Melanotan-2: research reference

Describe the model before the result. A cellular signal, behavioral observation and clinical outcome are not interchangeable evidence labels.

Cyclization restricts the peptide's conformation and modifies its relative affinity for receptor subtypes. All of these are Gs protein-coupled receptors in cellular models.

The purity value is a product-label specification, not an assay result. A batch result can only be asserted from that batch’s certificate.

These names help identify the catalog entry. A descriptive label is not evidence of efficacy, and structural identity still requires appropriate documentation.

Melanocortin analog

Reconstitution: Laboratory procedure: allow the closed vial to reach room temperature, disinfect the septum and slowly transfer the diluent against the inner wall of the vial. Do not shake; gently swirl the vial until fully dissolved. Record the volume, diluent and date in the batch log.

Storage: Sealed vial of lyophilized material: store at −20 °C, protected from light and moisture. Avoid repeated freeze-thaw cycles of reconstituted material; aliquot when the experimental design permits.

Personal protective equipment: Handle in a clean work area with a lab coat, nitrile gloves and eye protection. Dispose of vials, tips and sharps according to the laboratory waste procedure.

The introductory paper did not test a mammal. Seven related cyclic alpha-melanotropin lactams with different ring sizes were prepared and tested in Rana pipiens frog skin and Anolis carolinensis lizard skin (PMID 2555512). The 23- and 24-membered rings retained prolonged residual activity, while smaller rings did not.

Two references are reviews rather than original measurements of this heptapeptide. One title addresses discovery and development of Melanotan-I and Melanotan-II, but PubMed supplies no abstract, preventing further content verification from that record (PMID 9760697). The other surveys the melanocortin family, describes analogs designed for high potency, prolonged action and enzyme resistance, and records that both melanotans reached clinical study (PMID 16412534).

The instrumental study is analytical: liquid chromatography–tandem mass spectrometry quantified the heptapeptide in mouse plasma and brain homogenate with reported thresholds below previous methods, then examined intraperitoneal exposure (PMID 17610239).

The remaining human observations concern unsupervised use: thematic analysis of online-forum posts and self-reported adverse effects (PMID 34464955), and one renal-infarction case with literature review (PMID 31953620). These comprise the human observations cited here. Sources: PMID 2555512; PMID 9760697; PMID 16412534; PMID 17610239; PMID 34464955; PMID 31953620.

One preclinical paper describes rapid plasma clearance after intraperitoneal exposure in mice (PMID 17610239). At thirty minutes, brain concentration was far below simultaneous plasma concentration, interpreted as limited entry into mouse brain.

The only direct stability-related observation is qualitative design evidence: 23- and 24-membered rings retained prolonged residual activity in amphibian and reptile skin, while smaller rings did not (PMID 2555512). The class review calls these analogs resistant to enzymatic degradation without identifying or quantifying the pathway for this heptapeptide (PMID 16412534).

These sources do not quantify plasma half-life or albumin-bound fraction and do not compare entry routes. Exposure figures from elsewhere do not come from the bibliography cited here. Sources: PMID 17610239; PMID 2555512; PMID 16412534.

The molecule is a shortened, cyclized fragment of thirteen-residue alpha-melanocyte-stimulating hormone rather than a copy. Its predecessor was the linear analog with norleucine at position 4 and D-phenylalanine at position 7, described as highly potent in earlier literature (PMID 2555512).

The defining step shortened the chain to fragment 4–10 and closed a lactam bridge between the side chains of an acidic residue at position 5 and a basic residue at position 10. In 1989, Al-Obeidi, Castrucci, Hadley and Hruby prepared seven closures using glutamate or aspartate with lysine, ornithine, diaminobutyric acid or diaminopropionic acid (PMID 2555512). Relative melanotropic activity in frog and lizard skin depended on ring size, peaking at 23 members and declining in either direction.

Among fragment 4–10 closures, the aspartate–lysine combination gave the highest relative melanotropic activity in lizard-skin models and matches the declared chemical name in this catalog record (PMID 2555512). Sources: PMID 2555512.

Melanotan-1 and PT-141 represent successive points in the same development line. The class review describes Melanotan-I as linear, Melanotan-II as truncated and cyclic, and PT-141 as a later derivative of Melanotan-II (PMID 16412534). Melanotan-1 retains thirteen residues with two substitutions; Melanotan-2 retains those changes, truncates to fragment 4–10 and closes a ring (PMID 2555512).

The catalog’s PT-141/Melanotan-2 distinction is terminal chemistry: free carboxylic acid versus amide. Target evidence is divided: the forum analysis attributes skin hyperpigmentation to MC1 interaction (PMID 34464955), while the mouse analytical paper attributes central action to MC3R and MC4R (PMID 17610239). No reference measures all three compounds in one assay or ranks their quality. Sources: PMID 2555512; PMID 16412534; PMID 17610239; PMID 34464955.

No clinical-trial article is included, although a review records that the compound reached clinical study (PMID 16412534). Human observations are forum-message analysis (PMID 34464955) and one case (PMID 31953620), without comparison groups or exposure measurements. The forum analysis identifies unregulated sourcing.

Mouse analytical findings suggest limited brain entry through one route, without a cited extension to other species or routes (PMID 17610239).

No reference provides quantitative binding constants for each receptor subtype. A further gap separates the defining activity measurements in amphibian and reptile skin, which differed by species (PMID 2555512), from the human-use context described in forum posts (PMID 34464955). Sources: PMID 16412534; PMID 34464955; PMID 31953620; PMID 17610239; PMID 2555512.