Cartalax

What Cartalax is, structurally

Cartalax is a tripeptide. At 333.31 g/mol it is among the smallest peptides in this catalogue.

The formula accounts for the sequence with nothing left over, worth checking at this size. Three nitrogens means three backbone amides, one per residue, with no side chain contributing another, which rules out lysine, arginine, histidine, asparagine and glutamine in one step. The eight oxygens divide as four on the backbone, two of them the free C-terminal acid, and four across the acidic side chains.

Charge is the defining property here. Glutamate and aspartate each carry a carboxylate, the C-terminus carries a third, and the only opposing charge in the molecule is the free N-terminal amine. That leaves a strongly net negative peptide across the ordinary working range, and it is what makes this one of the more acidic compounds in the catalogue. It is therefore very hydrophilic, with no aromatic ring and no aliphatic side chain beyond alanine's methyl. It is freely water soluble, though no quantitative figure is quoted here.

There is no cysteine, so no thiol, no disulfide bonding and no reducing agent, and no proline to constrain a backbone that is too short for secondary structure anyway.

Reconstitution and handling

Sterile water is the default solvent. There is no metal center here, so PBS or an appropriate assay buffer are equally reasonable. Add diluent down the inside wall of the vial, swirl gently, and let it stand briefly to clarify.

Dissolution is rarely the difficulty at this size. pH is what to watch: with three carboxylates against one amine, the charge state shifts noticeably across the mildly acidic range. Vortexing only introduces foaming.

At low concentration, adsorption onto plasticware is worth allowing for and low-protein-binding tubes reduce it. A small, strongly anionic peptide has little affinity for polypropylene, so this is less pressing than for a hydrophobic sequence.

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. Let a cold vial reach room temperature before opening so condensation does not reach the powder. Reconstituted, hold at 2 to 8 degrees C for short-term work, or aliquot and freeze rather than thawing one vial repeatedly.

The liability profile follows from the sequence and is unusually clean. No cysteine to oxidize, no methionine to form a sulfoxide, no asparagine or glutamine to deamidate, which removes the three commonest peptide degradation routes at a stroke.

The aspartate does not supply a fourth, for positional rather than compositional reasons. Aspartyl residues rearrange to isoaspartate through a succinimide intermediate, and that ring forms when the aspartate side chain is attacked by the backbone nitrogen of the following residue. Here the aspartate is C-terminal, so no following residue exists and no such nitrogen is available. The route is closed by the architecture of the sequence, not merely slowed.

That leaves ordinary amide hydrolysis under strongly acidic or alkaline conditions, which is slow near neutral pH. Cold, dry, near-neutral storage is sufficient, and this peptide has no single vulnerable residue to protect.

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

How Cartalax is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. Two things shape the method. There is no aromatic residue in the sequence, so no absorbance at 280 nm, and detection sits near 214 nm where the amide bond absorbs. And the peptide is small and strongly polar, retaining weakly on C18 and eluting early, which calls for high-aqueous conditions.

Area percent is a chromatographic measure, not peptide content by weight. Solid-phase synthesis delivers a salt, commonly trifluoroacetate or acetate, falling outside the molecular weight above. On a tripeptide that salt fraction is proportionally large, simply because the peptide weighs so little. Residual trifluoroacetate and deletion sequences are the classes to resolve, and on a sequence this short a deletion is a large relative mass change that separates cleanly.

Mass spectrometry confirms identity against the expected weight. The isobaric-isoaspartate blind spot that complicates most aspartate-containing sequences does not arise here, since that rearrangement cannot occur.

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