Cartalax

What Cartalax is, structurally

Cartalax is a tripeptide, three residues and nothing else. At 333.31 g/mol it is among the smallest peptides in this catalogue.

The formula accounts for the sequence with nothing left over, which is worth checking on a peptide this short. Three nitrogens means three backbone amide nitrogens, one per residue, and no side chain contributes another. That single observation rules out lysine, arginine, histidine, asparagine and glutamine in one step. The eight oxygens divide as four on the backbone, counting two for the free C-terminal acid, and four more across the two 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 group. 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 with a peptide this small and polar. pH is what to watch: with three carboxylates against one amine, the charge state shifts noticeably across the mildly acidic range. Vortexing is unnecessary and 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, but the precaution costs nothing.

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 weak point follows from the sequence. There is no cysteine to oxidize, no methionine to form a sulfoxide, and no asparagine or glutamine to deamidate, which removes the three most common peptide degradation routes at a stroke. What remains is the aspartate, which can cyclise to a succinimide and reopen as isoaspartate, rearranging the backbone at constant mass. Mildly acidic conditions and warmth accelerate it, so cold near-neutral storage is the practical answer.

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 about this compound shape the method. There is no aromatic residue anywhere in the sequence, so there is no absorbance at 280 nm and detection has to sit in the low UV near 214 nm where the amide bond absorbs. And the peptide is small and strongly polar, so it retains weakly on a standard C18 column and elutes early, which typically calls for high-aqueous conditions or a column that tolerates them.

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

Mass spectrometry confirms identity against the expected weight, with the same blind spot that applies to any aspartate-containing sequence: isoaspartate is isobaric with aspartate, so the rearrangement above does not change the mass and only chromatography will show it.

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

Handling FAQ

Why does this elute so early on a reversed-phase column? Because there is almost nothing for the stationary phase to hold. Three residues, three carboxylates, and one alanine methyl group as the only non-polar feature. Small, highly charged material retains weakly on C18 and elutes close to the void volume.

Does the salt form matter more on a peptide this small? Proportionally, yes. A counter-ion weighs the same whatever it is paired with, so on a 333 g/mol peptide it is a larger share of the vial contents than on one of several thousand. Area-percent purity does not describe that fraction either way.

Full specifications for Cartalax.