Semax vs Selank: Two Research Heptapeptides Compared
Semax and Selank are both seven-residue synthetic peptides that end in the same Pro-Gly-Pro tail, and both came out of the same research institute. They are built on different parent peptides, though. This post compares their sequences, sizes, the questions the literature asks about each, and how each is checked in the laboratory.
Research blog: general laboratory-science and literature context. Not medical advice. Sealed Peptides materials are for laboratory research use only, and are not for human or veterinary use.
Two parent peptides, one design idea
Semax starts from ACTH(4-7), the Met-Glu-His-Phe stretch of adrenocorticotropic hormone. Selank starts from tuftsin, the tetrapeptide Thr-Lys-Pro-Arg that is a fragment of an immunoglobulin heavy chain.
In both cases the developers, at the Institute of Molecular Genetics in Moscow, added a C-terminal Pro-Gly-Pro tripeptide to the short parent sequence. Proline-rich ends resist many peptidases, and this tail is the main reason the two molecules are so often discussed together.
Sequence and size at a glance
- Semax: Met-Glu-His-Phe-Pro-Gly-Pro (MEHFPGP), formula C37H51N9O10S, listed molecular weight 813.9 Da. The methionine makes it the one of the two that can oxidize at sulfur.
- Selank: Thr-Lys-Pro-Arg-Pro-Gly-Pro (TKPRPGP), formula C33H57N11O9, listed molecular weight 751.9 Da. Lysine and arginine give it a stronger net positive charge.
- Shared: seven residues, the same Pro-Gly-Pro end, and both supplied as lyophilized powders.
What the literature examines
Semax papers largely use rodent and cell models and measure gene expression, with brain-derived neurotrophic factor (BDNF) transcripts a frequent endpoint. Selank papers more often examine enkephalin-degrading enzymes and GABA-related gene expression in rodent tissue.
Most of this work comes from a small number of groups, and much of it is published in Russian-language journals, which is worth keeping in mind when reading it. The Selank research overview and the Semax guide summarize the literature with citations.
Checking each one in the lab
Because the two peptides differ by about 62 Da and in charge, mass spectrometry separates them easily, and they elute at different times on reversed-phase HPLC. For Semax, a peak 16 Da heavier than expected is the classic sign of methionine Oxidation.
Both are small enough that the peptide molecular weight estimator reproduces their listed masses from the sequence, which is a quick way to check a label.
Handling notes
Both are stored sealed and frozen as lyophilized powders. Semax benefits from limited air exposure in solution because of its methionine. For solution arithmetic, the per-compound calculators fill in each molecular weight: Semax and Selank.
Terms used in this guide
Related tools and guides
For laboratory research use only. Not for human or veterinary use. This post is general chemistry and literature context and does not describe or endorse any use of Sealed Peptides products.
