What Is Epithalon? Tetrapeptide Sequence and Molecular Weight

Key takeaways

• Epithalon (also spelled Epitalon) is a synthetic tetrapeptide with the amino acid sequence Ala-Glu-Asp-Gly (alanine-glutamic acid-aspartic acid-glycine).
• Its monoisotopic molecular formula is C14H22N4O9, with a molecular weight of roughly 390.35 g/mol.
• It is the synthetic peptide analog of the naturally occurring tetrapeptide derived from the polypeptide bioregulator Epithalamin.
• It ships as a lyophilized (freeze-dried) powder and is reconstituted with bacteriostatic or sterile water for in-vitro research handling.
• Lyophilized powder is stored frozen and protected from light; reconstituted solution is kept refrigerated and used within a short window.
• Every Ascend Bio Labs batch carries a unique batch ID linking to a public, third-party HPLC and LC-MS certificate of analysis.

Epithalon, often written Epitalon, is one of the most structurally simple peptides in the research catalog: a four-residue chain. Despite that brevity, it is frequently misdescribed online, so this reference sticks to what the molecule physically is rather than any speculation about effects. This is a research-use-only material, and the discussion below is strictly limited to structure, composition, molecular weight, physical form, reconstitution, and storage.

If you handle, characterize, or store this compound in a laboratory setting, the practical questions are consistent: what is the exact sequence, what molecular weight should a mass spectrum confirm, and how should a lyophilized vial be reconstituted and kept stable? This post answers each in turn.

Peptide Class and Origin

Epithalon belongs to the class of short synthetic oligopeptides sometimes described as peptide bioregulators. It is the synthetic analog of a tetrapeptide associated with Epithalamin, a polypeptide preparation originally derived from pineal tissue and studied in the peptide-bioregulator literature. The synthetic version reproduces only the four-residue active fragment, manufactured by solid-phase peptide synthesis rather than extracted from tissue.

As a tetrapeptide, Epithalon sits at the very short end of the peptide-length spectrum. For contrast, copper-binding tripeptides like the one covered in What Is GHK-Cu? are even shorter at three residues, while growth-hormone-releasing-hormone analogs such as the one in What Is CJC-1295? are far longer at roughly 30 residues. Length matters for synthesis complexity, purification, and the analytical signatures a lab expects to see on HPLC and mass spectrometry.

The Ala-Glu-Asp-Gly Sequence

Epithalon's defining feature is its four-amino-acid sequence: alanine, glutamic acid, aspartic acid, glycine. Written in the standard single-letter notation reading from the N-terminus to the C-terminus, that is A-E-D-G; in three-letter notation it is Ala-Glu-Asp-Gly.

Two of those four residues are acidic: glutamic acid (Glu, E) and aspartic acid (Asp, D) each carry a side-chain carboxyl group. This gives the unmodified tetrapeptide a net acidic character at neutral pH, which is relevant to how it behaves in aqueous solution and on reversed-phase HPLC. The flanking residues are the smallest in the amino-acid set: alanine at the N-terminus and glycine, the only achiral amino acid, at the C-terminus.

• Position 1 (N-terminus): Alanine (Ala, A)
• Position 2: Glutamic acid (Glu, E)
• Position 3: Aspartic acid (Asp, D)
• Position 4 (C-terminus): Glycine (Gly, G)

Molecular Formula and Molecular Weight

The unmodified Epithalon tetrapeptide has the molecular formula C14H22N4O9. Its average molecular weight is approximately 390.35 g/mol, and its monoisotopic mass is near 390.14 Da. These values are what a laboratory should expect when confirming identity by mass spectrometry; an LC-MS run is generally used to verify that the observed mass matches this calculated value within instrument tolerance.

Because the peptide is small and contains no aromatic residues (no tryptophan, tyrosine, or phenylalanine), it has weak intrinsic UV absorbance at 280 nm. Analytical HPLC for purity assessment typically relies on detection at lower wavelengths, around 210-220 nm, where the peptide bond itself absorbs. This is a routine consideration when interpreting a purity chromatogram for a short, non-aromatic peptide like this one.

• Molecular formula: C14H22N4O9
• Average molecular weight: ~390.35 g/mol
• Monoisotopic mass: ~390.14 Da
• Sequence length: 4 residues (tetrapeptide)
• Net charge: acidic at neutral pH (two carboxyl-bearing residues)

Physical Form and Reconstitution

Research-grade Epithalon is supplied as a lyophilized (freeze-dried) white-to-off-white powder in a sealed vial. Lyophilization removes water and yields a dry, stable form suited to cold storage and shipping. The vial is intended to be reconstituted into solution only at the point of use in the laboratory.

Reconstitution is typically performed by introducing a measured volume of bacteriostatic water or sterile water against the inside wall of the vial, allowing the powder to dissolve without vigorous agitation. The choice of diluent and volume depends entirely on the concentration a given research protocol calls for; because this is short, acidic peptide, it generally dissolves readily in aqueous solution. For broader handling context across compounds, see Peptide Storage and Cold-Chain Handling.

Nothing in this section constitutes a use, dosing, or administration recommendation. Reconstitution here means preparing a solution for in-vitro laboratory work only.

Storage and Cold-Chain Handling

As a lyophilized powder, Epithalon is best kept frozen and protected from light and moisture; many labs store dry peptide at -20 C or colder for long-term stability. Once reconstituted, the peptide solution is far less stable and should be refrigerated and used within a short window, with freeze-thaw cycling minimized because repeated cycles can degrade short peptides.

Cold-chain integrity from synthesis through shipping to the bench is part of why insulated, tracked shipping matters for these materials. The general principles, dry frozen storage, refrigerated working solution, minimal light exposure, and limited freeze-thaw, are covered in more depth in our Peptide Storage and Cold-Chain Handling reference. For comparing the structural profiles of other short synthetic peptides, Semax vs Selank walks through two related sequences.

Verifying Identity and Purity With a COA

For any research peptide, the certificate of analysis (COA) is the document that ties a physical vial to its analytical data. A meaningful COA reports the batch or lot identifier, the HPLC purity result, and the LC-MS identity confirmation, so the molecular weight observed on the mass spectrum can be checked against the ~390 Da expected for the Epithalon tetrapeptide.

Ascend Bio Labs runs independent third-party HPLC for purity and LC-MS for molecular identity on every batch, and publishes a per-batch COA. Each vial carries a unique batch ID that links to its own certificate, and synthesis, testing, storage, and shipping are fully US-domestic with insulated, tracked delivery. The standard you should apply to any vendor is the same: a batch-specific COA you can actually inspect, with both purity and identity data attached to the exact lot you received.

Related research notes

• What Is GHK-Cu? Copper-Binding Tripeptide Structure Explained
• What Is CJC-1295? GHRH Analog Structure, With and Without DAC
• Semax vs Selank: Comparing Two Synthetic Peptide Structures
• Peptide Storage and Cold-Chain Handling: A Research Reference