Research Use Only — Not for Human or Veterinary Use
TB-500 is supplied exclusively for in vitro and pre-clinical laboratory research. It is not a medicinal product, has not been approved for therapeutic use in any jurisdiction, and must not be administered to humans or animals. Procurement confirms the purchaser is a qualified researcher operating within an institutional or commercial laboratory setting.
TB-500 (Ac-LKKTETQ) — Research Grade, 10 mg Lyophilised Vial
TB-500 is the synthetic, N-terminally acetylated heptapeptide Ac-LKKTETQ, corresponding to residues 17–23 of the 43-amino-acid protein thymosin beta-4 (Tβ4; CAS 61512-21-8; MW ≈ 4,963 Da). TB-500 is not thymosin beta-4: it is a structurally distinct synthetic fragment with a molecular weight of 760.90 Da, differing from the full-length protein in sequence length, molecular mass, and pharmacokinetic behaviour. This distinction is essential for correct experimental design and data interpretation. AbsoluteBioLab supplies TB-500 as a lyophilised acetate salt, manufactured to analytical grade (≥99.0% HPLC purity) and verified by electrospray ionisation mass spectrometry (ESI-MS) prior to release. Each 10 mg vial is accompanied by a batch-specific Certificate of Analysis.
Analytical Specification
| Parameter | Specification |
|---|---|
| Sequence (single-letter) | Ac-LKKTETQ |
| Parent Protein | Thymosin beta-4 (Tβ4), residues 17–23 only |
| Molecular Formula | C33H60N10O9 |
| Molecular Weight | 760.90 Da (cf. full-length Tβ4: ≈ 4,963 Da) |
| CAS Number | 77591-33-4 (Ac-LKKTETQ acetate) |
| Salt Form | Acetate |
| Physical Form | White to off-white lyophilised powder |
| Purity (HPLC) | ≥99.0% |
| Identity Confirmation | ESI-MS (observed vs. theoretical monoisotopic mass) |
| Fill per Vial | 10 mg |
| Sterility | Non-sterile lyophilised research material |
Storage and Transport Conditions
| Condition | Specification | Notes |
|---|---|---|
| Lyophilised (sealed vial) | −20 °C, desiccated, protected from light | Store in original sealed vial until use |
| Transit | Ambient; cold-chain packaging included | Lyophilised form is stable during standard UK domestic shipping |
| Intended Use | In vitro and pre-clinical laboratory research only | Not for human or veterinary use |
Note: Reconstituted solution storage guidance is not provided, consistent with AbsoluteBioLab’s Research Use Only supply policy. Researchers should refer to their institutional SOPs for handling reconstituted peptide solutions.
Batch Documentation and Quality Assurance
Every batch of TB-500 dispatched by AbsoluteBioLab is accompanied by a batch-specific Certificate of Analysis (CoA) confirming HPLC purity (≥99.0%) and ESI-MS identity. CoA documents are available via the Certificate of Analysis Portal. For further information on our analytical methodology, refer to the HPLC Purity in Peptide Research guide.
Structural Identity: TB-500 and Its Relationship to Thymosin Beta-4
The relationship between TB-500 and thymosin beta-4 is a source of consistent nomenclature confusion in the research literature, and understanding it is essential for correct experimental interpretation. Thymosin beta-4 (Tβ4) is a 43-amino-acid, water-soluble protein encoded by the X-linked TMSB4X gene, with a molecular weight of approximately 4,963 Da. It is the predominant β-thymosin in mammalian cells, constituting roughly 70–80% of all β-thymosins expressed in human tissue.[1]
TB-500 is not thymosin beta-4. It is the synthetic, N-terminally acetylated heptapeptide fragment Ac-LKKTETQ corresponding to residues 17–23 of the full-length Tβ4 sequence. This seven-residue segment contains the WH2 (Wiskott-Aldrich Homology 2) actin-binding motif of Tβ4 — the structural locus responsible for G-actin sequestration and the downstream regulation of actin polymerisation dynamics. Esposito et al. (2012) first characterised and confirmed the identity of Ac-LKKTETQ in commercial TB-500 preparations using high-resolution Orbitrap mass spectrometry, establishing the analytical framework now used for anti-doping and quality control purposes.[2]
The acetylation of the N-terminus is a deliberate synthetic modification that confers metabolic stability relative to the unmodified LKKTETQ sequence. Rahaman et al. (2024) characterised the metabolic profile of Ac-LKKTETQ in human serum and rat urine, identifying Ac-LK as the primary short-term metabolite and Ac-LKK as a longer-term metabolite detectable in animal models. Notably, the study found that wound-healing activity in fibroblast assays was attributable primarily to the metabolite Ac-LKKTE rather than the parent compound — a finding with significant implications for in vitro experimental design when selecting the appropriate test article.[3]
For a detailed structural comparison of TB-500 and thymosin beta-4 — including sequence alignment, molecular mass differences, and the nomenclature inconsistencies commonly encountered in commercial and academic literature — refer to the TB-500 vs Thymosin Beta-4: Structural and Nomenclature Distinctions guide.
Research Context: Actin Dynamics, Cell Migration, and Tissue Repair Pathways
The biological activity of thymosin beta-4 is rooted in its role as the principal G-actin sequestering molecule in mammalian cells. Tβ4 binds monomeric G-actin in a 1:1 ratio through conformational and spatial interactions at the WH2 domain, controlling the threshold concentration of free G-actin available for polymerisation into filamentous F-actin. This regulation of the G-actin/F-actin equilibrium — known as actin treadmilling — governs cell motility, morphological change, and the cytoskeletal remodelling required for tissue repair processes. [Tβ4 evidence: Gao et al., 2022][1]
Beyond actin sequestration, Tβ4 exerts pleiotropic effects across multiple repair-relevant pathways. Goldstein and Kleinman (2012) reviewed the full spectrum of Tβ4 biological activities, noting its capacity to downregulate inflammatory chemokines and cytokines, promote endothelial cell migration and angiogenesis, reduce apoptosis, and inhibit myofibroblast differentiation — thereby attenuating fibrosis and scar formation in wound models. These activities have provided the scientific rationale for clinical trials evaluating Tβ4 in dermal wound repair, corneal injury, and cardiac ischaemia. [Tβ4 evidence][4]
In skeletal muscle, Tokura et al. (2010) demonstrated that muscle injury upregulates Tβ4 expression in regenerating fibres and inflammatory haematopoietic cells, and that both Tβ4 and its sulphoxidised form act as chemoattractants for myoblasts — accelerating wound closure and promoting satellite cell migration to sites of injury in murine models. [Tβ4 evidence][5]
A 2026 scoping review by McGuire et al. mapped the full evidence base for Tβ4 and TB-500 in tissue healing and musculoskeletal repair across 80 studies. The review noted that the literature is heavily weighted towards in vitro and mixed designs, with direct TB-500 (Ac-LKKTETQ) evidence limited to a single included study — an important caveat for researchers designing pre-clinical experiments using TB-500 specifically rather than full-length Tβ4. [Mixed Tβ4/TB-500 evidence][6]
The pharmacokinetic profile of synthetic Tβ4 in humans was characterised by Ruff et al. (2010) in a first-in-human randomised, placebo-controlled phase I study. Intravenous doses ranging from 42 to 1,260 mg were well tolerated, with a dose-proportional pharmacokinetic response and an increasing half-life with ascending dose. No dose-limiting toxicities or serious adverse events were observed across single and 14-day multiple-dose cohorts. Note: this study evaluated full-length Tβ4, not TB-500 (Ac-LKKTETQ). [Tβ4 evidence][7]
Researchers working with TB-500 in connective tissue models may also find the Repair & Recovery catalogue relevant, particularly the BPC-157 10mg vial, which operates through a distinct mechanistic axis (VEGFR2–Akt–eNOS and FBXO22–BACH1). BPC-157 and TB-500 are separate compounds with different structures, molecular weights, and mechanisms; any co-investigation should be designed with reference to the specific published evidence for each compound independently.
Analytical Note — AbsoluteBioLab Quality Team
TB-500 (Ac-LKKTETQ) is a small, hydrophilic heptapeptide that presents fewer analytical challenges than larger or more hydrophobic research peptides. Our QC team performs ESI-MS identity confirmation on every batch to verify that the N-terminal acetyl modification is intact at release — a critical check given that deacetylation would produce a structurally distinct compound (LKKTETQ) with different pharmacokinetic properties. Batches are also assessed by RP-HPLC to confirm purity ≥99.0% before dispatch. Researchers requiring batch-specific analytical data should access the CoA Portal or contact the laboratory team directly.
Regulatory and Compliance Status
TB-500 (Ac-LKKTETQ) is not approved as a medicinal product by the MHRA, FDA, or EMA. It is supplied as a research chemical for laboratory use only, consistent with AbsoluteBioLab’s Research Use Only supply policy. TB-500 and thymosin beta-4 appear in anti-doping literature and are referenced on the World Anti-Doping Agency (WADA) Prohibited List; researchers involved in anti-doping science or sports medicine research should consult the current WADA List directly at wada-ama.org for the most up-to-date classification. AbsoluteBioLab does not make representations about the regulatory or anti-doping status of any compound beyond the Research Use Only supply boundary described in our RUO Compliance Policy.
Frequently Asked Questions
What is the difference between TB-500 and thymosin beta-4?
Thymosin beta-4 (Tβ4) is a 43-amino-acid protein (MW ≈ 4,963 Da) encoded by the TMSB4X gene. TB-500 is the synthetic, N-terminally acetylated heptapeptide fragment Ac-LKKTETQ (MW 760.90 Da) corresponding to residues 17–23 of Tβ4. TB-500 contains the WH2 actin-binding domain of Tβ4 but is structurally, pharmacokinetically, and analytically distinct from the full-length protein. A detailed structural comparison is available in the TB-500 vs Thymosin Beta-4 guide.
Is a Certificate of Analysis available for this batch?
Yes. Every vial is accompanied by a batch-specific CoA confirming HPLC purity (≥99.0%) and ESI-MS identity. CoA documents are accessible via the CoA Portal.
Can TB-500 be used alongside BPC-157 in the same experimental model?
TB-500 and BPC-157 appear together in some pre-clinical literature investigating musculoskeletal repair. They are structurally unrelated compounds operating through distinct molecular pathways. Researchers designing experiments involving both compounds should consult the published evidence for each independently. The BPC-157 10mg vial is available separately in the Repair & Recovery catalogue.
What is the WADA classification of TB-500?
TB-500 and thymosin beta-4 appear in anti-doping literature and on the WADA Prohibited List. Researchers should consult the current WADA List directly at wada-ama.org for the most up-to-date classification. AbsoluteBioLab supplies TB-500 strictly for laboratory research under its Research Use Only policy.
References
- Gao J, et al. Thymosin β4 and actin: binding modes, biological functions and clinical applications. Current Protein & Peptide Science. 2022;23(5):323–335. DOI: 10.2174/1389203723666220330094827 [Tβ4 evidence]
- Esposito S, et al. Synthesis and characterisation of the N-terminal acetylated 17–23 fragment of thymosin beta 4 identified in TB-500. Drug Testing and Analysis. 2012;4(12):1000–1005. DOI: 10.1002/dta.1397 [TB-500 direct evidence]
- Rahaman KA, et al. Simultaneous quantification of TB-500 and its metabolites in in-vitro experiments and rats by UHPLC-Q-Exactive orbitrap MS/MS. Journal of Chromatography B. 2024;1236:124035. DOI: 10.1016/j.jchromb.2024.124035 [TB-500 direct evidence]
- Goldstein AL, Kleinman HK. Advances in the understanding and treatment of hemostasis and thrombosis using thymosin β4 and its derivatives. Expert Opinion on Biological Therapy. 2012;12(Suppl 1):S219–S224. DOI: 10.1517/14712598.2012.652500 [Tβ4 evidence]
- Tokura Y, et al. Muscle injury-induced thymosin β4 acts as a chemoattractant for myoblasts. Journal of Biochemistry. 2010;149(1):43–48. DOI: 10.1093/jb/mvq073 [Tβ4 evidence]
- McGuire F, et al. Thymosin Beta-4 and TB-500 in Tissue Healing, Regeneration, and Musculoskeletal Repair: A Scoping Review. Applied Sciences. 2026;16(10):4226. DOI: 10.3390/app16104226 [Mixed Tβ4/TB-500 evidence]
- Ruff D, et al. A randomized, placebo-controlled, single and multiple dose study of intravenous thymosin β4 in healthy volunteers. Annals of the New York Academy of Sciences. 2010;1194:223–229. DOI: 10.1111/j.1749-6632.2010.05464.x [Tβ4 evidence]
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