MT-2

Product Details

MT-2 (Melanotan II Acetate) — Research Grade Peptide, ≥98% Purity (HPLC)

Cyclic melanocortin receptor agonist. Lyophilized powder. Lot-specific COA included.

MT-2, also known as Melanotan II (MT-II) or Melanotan 2 Acetate, is a synthetic cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH). Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂, incorporating a lactam bridge between the Asp and Lys side chains that stabilizes the peptide backbone against proteolysis and increases receptor residence time. The compound was developed at the University of Arizona in the late 1980s and early 1990s as a candidate chemopreventive agent, with the hypothesis that controlled induction of melanogenesis might reduce UV-induced DNA damage and skin cancer risk. MT-2 

MT-2 is a non-selective agonist at the peripheral melanocortin receptors MC1R, MC3R, MC4R, and MC5R. This non-selectivity is the central pharmacological fact about the compound. MC1R activation drives eumelanin synthesis in melanocytes, MC3R and MC4R activation influence food intake and energy balance in the central nervous system, and MC4R activation also mediates erectile response. Binding affinity data show Ki values of 0.67 nM for MC1R, 34 nM for MC3R, 6.6 nM for MC4R, and 46 nM for MC5R. The compound was clinically trialed for erectile dysfunction in the late 1990s and early 2000s, but development was discontinued and it has never received regulatory approval in any jurisdiction.

Supplied as a sterile-filtered, lyophilized powder for in vitro and preclinical research applications. Each lot is independently verified for purity and identity and ships with a Certificate of Analysis.

Specifications

Note: Sigma-Aldrich’s own COA for Melanotan II acetate salt lists a formula weight of 1,024.18 g/mol and a peptide content specification of ≥60%, with a batch result of 82.0%. This means the “≥98% purity” figure and the “peptide content” figure describe different things — purity is the HPLC peak area percentage, while peptide content accounts for counterions, water, and acetate. Gray-market vials tested by Breindahl and colleagues contained actual peptide content ranging from 4.32 to 8.84 mg despite a 10 mg label. Verify both figures against the Certificate of Analysis supplied with your lot.

Research applications

MT-2 is used in laboratory settings to investigate:

• Melanocortin receptor signaling — non-selective activation of MC1R–MC5R and downstream cAMP accumulation in transfected cell lines

• Melanogenesis and pigmentation research — MC1R-mediated eumelanin synthesis in melanocyte cultures, and the compound’s activity as an in vitro and in vivo probe for melanocortin pathways

• Central MC3R/MC4R signaling — anorexigenic effects of central MT-II administration, with intracerebroventricular injection inhibiting food intake in mice

• Antidepressant-like and antistress effects — chronic MT-II treatment reversing chronic unpredictable stress (CUS)-induced anhedonia and attenuating stress-induced body weight loss and adrenal hypertrophy in male rats

• Social behavior and oxytocin research — MT-II-induced central oxytocin release and acceleration of partner preference formation in prairie voles, with selective oxytocin-dependent activation of the nucleus accumbens

• Atherosclerosis and vascular function — chronic MT-II administration reducing ¹⁸F-FDG uptake by atherosclerotic plaques and improving aortic vascular function

• PET imaging tracer development — MT-II-derived radioligands for melanocortin receptor imaging

• Analytical method development — LC-MS/MS quantification and reference standard preparation for melanocortin peptide analysis

Handling and storage

Reconstitute under aseptic conditions using sterile water (18 MΩ-cm resistivity) at a concentration of not less than 100 μg/mL. The lyophilized powder is soluble in water, though some sources report lower aqueous solubility (~0.70 mg/mL) and higher solubility in DMSO (~15 mg/mL) and ethanol (~1 mg/mL). Aliquot immediately after reconstitution to avoid repeated freeze-thaw cycles. Lyophilized powder is stable for up to 2 years at −20 °C under sealed, desiccated, light-protected conditions. Reconstituted solutions should be stored at 2–8 °C for 2–7 days for short-term use; for longer-term storage, store at −20 °C and consider adding a carrier protein (0.1% HSA or BSA) to improve stability. Do not freeze reconstituted solution repeatedly.

For laboratory use by qualified personnel only.