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TB-500

TB-500

Thymosin beta-4, a 43-amino-acid N-acetylated actin-sequestering peptide
CAS 77591-33-4C₂₁₂H₃₅₀N₅₆O₇₈SApproximately 4963 g/mol43 amino acidsLinear peptideLyophilized powder

Price range: $60.00 through $450.00

Ships from lot Black Cap · 2 mg vial · >99.9 % purity · Krause Analytical See the COA

UPS Ground $9.95. Free at $150. Orders before 2 pm ET ship the same business day.

Also available in the Pro Series.Its own lot. Its own certificate.
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Ships from Austin, TexasUnited States only
Tested by an outside labNever in-house
Every lot publishedIncluding rejected lots
Same-day dispatchOn orders before 2pm ET
SKU: N/A Category:
BATCH
VERIFICATION
LOT NUMBER
Black Cap
2 mg vial
IDENTITY
Confirmed
CHROMATOGRAPHIC PURITY
>99.9 %
NET CONTENT
1.83 mg
Analytical characterization

Every result against its specification.

Lot Black Cap · 2 mg vial · Krause Analytical · reported 2 March 2026 . The bar shows where the reported result falls against Astramide’s published release criterion. The notch marks the criterion.
Within criterion Above criterion Not on this COA
Test
Method
Criterion
Result
Result vs criterion
Status
Identity
HPLC-UV-MS
Mass spectral match to the labelled compound
Confirmed
WITHIN SPEC
Chromatographic purity
HPLC-UV/MS
at or above 98.0%
>99.9 %
95 at or above 98.0% 100
WITHIN SPEC
Net content
HPLC-UV-MS
1.83 mg
80 120
REPORTED
Endotoxin
LAL, USP <85>
below 0.5 EU/mL
<0.5 EU/mL
WITHIN SPEC
Values are reported per vial or bottle unless otherwise noted. Every figure here is taken from the batch Certificate of Analysis and nothing else.
Certificate of Analysis
TB-500 · Lot Black Cap · 2 mg vial · Lab No. 200511
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Quick reference

How to read this report

Same six keys on every Astramide product page. Only the values change.
1Lot numberMatch it to the number printed on your product label. If they differ, this report is not for your product.
2IdentityMass spectrometry confirms the molecule is the one on the label. It conforms or it does not. There is no partial result.
3Chromatographic purityThe share of the material that is the target peptide. A purity figure quoted without a method is not a purity figure.
4Net contentHow much compound is in each vial or bottle, as measured by the laboratory. A different question from purity.
5EndotoxinMeasured against a ceiling, not a floor. Sensitivity differs by laboratory, so results are not compared across labs.
6Laboratory, method, dateWho ran it, on what instrument, and when. A report with no named laboratory or no date is not a report.
Molecular profile

TB-500, in structural terms.

TB-500 molecular structure
Sequence
Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln-Glu-Lys-Asn-Pro-Leu-Pro-Ser-Lys-Glu-Thr-Ile-Glu-Gln-Glu-Lys-Gln-Ala-Gly-Glu-Ser-OH (Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES)
Molecular formula
C₂₁₂H₃₅₀N₅₆O₇₈S
Molecular weight
Approximately 4963 g/mol
CAS number
77591-33-4
Peptide length
43 amino acids
Structure type
Linear peptide
Parent sequence
Thymosin beta-4 (TMSB4X gene product)
Primary molecular target
Monomeric (G-) actin. Thymosin beta-4 binds actin monomers in a 1:1 complex and sequesters them from polymerization.
Physical form
Lyophilized powder
PubChem CID
16132341

Thymosin beta-4 is a 43-amino-acid linear peptide with an acetylated N-terminal serine. It belongs to the beta-thymosin family of small, highly charged actin-binding peptides and is largely unstructured in solution, adopting an extended conformation when bound to actin. The commercial name TB-500 is used here for synthetic full-length thymosin beta-4.

Research profile

Where TB-500 appears in the literature.

Cell Biology; Cytoskeletal Biology; Biochemistry; Structural Biology
Research applications
  • Published studies have used thymosin beta-4 in:
  • G-actin binding and sequestration studies
  • Actin polymerization studies
  • Beta-thymosin structure-function studies
  • Structural biology of actin complexes
Experimental systems
  • Purified actin in vitro
  • Cultured mammalian cell lines
  • Actin complexes with thymosin beta-4 constructs for X-ray crystallography
Specific assays
  • Actin polymerization assays
  • Actin monomer binding and sequestration assays
  • Amino acid sequencing
  • X-ray crystallography
Measured endpoints
  • Affinity for monomeric actin
  • Unpolymerized actin pool and polymerization kinetics
  • Ligand-actin contact residues
  • Primary amino acid sequence
Pcs

Single Vial, 3-Pack, 6-Pack, Pack of 10
Mechanism and research context

What has been studied, and in what systems.

Thymosin beta-4 was isolated from thymus tissue, and its complete 43-residue sequence with an acetylated N-terminus was reported in 1981 (Low et al., 1981).

Biochemical studies later showed that thymosin beta-4 and its relative thymosin beta-10 both bind and sequester actin monomers, holding them in an unpolymerized pool (Yu et al., 1993).

A crystal structure of an actin complex with a thymosin beta-4 construct showed how the peptide stretches across the actin monomer and contacts both its ends, explaining how it blocks polymerization (Irobi et al., 2004). These studies place thymosin beta-4 in cytoskeletal and structural biology research.

These are published research systems. They do not describe approved clinical applications, and they do not establish efficacy or safety in humans.

Cited literature

Low TL et al., 1981. Complete amino acid sequence of bovine thymosin beta 4: a thymic hormone that induces terminal deoxynucleotidyl transferase activity in thymocyte populations. Proc Natl Acad Sci U S A. PMID 6940133. https://pubmed.ncbi.nlm.nih.gov/6940133/
Yu FX et al., 1993. Thymosin beta 10 and thymosin beta 4 are both actin monomer sequestering proteins. J Biol Chem. PMID 8416954. https://pubmed.ncbi.nlm.nih.gov/8416954/
Irobi E et al., 2004. Structural basis of actin sequestration by thymosin-beta4: implications for WH2 proteins. EMBO J. PMID 15329672. https://pubmed.ncbi.nlm.nih.gov/15329672/

Evidence level
Actin binding and sequestration by thymosin beta-4 are well characterised in biochemical and structural studies. Statements on this page describe experimental systems, not outcomes in humans.
Handling and storage
As supplied
Lyophilized powder in a sealed vial. Held in laboratory-rated freezers from arrival to shipment.
Storage
Store per the conditions printed on the vial label. Avoid heat, moisture and repeated temperature cycling.
Handling
For qualified professionals in controlled laboratory environments, following validated laboratory procedures.
Frequently asked questions

About this compound and its batch data.

What purity did this thymosin beta-4 batch achieve?

This lot was analysed by Krause Analytical and returned chromatographic purity above 99.9% by HPLC with UV detection coupled to mass spectrometry. Identity was confirmed by mass spectral match. The full certificate is published on this page, and every figure shown here is taken from it.

How much peptide is in the vial?

The laboratory measured 1.83 mg against a 2 mg label claim, which is 91.6% of label. Net content is reported on a per-vial basis. Astramide publishes the measured figure rather than the label claim, whether it falls above or below.

Was this batch tested for endotoxins?

Yes. Endotoxin testing was performed using the Limulus Amebocyte Lysate assay in accordance with USP <85>, and this batch returned <0.5 EU/mL. The result appears on the certificate published on this page.

How should this material be stored for research use?

As supplied, the lyophilized powder should be held at -20°C and protected from light and moisture. Once reconstituted, store at 2-8°C and use within 14 to 30 days. Avoid repeated freeze-thaw cycles and follow the handling procedures appropriate to your laboratory.

What is the difference between research-grade and pharmaceutical-grade thymosin beta-4?

These are separate classifications. Research-grade material is supplied for laboratory research use only and is not intended for human or animal consumption. Pharmaceutical-grade is an FDA classification that applies to drugs manufactured for human use. Astramide supplies research-grade material only.

Why does this certificate show no lot number?

The laboratory issued this certificate with the Batch/Lot field left blank. Astramide identifies the lot by its black vial cap, lot Black Cap. The certificate can still be verified against Krause Analytical laboratory reference 200511.

Research use only

This product is intended strictly for in-vitro laboratory research conducted by qualified professionals. It is not intended for human or animal consumption, clinical use, or therapeutic application. The statements on this page have not been reviewed by the FDA. These research peptides are not intended to diagnose, treat, cure, or prevent any disease. Research Use Only.

COA library Every lot we have tested Search by batch number. Past lots stay published. How we test The analytical panel What each method measures and the criterion each lot must meet. Open Lab Send us your peptides Any vendor. Same lab. Your own Certificate of Analysis.
Ships from Austin, TexasUPS Ground, about 3 business days
United States onlyFree shipping at $150 and over
Tracked on every orderTracking number emailed when it ships
Replacement or store creditOn approved claims. See refund policy.

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