N-Acetyl Semax

The acetyl group at the N-terminus is doing one specific job: blocking the first cut. Unmodified Semax presents a free methionine amine to leucine aminopeptidase and the other N-terminal exopeptidases, which is the dominant first-pass degradation route for short peptides in serum and brain tissue. Cap that amine with an acetyl, and that route closes. The rest of the MEHFPGP backbone is unchanged. What you get is a molecule with the same receptor-facing chemistry as Semax and a measurably longer in vitro half-life in incubations with rat brain homogenate or plasma. That trade is the entire reason this variant exists, and it is the reason research groups working on intranasal or systemic delivery often switch to it after running base Semax first.

Acetylation, amidation, and how the two cousins differ

The naming around this peptide gets blurry, so it is worth being precise. N-Acetyl Semax is Ac-Met-Glu-His-Phe-Pro-Gly-Pro with a free C-terminal carboxylate. N-Acetyl Semax Amidate is Ac-Met-Glu-His-Phe-Pro-Gly-Pro-NH2, with both ends protected. The amidate version closes the second exopeptidase route as well, at the C-terminus. Some suppliers conflate the two under one SKU; we list them separately because they are chemically distinct compounds with different masses, different CoAs, and different stability profiles. If your protocol cites the amidated form, the non-amidated vial will not behave the same way in a degradation assay.

Where this variant came from

The base Semax sequence was developed at the Institute of Molecular Genetics in Moscow as a stable ACTH(4-7) analogue with a Pro-Gly-Pro tail. Adding the N-terminal acetyl was a later medicinal-chemistry move, and most of the published characterisation of the acetylated form sits in pharmacokinetic and metabolic-stability papers rather than in the early behavioural literature. If you are familiar with the Russian neuroprotection work on base Semax, the acetylated variant is what shows up when those groups push toward longer dosing intervals or want a cleaner peripheral pharmacokinetic profile in their rodent work.

The pair-comparison angle

A non-trivial slice of orders for this peptide comes from labs that have already run a protocol with base Semax and want to repeat it with the acetylated variant as a stability-controlled comparator. The two compounds have the same in vitro receptor-side behaviour at matched concentrations; the difference shows up over time, after several enzymatic half-lives have passed. If that is the comparison you are setting up, order both at the same time so the lots travel together and the CoAs sit next to each other in the binder.

What arrives, and the paperwork that comes with it

• Sealed glass vial of lyophilised Ac-Met-Glu-His-Phe-Pro-Gly-Pro, inert-gas flushed before sealing
• Batch-specific Certificate of Analysis with the reverse-phase HPLC chromatogram and the mass-spec trace, showing the +42 Da shift from the acetyl group versus base Semax
• Lot number printed on the vial label, matching the CoA

Purity on our lots runs at 98 percent or better by RP-HPLC. The mass-spec confirmation is the part worth checking against your records, because the acetyl shift is the cleanest way to distinguish this peptide from a mislabelled base-Semax vial at receiving. If a vial does not match its CoA on arrival, we refund it. That has been a rare event on this SKU, and the person who handles those messages is the same person who handles the stock.

UK stock, EU-audited manufacturers

Every batch comes from a UK or EU contract peptide house we have audited in person or through documentation. We avoid unverified Asian supply for the acetylated variants in particular, because the failure modes (incomplete acetylation giving a mixed-population vial, or counter-ion swaps that change the salt mass) are silent on a casual visual check and only surface in the mass spec. UK orders placed Monday to Thursday by late afternoon go out the same working day, and around nine in ten land within 48 hours.

After the vial arrives

Keep the lyophilised powder at minus 20 C for any storage beyond the transit window. Reconstituted in bacteriostatic water, most groups refrigerate it and use it within a couple of weeks where the stability gain over base Semax is the whole point of using the acetylated form. For ten or more vials, message support for a custom quote rather than going through the cart. Live chat during UK hours is staffed by people who work with the stock, so reconstitution and CoA questions get answered properly rather than routed through a script.

Sold strictly for in vitro laboratory research. Not for human or veterinary use. UK 18+.