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Molecular Weight
Purity
Storage
Appearance
Solubility
01
TB-500, as supplied here, is synthetic thymosin β4: the complete 43-residue sequence of the naturally occurring protein, with an acetylated N-terminal serine. Thymosin β4 is one of the most abundant intracellular peptides in many cell types, where it binds monomeric (G-) actin and helps regulate the actin cytoskeleton.
Note that the name “TB-500” is not used consistently: some suppliers apply it to the full-length peptide, others to a short fragment containing the actin-binding motif. The material described on this page is the full-length 43-residue sequence (CAS 77591-33-4). At about 5 kDa and highly charged, it is also a demanding analyte for large-peptide chromatography and mass spectrometry. It is supplied as a lyophilized reference material for in vitro research only.
02
TB-500 reproduces the native thymosin β4 sequence exactly.
N-terminal acetyl group
As in the natural protein, Ser1 is acetylated. This removes the free N-terminal amine, adds 42 Da and protects against aminopeptidases.
Highly charged composition
The sequence contains nine lysines, eight glutamates and four aspartates, making it very hydrophilic and freely water-soluble.
Actin-binding motif (residues 17–23)
The sequence Leu-Lys-Lys-Thr-Glu-Thr-Gln (LKKTETQ) is central to G-actin binding in the parent protein, together with flanking regions that contact actin.
Met6
The only sulfur-containing residue and the main oxidation site (+16 Da).
Flexible structure
In water the peptide is largely unstructured, with transient helices that form on binding actin. This flexibility can broaden chromatographic peaks if conditions are not optimised.
03
Research on TB-500 centres on the actin-binding activity of thymosin β4.
G-actin sequestration
In purified systems, thymosin β4 binds actin monomers and slows filament assembly. This is measured with fluorescence-based polymerisation assays and co-sedimentation.
Cell migration
Scratch-wound and migration assays in keratinocyte and endothelial cell cultures have examined changes in migration after exposure.
Endothelial assays
Tube-formation assays on basement-membrane matrix have been used to study effects on endothelial network formation.
The actin-binding mechanism is well characterised structurally. Other signalling effects reported in cell culture, involving pathways such as Akt, ERK and NF-κB, are less well understood. All research context described here refers to in vitro systems.
04
Large-peptide chromatography
A demanding test compound for reversed-phase methods for peptides near 5 kDa, where pore size, temperature and ion-pairing all affect peak shape.
Actin-binding assays
Used in polymerisation kinetics, competition binding and co-sedimentation experiments to characterise peptide–actin interactions.
Single-site oxidation model
Met6 provides one well-defined oxidation site for studying sulfoxide formation under peroxide, metal-catalysed or light stress.
Blend analysis
A frequent component of multi-peptide research blends, where it must be separated from much smaller co-formulated peptides such as BPC-157 and GHK-Cu.
05
Storage
Store the lyophilized powder at −20 °C, sealed, desiccated and protected from light. Keep the vial closed until use, as moisture uptake can promote aggregation.
Oxidation
Met6 oxidises in the presence of oxygen, trace metals (such as copper and iron) and light. Use degassed buffers for sensitive work and use solutions promptly. Note that blends containing copper peptides may accelerate this.
Reconstitution
Dissolves readily in water or neutral aqueous buffer. Swirl gently; vigorous vortexing causes foaming and losses at the air–liquid interface.
Temperature
Keep working solutions cold (2–8 °C) during experiments and return aliquots to −20 °C for storage. Avoid repeated freeze–thaw cycles.
Labware
Use low-binding polypropylene tubes and tips. At low concentrations, losses to surfaces can be significant for quantitative work.
06
TB-500 needs methods suited to large, highly charged peptides.
HPLC
Wide-pore (300 Å) C18 or C8 columns with a shallow acetonitrile gradient at elevated temperature (around 40–60 °C) give the best peak shape. TFA gives sharper peaks; formic acid is better for LC-MS.
Mass spectrometry
ESI-MS produces a series of multiply charged ions, commonly around +4 to +7 (roughly m/z 710–1242), that deconvolute to about 4963.4 Da. The Met6 sulfoxide appears at +16 Da.
Sequence confirmation
MS/MS, or LC-MS/MS of enzymatic digests, gives b- and y-ion series for sequence coverage. The N-terminal acetyl group shifts N-terminal b-ions by 42 Da.
Impurity profile
Typical checks include truncated and deletion sequences from synthesis, the non-acetylated form, Met6 oxidation, deamidation at Gln and Asn26, and aggregates (by size-exclusion chromatography) for material used in cell assays.
07
The material on this page is synthetic thymosin β4: the full 43-residue sequence with an acetylated N-terminus, identical to the natural peptide (CAS 77591-33-4). The name “TB-500” is used inconsistently, and some suppliers apply it to a short fragment containing the LKKTETQ actin-binding motif, so check the sequence and molecular weight on the certificate of analysis.
Met6 is the only sulfur-containing residue and oxidises readily to the sulfoxide (+16 Da) when exposed to oxygen, trace metals or light. It is a single, well-defined site, which makes it the most important marker in stability studies.
Typically a series around +4 to +7, roughly m/z 710 to 1242, which deconvolutes to about 4963.4 Da. The exact distribution depends on the solvent and instrument settings.
TB-500 is most often combined with BPC-157, and some multi-peptide blends also contain GHK-Cu and other peptides. Check the blend listings in this catalogue for the exact composition of each product.
By reversed-phase HPLC, where the more polar sulfoxide form usually elutes slightly earlier, combined with LC-MS to confirm the +16 Da species. Peptide mapping can localise the oxidation to Met6. Results are reported as a percentage of the main peak at each time point.
Yes. As the full-length sequence, it contains the LKKTETQ motif at residues 17–23, along with the flanking regions that contribute to actin binding in the natural protein.
No. It is supplied strictly as a reference compound for laboratory and analytical research and is not for human or animal use.
TB-500 Research Reference. (2026). Pure Peptides Labs Research Catalogue. Retrieved from https://purepeptideslabs.net/research-catalogue/structural-research-peptides/tb-500/
Materials listed on this platform are supported by independent testing and published documentation for laboratory research contexts.
