N-Acetyl Selank

N-Acetyl Selank is the heptapeptide Selank carrying an acetyl group on the threonine at its N-terminus. It is registered at PubChem as CID 133082488 and at FDA GSRS under UNII J3PM702O93.

Base Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, confirmed independently by FDA GSRS and PubChem, and is built from two recognisable pieces: the tuftsin tetrapeptide Thr-Lys-Pro-Arg followed by the glyproline tripeptide Pro-Gly-Pro. The acetyl group here sits on the alpha-amino group of that first threonine.

The C-terminus needs stating explicitly, because the trade name for this material usually does not match the chemistry. Material is widely sold as N-Acetyl Selank Amidate, but the registered compound - the one with a PubChem record, an FDA unique ingredient identifier and the formula above - carries a free carboxylic acid at Pro7, not an amide. Its deposited structure and its systematic name both terminate in a pyrrolidine-2-carboxylic acid. An exact-structure search of PubChem for the amidated form returns no hits at all, and FDA GSRS holds no record of it, so the figures on this page are the registered free-acid compound and no mass is offered for an amidate that no registry describes.

No CAS number is printed because none has been assigned to this compound in either registry. Base Selank does have one, 129954-34-3, carried by both PubChem and FDA GSRS, but it belongs to the unacetylated peptide and is not interchangeable with this material. FDA GSRS additionally carries a six-residue synonym string on this record that is missing a proline; the registered structure on the same record is unambiguously seven residues.

The acetyl group is there for a documented chemical reason. Shevchenko and colleagues showed in Bioorganicheskaia Khimiia in 2013 that the Pro-Gly-Pro motif is what resists leucine aminopeptidase and the enzymes of nasal mucus, brain microsomal fractions and blood, which is what resists attack at the C-terminal end; acetylation removes the free alpha-amino group that aminopeptidases require as a handle at the other end.

There are no aromatic residues in the sequence at all, so absorbance at 280 nm cannot be used to determine concentration. There is also no cysteine and no methionine. Acetylation removes the terminal ammonium group, which lowers the net charge by one relative to base Selank and shifts ion-exchange behaviour accordingly.

No molecular target is identified for this compound or for base Selank. Neither appears in ChEMBL at all, so there is no curated binding dataset of any kind, and the neuropilin-1 interaction reported for tuftsin by von Wronski and colleagues in 2006 belongs to that tetrapeptide and has not been demonstrated for the heptapeptide. Enzyme-level observations exist - inhibition of enkephalin-degrading activity in plasma, reported by Zolotarev and colleagues in 2004 - but an enzyme inhibited is not a receptor.