ACE-031

What ACE-031 is, and why it has no molecular formula

ACE-031 is not a peptide, and the product page says so directly. It is a fusion protein: the extracellular domain of the human activin receptor type IIB joined to the Fc region of human IgG1, assembled as a homodimer of about sixty thousand daltons.

Three of the fields a peptide page would fill are marked not applicable above, and each is absent for a reason rather than by oversight.

There is no CAS registry number, and there should not be. Registry numbers identify defined chemical substances, and a glycosylated protein of this size is not one. The product's own copy makes the same point: an absent CAS here is a correct specification, not a data gap.

There is no molecular formula for the same reason, compounded by a second. A formula could be written for the polypeptide chains, but it would describe only part of the material: proteins of this construction carry N-linked glycans, and that population is heterogeneous, so individual molecules in the same vial differ in the sugars attached to them.

The molecular weight is therefore approximate by nature, not merely rounded. There is no single exact mass to quote, because the material is a population of closely related molecules rather than copies of one.

The dimer is the last structural point, and the one that matters most for verification. Two identical chains are held together by disulfide bonds in the Fc hinge, so the assembled protein and its separated chains behave differently on analysis.

Reconstitution and handling

Reconstitute gently. Add diluent slowly down the inside wall of the vial and let the solid dissolve without agitation, then swirl if needed.

Do not vortex, and the reason is stronger here than on a peptide. Proteins denature at air-liquid interfaces, and vortexing creates a very large one. Foaming here is not untidiness but the visible sign of a process that unfolds and aggregates protein.

Carrier protein is a genuine consideration rather than an afterthought. Adsorptive losses to plasticware and glass are severe for proteins at low concentration, and a carrier such as bovine or human serum albumin is conventionally included where the working concentration is dilute. Low-protein-binding tubes help but do less than a carrier.

Avoid reducing agents. The two chains are held together by disulfide bonds, so a reducing agent separates the dimer into monomers, which is a different material from the one supplied.

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 reach room temperature before opening.

Aggregation is the dominant failure route, displacing the deamidation and oxidation chemistry that governs small peptides. It is irreversible: aggregated material does not return to its original form when conditions are corrected. Concentration, agitation, temperature excursions and air-liquid interfaces all promote it.

Freeze-thaw is therefore damage, not untidiness. Each cycle concentrates solutes as ice forms and exposes protein to new interfaces, and the losses accumulate. Aliquot on first reconstitution so no vial is thawed twice.

Reconstituted material should be held at 2 to 8 degrees C and used within a short working period: a protein solution has a physical stability limit as well as a chemical one.

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

How ACE-031 is verified

Reversed-phase HPLC is the wrong method here, worth stating because it is the default for everything else in this catalogue. The acidic organic mobile phases that separate peptides denature proteins on the column, so an area-percent figure obtained that way does not describe the material as supplied.

SDS-PAGE run both reduced and non-reduced is the informative identity check, and it exploits the dimer directly. Non-reduced, the assembled protein runs near sixty kilodaltons; reduced, it resolves to monomers at roughly half that, the interchain disulfides having been broken. Both results together are stronger evidence of correct assembly than either alone. The band should be expected to run diffuse and higher than the polypeptide mass predicts, both consequences of glycosylation.

Size-exclusion chromatography reports what actually matters for a protein: the proportion present as aggregate rather than as the intended dimer. That figure, not a reversed-phase purity percentage, is the meaningful measure here.

Mass spectrometry gives a distribution rather than a single molecular ion, for the glycosylation reason above.

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

Handling FAQ

Why does this product have no CAS number? Because registry numbers identify defined chemical substances, and a glycosylated fusion protein is not that kind of material. Its absence is expected for a protein of this construction and is not a missing specification.

Why is the molecular weight given as approximately 60,000 rather than an exact figure? Because there is no exact figure to give. The glycans attached to such proteins vary between individual molecules, so a vial contains a population of closely related species rather than copies of one.

Full specifications for ACE-031.