AICAR

What AICAR is, structurally

AICAR is not a peptide. It is a small-molecule nucleoside analogue with no amino acid sequence, no peptide bonds and no residues. The structural questions that matter for a peptide, proline rigidity, disulfide bonding, terminal modifications, do not arise here.

The molecule has two parts: a heteroaromatic base, 5-amino-1H-imidazole-4-carboxamide, joined through an N-glycosidic bond to a beta-D-ribofuranose sugar. The formula accounts for both. Two of the four nitrogens belong to the imidazole ring, one to the 5-amino group, one to the carboxamide. Four of the five oxygens belong to the sugar, the ring oxygen and three hydroxyls, and the fifth is the carboxamide carbonyl.

One absence carries real weight: there is no phosphorus. AICAR is a riboside, base plus sugar, not a ribotide, which would carry a phosphate. The phosphorylated counterpart is a different substance with a different formula and weight, and since the naming invites confusion, the formula is the reliable check.

Polarity follows from the groups present. Three free hydroxyls, a primary carboxamide that both donates and accepts hydrogen bonds, and an aromatic amine give a strongly hydrogen-bonding molecule with no hydrophobic bulk. It is water soluble, though no quantitative figure is quoted here.

Stereochemistry is part of the identity. The sugar is beta-D-ribofuranose with four defined stereocenters, and the beta configuration at the anomeric carbon distinguishes it from the alpha anomer, which shares the same formula and mass.

Reconstitution and handling

Sterile water is a reasonable default, and PBS or an assay buffer are equally suitable, since there is no metal center to compete for. Add diluent slowly down the inside wall of the vial, swirl gently, and let it stand until it clarifies.

Swirling rather than vortexing matters for a different reason than with peptides. A small molecule has no chain to unfold and no interfacial aggregation, so the concern is complete dissolution and avoiding loss to foam.

One caution applies. N-glycosidic bonds in nucleosides are acid-labile, so strongly acidic diluents can hydrolyze the bond into free base and sugar. Keep preparations near neutral pH.

Adsorptive loss is worth a mention, though it is less of a concern here than for a peptide. Peptides and small polar molecules can adsorb onto polypropylene and other plasticware, and low-protein-binding tubes reduce measured loss. This molecule is small and neutral, with no charged side chains and no extended hydrophobic surface, so it has less to bind with than a typical peptide. The precaution still costs nothing at low concentration.

This is laboratory preparation chemistry, not dosing, administration, or protocol guidance of any kind.

Storage and stability

Store the lyophilized solid 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.

Once in solution, hold it at 2 to 8 degrees C for short-term work, or aliquot and freeze for longer storage. Freeze-thaw cycling is less damaging here than for a peptide, since there is no conformation to lose, but aliquoting still limits contamination and concentration drift.

The weak point is identifiable from the structure. The N-glycosidic bond joining base to sugar is acid-labile and is the first thing to fail if a solution drifts acidic, hydrolyzing to free 5-aminoimidazole-4-carboxamide and ribose. The primary carboxamide is a second, more robust liability, since amides hydrolyze to the corresponding carboxylic acid under strongly acidic or alkaline conditions. There is no thiol, no ester and no metal-ligand bond, so the failure routes that dominate peptides and metal complexes do not apply here.

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

How AICAR is tested

Reversed-phase HPLC establishes chromatographic purity as area percent, and the imidazole carboxamide ring is a strong UV chromophore, so UV detection is straightforward. Being markedly more polar than a typical peptide, it retains weakly on standard reversed-phase columns, so methods generally run high-aqueous.

Mass spectrometry confirms identity against the expected molecular weight. The compound-specific signature here is fragmentation rather than an isotope pattern, since there is no metal. The same acid-labile glycosidic bond cleaves readily under collision-induced dissociation, releasing the ribose as a neutral loss of 132 and leaving the protonated base. That transition confirms base and sugar are genuinely connected.

Mass spectrometry cannot distinguish stereoisomers, so the beta anomeric configuration needs NMR or optical rotation to confirm. Peptide-specific methods such as amino acid analysis have nothing to act on.

One contrast with the peptides in this catalog is worth stating plainly. This compound is not made by solid-phase synthesis, so residual trifluoroacetate, truncated chains and deletion sequences, the impurity classes that dominate peptide chromatograms, are not relevant here. It is a neutral molecule with no counter-ion, so the observed mass carries no salt offset. The impurity classes that matter instead are the hydrolysis products, free base and free sugar, and isomeric material such as the alpha anomer, which chromatography can separate but mass spectrometry cannot.

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

Full specifications for AICAR.

Handling FAQ

Is this supplied as a salt, the way most peptides are? No. AICAR is a neutral molecule with no ionizable counter-ion in its formula, so there is no trifluoroacetate or acetate accompanying it as there would be with a peptide from solid-phase synthesis. The mass in the vial is not offset by salt in the same way.

Can PBS or an assay buffer be used instead of sterile water? Yes. There is no metal center to protect, so the chelator and phosphate cautions that apply to metal-complexed compounds are not relevant. Sterile water, PBS and an appropriate assay buffer are all reasonable, provided the pH stays near neutral.

What breaks first if a solution is stored badly? The N-glycosidic bond between base and sugar. It is acid-labile, so an acidic solution hydrolyzes it and splits the molecule into free base and free ribose. Keeping preparations near neutral pH addresses the main structural liability.