GHRP-2

What GHRP-2 is, structurally

GHRP-2 is a hexapeptide with a free N-terminal amine and a C-terminal amide. Two things are unusual for six residues: half are in the D-configuration, and one is not a proteinogenic amino acid at all.

The formula reconciles exactly. Nine nitrogens comes from six backbone amides, one for the tryptophan indole, one for the lysine side chain and one for the C-terminal amide. Nothing is unaccounted for, which is a useful check on a sequence carrying non-standard residues.

Three residues are D-configured: alanine at one, naphthylalanine at two, phenylalanine at five. That inverts the backbone at half the positions rather than substituting on it, and such a chain is not a substrate for the enzymes that process ordinary peptides.

Position two is 2-naphthylalanine, which does not occur in proteins. Where phenylalanine carries one benzene ring, this carries a fused bicyclic naphthalene, making it bulkier and a considerably stronger ultraviolet absorber. With the tryptophan at four and phenylalanine at five, that is three separate ring systems in six residues.

Charge is cationic. The lysine side chain and free N-terminal amine each carry a positive charge, and the C-terminal amide contributes no compensating negative, so no acidic group exists anywhere in the molecule. It is water soluble, though no quantitative figure is quoted here. There is no cysteine and no methionine, so the formula contains no sulfur and no oxidation at sulfur is possible.

Reconstitution and handling

Sterile water is the default solvent, and with no metal centre present PBS or an appropriate assay buffer are equally suitable. Add diluent down the inside wall of the vial, swirl gently, and let the solution clarify. Vortexing adds foaming without dissolving anything faster.

Work in subdued light and avoid leaving solutions standing under illumination. The tryptophan at position four is photosensitive, and on a molecule this small a single oxidised residue is a large proportional change.

Adsorption is worth allowing for at low concentration, and low-protein-binding tubes reduce measured loss. Being cationic and carrying three aromatic rings, this peptide has both electrostatic and hydrophobic routes to a surface, so it adsorbs more readily than a small polar peptide.

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. Reconstituted, hold at 2 to 8 degrees C, or aliquot and freeze rather than thawing repeatedly.

The weak point is the tryptophan, with nothing competing for the role. No cysteine, no methionine, no asparagine or glutamine and no aspartate means the routes dominating most peptides are all closed. What remains is oxidation of the single indole ring, driven by air, light and trace metals.

The D-configuration works in the opposite direction. Three inverted residues make the chain resistant to proteolysis, so this is a chemically simple stability picture: one vulnerable residue, one set of conditions that attack it, and a backbone that is otherwise robust.

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

How GHRP-2 is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. Detection is easier here than on most short peptides, because three aromatic ring systems give strong absorbance near 280 nm alongside the low-UV amide signal at 214 nm. The naphthalene of the position-two residue is the dominant contributor.

Aromatic content also affects retention. Three ring systems and no acidic group make this far more hydrophobic than a short polar peptide, so it retains well on C18 and elutes as a defined peak rather than near the void volume.

Area percent is a chromatographic measure rather than peptide content by weight. Solid-phase synthesis delivers a salt, usually trifluoroacetate or acetate, associating with the two basic sites. Residual trifluoroacetate and deletion sequences are the impurity classes to resolve.

Mass spectrometry confirms identity against the expected weight and reads the degradation route directly. Tryptophan oxidation adds oxygen, so oxidised material appears sixteen and thirty-two mass units above the molecular ion. One further check is worth naming: because the sequence contains D-residues, mass spectrometry cannot verify their configuration, since a D-residue and its L-counterpart are identical in mass. Chiral analysis or the synthesis record is what establishes that.

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

Handling FAQ

Why does this absorb so strongly at 280 nm? Because it carries three aromatic ring systems in six residues: a naphthalene at position two, an indole at position four and a benzene at position five. The naphthalene in particular is a stronger absorber than any proteinogenic side chain.

Can mass spectrometry confirm the D-residues? No. A D-residue has exactly the same mass as its L-form, so an inverted centre is invisible to mass. Confirming stereochemistry needs chiral analysis or reliance on the synthesis record.

Full specifications for GHRP-2.