ARA-290

What ARA-290 is, structurally

ARA-290 is a peptide of eleven residues, corresponding to one face of a single helix within a much larger protein. The supplied material is therefore a defined synthetic fragment, not the parent, and the two are different substances with different masses.

No molecular formula appears in the product database, but one can be supplied with confidence. The deposited record for this CAS gives C51H84N16O21, which computes to 1257.32 against the product's stated 1257.32, an exact match. The observations below build on that formula, with its external origin noted.

The composition points firmly in one direction. Of sixteen nitrogens, eleven belong to backbone amides, leaving five on side chains. Of twenty-one oxygens, twelve belong to the backbone carbonyls and the C-terminal acid, leaving nine. Nine side-chain oxygens against five side-chain nitrogens, on a chain of only eleven residues, is an oxygen-rich and distinctly acidic composition: several carboxyl or hydroxyl side chains against few basic ones.

The practical consequence runs against a common bench habit. A peptide built this way carries net negative charge at neutral pH and a low isoelectric point, so a drop of dilute acetic acid, which helps many peptides dissolve, moves this one toward the point of minimum net charge and therefore minimum solubility. Neutral water is the better starting position, with a mildly alkaline buffer as the second attempt.

There is no sulfur in the formula: no disulfide to protect or scramble, no free thiol to oxidise, no methionine sulfoxide route. The oxidative chemistry that dominates many peptides is closed here.

Reconstitution and handling

Sterile water is the default solvent, and for this peptide it is also the better one, for the reason above. Where a buffer is wanted, neutral to slightly alkaline assay buffers suit an acidic peptide well.

Add diluent slowly down the inside wall of the vial, swirl gently, and let the solution clarify. Do not vortex; it introduces foam without dissolving anything faster.

No reducing agent is needed, since the formula contains no sulfur.

Adsorptive loss deserves the usual allowance at low concentration, with low-protein-binding tubes reducing it. The charge picture adds one refinement: a net negative peptide has little affinity for ordinary glass, itself negatively charged, but will bind cationic surfaces, so amine-coated plasticware is the wrong choice.

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.

With no sulfur present, the oxidation routes that dominate many peptides are closed, and air exposure matters correspondingly less.

The hydrolytic routes remain and are the ones to design storage around. The five side-chain nitrogens leave room for asparagine or glutamine, both deamidating to their acidic counterparts and adding about one mass unit each, which on an already acidic peptide compounds itself. The high oxygen count also indicates aspartate positions carrying the ordinary isomerisation liability. Both need water, so the dry solid is largely protected while solutions are not, and warmth and alkaline pH accelerate them.

The stated sequence names them: a glutamine and an asparagine are the deamidation candidates. There is no aspartate in the chain, so aspartyl isomerisation does not arise.

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

How ARA-290 is tested

Reversed-phase HPLC establishes chromatographic purity as area percent. Standard acidic mobile phases suit the analysis even though acid is unhelpful for dissolution, since trifluoroacetic acid protonates the carboxylates and improves both retention and peak shape on a short, polar peptide that would otherwise elute early.

Area percent is a chromatographic measure and not peptide content by weight. Solid-phase synthesis delivers a salt, and on a peptide of about 1250 daltons the counter-ion is a meaningful proportional share of the vial contents.

Detection should be assumed near 214 nm. The carbon count is modest relative to the residue count, indicating little aromatic character, so 280 nm should not be relied upon.

Mass spectrometry confirms identity against 1257.32. Deamidation adds about one unit, which at this mass is comfortably resolvable on ordinary instrumentation, and a shift of that size is the most likely small anomaly to encounter.

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

Handling FAQ

The vial is slow to dissolve. Should acid be added? Not as a first move. The composition is distinctly acidic, so the isoelectric point is low, and adding acid drives the solution toward minimum solubility rather than away from it. Neutral water and patience are the better approach, with a mildly alkaline buffer as the second attempt.

Is there a molecular formula for this compound? Not in the product database, though one is available externally and is well corroborated: C51H84N16O21 computes to 1257.32, matching the stated molecular weight exactly. This page treats it as reliable while noting it is not the product's own specification.

Full specifications for ARA-290.