Selank and Semax Canada

Selank and Semax are two synthetic heptapeptides that tend to be ordered together, and because both are seven residues long and both end in Pro-Gly-Pro they get treated as a pair. They have different parent molecules, different masses and one important difference in how they age. This page covers both, what to look for on each certificate, and how to order them within Canada.

Two heptapeptides, one shared tail

Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro: the tetrapeptide tuftsin (Thr-Lys-Pro-Arg) extended with a Pro-Gly-Pro tail. Calculated monoisotopic mass is close to 751 Da. It contains no aromatic residue and no methionine.

Semax is Met-Glu-His-Phe-Pro-Gly-Pro: residues 4 to 7 of ACTH (Met-Glu-His-Phe) with the same Pro-Gly-Pro tail. Calculated mass is close to 813 Da. It contains a methionine at the N-terminus and a phenylalanine.

The shared Pro-Gly-Pro extension is a stabilising motif that slows degradation by exopeptidases, and it is the reason both compounds were designed the way they were. Our articles on Selank, tuftsin and the Pro-Gly-Pro tail and Semax, the ACTH fragment and methionine oxidation cover each one in detail.

The methionine difference

Semax has a methionine; Selank does not. That one residue is the main practical difference between the two in the laboratory. Methionine oxidises to the sulfoxide in the presence of dissolved oxygen, adding 16 Da and shifting the peak earlier on a reversed-phase column, and the N-terminal position in Semax is exposed. A Semax certificate should show the main peak at about 813 Da with, at most, a small shoulder at about 829 Da. A Selank certificate has no equivalent concern.

In practice this means Semax solutions should be prepared in degassed water or buffer, aliquoted, frozen, and used within a short period, while Selank solutions are more forgiving. Both are stable as lyophilised powder at minus 20 °C.

What each certificate should show

Neither peptide has a tryptophan or tyrosine, so neither absorbs usefully at 280 nm; Semax’s single phenylalanine gives weak absorbance near 257 nm that is not useful for quantitation. Detection has to be at 210 to 220 nm, and a certificate should state the wavelength. Purity by HPLC area should meet our 99%+ specification, and identity should be confirmed by an observed mass within a few daltons of the calculated value: about 751 Da for Selank and 813 Da for Semax.

Both are small enough that counter-ion and water are a noticeable share of the gross vial mass. Selank in particular, with a lysine and an arginine, carries two counter-ions per molecule in the salt form. Where quantitation matters, use the net peptide content figure if the laboratory reports it. The net peptide content guide covers the conversion.

Sizes we supply

• Selank 5 mg and Selank 10 mg.
• Semax 10 mg.

All are supplied as lyophilised powder at 99%+ purity. Published certificates are on the certificates page, and vials are matched to their report by cap and crimp colour.

Buying Selank and Semax in Canada

Stock is held inside Canada and ships domestically, so there is no customs declaration, no duty and no brokerage fee. Dispatch is usually within one business day, with tracked Canada Post, Purolator, FedEx or UPS service chosen at checkout. Tracked shipping is free on orders over $200, and GST or HST is charged at the delivery province’s rate.

Volume pricing applies across the whole cart, so a Selank and a Semax vial ordered together count as two toward the break. The per-milligram price list shows all three vials on one scale.

Research use only

Selank and Semax from ExoLabz are laboratory reference materials for in vitro and analytical research. They are not drugs and not for human or veterinary use. We do not provide dosing or administration information. The purity guarantee refunds the product and the cost of the test if an independent laboratory finds a vial below its stated purity.