Sable · Question
What is the difference between Melanotan I and P21?
Melanotan I is a linear 13-residue alpha-MSH analogue used in melanocortin-1 receptor research (peptide, MW about 1646.8 g/mol).
Research use only. Not for human consumption. No health claims.
Last verified 2026-10-10
What is the difference between Melanotan I and P21?
Melanotan I is a linear 13-residue alpha-MSH analogue used in melanocortin-1 receptor research (peptide, MW about 1646.8 g/mol).
Which is heavier, Melanotan I or P21?
Melanotan I has a molecular weight of about 1646.8 g/mol and P21 about 578.7 g/mol (PubChem), so Melanotan I is heavier by 1,068.1 g/mol, a ratio of 2.85. This means 1 mg of Melanotan I contains 607.2 nmol versus 1,728 nmol for P21.
How many mg of P21 are equimolar to 1 mg of Melanotan I?
1 mg of Melanotan I (MW 1646.8) is 607.2 nmol. The same number of moles of P21 (MW 578.7) weighs 0.3514 mg. Equimolar comparisons matter when testing two compounds side by side in the same assay.
Compare the molecular formulas of Melanotan I and P21
PubChem lists Melanotan I as C78H111N21O19 (1646.8 g/mol) and P21 as C27H42N6O8 (578.7 g/mol). Melanotan I is a peptide; P21 is a peptidomimetic. These formulas refer to the parent compounds without salt counter-ions.
A 5 mg vial of Melanotan I equals how many mg of P21 in moles?
5 mg of Melanotan I (MW 1646.8) is 3.036 µmol. The same amount of P21 (MW 578.7) would weigh 1.757 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 10 mg vial of Melanotan I equals how many mg of P21 in moles?
10 mg of Melanotan I (MW 1646.8) is 6.072 µmol. The same amount of P21 (MW 578.7) would weigh 3.514 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 10 mg vial of P21 equals how many mg of Melanotan I in moles?
10 mg of P21 (MW 578.7) is 17.28 µmol. The same amount of Melanotan I (MW 1646.8) would weigh 28.457 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 5 mg vial of P21 equals how many mg of Melanotan I in moles?
5 mg of P21 (MW 578.7) is 8.64 µmol. The same amount of Melanotan I (MW 1646.8) would weigh 14.228 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
More questions about melanotan-i
A CoA for every lot; each vial carries a printed lot number that matches it. Ask with the lot number and we send it.
Cite this
Research use only. Not for consumption. No health claims.
Plain
Sable Peptides. (2026). What is the difference between Melanotan I and P21?. UK Research Peptide Reference. Retrieved 11 October 2026, from https://www.sablepeptides.co.uk/questions/compare/melanotan-i-vs-p21/#sqa-040148
APA
Sable Peptides. (2026, October 11). *What is the difference between Melanotan I and P21?*. UK Research Peptide Reference. https://www.sablepeptides.co.uk/questions/compare/melanotan-i-vs-p21/#sqa-040148
BibTeX
@misc{sable_#sqa-040148_2026,
author = {{Sable Peptides}},
title = {{What is the difference between Melanotan I and P21?}},
year = {2026},
howpublished = {\url{https://www.sablepeptides.co.uk/questions/compare/melanotan-i-vs-p21/#sqa-040148}},
note = {Accessed 11 October 2026. CC BY 4.0}
}Badge
<a href="https://www.sablepeptides.co.uk/ref"><img src="https://www.sablepeptides.co.uk/badge/ref.svg" alt="Data: UK Research Peptide Reference — Sable Peptides" width="220" height="40"></a>
Date modified: 2026-10-10