Prostamax

What Prostamax is, structurally

Prostamax is a tetrapeptide with a free N-terminal amine and a C-terminal proline carrying a free acid.

The formula reconciles exactly. Five nitrogens means four backbone amides plus the lysine's epsilon-amino group; glutamate, aspartate and proline contribute none. The nine oxygens divide as three backbone carbonyls, two for the terminal acid, and four across the two acidic side chains.

Charge is mixed. Lysine and the free N-terminal amine give two positive charges against glutamate, aspartate and the terminal acid, leaving the molecule modestly net negative rather than strongly so.

The proline at position four does two things at once, and they pull in opposite directions. Structurally it stiffens the C-terminal end, since its side chain loops onto its own backbone nitrogen and restricts rotation. Chemically it creates an aspartyl-prolyl linkage at positions three and four, and that specific pair is simultaneously the most acid-sensitive bond in ordinary peptide chemistry and immune to the rearrangement that affects most aspartates. Both consequences are set out under storage.

There is no cysteine, no methionine and no aromatic residue, so the formula carries no sulfur and the molecule has no 280 nm chromophore. It is polar and freely water soluble, though no quantitative figure is quoted here.

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 vial wall, swirl gently, and let it stand until clear.

Do not use an acidic diluent. The aspartyl-prolyl bond hydrolyses far faster in mild acid than an ordinary peptide bond, and a peptide this polar dissolves perfectly well without acid. This is the one handling instruction on the page that is specific rather than general.

Adsorption onto plasticware is worth allowing for at low concentration, with low-protein-binding tubes reducing measured loss, though a small mixed-charge peptide has limited affinity for polypropylene.

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.

Most peptide degradation routes are unavailable to this sequence. There is no cysteine to oxidise, no methionine to form a sulfoxide, no tryptophan to photo-oxidise, and no asparagine or glutamine to deamidate. Air exposure is not a concern.

The aspartate would ordinarily supply the remaining route, and here it does not. Rearrangement to isoaspartate proceeds through a succinimide ring formed when the backbone nitrogen of the following residue attacks the aspartate side chain, and that nitrogen must carry a hydrogen. Proline's sits inside its ring, is tertiary, and has none. The attack cannot happen, so this sequence does not form isoaspartate at all.

What the same pairing does create is acid sensitivity. An aspartyl-prolyl bond cleaves considerably faster in mild acid than a normal peptide bond, splitting the molecule into two fragments. That single reaction is the entire stability concern for this compound, and it is governed by pH rather than by temperature, oxygen or light. Near-neutral handling addresses it completely.

How Prostamax is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. With no aromatic residue there is no 280 nm absorbance, so detection sits near 214 nm.

One method caution follows from the chemistry and is easy to overlook, since it concerns the analysis rather than the sample. Peptide methods routinely use trifluoroacetic acid as an ion-pairing additive, making the mobile phase acidic, and an aspartyl-prolyl bond can cleave there during the run, generating the very products the analysis is meant to detect. Prompt injection matters more here than usual.

Area percent is a chromatographic measure rather than peptide content by weight. Solid-phase synthesis delivers a salt associating with the single basic site.

Mass spectrometry confirms identity and reads the degradation route directly, which is not true of most aspartate-containing peptides. Acid cleavage produces two smaller fragments rather than an isobaric rearrangement, so it is plainly visible by mass. The isoaspartate blind spot that limits mass analysis elsewhere does not arise here, because that reaction cannot occur.

Handling FAQ

Why is acid singled out when other peptides tolerate it? Because of the aspartate-proline bond at positions three and four. That linkage is the most acid-labile in ordinary peptide chemistry and cleaves where a normal peptide bond would not. Temperature, light and oxygen are comparatively unimportant for this molecule; pH is the whole concern.

Does the aspartate make this prone to isoaspartate formation? No. The rearrangement needs the following residue's backbone nitrogen to bear a hydrogen, and proline's does not. The same residue that makes this compound acid-sensitive also protects it from the rearrangement most aspartate-containing sequences undergo.

Full specifications for Prostamax.