melanocyte and Pigmentation Biology Research

In melanocyte cell lines such as B16-F10 (mouse) and SK-MEL-28 (human), MT-2 is used to study MC1R signaling, cAMP responses, MITF regulation, and tyrosinase-driven melanin synthesis. These are some of the most well-established in vitro applications in the MT-2 literature.

MC4R and CNS-Related Cell Studies

MC4R is among the most studied GPCRs in neuroscience. In hypothalamic cell lines (GT1-7) and HEK293 cells stably expressing MC4R, MT-2 is used to characterize receptor activity, downstream signaling effectors, and the effects of novel MC4R ligands relative to this reference agonist.

Structure-Activity Relationship (SAR) Research

Medicinal chemists studying new melanocortin ligands use MT-2 as the reference compound against which novel analogs are compared. MT-2's thoroughly documented binding profile across four receptor subtypes makes it the natural baseline for selectivity optimization studies.

Assay Development and Validation

MT-2 is the positive control of choice in melanocortin receptor functional assays. When researchers develop or validate a new cAMP assay system, MT-2's known EC50 is used to benchmark assay performance before the system is used on test compounds.

For the full picture of research applications, see: Current Research Applications of MT-2 Peptide in Scientific Cell and Receptor Studies.

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MT-2 Purity and Quality: What Researchers Need to Know

The quality of your MT-2 research peptide directly affects the reliability of your data. A lower-purity peptide introduces unknown compounds — synthesis impurities, deletion sequences, oxidized variants — that can interact with your receptors or cell systems in ways you cannot control or account for.

Minimum Purity Standard: 98% by RP-HPLC

Research-grade MT-2 should be at minimum ≥98% pure as determined by reverse-phase HPLC (RP-HPLC). This is the industry standard for peptides used in receptor pharmacology. Some suppliers advertise 95% as "research grade" — it is not adequate for receptor binding assays or cell-based work where impurities can confound results.

Identity Confirmation: Mass Spectrometry

HPLC tells you purity. Mass spectrometry tells you identity. Every legitimate MT-2 supplier should provide lot-specific MS data confirming the observed molecular mass is consistent with MT-2's theoretical weight of 1024.18 g/mol.

Certificate of Analysis: What to Require

Before purchasing MT-2 from any supplier, researchers should confirm that a lot-specific Certificate of Analysis (CoA) is available. The CoA should include an HPLC chromatogram (not just a purity number), MS identity data, the lot number matching the vial, and storage recommendations.

What a Quality CoA Looks Like

CoA Element	Acceptable	Red Flag
HPLC purity	≥98% with chromatogram	Number only, no trace
MS data	Matches 1024.18 Da	Missing or doesn't match
Lot number	Specific to the vial	Generic or undated
Endotoxin	EU/mg value provided	Not tested
Storage	-20°C lyophilized	Not specified

For a full guide to evaluating supplier quality, see: Purity Testing and Quality Control Methods for MT-2 Research Peptides. And for guidance on what to look for when purchasing, see: Buyer's Guide: What to Consider When Purchasing MT-2 Research Peptide Online.

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Storing MT-2 Research Peptide: The Essentials

Improper storage is one of the most common reasons researchers get inconsistent results from peptide experiments. MT-2 is not uniquely fragile, but it does degrade through predictable pathways — all of which are manageable with correct protocols.

Lyophilized MT-2 Storage

Store sealed vials at -20°C or lower, protected from light and moisture. Under these conditions, properly stored lyophilized MT-2 maintains stability for 24–36 months. For archive storage beyond 18 months, -80°C is preferable.

One rule that many researchers skip: allow the sealed vial to equilibrate to room temperature before opening. Opening a cold vial in a warm, humid lab environment allows condensation to enter and absorb into the lyophilized powder — introducing the moisture that drives hydrolytic degradation before reconstitution even begins.

Reconstituted MT-2 Storage

Once dissolved, MT-2 solution is more vulnerable than the lyophilized powder. Best practices:

• Store at 4°C for short-term use (up to 4 weeks)
• Store at -20°C for longer periods (up to 3 months)
• Aliquot into single-use volumes before first freeze — repeated freeze-thaw cycles degrade peptide activity incrementally
• Use low-bind (LoBind) microcentrifuge tubes — standard plastic adsorbs peptide at nanomolar concentrations
• Protect from light at all stages

For the full storage protocol, see: Best Practices for Storing MT-2 Research Peptide to Preserve Potency in the Lab.

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How to Reconstitute MT-2 Research Peptide

Reconstitution is the process of dissolving lyophilized MT-2 in solvent to create a working stock solution. It takes less than 15 minutes but has a few non-obvious details that matter for data quality.

Recommended Solvent: 0.1% Acetic Acid

The most widely used and best-supported solvent for MT-2 reconstitution is 0.1% acetic acid in sterile water. The slightly acidic pH slows hydrolysis and promotes peptide solubility better than neutral water or PBS.

To prepare: add 1 µL of glacial acetic acid per 1 mL of sterile water. Alternatively, purchase pre-made sterile 0.1% acetic acid from a lab supply vendor.

Concentration Calculation Shortcut

MT-2 molecular weight: 1024.18 g/mol

To make a 1 mg/mL stock (approximately 1 mM):

• Add 1 mL of solvent per 1 mg of peptide
• For a 5 mg vial: add 5 mL of solvent

Reconstitution Protocol (Condensed)

1. Allow sealed vial to reach room temperature (10–15 minutes, sealed)
2. Inspect lyophilized powder (white to off-white, consistent appearance)
3. Add calculated solvent volume slowly against the vial wall
4. Gently swirl or roll until dissolved — do not vortex vigorously
5. Solution should be clear and colorless
6. Filter through 0.22 µm if using in cell culture applications
7. Divide into single-use aliquots in labeled low-bind tubes
8. Store at 4°C (short-term) or -20°C (long-term)

For the complete step-by-step protocol, see: Step-by-Step Reconstitution of MT-2 Research Peptide for Laboratory Experiments.

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Reconstituted MT-2 Stability and Shelf Life

Once reconstituted, MT-2's usable life depends on storage conditions and how many times the solution has been frozen and thawed.

Stability by Condition

Storage Condition	Expected Usable Period
4°C in 0.1% acetic acid	2–4 weeks
-20°C, single-use aliquots	Up to 3 months
-80°C, single-use aliquots	Up to 6+ months
nM working solution (any condition)	Prepare fresh before each run

Key Stability Rules

• Maximum 3 freeze-thaw cycles per aliquot before replacing
• Yellow or brown discoloration signals oxidation of Trp or His residues — do not use
• Cloudiness or visible particulate indicates aggregation — do not use
• At nanomolar concentrations, prepare working solutions fresh before each assay from a frozen stock

For detailed stability data and monitoring guidance, see: Long-Term Stability of Reconstituted MT-2 Research Peptide Solutions for Lab Protocols.

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Purchasing MT-2 Research Peptide: What to Look For

The research peptide market varies widely in quality. Researchers who rely on poorly documented or low-purity MT-2 introduce experimental variables that undermine reproducibility — and that can take significant time to diagnose.

Non-Negotiable Standards When Buying MT-2

• Lot-specific CoA with HPLC chromatogram included
• ≥98% purity by RP-HPLC
• Mass spectrometry identity confirmation
• Research-use-only labeling on all products and marketing
• Cold chain shipping to maintain lyophilized peptide integrity

Red Flags

• Generic CoA not matched to your lot
• Purity listed without supporting chromatogram
• No mass spectrometry data
• No verifiable business address or contact
• Unusually low pricing (which often reflects compromised purity or testing shortcuts)

See the full purchasing guide: Buyer's Guide: What to Consider When Purchasing MT-2 Research Peptide Online.

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Why Researchers Choose Palmetto Peptides for MT-2

At Palmetto Peptides, every MT-2 research peptide we supply meets the following standards:

• ≥98% purity by RP-HPLC (many lots achieve ≥99%), confirmed by lot-specific chromatogram
• Mass spectrometry identity verification on every lot
• Lot-specific Certificate of Analysis with full analytical data available with every order
• Research-use-only labeling and FDA compliance disclaimers on all products
• Cold chain shipping to protect lyophilized integrity during transit

We sell exclusively to researchers for in vitro laboratory applications. MT-2 and all Palmetto Peptides products are not sold for human or veterinary use under any circumstances.

Explore our MT-2 Research Peptide product page to view current lot availability and request documentation.

Looking for related research compounds? See our BPC-157 Research Peptide, TB-500 Research Peptide, and our full Research Peptide catalog for additional options.

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MT-2 Research Cluster: All Supporting Articles

This pillar page is the hub for Palmetto Peptides' complete MT-2 research content cluster. Each supporting article covers a specific aspect of MT-2 science in deeper detail:

Article	Focus
History and Development of MT-2 Research Peptide	Discovery, University of Arizona program, scientific timeline
Chemical Structure and Synthesis of Melanotan II	Amino acid sequence, cyclic backbone, SPPS synthesis
Mechanism of Action of MT-2 in Melanocortin Receptor Studies	Receptor binding, cAMP signaling, downstream pathways
MT-2 vs Melanotan I: Key Differences for Lab Applications	Receptor selectivity comparison, when to use each
Best Practices for Storing MT-2 Research Peptide	Lyophilized and reconstituted storage protocols
Step-by-Step Reconstitution of MT-2 Research Peptide	Full lab protocol with troubleshooting
Purity Testing and Quality Control for MT-2	HPLC, MS, endotoxin testing, CoA evaluation
Current Research Applications of MT-2 Peptide	Pigmentation, MC4R, SAR, assay development
Buyer's Guide: Purchasing MT-2 Research Peptide Online	Supplier evaluation, documentation standards, red flags
Why Researchers Choose Palmetto Peptides MT-2	Quality standards, testing protocols, compliance
Long-Term Stability of Reconstituted MT-2 Solutions	Stability by condition, freeze-thaw guidance, degradation signals

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Frequently Asked Questions About MT-2 Research Peptide

Q: What is MT-2 (Melanotan II) used for in laboratory research?
In laboratory settings, MT-2 is used primarily as a melanocortin receptor agonist in receptor binding assays, cAMP functional assays, melanocyte cell culture studies, and as a reference compound in structure-activity relationship (SAR) research. It activates MC1R, MC3R, MC4R, and MC5R and is one of the most thoroughly characterized synthetic peptides in melanocortin receptor pharmacology.

Q: Is MT-2 research peptide legal to purchase?
Purchasing MT-2 for legitimate in vitro laboratory research is legal in the United States. MT-2 is not approved by the FDA for human or veterinary use and cannot be legally sold for those purposes. Researchers should purchase only from suppliers that clearly label all products as research-use-only and maintain appropriate compliance documentation.

Q: What is the molecular weight of MT-2?
MT-2 (Melanotan II) has a molecular weight of approximately 1024.18 g/mol and the molecular formula C₅₀H₆₉N₁₅O₉.

Q: What receptors does MT-2 bind to?
MT-2 binds and activates MC1R, MC3R, MC4R, and MC5R. It does not have meaningful binding affinity for MC2R (the ACTH receptor). This broad, non-selective binding profile makes MT-2 useful as a pan-agonist reference in melanocortin receptor research but means it is not suitable for experiments requiring subtype-selective activation without additional pharmacological controls.

Q: What purity should research-grade MT-2 have?
A minimum of ≥98% purity by reverse-phase HPLC is the standard for research-grade MT-2. This should be confirmed by a lot-specific Certificate of Analysis that includes an actual HPLC chromatogram and mass spectrometry identity data, not just a stated purity value.

Q: How should MT-2 be stored in the lab?
Lyophilized MT-2 should be stored at -20°C or lower in a sealed vial, protected from light and moisture. After reconstitution, store at 4°C for short-term use (up to 4 weeks) or at -20°C in single-use aliquots for up to 3 months. Working solutions at nanomolar concentrations should be prepared fresh before each assay run.

Q: What is the best solvent for reconstituting MT-2?
0.1% acetic acid in sterile water is the most widely used and recommended solvent for MT-2 reconstitution. Its slight acidity improves peptide solubility and slows hydrolytic degradation compared to neutral water or PBS.

Q: How is MT-2 different from Melanotan I?
Melanotan I (MT-1) is a longer (13-amino acid) linear peptide with strong selectivity for MC1R. MT-2 is a shorter (7-amino acid) cyclic peptide that activates MC1R, MC3R, MC4R, and MC5R with comparable affinity. Researchers choose MT-1 for isolated MC1R studies and MT-2 for MC4R research, pan-melanocortin activation, or SAR reference applications.

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Peer-Reviewed Citations

1. Hruby, V.J., et al. (1987). Cyclic lactam analogs of α-melanotropin with high potency and selectivity. Journal of Medicinal Chemistry, 30(6), 1094–1098.
2. Al-Obeidi, F., et al. (1989). Design of a new class of superpotent cyclic alpha-melanotropins based on quenched dynamic simulations. Journal of the American Chemical Society, 111(9), 3413–3416.
3. Mountjoy, K.G., et al. (1992). The cloning of a family of genes that encode the melanocortin receptors. Science, 257(5074), 1248–1251.
4. Cone, R.D. (2005). Anatomy and regulation of the central melanocortin system. Nature Neuroscience, 8(5), 571–578.
5. Wikberg, J.E.S. (1999). Melanocortin receptors: perspectives for novel drugs. European Journal of Pharmacology, 375(1–3), 295–310.
6. Hadley, M.E., & Dorr, R.T. (2006). Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides, 27(4), 921–930.
7. Gantz, I., & Fong, T.M. (2003). The melanocortin system. American Journal of Physiology — Endocrinology and Metabolism, 284(3), E468–E474.
8. Sawyer, T.K., et al. (1982). 4-Norleucine, 7-D-phenylalanine-α-melanocyte-stimulating hormone: a highly potent α-melanotropin with ultralong biological activity. Proceedings of the National Academy of Sciences, 79(5), 1751–1755.

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Palmetto Peptides Research Team
All products are sold for research and laboratory use only. Not for human or veterinary use. These statements have not been evaluated by the Food and Drug Administration.