Melanotan II (MT-II, CAS 121062-08-6) is a non-selective melanocortin receptor agonist developed at the University of Arizona in the 1990s. It binds to MC1R, MC3R, MC4R, and MC5R, giving it a broader receptor profile than its more selective counterpart Melanotan I (afamelanotide).
The peptide was originally investigated as a photoprotective agent because activation of MC1R stimulates melanogenesis, the biological process that produces melanin pigment in skin. Researchers who buy Melanotan II typically study melanocortin signaling, pigmentation biology, and energy homeostasis in laboratory models.
The cyclic lactam structure gives Melanotan II markedly better proteolytic stability than linear α-MSH analogs, which makes it practical for multi-hour in vitro incubations and standardized bench workflows. Laboratories that buy Melanotan II typically store it lyophilized and reconstitute small working aliquots as needed to preserve potency.
Detailed Mechanism of Action
Researchers who buy Melanotan II work with a cyclic heptapeptide (Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2) designed as a stable, receptor-promiscuous α-MSH mimetic. The cyclic lactam bridge between Asp and Lys stabilizes the bioactive conformation and dramatically extends half-life versus native α-MSH, enabling practical use in bench assays.
The peptide activates all five melanocortin receptor subtypes with especially high affinity at MC1R, MC3R, MC4R, and MC5R. MC1R activation on melanocytes drives cAMP-mediated signaling through adenylyl cyclase, upregulating microphthalmia-associated transcription factor (MITF) and tyrosinase, which increases eumelanin synthesis within melanosomes.
At MC3R and MC4R, Melanotan II modulates hypothalamic circuits relevant to appetite and energy balance. MC4R signaling in the paraventricular nucleus reduces food intake in rodent models, while MC3R contributes to nutrient partitioning and feed efficiency. MC5R activity has been studied in exocrine gland function and immune modulation.
Because Melanotan II is non-selective, researchers often pair it with subtype-selective antagonists to isolate individual receptor contributions. This promiscuity is both a strength and a limitation — making Melanotan II valuable for mapping melanocortin biology in whole-system models, but requiring controls when targeting a single receptor.
Downstream of MC1R activation, elevated intracellular cAMP drives protein kinase A activity and CREB phosphorylation, which increases transcription of pigment-pathway genes. Researchers studying the melanogenesis cascade often use Melanotan II to stimulate a predictable pigment response in B16 mouse melanoma cells, normal human epidermal melanocytes (NHEM), and three-dimensional skin-equivalent cultures.
In central nervous system work, Melanotan II crosses the blood-brain barrier poorly on its own but is widely used in direct intracerebroventricular (ICV) administration studies. These models have helped define the role of hypothalamic MC4R in satiety, leptin-melanocortin signaling, and obesity-related metabolic phenotypes in knockout animal lines.
Published Research
The scientific literature on Melanotan II spans more than three decades. Dorr and colleagues (1996) published foundational work in Archives of Dermatology showing that superpotent melanotropic peptides combined with solar UV radiation produced measurable tanning responses in human volunteer models. Their data established the dose-response relationship that later researchers replicated.
Wessells and colleagues (2000), writing in the Journal of Urology, reported that synthetic melanotropic peptides initiated erectile responses in men with psychogenic erectile dysfunction, implicating MC4R central pathways. This line of work contributed to the later development of bremelanotide (PT-141), a selective MC3R/MC4R agonist derived from the Melanotan II scaffold.
More recent studies have examined the role of melanocortin signaling in metabolic disease, obesity, and inflammation. Reviews on PubMed consolidate findings across MC1R pigmentation work, MC3R/MC4R feeding research, and MC5R exocrine studies. Laboratories that buy Melanotan II for research typically reference these primary sources when designing assays.
Hadley and Dorr (2006) reviewed the three-decade development arc of melanotropic peptides in Peptides, summarizing structure-activity work that identified the Nle4, D-Phe7 substitutions as central to potency. Their review remains a useful entry point for laboratories new to melanocortin research and a useful reference when evaluating purity and identity in newly received lots. Additional work indexed on NIH PubMed continues to define structure-activity relationships and cross-species receptor behavior.
Researchers exploring appetite circuits often cite work by Cone and colleagues on melanocortin receptor knockout phenotypes. These studies showed that loss of MC4R function produced a hyperphagic, obese phenotype in mice that closely mirrors monogenic human obesity syndromes linked to MC4R mutations, reinforcing the relevance of Melanotan II as a pharmacological tool in the same circuit.
Melanotan II vs Alternatives
| Feature |
Melanotan II |
Melanotan I |
PT-141 |
| Receptor profile |
MC1R, MC3R, MC4R, MC5R |
MC1R selective |
MC3R / MC4R selective |
| Structure |
Cyclic heptapeptide |
Linear 13-mer |
Cyclic heptapeptide |
| Primary research use |
Broad melanocortin biology |
Photoprotection |
Central arousal pathways |
| Half-life (est.) |
~30 minutes |
~30 minutes |
~2 hours |
| Pigmentation effect |
Strong |
Strong |
Minimal |
| Form supplied |
Lyophilized powder |
Lyophilized powder |
Lyophilized powder |
| Selectivity |
Non-selective |
Selective |
Selective |
| Purity standard |
99%+ HPLC |
99%+ HPLC |
99%+ HPLC |
When researchers buy Melanotan II rather than a selective alternative, they gain the ability to probe multiple melanocortin receptors with a single compound. The trade-off is reduced specificity, which makes a good experimental design — including vehicle controls and, where necessary, selective antagonists — essential.
Reconstitution & Handling
To buy Melanotan II lyophilized powder is only the first step — proper reconstitution is essential for reproducible assay results. The standard laboratory protocol uses bacteriostatic water or sterile water for injection as the diluent. Add the chosen volume slowly along the vial wall to avoid foaming, which can denature the peptide.
A common working stock is 10 mg reconstituted in 2 mL of bacteriostatic water, yielding 5 mg/mL. For detailed volume math and syringe unit conversions, see the reconstitution guide and the dosage calculator walkthrough. Always allow the vial to reach room temperature before reconstitution to reduce the risk of condensation.
After reconstitution, gently swirl rather than shake the vial. Label each working aliquot with the concentration, date, and lot number, and record the diluent used. These records support reproducibility across multi-day experiments and help trace back any unexpected results to a specific preparation.
Storage & Stability
Store lyophilized Melanotan II at -20°C protected from light; under these conditions the peptide is stable for 24+ months. Once reconstituted, aliquot into low-binding tubes and store at 2–8°C for short-term use (up to ~30 days) or at -20°C for longer-term archiving. Avoid repeat freeze-thaw cycles, which accelerate aggregation.
For a full breakdown of temperature ranges, light sensitivity, and signs of degradation, see the peptide storage guide and how to tell if a peptide has degraded. Visible cloudiness, color change, or precipitate in reconstituted solution indicates the stock should be discarded.
Temperature cycling is the most common cause of degradation in working stocks. Dedicate a labeled tray in the -20°C freezer to peptide aliquots and avoid storing them in the door, where temperature swings are largest. For long projects, prepare many small single-use aliquots up front so each experiment draws from a freshly thawed tube.
Certificate of Analysis
Every lot includes a batch-specific Certificate of Analysis listing HPLC purity, mass spectrometry confirmation of molecular weight, water content, and appearance. Reading a COA correctly is part of good laboratory practice — the COA reading guide explains every line item in plain language.
Researchers who buy Melanotan II from PSPeptides receive independently verified testing, not a self-issued certificate. Independent testing confirms that the material in the vial matches the label claim within strict tolerances.
The COA also lists the peak retention time, column used, and any impurity peaks above threshold. Cross-check the observed monoisotopic mass on the mass-spectrometry trace against the expected value for Melanotan II before beginning critical experiments.
Why Researchers Choose PSPeptides
- US Manufactured: Synthesized and lyophilized in American facilities, not rebranded offshore product.
- Third-Party Tested: Independent HPLC and mass spectrometry on every lot, with COA provided.
- Fast Shipping: Free UPS 2nd Day Air over $150; same-day processing on orders placed before 2 PM EST.
- Flexible Payments: Credit cards, Afterpay, Klarna, Apple Pay, and Google Pay all accepted.
- 7-Day Support: Email, phone, or text support available every day of the week.
- Consistent Lot Quality: Tight quality control across batches means less assay-to-assay variability.
Frequently Asked Questions
What purity should I look for when I buy Melanotan II?
For reproducible research, minimum acceptable purity is 98% by HPLC, with 99%+ strongly preferred. Always verify with a third-party COA rather than a vendor-issued certificate, and confirm mass spectrometry identity for the expected molecular weight.
How is Melanotan II different from Melanotan I?
Melanotan I (afamelanotide) is a linear 13-amino-acid peptide that selectively activates MC1R. Melanotan II is a shorter cyclic heptapeptide that activates MC1R, MC3R, MC4R, and MC5R. The broader receptor profile makes Melanotan II useful in studies beyond pigmentation alone.
How should I reconstitute Melanotan II?
Use bacteriostatic water or sterile water for injection, adding slowly along the vial wall to avoid foaming. A 10 mg vial reconstituted in 2 mL of diluent yields 5 mg/mL. Detailed volume math is in the reconstitution guide linked above.
Is a Certificate of Analysis included?
Yes. Every order ships with a batch-specific COA showing HPLC purity, mass spectrometry, water content, and appearance. The COA is matched to the lot number printed on your vial.
Where can I buy Melanotan II with confidence in its purity?
Look for vendors that publish third-party COAs, document US manufacturing, and provide batch-level testing rather than generic certificates. PSPeptides meets those criteria and supplies HPLC and mass-spec data for every lot of Melanotan II.
How long is reconstituted Melanotan II stable?
When aliquoted into low-binding tubes and stored at 2–8°C, reconstituted Melanotan II is generally stable for roughly 30 days. Long-term storage at -20°C extends viability, but repeated freeze-thaw cycles should be avoided. Discard any stock that develops cloudiness or discoloration.
Related Resources
All PSPeptides products are sold exclusively for laboratory and research use. Not intended for human consumption.
Choosing a Research Peptide Supplier for Melanotan II
When researchers buy Melanotan II for laboratory use, supplier selection has a measurable effect on data quality. The peptide itself is structurally straightforward to synthesize by solid-phase methods, but purification, lyophilization, and quality control vary widely across manufacturers. The difference between a 95% purity lot and a 99%+ purity lot can show up as inconsistent EC50 values, baseline noise in cAMP assays, or unexpected side activity in receptor panels.
Laboratories that consistently buy Melanotan II from verified suppliers build a reliable record of lot-to-lot consistency. PSPeptides supports this by documenting each lot with independent third-party testing and retaining samples for follow-up verification if a user reports anomalous data. The how to choose a research peptide supplier guide details red flags to watch for and green flags that indicate a quality-first operation.
Another consideration when researchers buy Melanotan II is the packaging. A well-sealed amber vial, tight crimp cap, and internal vacuum that collapses the cake into a compact lyophilized plug are all visual signals of proper handling. If the vial arrives with visible moisture, a discolored cake, or a loose closure, document the condition photographically and contact the supplier before reconstituting.
Melanotan II Research Design Considerations
Because Melanotan II is a non-selective melanocortin agonist, experimental design needs to account for off-target receptor effects. When the research question focuses on MC1R-driven pigmentation, parallel arms using a selective MC1R agonist or a Melanotan I comparator help confirm that observed effects are melanocortin-mediated rather than driven by MC3R or MC4R pathways.
For studies that buy Melanotan II as a tool to probe central feeding circuits, inclusion of the MC3R/MC4R antagonist SHU9119 or the selective MC4R antagonist HS014 supports interpretation of which receptor subtype contributes to a given behavioral or metabolic phenotype. Vehicle-only controls, reconstituted from the same diluent lot used for the active compound, should always accompany dosed arms.
Dose-response design is another area where Melanotan II research benefits from careful planning. A typical in vitro concentration range spans from low nanomolar to low micromolar depending on the receptor assay. Pilot runs at three log-spaced concentrations help identify the linear portion of the curve before committing to a full EC50 determination, conserving peptide and reducing variance.
Quality Control Standards for Melanotan II
PSPeptides tests every lot of Melanotan II against a defined internal specification. HPLC with UV detection quantifies purity against a reference standard, and the acceptable release criterion is ≥99% main peak area. Mass spectrometry confirms the expected monoisotopic mass within a tight tolerance window, and any lot that fails either criterion is rejected.
Water content is measured by Karl Fischer titration and held below a maximum threshold to ensure efficient reconstitution and long shelf life. Residual solvents from synthesis are screened by gas chromatography, and appearance is documented before vials are labeled and sealed. The full specification is summarized on the COA that ships with every Melanotan II order.
Researchers who buy Melanotan II and want to perform incoming QC at their own facility can re-run purity analysis on arrival. This is common practice in regulated environments and adds a confirming data point. The retention time, peak symmetry, and mass-spec fingerprint should match the supplier COA within instrument tolerance.
Handling Safety and Laboratory Best Practices
Standard laboratory peptide-handling precautions apply. Work in a clean, draft-free space, wear gloves and a lab coat, and avoid inhalation of the lyophilized powder when opening the vial. A brief equilibration to room temperature before breaking the seal reduces condensation inside the vial, which in turn reduces the risk of introducing moisture into long-term storage stock.
Dispose of Melanotan II waste through your institution’s chemical waste stream, not general trash. Keep documentation of received lots, COAs, and usage logs — this is often required under institutional research protocols and is useful when troubleshooting unexpected results. Laboratories that buy Melanotan II for multi-year projects benefit from a simple spreadsheet tracking vial number, reconstitution date, and assay runs.
Summary: Why Laboratories Buy Melanotan II from PSPeptides
Researchers buy Melanotan II from PSPeptides because every lot ships with independent HPLC and mass-spec data, a batch-specific COA, and documented US manufacturing. The non-selective melanocortin agonist profile makes it a flexible tool across pigmentation, photoprotection, appetite, and comparative receptor pharmacology projects. When you buy Melanotan II in lyophilized form, you retain full control over reconstitution volumes, aliquot size, and storage strategy.
Before you buy Melanotan II for a new project, read the linked reconstitution, storage, and COA guides above to align your lab protocols with current best practices. For teams running multi-arm studies, ordering enough lots of Melanotan II up front ensures consistent material across the entire experimental timeline. Laboratories that buy Melanotan II from PSPeptides also gain seven-day-a-week technical support and flexible fast-shipping options on research orders.
When you buy Melanotan II at research scale, factor in freezer capacity, aliquot counts, and expected run duration. A single 10 mg vial of Melanotan II supports a substantial number of in vitro dose-response runs when aliquoted carefully. Teams that buy Melanotan II in parallel with bacteriostatic water and low-binding tubes at the outset of a project avoid stock-out delays mid-experiment.
Ready to buy Melanotan II? Order now from PSPeptides for same-day processing on lab-ready lyophilized vials, independent COA, and fast UPS shipping to qualified research facilities across the USA.
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