Epitalon

What Epitalon is, structurally

Epitalon is a tetrapeptide with a free N-terminal amine and a free C-terminal acid, and at 390.35 g/mol it is among the smallest compounds in this catalogue.

The formula reconciles with the sequence exactly. Four nitrogens means four backbone amides and no side-chain nitrogen, ruling out lysine, arginine, histidine, asparagine and glutamine at once. The nine oxygens divide as five on the backbone, two of them the terminal acid, and four across the acidic side chains.

Charge is firmly negative. Glutamate and aspartate each carry a carboxylate and the C-terminus a third, against one N-terminal amine and no basic residue anywhere. The peptide is polar and freely water soluble, though no quantitative figure is quoted here. There is no cysteine, so no thiol and no disulfide chemistry, no methionine, and no aromatic residue anywhere in the chain.

The glycine at position four is where this compound parts from otherwise similar sequences. Glycine has no side chain, making it the most conformationally permissive residue available. More importantly it sits immediately after the aspartate, and that pairing is the single most reactive two-residue combination in ordinary peptide chemistry. Its consequences are covered under stability below.

Reconstitution and handling

Sterile water is the default solvent. With no metal centre present, PBS or an appropriate assay buffer are equally reasonable. Add diluent down the inside wall of the vial, swirl gently, and let it stand until clear. Vortexing adds foaming and nothing else on a peptide this small.

Prepare solutions near neutral pH and use them promptly rather than leaving them at room temperature. That is not generic advice here: the aspartate-glycine pairing below is fastest in neutral to mildly alkaline solution, precisely where a working buffer sits.

Adsorption onto plasticware is worth allowing for at low concentration, and low-protein-binding tubes reduce it. A small, strongly anionic peptide has limited affinity for polypropylene, so it is less pressing than for a large or hydrophobic molecule.

This is laboratory preparation chemistry, not dosing, administration, or protocol guidance of any kind.

Storage and stability

Store the lyophilized powder at -20 degrees C, sealed, desiccated and protected from light, and let a cold vial warm before opening so condensation does not reach the powder. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze rather than thawing repeatedly.

The weak point is identifiable from the sequence and worse here than in most short peptides. Aspartate followed by glycine is the classic succinimide-forming pair: the aspartate side chain attacks the following backbone nitrogen, closes to a five-membered ring, and reopens as aspartate or isoaspartate. Glycine accelerates this more than any other following residue, having no side chain to obstruct the closure. Epitalon places that motif at positions three and four.

The rearrangement leaves the molecular weight unchanged, so the product is a rearranged backbone of identical mass rather than a fragment. Cold, dry storage of the solid is the effective control, since the reaction requires water.

Nothing else in the sequence competes. There is no cysteine to oxidise, no methionine to form a sulfoxide, and no asparagine or glutamine to deamidate.

These are storage conditions for the material, not dosing or administration guidance.

How Epitalon is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. With no tryptophan, tyrosine or phenylalanine in the sequence there is no absorbance at 280 nm, so detection sits in the low UV near 214 nm where the amide bond absorbs. The peptide is also small and strongly polar, so it retains weakly on a standard C18 column and elutes early, which usually calls for high-aqueous conditions.

Area percent is a chromatographic measure and not peptide content by weight. Solid-phase synthesis delivers a salt, commonly trifluoroacetate or acetate, and on a peptide of only 390 g/mol that counter-ion is a proportionally large share of the vial contents. Residual trifluoroacetate and deletion sequences are the impurity classes to resolve.

Mass spectrometry confirms identity against the expected weight, with a blind spot that matters more here than usual. Isoaspartate is isobaric with aspartate, so this compound's principal degradation route produces a species mass cannot distinguish from the intact peptide. Chromatographic resolution is doing the real work, and a method that separates the isoaspartyl form is worth confirming rather than assuming.

These describe general methodology, not a claim about any particular batch.

Handling FAQ

Why does the glycine matter so much for stability? Because of what precedes it. An aspartate followed by glycine forms a succinimide ring far faster than the same aspartate followed by anything bulkier, since glycine has no side chain to get in the way. The ring reopens as isoaspartate, rearranging the backbone.

Would that rearrangement show up in a mass spectrum? No. Isoaspartate has exactly the same mass as aspartate, so the rearranged molecule is indistinguishable by mass alone. Only a chromatographic separation, or a method specific to isoaspartate, will show it.

Full specifications for Epitalon.