The Semax peptide sequence is a key identifier used in scientific literature, peptide chemistry, analytical documentation, and research databases. Semax is a synthetic heptapeptide, meaning that its primary sequence contains seven amino-acid residues.

The sequence is:

Met-Glu-His-Phe-Pro-Gly-Pro

Using one-letter amino-acid notation:

MEHFPGP

The U.S. FDA Global Substance Registration System and PubChem identify Semax with this sequence. The free-base peptide is listed with the molecular formula C₃₇H₅₁N₉O₁₀S and a molecular weight of approximately 813.92–813.93 g/mol.

Understanding the Semax peptide sequence is useful for several scientific purposes, including:

Confirming peptide identity
Comparing research materials
Reviewing analytical documentation
Understanding amino-acid composition
Interpreting mass-spectrometry data
Reviewing peptide-related literature
Supporting lot and sample traceability

This guide focuses on scientific identity and research information. It does not provide dosing, administration, or treatment instructions.

Research-use notice: Information about the Semax peptide sequence is intended for scientific and laboratory research purposes. Chemical identity and published experimental findings should not be interpreted as evidence of clinical safety, therapeutic effectiveness, or regulatory approval.

What Is the Semax Peptide Sequence?

The c

Met-Glu-His-Phe-Pro-Gly-Pro

The one-letter abbreviation is:

MEHFPGP

A commonly used condensed representation is:

H-Met-Glu-His-Phe-Pro-Gly-Pro-OH

Official FDA material prepared for a 2026 Pharmacy Compounding Advisory Committee meeting lists the Semax free-base sequence in this condensed form and identifies its molecular weight as approximately 813.93 g/mol.

The sequence contains seven amino acids, making Semax a heptapeptide.

Each amino acid contributes to the overall chemical identity of the molecule. The exact order of those amino acids is also important. Changing the composition or sequence order creates a different molecular entity.

Understanding MEHFPGP

The one-letter notation MEHFPGP provides a compact representation of the seven residues.

Position	One-Letter Code	Amino Acid	Three-Letter Code
1	M	Methionine	Met
2	E	Glutamic acid	Glu
3	H	Histidine	His
4	F	Phenylalanine	Phe
5	P	Proline	Pro
6	G	Glycine	Gly
7	P	Proline	Pro

Together:

M → E → H → F → P → G → P

or:

Met-Glu-His-Phe-Pro-Gly-Pro

Both PubChem and the FDA’s substance records associate Semax with the MEHFPGP sequence.

The Seven Amino Acids in Semax

1. Methionine — M

Methionine is the first residue in the Semax sequence.

The sequence begins:

Met-Glu-His-Phe-Pro-Gly-Pro

Methionine contains sulfur and contributes to the elemental composition of the complete peptide.

2. Glutamic Acid — E

The second residue is glutamic acid.

This produces the beginning sequence:

Met-Glu

Glutamic acid is one of the acidic amino acids and contributes to the chemical properties of the peptide.

3. Histidine — H

Histidine occupies the third position:

Met-Glu-His

Histidine contains an imidazole-containing side chain, an important structural feature in peptide chemistry.

4. Phenylalanine — F

The fourth residue is phenylalanine:

Met-Glu-His-Phe

Phenylalanine contains an aromatic side chain.

5. Proline — P

The fifth residue is proline:

Met-Glu-His-Phe-Pro

Proline has a distinctive cyclic structure compared with many other amino acids.

6. Glycine — G

Glycine occupies position six:

Met-Glu-His-Phe-Pro-Gly

Glycine is the smallest standard amino acid residue.

7. Proline — P

The final residue is another proline:

Met-Glu-His-Phe-Pro-Gly-Pro

This gives Semax its complete seven-residue sequence:

MEHFPGP

Semax Molecular Formula and Molecular Weight

For the Semax free base, the molecular formula is:

C₃₇H₅₁N₉O₁₀S

The molecular weight is approximately:

813.92–813.93 g/mol

The FDA Global Substance Registration System lists Semax with molecular formula C₃₇H₅₁N₉O₁₀S and molecular weight 813.92 g/mol. PubChem likewise lists the free-base compound at approximately 813.9 g/mol.

Important distinction: peptide vs. salt form

The molecular weight can differ depending on how a research material is represented.

For example, official FDA material distinguishes between:

Semax free base: approximately 813.93 g/mol
Semax acetate: approximately 874.0 g/mol

The peptide sequence remains H-Met-Glu-His-Phe-Pro-Gly-Pro-OH, while the associated form changes the overall molecular composition.

This is why researchers should distinguish between the peptide sequence itself and the exact chemical form documented for a particular material.

Why Peptide Sequence Identity Matters

The primary amino-acid sequence is one of the defining characteristics of a peptide.

For Semax, the expected sequence is:

MEHFPGP

This information can help researchers compare:

Product labels
Certificates of Analysis
Supplier documentation
Scientific publications
Analytical records
Research databases

For example, consistent documentation may follow this structure:

Product name
↓
Semax

Sequence
↓
MEHFPGP

Molecular identity
↓
C₃₇H₅₁N₉O₁₀S

Molecular weight
↓
Approximately 813.92 g/mol

Lot number
↓
Linked to analytical documentation

This documentation chain can support research organization and traceability.

However, a database record describing Semax does not independently verify the identity or purity of a specific commercial lot. Product-specific analytical documentation is needed to evaluate a particular sample.

Semax and ACTH-Derived Peptide Research

Semax is commonly described in scientific records as related to the ACTH(4–10) sequence with a Pro-Gly-Pro extension.

PubChem lists Semax among synonyms associated with ACTH (4-7), Pro-Gly-Pro-, while FDA substance information identifies both Semax and Met-Glu-His-Phe-Pro-Gly-Pro as names associated with the substance.

This relationship provides scientific context for research into Semax and related peptide structures.

Research involving ACTH-derived or related peptides may investigate:

Molecular structure
Sequence identity
Structure–activity relationships
Gene expression
Neurobiological pathways
Experimental biological responses

A peptide’s sequence is central to this type of research because even small structural changes can alter the identity and characteristics of the resulting molecule.

Semax Peptide Sequence and Scientific Research

The Semax sequence has been investigated in published experimental research involving neurobiological and molecular questions.

For example, one study examined Semax and the C-terminal peptide PGP in an experimental rat model of incomplete global ischemia. Researchers measured neurotrophin and receptor gene expression using real-time RT-PCR and reported region-specific changes under those experimental conditions.

These findings provide research context for Semax, but it is important to interpret them accurately.

Experimental research does not automatically establish:

Human clinical effectiveness
Medical treatment outcomes
Long-term safety
Regulatory approval

A molecular or preclinical observation is not equivalent to a proven clinical outcome.

Responsible scientific content should therefore describe such findings as:

Experimental
Preclinical
Mechanistic
Animal-model research

where appropriate.

Semax Peptide Structure and Primary Sequence

A peptide’s primary structure refers to the linear order of amino acids.

For Semax:

Met → Glu → His → Phe → Pro → Gly → Pro

This linear sequence is:

MEHFPGP

The primary sequence provides a foundation for understanding the molecule’s chemical identity.

However, the behavior of a peptide in an experimental environment may also depend on factors beyond the written sequence, including:

Chemical form
Sample composition
Experimental conditions
Solvent environment
Analytical methodology
Storage history
Other research variables

Therefore, the sequence is a crucial starting point, but sequence information alone does not describe every characteristic of a physical sample.

How Is the Semax Peptide Sequence Verified?

Peptide identity can be evaluated using analytical techniques appropriate to the research objective.

Potential analytical approaches may include:

Mass spectrometry
Liquid chromatography
Peptide sequencing methods
Chromatographic comparison
Other validated analytical techniques

Different methods provide different types of information.

Mass Spectrometry

Mass spectrometry can provide information related to molecular mass and peptide characterization.

For Semax free base, reference records list a molecular weight of approximately 813.92–813.93 g/mol.

A mass-based result may be compared with expected molecular characteristics, depending on the analytical method and the chemical form of the sample.

It is important to remember that:

Expected mass ≠ complete characterization by itself.

A comprehensive analytical strategy may use more than one technique.

Chromatography

Liquid chromatography, including HPLC-based methods, can help separate components in a sample.

Depending on the analytical method, chromatography may be used to examine:

Sample composition
Chromatographic profiles
Relative peak areas
Reported purity

A chromatographic purity result should be interpreted alongside:

The analytical method
Sample identification
Lot number
Test conditions
Other available analytical evidence

HPLC and the Semax Peptide Sequence

HPLC does not directly replace sequence information.

Instead, these forms of information answer different questions.

Sequence

What peptide is expected?

Answer:

MEHFPGP

Mass-based analysis

Does the measured molecular information align with the expected material?

Chromatography

What does the sample’s chromatographic profile indicate under the defined method?

Using multiple analytical approaches can provide a broader understanding of a research material than relying on a single measurement.

Semax Sequence and Certificate of Analysis Documentation

A Certificate of Analysis, or COA, may contain analytical information about a tested sample.

Depending on the documentation, a Semax COA may include:

Product identification
Peptide sequence
Lot or batch number
Analytical method
Purity specification
Reported analytical result
Test date
Molecular characterization information

The most useful documentation is generally linked to a specific lot.

For example:

Research material: Lot SMX-001
↓
Certificate of Analysis: Lot SMX-001
↓
Analytical documentation: Lot SMX-001

This creates a clearer connection between the physical material and the analytical records.

A generic document that cannot be associated with a specific product lot provides less traceability.

Purity and Sequence Are Different Quality Concepts

It is important not to confuse peptide sequence with purity.

Sequence identity asks:

Is the intended peptide MEHFPGP?

Purity asks:

What proportion of the tested sample corresponds to the primary component according to the analytical method used?

Both are relevant, but they answer different questions.

A research-quality review may therefore consider:

Sequence identity
+
Molecular characterization
+
Chromatographic analysis
+
Purity results
+
Lot-specific documentation

This provides more useful scientific context than a purity percentage alone.

Semax Peptide Sequence and Lot Traceability

For laboratories working with peptide research materials, lot traceability can support reproducibility and recordkeeping.

Researchers may document:

Material name
Semax peptide sequence
Supplier
Lot number
Date received
Analytical reports
COA reference
Experimental project

This creates a traceable relationship:

Material → Identity → Analytical documentation → Research record

If research outcomes differ between experiments, documentation may help researchers determine whether relevant variables included:

Different lots
Different sample histories
Different analytical documentation
Different experimental conditions

Traceability does not guarantee reproducibility, but it can make research records more systematic and transparent.

Research-Use and Regulatory Considerations

Chemical identity should not be confused with regulatory approval.

An FDA UNII or FDA substance record identifies and standardizes information about a substance, but FDA itself notes that UNII availability does not imply regulatory review or approval.

Similarly, scientific publications about Semax should be interpreted according to the evidence they provide.

A product page discussing the Semax peptide sequence should avoid unsupported claims such as:

“Clinically proven”
“FDA-approved treatment”
“Guaranteed neurological benefits”
“Proven safe for human administration”

The strongest scientific content separates:

Chemical identity
from
Experimental research
from
Clinical evidence
from
Regulatory status

This distinction improves both scientific accuracy and content quality.