N-Acetyl Semax and Selank Amidate, Adamax, PE-22-28: why peptide ends are modified

Why peptide ends are modified at all

A peptide is a chain of amino acids, and its two ends are chemically different. One end carries a free amino group (the N-terminus), the other a free carboxyl group (the C-terminus). Both sites are natural targets for enzymes that cut amino acids off the ends of a chain. Short neuropeptide sequences often lose stability precisely there rather than in the middle of the molecule, which is why researchers designing analogues pay close attention to the termini.

The ends of a chain matter for more than stability. Their chemistry also shapes how a molecule interacts with its surroundings in solution, for example with other buffer components or with the surfaces of the vessels in which working solutions are prepared. Researchers usually control these factors within the same setup, so they are not confused with the effect of the sequence itself.

Modifying the ends leaves the core sequence untouched. Only the chemistry of the chain termini changes. When a project compares a modified version with its starting version, every difference in the result has one known explanation rather than several at once. This is the main reason laboratories often work in pairs: the base peptide and its form with an acetylated N-terminus and an amidated C-terminus.

Acetylation and amidation: what exactly changes

Acetylation adds an acetyl group to the free amino group of the first amino acid. The positive charge at the N-terminus disappears, and enzymes that recognise the free start of a chain usually bind such a substrate less readily.

Amidation replaces the free carboxyl group with an amide group. The end no longer carries a negative charge, and the shape and polarity of the site that carboxypeptidases act on also change. In many research peptides both modifications are combined, and the product name alone tells you that both termini have been changed.

N-Acetyl Semax Amidate and N-Acetyl Selank Amidate

Both molecules are modified forms of well-known neuropeptides, built on the same logic. N-Acetyl Semax Amidate has the sequence Met-Glu-His-Phe-Pro-Gly-Pro, with an acetylated N-terminus and an amidated C-terminus. Semax derives from a fragment of the ACTH hormone, and research on it includes the expression of the neurotrophic factors BDNF and NGF in in vitro and animal models. The N-acetylated version remains a subject of comparative studies.

N-Acetyl Selank Amidate carries a Thr-Lys-Pro-Arg-Pro-Gly-Pro core derived from tuftsin, with the same terminal modifications. The literature on selank concerns mainly the GABA system and the metabolism of enkephalins. Data for the N-acetylated form are scarcer, which is why unmodified selank serves as the reference point.

A good question to open a project with is whether acetylation and amidation change how long the peptide stays intact in solution. The answer comes from HPLC measurement run under the same conditions for both versions, not from an assumption made in advance.

Semax and Selank in one vial

Semax + Selank is a blend of 10 mg of semax and 10 mg of selank in a single vial of lyophilisate. Combining two heptapeptides with different origins, ACTH and tuftsin, makes research sense because it allows you to check whether combined exposure gives a result different from each component on its own. The literature on such combinations is narrow, so a project should have separate arms for semax, for selank and for the blend.

Do not draw conclusions about the blend from results for its individual components alone. Any interactions between them require a separate measurement.

Adamax: semax with an adamantyl group

Adamax is a semax derivative to which an adamantyl group has been attached. Adamantyl is a compact, rigid carbon cage with high lipophilicity. The modification changes the physicochemical properties of the molecule, and researchers examine how this affects the peptide’s behaviour in cell models and its passage across membranes in experimental models. Adamax is available in 5 mg and 10 mg vials, so the batch size can be matched to the planned setup.

The cleanest comparison is Adamax against semax under identical conditions: the same solvent, the same molar concentration calculated in the calculator, the same incubation time and the same cell line or model. Any difference in the result then comes from the adamantyl group rather than from accidental protocol changes. This setup demands more planning, but it usually saves time when the data are interpreted.

PE-22-28: a different starting point

PE-22-28 does not belong to the semax and selank family, but it illustrates a different route to a new research tool. It is a synthetic analogue of a spadin fragment. In the literature it is described as a blocker of the TREK-1 potassium channel, and changing the flow of potassium ions affects membrane potential and neuronal excitability. Rather than modifying the ends of a hormone analogue, researchers here ask about ion channels.

Which question, which product

Research question	Starting point	Product
Stability of the ends against enzymes	Semax in the N-acetyl amidate form	N-Acetyl Semax Amidate
The same question for selank	Selank in the N-acetyl amidate form	N-Acetyl Selank Amidate
Effect of combined components	Semax and Selank	Semax + Selank
Effect of a lipophilic group	Semax with adamantyl	Adamax
Ion channels and excitability	Spadin fragment	PE-22-28

Order every variant in one shipment

All the products listed are lyophilisates in vials. Each batch has a purity of at least 99% (HPLC), and the molecular mass is confirmed by mass spectrometry (MS). We dispatch within 24 hours of the order. In Poland the parcel goes to an InPost parcel locker, and across Europe DPD delivers the shipment.

If you plan to compare modified versions with their starting versions, order the full set in one cart. This way the whole series of experiments starts from the same supply, and you do not wait for further deliveries in the middle of a protocol. The complete range is in the neuropeptides category.

Working in the lab

Store the lyophilisate at -20 °C, tightly closed and protected from light. Before opening a vial, let it warm to room temperature to limit moisture condensation. Bacteriostatic water is usually used for reconstitution, and dilute acetic acid for peptides that dissolve poorly in water, always following your own protocol. Keep the solution at 2-8 °C, divide it into portions and avoid repeated freezing and thawing. Record the reconstitution date, the batch number and the concentration adopted, and calculate working concentrations in the concentration calculator.

All products are research reagents (RUO) and are not intended for use in humans or animals.