What is follistatin?
Follistatin is a glycoprotein first characterized as a factor that suppresses follicle-stimulating hormone secretion, which is the origin of its name. In the research literature it is best known as a binding protein for activin and for several related members of the transforming growth factor beta family, including myostatin. Upper Meadows catalogs follistatin under CAS number 117628-82-7. The catalog records a molecular weight of approximately 37,000 to 40,000 Da for the recombinant form and approximately 3780 Da for a synthetic truncated form, and lists no single molecular formula because the recombinant material is a protein rather than a defined small peptide. It is supplied as a lyophilized powder for laboratory research use only and is not for human use.
This FAQ covers identity and specification questions first, then turns to the subject that matters most to this brand's lane: how follistatin is stored, how stability is protected, and how a stored batch is verified. Larger proteins behave differently from short peptides in storage, and that difference is easy to overlook.
Why does follistatin have two different molecular weights in the catalog?
The two figures describe two different kinds of material. The recombinant form is a full-length or near full-length protein produced in a cell expression system, and its mass falls in the tens of thousands of daltons. The range in the catalog reflects the fact that follistatin circulates as several isoforms produced by alternative splicing and by variable post-translational modification. Glycosylation in particular adds mass and is heterogeneous, so a recombinant preparation is a population of closely related species instead of a single molecule with one exact mass.
The synthetic truncated form is a much shorter chain assembled by chemical synthesis, with a molecular weight near 3780 Da. It represents a fragment, not the whole protein, and it should not be assumed to share the folded structure of the full-length protein.
This is why a single molecular formula is not given. A formula implies one exact composition, which holds for a synthetic peptide but not for a glycosylated recombinant protein. A researcher reading a specification should check which form a given batch refers to before comparing any mass result against it.
How is the identity of a follistatin batch confirmed?
Identity confirmation for a protein relies on methods suited to larger molecules. Mass spectrometry can establish the intact mass or, after enzymatic digestion, the masses of peptide fragments that map back to the expected sequence. For the glycosylated recombinant form, intact mass measurement shows a distribution of values rather than one sharp peak, which is the expected signature of heterogeneous glycosylation and not a sign of contamination.
Purity is assessed separately, typically by chromatography and often alongside gel electrophoresis for proteins. Upper Meadows lists follistatin at 99%+ purity in its catalog. As with any compound, purity and identity answer different questions: purity describes how much of the sample is the target species relative to impurities under a stated method, and identity describes whether the target species is the intended molecule. Each batch is documented on a Certificate of Analysis so both can be reviewed.
How should lyophilized follistatin be stored?
The catalog storage condition is -20 °C, lyophilized, which matches the condition used across the Upper Meadows range. Freeze-drying removes the water that drives hydrolytic degradation, and low temperature slows the remaining chemical pathways. Protection from light and moisture completes the picture.
For proteins, storage has an added dimension. Short peptides are mostly concerned with chemical degradation: hydrolysis, deamidation, oxidation. Proteins face those too, and in addition face physical instability. A protein's activity in a research setting depends on its folded three-dimensional structure, and that structure can be lost through unfolding, aggregation, or surface adsorption even when the amino acid sequence is chemically intact. Lyophilized storage at -20 °C limits molecular mobility, which suppresses both chemical and physical change. This is why the dry, frozen state is the recommended condition for a protein like follistatin held over any extended period.
What are the main degradation risks for a protein like follistatin?
Four categories are most relevant.
Moisture uptake. Lyophilized powders are typically hygroscopic. Absorbed water restores molecular mobility, which allows hydrolysis and aggregation to proceed even at low temperature. A compromised container seal is the most common route.
Oxidation. Methionine and cysteine residues are sensitive to oxidation, and follistatin is a cysteine-rich protein whose structure depends on disulfide bonds. Disruption of those bonds alters the folded form. Sealing under an inert headspace gas, where used, reduces oxygen available for these reactions.
Aggregation. Proteins can associate into larger assemblies that are no longer the intended species. Aggregation is accelerated by temperature rise, moisture, and freeze-thaw stress, and it is often irreversible.
Deamidation and fragmentation. Asparagine and glutamine residues can deamidate over time, and peptide bonds can cleave, producing lower-mass fragments that appear as additional species on analysis.
None of these categories is unique to follistatin, but a large, disulfide-bonded, glycosylated protein has more ways to change than a short synthetic chain, which is why the storage specification is treated as part of the compound's definition and not an afterthought.
How do temperature excursions and freeze-thaw cycles affect stored follistatin?
A temperature excursion is a period outside the specified storage condition, for example during transit or after a freezer failure. Its impact depends on magnitude and duration, and the effect is cumulative: a longer or warmer excursion produces more change than a brief, mild one. Cold-chain packaging is designed around holding a defined temperature band for an expected transit time, and a temperature indicator that shows no excursion is direct evidence the material stayed within its validated envelope.
Freeze-thaw cycling is a separate concern that applies strongly to proteins. Repeated transitions across the freezing point can stress folded structure through ice crystal formation and concentration effects, promoting aggregation. For this reason researchers commonly plan material handling so that a stock container is opened as few times as possible, with portions apportioned in advance as aliquots according to the laboratory's own protocols. Each opening of a container also admits moisture and air, so limiting access protects the headspace and moisture barrier of the remaining material.
How is the stability of a stored follistatin batch verified?
Verification compares a stored sample against its original Certificate of Analysis. For purity, a follow-up chromatographic run is compared to the original profile: a decline in the main peak area and growth of new peaks point to degradation. For identity, mass spectrometry on the stored sample is compared against the original result. A shift in mass can indicate specific modifications, such as a mass increase near 1 Da per site for deamidation or a gain of 16 Da for oxidation of a residue.
For proteins, aggregation is checked with methods that separate species by size, since aggregates may not show up as new chromatographic impurities by purity assays alone. A stored batch that matches its original profile gives direct evidence of continued integrity, whereas a batch showing new species or shifted masses warrants exclusion from further work pending investigation. Duration in storage alone is not evidence of stability; the re-test is.
How does follistatin compare with short synthetic peptides on stability?
Short peptides such as BPC-157, recorded in the Upper Meadows catalog with CAS 137525-51-0, formula C62H98N16O22, and a molecular weight of 1419.56 g/mol, are single defined molecules. Their stability questions are mostly chemical, and identity is confirmed against one exact theoretical mass. Follistatin's recombinant form is a heterogeneous protein whose stability questions include folding, glycosylation consistency, and aggregation, and whose identity is confirmed against a distribution rather than a single value.
The practical consequence is that a researcher handling both types should not apply identical expectations. The same -20 °C lyophilized condition applies, but the analytical checks that confirm a stored protein is intact are broader than those for a short peptide, and the tolerance for handling deviations is generally narrower.
How does Upper Meadows document follistatin?
Upper Meadows supplies follistatin as a lyophilized research compound at 99%+ purity, stored at -20 °C, with a Certificate of Analysis for each batch. Catalog entries state the form, molecular weight range, and storage condition so that a researcher can match a specification to the material in hand before beginning work.
Research-use disclaimer
This FAQ is provided for educational and informational purposes and describes a laboratory research material only. Follistatin is intended for in vitro and laboratory research, is not for human or veterinary use, is not for consumption, and is not intended to diagnose, treat, cure, or prevent any condition. For research purposes only.
