Sable · Question
What is the difference between Semax and P21?
Semax is a heptapeptide analogue of the ACTH(4-7) fragment extended with Pro-Gly-Pro, studied in neuropeptide and BDNF-expression research in rodent models (peptide, MW about 813.9 g/mol).
Research use only. Not for human consumption. No health claims.
Last verified 2026-10-10
What is the difference between Semax and P21?
Semax is a heptapeptide analogue of the ACTH(4-7) fragment extended with Pro-Gly-Pro, studied in neuropeptide and BDNF-expression research in rodent models (peptide, MW about 813.9 g/mol).
Which is heavier, Semax or P21?
Semax has a molecular weight of about 813.9 g/mol and P21 about 578.7 g/mol (PubChem), so Semax is heavier by 235.2 g/mol, a ratio of 1.41. This means 1 mg of Semax contains 1,228.7 nmol versus 1,728 nmol for P21.
How many mg of P21 are equimolar to 1 mg of Semax?
1 mg of Semax (MW 813.9) is 1,228.7 nmol. The same number of moles of P21 (MW 578.7) weighs 0.711 mg. Equimolar comparisons matter when testing two compounds side by side in the same assay.
Compare the molecular formulas of Semax and P21
PubChem lists Semax as C37H51N9O10S (813.9 g/mol) and P21 as C27H42N6O8 (578.7 g/mol). Semax is a peptide; P21 is a peptidomimetic. These formulas refer to the parent compounds without salt counter-ions.
A 10 mg vial of P21 equals how many mg of Semax in moles?
10 mg of P21 (MW 578.7) is 17.28 µmol. The same amount of Semax (MW 813.9) would weigh 14.064 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 Semax in moles?
5 mg of P21 (MW 578.7) is 8.64 µmol. The same amount of Semax (MW 813.9) would weigh 7.032 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 5 mg vial of Semax equals how many mg of P21 in moles?
5 mg of Semax (MW 813.9) is 6.143 µmol. The same amount of P21 (MW 578.7) would weigh 3.555 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 10 mg vial of Semax equals how many mg of P21 in moles?
10 mg of Semax (MW 813.9) is 12.287 µmol. The same amount of P21 (MW 578.7) would weigh 7.11 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
A 30 mg vial of Semax equals how many mg of P21 in moles?
30 mg of Semax (MW 813.9) is 36.86 µmol. The same amount of P21 (MW 578.7) would weigh 21.331 mg. This equimolar conversion lets two compounds be compared at matched molar amounts in the same experiment.
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 Semax and P21?. UK Research Peptide Reference. Retrieved 11 October 2026, from https://www.sablepeptides.co.uk/questions/compare/p21-vs-semax/#sqa-040859
APA
Sable Peptides. (2026, October 11). *What is the difference between Semax and P21?*. UK Research Peptide Reference. https://www.sablepeptides.co.uk/questions/compare/p21-vs-semax/#sqa-040859
BibTeX
@misc{sable_#sqa-040859_2026,
author = {{Sable Peptides}},
title = {{What is the difference between Semax and P21?}},
year = {2026},
howpublished = {\url{https://www.sablepeptides.co.uk/questions/compare/p21-vs-semax/#sqa-040859}},
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