Molecular Identity and Classification

Semax is the heptapeptide L-methionyl-L-α-glutamyl-L-histidyl-L-phenylalanyl-L-prolylglycyl-L-proline, written H-Met-Glu-His-Phe-Pro-Gly-Pro-OH or MEHFPGP. It is a designed molecule rather than a natural one: its first four residues reproduce positions 4 to 7 of adrenocorticotropic hormone (ACTH), and its last three residues are the tripeptide Pro-Gly-Pro, a member of the glyproline family of short proline- and glycine-rich peptides. For this reason the literature frequently calls it ACTH(4–7)PGP, and describes it as an analogue of ACTH(4–10), the heptapeptide Met-Glu-His-Phe-Arg-Trp-Gly from which it was derived.

The IUPAC name recorded by PubChem, (2S)-1-[2-[[(2S)-1-[(2S)-2-[[(2S)-2-[[(2S)-2-[[(2S)-2-amino-4-methylsulfanylbutanoyl]amino]-4-carboxybutanoyl]amino]-3-(1H-imidazol-5-yl)propanoyl]amino]-3-phenylpropanoyl]pyrrolidine-2-carbonyl]amino]acetyl]pyrrolidine-2-carboxylic acid, encodes six defined stereocentres, all of the S configuration (glycine, the seventh residue, is achiral). The molecular formula is C₃₇H₅₁N₉O₁₀S, the average molecular weight 813.9 g/mol and the monoisotopic mass 813.3480 Da. Semax is registered under CAS number 80714-61-0 and appears in PubChem as compound 9811102.

Two design ideas meet in this sequence. The ACTH(4–7) segment, Met-Glu-His-Phe, is the N-terminal half of the sequence that the melanocortin peptides share: ACTH, α-melanocyte-stimulating hormone (α-MSH, which is ACTH(1–13) with an acetylated N-terminus and an amidated C-terminus) and the related fragments all contain it, because they are all cut from the same precursor, pro-opiomelanocortin (POMC). The Pro-Gly-Pro extension replaces the Arg-Trp-Gly that follows in ACTH(4–10). Proline-rich C-termini are poor substrates for many exopeptidases, so the glyproline motif slows exopeptidase attack while removing the Arg-Trp pair that, with His-Phe, forms the classical His-Phe-Arg-Trp melanocortin pharmacophore.

The literature on Semax comes largely from one group: the papers cited below are authored at the Institute of Molecular Genetics of the Russian Academy of Sciences in Moscow, with N. F. Myasoedov and L. A. Andreeva recurring across them, and they place Semax in what those authors call the family of short regulatory peptides. The same group reported a series of glyproline-extended sequences, among them the tuftsin-derived heptapeptide Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro), which shares Semax's Pro-Gly-Pro C-terminus. One oxidizable sulfur, one metal-binding imidazole, one acidic side chain, one aromatic ring and two prolines mean a single short sequence raises most of the problems peptide analysis has to solve.

Structure and Chemical Features

Each residue contributes one distinctive chemical feature.

• Met¹ carries the free N-terminal α-amine (pK_a roughly 8.6–9.7 depending on the scale used) and a thioether side chain, –CH₂CH₂SCH₃. The sulfur is the molecule's main chemical liability: it is oxidized to the sulfoxide (+15.995 Da) by air, peroxides and metal-catalysed reactions, and to the sulfone (+31.990 Da) under harsher conditions.
• Glu² provides a side-chain carboxylic acid (pK_a about 4.25), which, with the C-terminal carboxylate, gives Semax its net negative charge at neutral pH.
• His³ carries an imidazole ring (pK_a about 6.0–6.5), which is partly protonated near neutral pH and is the strongest metal-binding side chain in the molecule.
• Phe⁴ supplies the only aromatic ring, the main hydrophobic element of the peptide and the source of its weak near-UV absorbance.
• Pro⁵-Gly⁶-Pro⁷ form the glyproline tail: two tertiary amide bonds (Phe–Pro and Gly–Pro), a flexible glycine between them, and a C-terminal proline whose carboxylic acid ends the chain.

Semax has no stable secondary structure in water: it is a flexible chain whose conformational ensemble is shaped mainly by its two prolines. Each proline ring fixes the backbone dihedral φ near −65° and removes an amide hydrogen-bond donor. More important for analysis, the Phe–Pro and Gly–Pro peptide bonds can each adopt the trans or the cis configuration. For ordinary peptide bonds cis is rare, but for X–Pro bonds the energy difference is small and interconversion slow, with half-times of seconds to minutes at room temperature; an aromatic residue immediately before proline, as in Phe–Pro, raises the cis population further through an interaction between the ring and the proline. Semax can therefore exist in solution as up to four slowly exchanging isomers (trans/trans, cis/trans, trans/cis and cis/cis), which appear as doubled or multiplied resonances in ¹H and ¹³C NMR spectra and can broaden HPLC peaks at low column temperatures.

The computed descriptors tabulated below describe a polar, hydrophilic and highly flexible molecule. Using standard side-chain pK_a values, the isoelectric point falls at about pH 5.1–5.4: two carboxylic acids (Glu² and the C-terminus) outnumber the one fully basic group (the N-terminal amine), while the histidine contributes a fractional positive charge that depends on pH. At pH 7 the net charge is close to −1; at pH 2, typical of reversed-phase HPLC with 0.1% TFA, it is close to +2.

An N-Terminal Copper(II)-Binding Site

The first three residues of Semax, a free α-amine followed by any residue and then histidine in position 3 (Xaa-Xaa-His), match the amino-terminal Cu(II)- and Ni(II)-binding motif known as ATCUN. In ATCUN peptides, Cu(II) is held in a square-planar arrangement by four nitrogen donors: the N-terminal amine, the two deprotonated backbone amide nitrogens of residues 2 and 3, and the imidazole nitrogen of His³. Tabbì and colleagues (2015) characterized the Cu(II) complexes of Semax by potentiometry and spectroscopy and found three species, [CuL], [CuLH₋₁]⁻ and [CuLH₋₂]²⁻; the first two coexist with the third between pH 3.6 and 5, and from pH 5 the [CuLH₋₂]²⁻ species, with a planar 4N coordination, predominates. This site recurs in the bioinorganic work below and in handling.

Synthesis and Manufacturing Chemistry

Semax is made by solid-phase peptide synthesis (SPPS), the method introduced by Merrifield in 1963 in which the chain is assembled residue by residue on an insoluble polymer support. Modern production uses Fmoc chemistry, based on the base-labile 9-fluorenylmethoxycarbonyl α-amine protecting group of Carpino and Han (1972), removed at each cycle with 20% piperidine in dimethylformamide. Side-chain protection follows the standard Fmoc/tBu scheme: Fmoc-Glu(OtBu)-OH for glutamic acid and Fmoc-His(Trt)-OH for histidine; methionine, phenylalanine, proline and glycine are used without side-chain protection.

The C-terminal Pro-Gly-Pro sequence dictates the choice of resin. When the Fmoc group is removed from a resin-bound dipeptide whose second residue is proline, the liberated amine can attack the ester that anchors the chain and cyclize to a diketopiperazine, cleaving the dipeptide from the support. This side reaction, described by Gisin and Merrifield in 1972, is especially fast for H-Gly-Pro-O-resin, which is exactly the intermediate formed during Semax synthesis. The sterically hindered 2-chlorotrityl chloride resin introduced by Barlos and colleagues suppresses the cyclization and allows the C-terminal free acid to be released under very mild acidic conditions. Prompt coupling of Pro⁵, or use of a preformed Fmoc-Gly-Pro-OH fragment, further limits the loss.

Three further points are specific to this sequence:

• Coupling onto proline. Phe⁴ and Gly⁶ are acylated onto the secondary amine of a proline, which reacts more slowly than a primary amine. Strong activators (HATU, or DIC/Oxyma) or double couplings are used for these steps, and completeness is monitored with a test suitable for secondary amines, such as the chloranil test, rather than the ninhydrin test.
• Histidine epimerization. Activated histidine derivatives racemize more readily than most amino acids because the imidazole can abstract the α-proton. Trityl protection, low-racemization activation and limited pre-activation times keep the D-His³ diastereomer, which has the same mass as Semax, at low levels.
• Methionine protection during cleavage. The final trifluoroacetic acid (TFA) step removes the tBu and Trt groups and liberates tert-butyl and trityl cations that can alkylate the methionine sulfur (S-tert-butylation, +56.063 Da) and acidic conditions favour oxidation to the sulfoxide. Cleavage cocktails for Met-containing peptides therefore include thiol or thioether scavengers (for example 1,2-ethanedithiol or dimethyl sulfide) in addition to water and triisopropylsilane, and are run under an inert atmosphere.

The crude peptide is precipitated in cold ether, purified by preparative reversed-phase HPLC on C18 silica with water/acetonitrile gradients containing TFA, and lyophilized. Material purified this way is obtained as a trifluoroacetate salt unless it is exchanged into acetate or chloride by ion exchange or repeated lyophilization from dilute acid.

Analytical Characterization

Reversed-phase HPLC. Purity is measured by reversed-phase HPLC with UV detection at 210–220 nm, where the six amide bonds absorb strongly. Semax contains no tryptophan or tyrosine, so its absorbance at 280 nm is negligible; the single phenylalanine contributes only a weak band near 257 nm, with a molar absorption coefficient of the order of 200 M⁻¹ cm⁻¹, too small for reliable concentration measurement. With a net charge of about +2 under 0.1% TFA and one aromatic ring, Semax is retained moderately on C18 columns and elutes in the low-to-middle part of a typical 5–50% acetonitrile gradient. Methionine sulfoxide variants are more polar and elute earlier, often as a closely spaced pair, because oxidation creates a new stereocentre at sulfur and gives two diastereomers. Proline cis/trans isomerism can broaden or shoulder the main peak at low temperature; raising the column temperature to 40–60 °C usually merges the isomers into one sharp peak.

Mass spectrometry. Electrospray ionization in positive mode gives the protonated ion [M+H]⁺ at m/z 814.355 and, because the N-terminal amine and the histidine are both protonated in acidic solution, a prominent doubly charged ion [M+2H]²⁺ at m/z 407.681. A weak [M+3H]³⁺ ion (m/z 272.123) and a sodium adduct [M+Na]⁺ (m/z 836.337) may also be seen. On collision-induced dissociation, cleavage N-terminal to proline is favoured (the "proline effect"), so the y₃ ion Pro-Gly-Pro (m/z 270.145) and the complementary b₄ ion Met-Glu-His-Phe (m/z 545.218) are characteristic, as are the y₁ proline ion (m/z 116.071) and immonium ions of His (m/z 110.071), Phe (m/z 120.081) and Met (m/z 104.053).

Recognizing common impurities. Each likely by-product has a characteristic mass shift, so LC-MS identifies a minor peak quickly.

Purity versus peptide content. HPLC purity is the fraction of UV-absorbing material that is Semax; peptide content is the fraction of the weighed powder that is peptide at all, rather than counterions, bound water or residual salts. Under acidic purification conditions the N-terminal amine and the histidine are both protonated, so a trifluoroacetate salt can carry up to two TFA counterions (114.02 g/mol each).

Bound water lowers the peptide fraction further. Amino-acid analysis after acid hydrolysis (expected ratio Met:Glu:His:Phe:Pro:Gly of 1:1:1:1:2:1, with methionine partly recovered as the sulfoxide unless hydrolysis is performed under protective conditions), quantitative NMR, or nitrogen determination establish peptide content when exact molar concentrations are needed. Complementary methods include ion chromatography or ¹⁹F NMR for trifluoroacetate, Karl Fischer titration for water, and chiral amino-acid analysis to quantify D-isomers.

Physicochemical Properties

Semax dissolves readily in water and aqueous buffers, and its negative partition coefficient and large polar surface area mean it does not cross lipid membranes by passive diffusion. Solubility is lowest near the isoelectric point, around pH 5, where net charge is smallest; at or below pH 4, and at pH 7 and above, it dissolves most easily.

Chemical stability is governed by three features: the methionine thioether, which oxidizes slowly in air and much faster with peroxides or with redox-active metals held by the adjacent ATCUN site; peptide bonds that hydrolyse only at extremes of pH or temperature; and a proline-rich C-terminus resistant to carboxypeptidases, while the free N-terminus stays open to aminopeptidases.

Research Context

In vitro research on Semax falls into four strands: its interaction with proteolytic enzymes, its specific binding to brain membrane preparations, its effects on neurotrophin gene expression and survival in primary neural cell cultures, and the bioinorganic chemistry of its copper complexes.

Proteolytic Stability and Peptidase Interactions

The Pro-Gly-Pro extension was designed to slow degradation, and enzymatic studies have tested where Semax is actually cleaved. Potaman and colleagues (1993) incubated ACTH/MSH(4–10) and Semax in serum with a panel of class-selective peptidase inhibitors. Bestatin, an aminopeptidase inhibitor, blocked up to 66% of the total degrading activity against both peptides, puromycin about 33% and the angiotensin-converting enzyme inhibitor lisinopril about 15%, while the contributions of neutral endopeptidase 24.11 (phosphoramidon) and prolyl endopeptidase (Z-Pro-prolinal) were less clear. The dominant attack is therefore at the free N-terminus, consistent with a proline-rich C-terminus that is a poor substrate for carboxypeptidases. Shevchenko and colleagues (2013) later compared the stability of an N-acetylated Semax derivative to proteolysis in several biological media, an approach that tests the complementary strategy of blocking the N-terminus.

Semax also acts on peptidases as an inhibitor. Kost and colleagues (2001) measured the hydrolysis of enkephalins by the enkephalin-degrading enzymes of human serum and found concentration-dependent inhibition by Semax (IC₅₀ about 10 µM) and by Selank (IC₅₀ about 20 µM), considerably more potent than puromycin (IC₅₀ about 10 mM) and bacitracin under the same conditions. Pentapeptide fragments of the two heptapeptides retained inhibitory activity, whereas tri-, tetra- and hexapeptide fragments did not. A peptide that is both substrate and inhibitor can change the apparent stability of other peptides in the same medium.

Membrane Binding and Primary Cell Culture Studies

Dolotov and colleagues (2006) used tritium-labelled Semax to look for specific binding sites in cell membranes isolated from basal forebrain tissue. Binding was time-dependent, reversible and specific, required calcium ions, and was characterized by a dissociation constant (K_D) of 2.4 ± 1.0 nM and a maximal binding capacity (B_max) of 33.5 ± 7.9 fmol per mg of membrane protein. The molecular identity of this site has not been established. Because Semax keeps only the His-Phe half of the His-Phe-Arg-Trp melanocortin pharmacophore, this binding site cannot simply be assumed to be one of the melanocortin receptors MC1R to MC5R; studies that compare Semax with ACTH(4–10), with α-MSH and with receptor-selective ligands are needed to locate any effect within the melanocortin system.

In primary glial cultures prepared from the basal forebrain, Shadrina and colleagues (2001) followed mRNA levels of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) after exposure to Semax. Expression rose rapidly, with the largest change at 30 minutes, when BDNF mRNA was about eight-fold and NGF mRNA about five-fold above control. Grivennikov and colleagues (2008) used primary neuronal and glial cultures from the same region, confirmed the stability of Semax in the culture medium by HPLC, and reported an increase of about 1.5- to 1.7-fold in the survival of cholinergic neurons in vitro and stimulation of choline acetyltransferase activity by 100 nM Semax in dissociated cultures, while numbers of GABAergic and total neuron-specific enolase-positive neurons, and glial proliferation across 1 nM to 10 µM, were unchanged. The read-outs are standard: quantitative RT-PCR for neurotrophin transcripts, immunocytochemistry for neuronal markers and choline acetyltransferase enzyme assays.

Copper Coordination and Amyloid-β Biophysics

The ATCUN-type copper site has made Semax a subject of in vitro bioinorganic research. Tabbì and colleagues (2015) combined their speciation study with MTT viability assays in the SH-SY5Y neuroblastoma and RBE4 brain endothelial cell lines, and reported reduced copper-induced loss of viability in the presence of Semax, which they read as sequestration of Cu(II) in the stable 4N complex. Sciacca and colleagues (2022) extended this to the amyloid-β peptide: using spectrofluorometric, calorimetric and MTT assays with artificial phospholipid membranes as a model surface, they reported that Semax prevents the formation of Aβ:Cu²⁺ complexes and interferes with the fibrillogenesis of Aβ, most clearly in the presence of Cu²⁺. Tomasello and colleagues (2025) reported that Semax extracts Cu(II) from preformed Cu(II)–Aβ species, alters the Cu(II)/Cu(I) redox cycling of that complex, and lowers the level of reactive oxygen species generated in the associated Fenton-like reaction, with a corresponding reduction in the loss of SH-SY5Y viability in that system.

The outcome of mixing Semax, Aβ and Cu(II) depends on the conditional stability constants of the competing complexes at the working pH, the order of addition and other ligands in the buffer. Typical designs include copper titrations followed by UV-visible d–d absorption or circular dichroism, thioflavin T kinetics with and without Cu(II) and Semax, and control peptides in which the His³ is replaced or the N-terminus is acetylated, which removes the ATCUN site.

Related Compounds and Structural Comparisons

Semax belongs to a group of ACTH- and glyproline-derived peptides; comparing their sequences shows how the Pro-Gly-Pro tail has been grafted onto different cores.

ACTH(6–9)PGP, which carries the full His-Phe-Arg-Trp pharmacophore, has been studied in SH-SY5Y cells, where Akimov and colleagues (2021) reported that it concentration-dependently preserved viability on exposure to hydrogen peroxide, tert-butyl hydroperoxide and potassium cyanide, together with changes in NF-κB- and NRF2-related gene expression. Selank is the closest structural relative in this catalogue: the two heptapeptides share the Pro-Gly-Pro C-terminus and give the same y₃ ion (m/z 270.145) in MS/MS, but Selank is strongly basic (Lys and Arg) where Semax is acidic, so the two separate readily by ion-exchange chromatography and differ markedly in reversed-phase retention.

KPV, the C-terminal tripeptide of α-MSH, comes from the opposite end of the same ACTH(1–13) sequence from which Semax's Met-Glu-His-Phe is taken. PT-141 is a cyclic heptapeptide built around the His-D-Phe-Arg-Trp variant of the melanocortin core that Semax lacks. And GHK-Cu is a copper complex of a peptide with histidine in position 2 rather than 3, so its Cu(II) coordination differs from the ATCUN geometry of Semax.

Laboratory Handling and Storage

Storage of the solid. Lyophilized Semax is best kept tightly closed at −20 °C, protected from light and moisture and ideally under argon or nitrogen to limit methionine oxidation. The powder is hygroscopic: a container taken from the freezer should reach room temperature in a desiccator before opening, so that moisture does not condense on the cold solid and add to the weighed mass.

Preparing solutions. Semax dissolves readily in high-purity water. Because solubility is lowest near pH 5, dissolving in water or a neutral buffer and then adjusting the pH is more reliable than adding the powder straight to a buffer near its isoelectric point. For accurate molar concentrations, correct the weighed mass for peptide content. As a worked example: 10.0 mg of a material with 80% peptide content contains 8.0 mg of Semax, which is 8.0 mg ÷ 813.92 g/mol = 9.83 µmol; dissolved in 1.00 mL this gives a 9.83 mM stock. A 1 mg/mL solution of the free peptide corresponds to 1.229 mM. Stock solutions are usually prepared at 1–10 mM, passed through a 0.22 µm membrane filter when destined for cell culture, divided into single-use aliquots and frozen at −20 °C or −80 °C; repeated freeze–thaw cycles should be avoided.

Protecting the methionine. Degassed water or buffers, low headspace in storage tubes and protection from light slow sulfoxide formation. Buffers should be free of peroxides (some grades of polysorbate and polyethylene glycol contain them) and of trace transition metals. Because Semax chelates Cu(II) with high affinity, metal-contaminated water or glassware both lowers the free-peptide concentration and catalyses oxidation; high-purity water, plasticware and, where the design allows, a trace of chelator in the stock reduce this risk, and chelators are omitted from experiments on Semax's own metal binding.

Protease-containing media. In serum-containing media the N-terminal methionine is exposed to aminopeptidases; sampling the medium and quantifying intact Semax by LC-MS (Grivennikov and colleagues used HPLC) gives the true concentration over time.

Verification. A short LC-MS run on a stock solution confirms identity and integrity after storage: look for [M+2H]²⁺ at m/z 407.68 and [M+H]⁺ at m/z 814.36, and for the sulfoxide at m/z 830.35 (415.68 doubly charged), the commonest degradation product. Each lot's certificate of analysis, linked on this page, records the analytical results for that lot.

Frequently Asked Research Questions

What is Semax?

Semax is the synthetic heptapeptide H-Met-Glu-His-Phe-Pro-Gly-Pro-OH (MEHFPGP), an analogue of ACTH(4–10) in which the ACTH(4–7) sequence Met-Glu-His-Phe is extended with the glyproline tripeptide Pro-Gly-Pro. Its molecular formula is C₃₇H₅₁N₉O₁₀S and its molecular weight 813.9 g/mol.

What is the CAS number of Semax?

Semax is registered under CAS number 80714-61-0 and appears in PubChem as compound 9811102.

How does Semax differ from ACTH(4–10)?

ACTH(4–10) is Met-Glu-His-Phe-Arg-Trp-Gly. Semax keeps the first four residues and replaces Arg-Trp-Gly with Pro-Gly-Pro, removing the Arg-Trp half of the His-Phe-Arg-Trp melanocortin core and adding a protease-resistant proline-rich C-terminus.

What masses should I see for Semax by mass spectrometry?

In positive electrospray ionization, [M+H]⁺ appears at m/z 814.355 and [M+2H]²⁺ at m/z 407.681; the monoisotopic mass of the neutral peptide is 813.3480 Da. In MS/MS the y₃ ion Pro-Gly-Pro (m/z 270.145) and the b₄ ion Met-Glu-His-Phe (m/z 545.218) are characteristic.

What is the peak at +16 Da in my Semax LC-MS data?

A +15.995 Da species ([M+H]⁺ at m/z 830.350) is almost always methionine sulfoxide, formed by oxidation of the Met¹ thioether. It elutes slightly earlier, often as two diastereomer peaks.

Why does Semax have almost no absorbance at 280 nm?

Semax contains no tryptophan or tyrosine. Its only aromatic residue, phenylalanine, absorbs weakly near 257 nm, so HPLC detection relies on the peptide bonds at 210–220 nm.

What is the isoelectric point of Semax?

Calculated from standard pK_a values, the isoelectric point is about pH 5.1–5.4. The peptide carries a net charge of about −1 at pH 7 and about +2 at pH 2, which explains its good solubility away from pH 5.

Does Semax bind copper?

Yes. Its N-terminal Met-Glu-His sequence is an ATCUN-type motif. Tabbì and colleagues (2015) showed that above pH 5 the predominant Cu(II) complex is [CuLH₋₂]²⁻, with four nitrogen donors in a square-planar arrangement.

Is Semax a melanocortin receptor ligand?

Not on the evidence of its sequence alone. The melanocortin pharmacophore is His-Phe-Arg-Trp (ACTH residues 6–9); Semax keeps only His-Phe and replaces Arg-Trp-Gly with Pro-Gly-Pro. Receptor involvement therefore has to be shown directly, by comparing Semax with ACTH(4–10), α-MSH and subtype-selective ligands in cells expressing a defined melanocortin receptor, with cyclic AMP accumulation or radioligand displacement as the read-out.

What binding affinity has been measured for Semax in membrane preparations?

Dolotov and colleagues (2006) measured calcium-dependent, specific and reversible binding of tritium-labelled Semax to basal forebrain plasma membranes, with a K_D of 2.4 ± 1.0 nM and a B_max of 33.5 ± 7.9 fmol/mg protein.

Which enzymes degrade Semax in serum?

Inhibitor studies by Potaman and colleagues (1993) attributed most of the degrading activity to aminopeptidases (bestatin inhibited up to 66%) and a smaller part to angiotensin-converting enzyme (lisinopril about 15%). The free N-terminal methionine is the main point of attack.

What is the difference between purity and peptide content for Semax?

HPLC purity is the fraction of UV-absorbing material that is Semax; peptide content is the fraction of the weighed powder that is peptide. A bis-trifluoroacetate salt is only 78.1% peptide by mass before water is counted.

Sources & Further Reading

1. National Center for Biotechnology Information. PubChem Compound Summary for CID 9811102, Semax. PubChem CID 9811102.
2. Eipper BA, Mains RE. Structure and biosynthesis of pro-adrenocorticotropin/endorphin and related peptides. Endocrine Reviews 1980;1(1):1–27. doi:10.1210/edrv-1-1-1
3. Potaman VN, Alfeeva LY, Kamensky AA, Nezavibatko VN. Degradation of ACTH/MSH(4–10) and its synthetic analog semax by rat serum enzymes: an inhibitor study. Peptides 1993;14(3):491–495. doi:10.1016/0196-9781(93)90137-6
4. Kost NV, Sokolov OY, Gabaeva MV, Grivennikov IA, Andreeva LA, Myasoedov NF, Zozulya AA. Semax and Selank inhibit the enkephalin-degrading enzymes of human serum. Russian Journal of Bioorganic Chemistry 2001;27(3):156–159. doi:10.1023/A:1011373002885
5. Shevchenko KV, Nagaev IY, Andreeva LA, Shevchenko VP, Myasoedov NF. Stability of Semax acetyl to proteolysis in various biological media. Doklady Biological Sciences 2013;449(1):110–112. doi:10.1134/S0012496613020166
6. Dolotov OV, Karpenko EA, Seredenina TS, Inozemtseva LS, Levitskaya NG, Zolotarev YA, Kamensky AA, Grivennikov IA, Engele J, Myasoedov NF. Semax, an analogue of adrenocorticotropin (4–10), binds specifically and increases levels of brain-derived neurotrophic factor protein in rat basal forebrain. Journal of Neurochemistry 2006;97(Suppl 1):82–86. doi:10.1111/j.1471-4159.2006.03658.x
7. Shadrina MI, Dolotov OV, Grivennikov IA, Slominsky PA, Andreeva LA, Inozemtseva LS, Limborska SA, Myasoedov NF. Rapid induction of neurotrophin mRNAs in rat glial cell cultures by Semax, an adrenocorticotropic hormone analog. Neuroscience Letters 2001;308(2):115–118. doi:10.1016/S0304-3940(01)01994-2
8. Grivennikov IA, Dolotov OV, Zolotarev YA, Andreeva LA, Myasoedov NF, Leacher L, Black IB, Dreyfus CF. Effects of behaviorally active ACTH (4–10) analogue – Semax on rat basal forebrain cholinergic neurons. Restorative Neurology and Neuroscience 2008;26(1):35–43. doi:10.3233/RNN-2008-00419
9. Tabbì G, Magrì A, Giuffrida A, Lanza V, Pappalardo G, Naletova I, Nicoletti VG, Attanasio F, Rizzarelli E. Semax, an ACTH4-10 peptide analog with high affinity for copper(II) ion and protective ability against metal induced cell toxicity. Journal of Inorganic Biochemistry 2015;142:39–46. doi:10.1016/j.jinorgbio.2014.09.008
10. Sciacca MFM, Naletova I, Giuffrida ML, Attanasio F. Semax, a synthetic regulatory peptide, affects copper-induced Abeta aggregation and amyloid formation in artificial membrane models. ACS Chemical Neuroscience 2022;13(4):486–496. doi:10.1021/acschemneuro.1c00707
11. Tomasello MF, Di Rosa MC, Naletova I, Sciacca MFM, Giuffrida A, Maccarrone G, Attanasio F. Semax, a copper chelator peptide, decreases the Cu(II)-catalyzed ROS production and cytotoxicity of aβ by metal ion stripping and redox silencing. Bioinorganic Chemistry and Applications 2025;2025:4226220. doi:10.1155/bca/4226220
12. Harford C, Sarkar B. Amino terminal Cu(II)- and Ni(II)-binding (ATCUN) motif of proteins and peptides: metal binding, DNA cleavage, and other properties. Accounts of Chemical Research 1997;30(3):123–130. doi:10.1021/ar9501535
13. Akimov MG, Fomina-Ageeva EV, Dudina PV, Andreeva LA, Myasoyedov NF, Bezuglov VV. ACTH(6–9)PGP peptide protects SH-SY5Y cells from H₂O₂, tert-butyl hydroperoxide, and cyanide cytotoxicity via stimulation of proliferation and induction of prosurvival-related genes. Molecules 2021;26(7):1878. doi:10.3390/molecules26071878
14. Merrifield RB. Solid phase peptide synthesis. I. The synthesis of a tetrapeptide. Journal of the American Chemical Society 1963;85(14):2149–2154. doi:10.1021/ja00897a025
15. Carpino LA, Han GY. 9-Fluorenylmethoxycarbonyl amino-protecting group. The Journal of Organic Chemistry 1972;37(22):3404–3409. doi:10.1021/jo00795a005
16. Gisin BF, Merrifield RB. Carboxyl-catalyzed intramolecular aminolysis. A side reaction in solid-phase peptide synthesis. Journal of the American Chemical Society 1972;94(9):3102–3106. doi:10.1021/ja00764a036
17. Barlos K, Chatzi O, Gatos D, Stavropoulos G. 2-Chlorotrityl chloride resin. Studies on anchoring of Fmoc-amino acids and peptide cleavage. International Journal of Peptide and Protein Research 1991;37(6):513–520. doi:10.1111/j.1399-3011.1991.tb00769.x
18. Vogt W. Oxidation of methionyl residues in proteins: tools, targets, and reversal. Free Radical Biology and Medicine 1995;18(1):93–105. doi:10.1016/0891-5849(94)00158-G
19. Wedemeyer WJ, Welker E, Scheraga HA. Proline cis–trans isomerization and protein folding. Biochemistry 2002;41(50):14637–14644. doi:10.1021/bi020574b
20. Mant CT, Chen Y, Yan Z, et al. HPLC analysis and purification of peptides. Methods in Molecular Biology 2007;386:3–55. doi:10.1007/978-1-59745-430-8_1

Last reviewed: October 22, 2026