Melanotan peptides: alpha-MSH structural comparison

The useful comparison is scaffold architecture

Melanotan I, Melanotan II, and PT-141 belong in the alpha-MSH analogue family, but they should not be collapsed into one product story. <a href="/product/cp-051">CP-051 Melanotan I</a> is cataloged as a linear tridecapeptide reference material at 1646.9 Da. <a href="/product/cp-050">CP-050 Melanotan II</a> is a cyclic heptapeptide reference standard at 1024.2 Da. <a href="/product/cp-052">CP-052 PT-141</a> is a cyclic heptapeptide melanocortin reference standard at 1025.2 Da. The chemistry difference is sequence length, ring constraint, and receptor-family context.

For in-vitro research, the page should explain the ring and sequence logic before it mentions receptor names. A linear tridecapeptide has more rotatable bonds and a longer alpha-MSH-derived chain. A cyclic lactam heptapeptide constrains the pharmacophore into a smaller conformation. PT-141 and Melanotan II are close in mass but not identical; that 1 Da catalog difference still needs lot-specific HPLC-MS verification. The article should keep these points structural and for in-vitro research use only and not for human or veterinary use.

Melanocortin receptors as classification anchors

The melanocortin receptor family gives the article its scientific map. MC1R is central to pigmentation research, MC4R is a common comparator for melanocortin signalling studies, and MC3R and MC5R can appear in broader panel screens. A procurement page does not need to rank the receptors. It needs to tell the reader that the same alpha-MSH pharmacophore can be presented through different scaffolds and then checked by receptor-panel methods in an in-vitro setting.

The internal glossary should support this page with entries for <a href="/glossary/mc1r">MC1R</a>, <a href="/glossary/mc4r">MC4R</a>, and <a href="/glossary/melanocortin-receptor-family">melanocortin receptor family</a>. The adjacent <a href="/product/cp-033">CP-033 KPV</a> link is useful because KPV is another alpha-MSH-derived fragment, although it should be an UPDATE entry rather than one of the primary orphan ADD entries for this article.

Linear Melanotan I: longer chain, different verification questions

Melanotan I is the longer, linear member in this set. The tridecapeptide length means HPLC impurity interpretation resembles other medium-length peptides: deletion sequences, deamidation where sequence permits, salt or water accounting, and method-specific retention. A linear chain can show conformational heterogeneity without having a covalent ring to confirm. The COA should therefore make identity and purity reproducible by reporting the mass method, gradient, detection wavelength, and integration threshold.

CP-051 also needs careful naming. Afamelanotide is a synonym used in the literature, but the article should lead with the catalog name and SKU. That keeps the content aligned to the PDP, not to outside naming habits. The reader should leave understanding that a linear alpha-MSH analogue is not the same analytical object as a cyclic heptapeptide even if the family name is shared.

Melanotan II and PT-141: similar masses, different identity files

Melanotan II and PT-141 are both cyclic heptapeptide melanocortin standards. Their catalog masses, 1024.2 Da and 1025.2 Da, sit close enough that a casual product comparison can blur them. A COA should not. The identity method must confirm the assigned cyclic species, and the release file should show whether any linear precursor, ring-opened impurity, or deletion species is present above the reporting threshold.

Ring closure creates a specific quality question. The mass of a cyclic product can be close to a dehydrated or side-product form, so the method should combine retention behaviour, MS identity, and synthesis-route awareness. A clean article can explain that without giving procedural instructions. It should tell the procurement reader what to look for in the record: HPLC-MS verified main peak, clear molecular weight, lot number, water content, and residual solvents.

Why HPLC-MS alone is necessary but not sufficient

HPLC-MS is the backbone of identity control for all three SKUs, but the release decision still depends on method context. The same mass window can mean different things if the peptide is linear, cyclic, salt-adjusted, or carrying an unresolved impurity. A reviewer should compare the chromatogram to the expected scaffold, not just check that the headline purity exceeds a threshold. That is why cross-linking to <a href="/research-guide/reading-a-coa">reading a COA</a> matters.

For alpha-MSH analogues, the receptor-family language can distract from the release chemistry. Keep the article grounded: scaffold, mass, ring, receptor names, and methods. Canada Peptides can state that the materials are research reference standards supplied from Toronto and HPLC-MS verified. It should not make consumer, cosmetic outcome, or clinical claims.

Cross-links that close the pigmentation gap

The primary internal links are CP-051, CP-050, and CP-052. The article should also link to <a href="/research-guide/ll37-magainin-cationic-peptides">LL-37 and Magainin II cationic peptide chemistry</a> because both pages use charge distribution and amphipathic structure as explanatory frames. A second cross-link to <a href="/research-guide/epitalon-tb500-nad-reference-standards">Epitalon, TB-500, and NAD+ reference standards</a> helps connect the non-metabolic orphan set without creating a claim of shared function.

The reverse-index patch should add one entry each for CP-051, CP-050, and CP-052. CP-033 can receive an UPDATE link if the site team wants an alpha-MSH-derived fragment to point to the melanocortin family article. This split keeps the patch mechanically mergeable and avoids pretending that every related fragment is part of the primary article target list.

Summary

Melanotan I, Melanotan II, and PT-141 should be compared by scaffold: linear tridecapeptide versus cyclic heptapeptide, mass, receptor-family context, and ring-verification evidence. The article supports CP-051, CP-050, and CP-052 while keeping CP-033 as an adjacent update link.

The content stays inside a structural, in-vitro reference-standard frame. It gives procurement readers a clear way to inspect the COA and gives the Canada Peptides research guide a long-tail alpha-MSH hub without drifting into outcome-framed copy.

Release-file review checklist

For release-file review, keep the chemistry anchored to the verified SKU list: CP-051, CP-050, CP-052, CP-033. Confirm sequence or scaffold, molecular weight, HPLC-MS verified identity, counter-ion or modification state, water content, and residual-solvent method before copying the article into a production CMS. Canada Peptides should keep each inline product reference tied to the lower-case PDP route and should keep the article language limited to research reference standard selection, analytical characterisation, and procurement traceability. If a future catalog update changes a molecular weight, adds a salt form, or introduces a new related product, revise the cross-links and the patch file before publication rather than editing the claim in isolation.

Human review should verify any production-page receptor-panel statements before publication. The article names MC1R and MC4R as classification anchors, not as lot-specific assay guarantees.

Procurement traceability notes

A procurement reader should be able to move from this article to a PDP, from the PDP to a lot COA, and from the COA to a reproducible method record without guessing. That means names, SKU codes, molecular weights, and analytical terms must stay consistent across the article body, glossary, and reverse-index patch. The article should therefore be handled as a controlled content asset: update the reviewed date, check the DOI links, rerun the banned-phrase scan, and confirm the article still links to at least three product pages and two research-guide resources before publication.

Publication integration notes

This page should become the pigmentation-family hub. The first paragraph already gives the three verified SKUs and masses, which is the right structure for search snippets and procurement scanning. The rest of the article should keep returning to scaffold architecture: linear tridecapeptide for Melanotan I, cyclic heptapeptide for Melanotan II, and cyclic heptapeptide melanocortin standard for PT-141. That scaffold comparison is safer and more useful than receptor-ranking language.

The editor should watch receptor terminology closely. MC1R and MC4R are appropriate as family anchors, but the article should not imply that a Canada Peptides lot includes receptor-panel data unless a COA or assay file says so. The glossary can carry the receptor definitions; the article can use them only to explain why alpha-MSH analogues are grouped together. If the production CMS adds related-article cards automatically by category, this page should sit with LL-37 and Epitalon pages as structural orphan-coverage content, not with metabolic-family comparison articles.

CMS acceptance notes

Before this object is pasted into the production article array, verify that the slug is unique, the title stays under the search-result length target, the meta description remains in the 150-160 character band, and each internal link resolves to an existing route. Keep the relatedSKUs array uppercase because the article object is a data artifact, while inline PDP links should stay lower-case to match the current route style. This separation prevents a reader-facing URL change from corrupting the SKU key used by the reverse index.

The publication checklist should be mechanical. Parse the JS file, count body words before the references section, scan the body for blocked phrases, confirm at least five DOI-backed citations, count FAQ objects, count H2 headings, and count PDP and research-guide links. Then compare the article's SKU list with pdp_to_article_map_v3_patch.json. If the content and patch disagree, fix both in the same edit. That discipline matters more than adding another paragraph because these articles exist to repair internal linking while preserving catalog truth.

References

1. Mountjoy, K. G., Robbins, L. S., Mortrud, M. T., & Cone, R. D. (1992). The Cloning of a Family of Genes That Encode the Melanocortin Receptors. Science, 257(5074), 1248–1251. DOI: 10.1126/science.1325670 2. Sawyer, T. K., Sanfilippo, P. J., Hruby, V. J., Engel, M. H., Heward, C. B., Burnett, J. B., & Hadley, M. E. (1980). 4-Norleucine, 7-D-phenylalanine-alpha-melanocyte-stimulating hormone: a highly potent alpha-melanotropin with ultralong biological activity. Proceedings of the National Academy of Sciences, 77(10), 5754–5758. DOI: 10.1073/pnas.77.10.5754 3. Yang, Y. (2011). Structure, function and regulation of the melanocortin receptors. European Journal of Pharmacology, 660(1), 125–130. DOI: 10.1016/j.ejphar.2010.12.020 4. Cai, M., Mayorov, A. V., Ying, J., Stankova, M., Trivedi, D., Cabello, C., & Hruby, V. J. (2005). Design of novel melanotropin agonists and antagonists with high potency and selectivity for human melanocortin receptors. Peptides, 26(8), 1481–1485. DOI: 10.1016/j.peptides.2005.03.020 5. Chhajlani, V., Muceniece, R., & Wikberg, J. E. S. (1993). Molecular Cloning of a Novel Human Melanocortin Receptor. Biochemical and Biophysical Research Communications, 195(2), 866–873. DOI: 10.1006/bbrc.1993.2125 6. Hadley, M. E., & Dorr, R. T. (2006). Melanocortin peptide therapeutics: Historical milestones, clinical studies and commercialization. Peptides, 27(4), 921–930. DOI: 10.1016/j.peptides.2005.01.029

Frequently asked questions

References

1. Mountjoy, K. G., Robbins, L. S., Mortrud, M. T., & Cone, R. D. (1992). The Cloning of a Family of Genes That Encode the Melanocortin Receptors. Science, 257(5074), 1248–1251. · link
2. Sawyer, T. K., Sanfilippo, P. J., Hruby, V. J., Engel, M. H., Heward, C. B., Burnett, J. B., & Hadley, M. E. (1980). 4-Norleucine, 7-D-phenylalanine-alpha-melanocyte-stimulating hormone: a highly potent alpha-melanotropin with ultralong biological activity. Proceedings of the National Academy of Sciences, 77(10), 5754–5758. · link
3. Yang, Y. (2011). Structure, function and regulation of the melanocortin receptors. European Journal of Pharmacology, 660(1), 125–130. · link
4. Cai, M., Mayorov, A. V., Ying, J., Stankova, M., Trivedi, D., Cabello, C., & Hruby, V. J. (2005). Design of novel melanotropin agonists and antagonists with high potency and selectivity for human melanocortin receptors. Peptides, 26(8), 1481–1485. · link
5. Chhajlani, V., Muceniece, R., & Wikberg, J. E. S. (1993). Molecular Cloning of a Novel Human Melanocortin Receptor. Biochemical and Biophysical Research Communications, 195(2), 866–873. · link
6. Hadley, M. E., & Dorr, R. T. (2006). Melanocortin peptide therapeutics: Historical milestones, clinical studies and commercialization. Peptides, 27(4), 921–930. · link

References

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3. Mowlazadeh Haghighi S., Zhou Y., Dai J. et al. (2018). Replacement of Arg with Nle and modified D-Phe in the core sequence of MSHs, Ac-His-D-Phe-Arg-Trp-NH2, leads to hMC1R selectivity and pigmentation. European Journal of Medicinal Chemistry. · DOI
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