Is TB-500 the same as Thymosin Beta-4?

Not exactly. Thymosin Beta-4 (Tβ4) is the full 43-amino-acid parent protein. TB-500 is a research-market name for a synthetic peptide commonly described as a fragment associated with the actin-binding region of Tβ4. Because the label is not a standardized chemical identifier, the precise sequence can vary by vendor — confirm it against the batch Certificate of Analysis.

What is the molecular weight of TB-500?

The most commonly referenced TB-500 research peptide has a molecular weight in the approximate 4.9 kDa range, close to that of the full Thymosin Beta-4 protein (roughly 4.9–5.0 kDa). Because exact values depend on the specific sequence supplied, the observed mass should be read off the LC-MS identity data in the batch documentation.

How is lyophilized TB-500 reconstituted?

Lyophilized TB-500 is dissolved using a diluent such as bacteriostatic water, added slowly down the side of the vial and gently swirled to avoid foaming. The diluent volume sets the final concentration, so the math should be calculated deliberately. This is for in-vitro laboratory preparation only.

How should TB-500 be stored?

Lyophilized powder is the more stable form and is generally stored sealed, cold, and away from light and moisture. Once reconstituted, the solution is typically refrigerated and used within a limited window, avoiding repeated freeze-thaw cycles. Always follow the batch-specific storage notes on the Certificate of Analysis.

How do I verify what is actually in a TB-500 vial?

Because TB-500 is a non-standardized market name, rely on batch documentation rather than the product name. Ascend Bio Labs publishes a per-batch Certificate of Analysis with independent third-party HPLC purity and LC-MS identity data, linked to a unique batch ID on each vial, so the purity and confirmed mass correspond to your exact lot.

All Research Notes

Compound Guides

What Is TB-500? Thymosin Beta-4 Fragment Structure and Specs

Ascend Bio Labs Research TeamApril 10, 2026 · Research Team

Key takeaways

TB-500 is a synthetic peptide commonly described as a fragment of Thymosin Beta-4 (Tβ4), a naturally occurring 43-amino-acid actin-binding protein.
The synthetic TB-500 sold as a research material is a short peptide, not the full 43-residue Tβ4 protein, and is typically associated with the actin-binding region of the parent molecule.
Like most research peptides, TB-500 ships as a white lyophilized (freeze-dried) powder that requires reconstitution with bacteriostatic water before use in vitro.
Lyophilized TB-500 is generally stored cold and protected from light and moisture; once reconstituted, it is kept refrigerated and used within a limited window.
Ascend Bio Labs publishes a per-batch Certificate of Analysis with independent third-party HPLC (purity) and LC-MS (identity) data, so the exact sequence and molecular weight you receive are verifiable against the documented batch.

TB-500 is one of the most frequently searched names in the research-peptide catalog, and it is also one of the most commonly misunderstood. The name is a research-market label rather than a formal biochemical identifier, which is why a clear, structure-first explanation matters before anything else.

This guide stays strictly within research framing. It describes what TB-500 is as a molecule — its relationship to Thymosin Beta-4, its peptide class, its molecular weight and sequence characteristics, and how a lyophilized vial is handled and stored in a laboratory setting. It makes no claims about effects in any organism. TB-500 is sold for in-vitro research and laboratory use only.

TB-500 and Thymosin Beta-4: what the name actually refers to

TB-500 is a synthetic peptide widely described in the research market as a fragment of Thymosin Beta-4 (often written Tβ4). Thymosin Beta-4 is a naturally occurring, highly conserved protein found across many tissues. It belongs to the beta-thymosin family and is a 43-amino-acid polypeptide whose best-characterized biochemical role is binding to monomeric G-actin, the building block of the actin cytoskeleton.

The key distinction for any researcher sourcing this material is that 'TB-500' and 'Thymosin Beta-4' are not strictly interchangeable. The full Tβ4 protein is the complete 43-residue sequence. TB-500, as commonly synthesized and sold, refers to a shorter peptide associated with the actin-binding portion of that parent molecule. Because the label is a market name rather than a regulated chemical identifier, the precise sequence supplied can vary between vendors — which is exactly why a documented, batch-specific Certificate of Analysis is the only reliable way to confirm what is in a given vial.

If you are evaluating combination products, the relationship between this peptide and others is worth understanding before purchase. See BPC-157 + TB-500 Blend: What the Combined Vial Contains for how TB-500 appears alongside BPC-157 in blended research vials.

Peptide class and structural classification

Structurally, TB-500 is a linear peptide — a single chain of amino acids without the disulfide bridges or cyclic structures seen in some other research compounds. The parent protein, Thymosin Beta-4, is classified within the beta-thymosin family and is characterized by an actin-binding motif. The conserved actin-binding sequence in Tβ4 is frequently cited in the literature as the region of biochemical interest for actin sequestration.

Parent molecule: Thymosin Beta-4 (Tβ4), a 43-amino-acid actin-binding protein in the beta-thymosin family.
Molecule class: linear synthetic peptide (no disulfide bonds, no cyclization in the standard fragment).
Biochemical association: the actin-binding region of the parent protein.
Physical form as supplied: white-to-off-white lyophilized powder.
Solubility for lab use: water-soluble; reconstituted with bacteriostatic or sterile water for in-vitro work.

Molecular weight and sequence considerations

Because TB-500 is a market label rather than a single fixed chemical, the exact molecular weight depends on the specific peptide a vendor synthesizes under that name. The most commonly referenced TB-500 research peptide is a short fragment with a molecular weight in the approximate 4.9 kilodalton range, well below the full Thymosin Beta-4 protein, which is roughly 4.9 to 5.0 kDa for the complete 43-residue chain. These figures are close enough that they are routinely confused, reinforcing why identity confirmation by mass spectrometry matters.

The practical takeaway: do not assume a molecular weight or sequence from the product name alone. The molecular weight, observed mass, and chromatographic purity should always be read off the actual batch documentation. A vendor that publishes LC-MS identity data lets you confirm the observed mass matches the theoretical mass for the sequence they claim to be shipping.

For a contrasting structure in the same research category, What Is BPC-157? Peptide Class, Sequence, and Reconstitution walks through a different short linear peptide and its sequence characteristics.

Lyophilized handling: what arrives in the vial

TB-500 is supplied as a lyophilized (freeze-dried) powder. Lyophilization removes water from the peptide under vacuum, leaving a stable solid that tolerates shipping and storage far better than a liquid would. The powder is typically a small white or off-white pellet or film at the bottom of the vial; the visible quantity can look deceptively small relative to the stated milligram amount, which is normal for freeze-dried peptides.

Before any in-vitro use, lyophilized TB-500 must be reconstituted — dissolved back into liquid — using an appropriate diluent, most commonly bacteriostatic water. The amount of diluent determines the resulting concentration, so the reconstitution math should be done deliberately rather than estimated. Our step-by-step walkthrough at Reconstituting Lyophilized Peptides: BAC Water Math Step by Step covers how to calculate diluent volume for a target concentration.

When reconstituting, the diluent is generally added slowly down the side of the vial rather than directly onto the pellet, and the vial is gently swirled rather than shaken, since peptides can be sensitive to mechanical agitation and foaming. The goal is a clear, particle-free solution.

Storage and stability

Storage requirements differ between the lyophilized and reconstituted states, and conflating the two is a common handling error.

Lyophilized TB-500, kept sealed and protected from light and moisture, is the more stable form and is generally stored cold. Once reconstituted into solution, the peptide is less stable and is typically refrigerated and used within a comparatively short window. The reconstituted solution should be kept away from repeated temperature cycling and direct light.

Lyophilized powder: store sealed, cold, away from light and humidity; the most stable form for long-term holding.
Reconstituted solution: refrigerate (typically 2–8°C) and use within a limited window per laboratory protocol.
Avoid repeated freeze-thaw cycles of reconstituted material, which can degrade peptide integrity.
Always confirm batch-specific storage notes against the Certificate of Analysis and accompanying documentation.

Why per-batch verification matters for TB-500 specifically

Because 'TB-500' is a non-standardized market name covering peptides that can differ in exact sequence and mass, third-party verification is not a marketing nicety here — it is the only way to know what you actually received. Two vials labeled TB-500 from different sources are not guaranteed to be the same molecule.

Every Ascend Bio Labs batch is independently third-party tested by HPLC for purity and LC-MS for molecular identity, and the resulting Certificate of Analysis is published per batch. A unique batch ID printed on each vial links back to that specific COA, so the purity figure and the confirmed mass you see are tied to the exact lot in your hand. All synthesis, testing, storage, and shipping are US-domestic, and vials ship insulated and tracked. This is sold strictly as a research material — not for human or veterinary use.

For another single-compound structural guide, see What Is GHK-Cu? Copper-Binding Tripeptide Structure Explained.

Frequently asked questions

Is TB-500 the same as Thymosin Beta-4?: Not exactly. Thymosin Beta-4 (Tβ4) is the full 43-amino-acid parent protein. TB-500 is a research-market name for a synthetic peptide commonly described as a fragment associated with the actin-binding region of Tβ4. Because the label is not a standardized chemical identifier, the precise sequence can vary by vendor — confirm it against the batch Certificate of Analysis.
What is the molecular weight of TB-500?: The most commonly referenced TB-500 research peptide has a molecular weight in the approximate 4.9 kDa range, close to that of the full Thymosin Beta-4 protein (roughly 4.9–5.0 kDa). Because exact values depend on the specific sequence supplied, the observed mass should be read off the LC-MS identity data in the batch documentation.
How is lyophilized TB-500 reconstituted?: Lyophilized TB-500 is dissolved using a diluent such as bacteriostatic water, added slowly down the side of the vial and gently swirled to avoid foaming. The diluent volume sets the final concentration, so the math should be calculated deliberately. This is for in-vitro laboratory preparation only.
How should TB-500 be stored?: Lyophilized powder is the more stable form and is generally stored sealed, cold, and away from light and moisture. Once reconstituted, the solution is typically refrigerated and used within a limited window, avoiding repeated freeze-thaw cycles. Always follow the batch-specific storage notes on the Certificate of Analysis.
How do I verify what is actually in a TB-500 vial?: Because TB-500 is a non-standardized market name, rely on batch documentation rather than the product name. Ascend Bio Labs publishes a per-batch Certificate of Analysis with independent third-party HPLC purity and LC-MS identity data, linked to a unique batch ID on each vial, so the purity and confirmed mass correspond to your exact lot.

For Research Use Only. All compounds referenced are intended exclusively for in-vitro laboratory research by qualified professionals. Nothing on this page is medical, dosing, or treatment guidance, and no statement should be read as describing a use in humans or animals.