TB-500 (Thymosin β-4 fragment)
TB-500 is a synthetic peptide corresponding to the actin-binding protein Thymosin β-4 (and its central LKKTETQ motif). It is supplied as a reference standard for in-vitro cytoskeletal, actin-sequestration, and cell-migration assay research.
View product · from $55What it is
TB-500 is the synthetic counterpart of Thymosin β-4 (Tβ4), a 43-residue, highly acidic member of the β-thymosin family of intracellular actin-sequestering peptides. In its native form the peptide carries an N-terminal acetyl group and adopts an unstructured, largely random-coil conformation in aqueous solution. The name "TB-500" is used commercially for both the full-length Tβ4 sequence and for constructs built around its central actin-binding motif (the heptapeptide LKKTETQ, residues ~17–23 of Tβ4), which is the minimal segment associated with monomeric (G-) actin binding. As a research reagent it is handled as a water-soluble lyophilized peptide and used as a reference analyte and assay tool rather than as part of any formulated product.
Mechanism (in-vitro research context)
In in-vitro systems, Thymosin β-4 functions as a G-actin-sequestering peptide: a single Tβ4 molecule binds one monomer of globular (G-) actin in a 1:1 complex through its conserved actin-binding motif (built around the LKKTETQ sequence), buffering the pool of polymerization-competent monomer and thereby modulating the G-actin/F-actin equilibrium in cytoskeletal assays. Unlike profilin, the Tβ4–actin complex does not readily donate monomer to growing filament barbed ends, so the peptide is studied as a tool for probing actin filament assembly/disassembly dynamics, monomer availability, and cytoskeletal turnover in cell-free and cell-culture models. Reported cell-surface and signaling associations of Tβ4 are an active area of in-vitro investigation and are described here only in that biochemical, research-assay context.
Research areas
- In-vitro actin-sequestration and G-actin binding assays (1:1 Tβ4–actin complex characterization)
- Actin polymerization/depolymerization kinetics and G-/F-actin equilibrium studies
- Cytoskeletal dynamics and cell-migration assay systems in cultured cells
- Structure–activity studies of the LKKTETQ actin-binding motif
- Analytical method development and reference-standard characterization (HPLC/MS) for β-thymosin peptides
Chemistry
- Molecular weight
- ~4963 Da (full-length acetylated Thymosin β-4)
- CAS
- 77591-33-4
- Formula
- C212H350N56O78S (full-length acetylated Thymosin β-4)
- Sequence
- Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES (full-length Thymosin β-4; central actin-binding motif LKKTETQ)
Laboratory handling
Supplied lyophilized. For laboratory storage, keep the lyophilized solid at -20 °C, protected from light and moisture, where it is stable long-term. For analytical work, reconstitute in deionized/ultrapure water or an appropriate aqueous buffer; prepare single-use aliquots and store frozen at -20 °C (or colder for extended periods) to limit freeze–thaw cycles. For working solutions held at 2–8 °C, confirm analytical stability (e.g., by HPLC) and analyze within the validated working window. As a highly acidic, hydrophilic peptide it is readily water-soluble; minimize repeated freeze–thaw to preserve purity.
FAQ
What is the amino-acid sequence?
Full-length Thymosin β-4 is a 43-residue peptide, Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES, N-terminally acetylated. Its central actin-binding motif is the heptapeptide LKKTETQ. Some material marketed as TB-500 corresponds to the full sequence; confirm the exact sequence against the lot Certificate of Analysis.
What molecular weight does the ~4963 Da figure refer to?
Approximately 4963 Da corresponds to the full-length, N-acetylated Thymosin β-4 peptide. The isolated LKKTETQ motif alone has a much lower mass (under ~1 kDa), so the ~4963 Da value indicates the full β-thymosin sequence rather than the short fragment.
How is purity verified?
Purity is typically assessed by reversed-phase HPLC (commonly ≥98% by area), with identity and mass confirmed by mass spectrometry (ESI-MS or MALDI-TOF). A lot-specific Certificate of Analysis should accompany the reference standard.
How should it be stored in the lab?
Store the lyophilized peptide at -20 °C, protected from light and moisture. After reconstitution in water or an appropriate aqueous buffer, aliquot and store at -20 °C or colder, minimize freeze–thaw cycles, and verify analytical stability before use.
Is it water-soluble?
Yes. Thymosin β-4 is a highly acidic, hydrophilic peptide that is readily soluble in water and aqueous buffers, which makes it convenient to prepare as stock solutions for in-vitro assays.
References
- Safer D, Elzinga M, Nachmias VT. Thymosin β4 and Fx, an actin-sequestering peptide, are indistinguishable. J Biol Chem. 1991;266(7):4029-4032.
- Huff T, Müller CSG, Otto AM, Netzker R, Hannappel E. β-Thymosins, small acidic peptides with multiple functions. Int J Biochem Cell Biol. 2001;33(3):205-220.
- UniProt P62328 — Thymosin beta-4 (TMSB4X), Homo sapiens.
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