What Is Thymosin Beta-4? TB-500 Fragment Research
Last updated: July 2026
Thymosin beta-4 (Tb4) is a 43-amino acid protein. It is found in many tissues in animals, including thymus, platelets, and wound fluid. Its main function is to bind G-actin (the globular form of actin). Actin is a key structural protein in cells. According to Goldstein AL et al. (2012) (PMID 22166892), thymosin beta-4 is a multi-functional tissue-protective peptide studied for effects on cell migration and actin dynamics in cell and animal models. All cited data come from cell and animal studies.
Next Level Pharm is a US-based supplier of research-grade peptides. TB-500 and the 17-23 fragment (Frag 17-23) are available as COA-verified research compounds. Each lot is tested to ≥99% purity by HPLC and mass spec. The average purity across the last 100 batches is 99.4%.
These compounds are not approved drugs. They are studied only in cell and animal models. All findings cited here come from such models.
Key Takeaways
- Thymosin Beta-4 Is a 43-Amino Acid Protein: Tb4 is found in many tissues. Its main role is to bind G-actin and regulate the cell skeleton. It is produced naturally in thymus, platelets, and other tissues.
- TB-500 Is a Research Label for Synthetic Tb4 Fragments: TB-500 refers to synthetic peptide fragments derived from the thymosin beta-4 sequence. The most studied fragment is residues 17 to 23 (LKKTETQ).
- The 17-23 Fragment Contains the Actin-Binding Region: The LKKTETQ sequence is the part of Tb4 that binds G-actin. Researchers study this region for effects on actin dynamics and cell movement markers.
- Both Are Studied for Cell Migration Markers: In cell models, Tb4 and its fragments changed cell migration markers. Scratch assay and tube formation assay results are tracked in treated vs. control groups.
- All Findings Come from Cell and Animal Models: Human clinical data have not been established. These compounds are for lab research use only.
Researchers use Tb4 and its fragments to study how actin dynamics change in cell models. The results guide further connective tissue and wound biology research.
What Is Thymosin Beta-4?
Thymosin beta-4 (Tb4) is a 43-amino acid protein. Its molecular weight is about 4,921 daltons. It is found in many tissues in animal models, including thymus, platelets, leukocytes, and wound fluid. It is also found in the eye.
The main function of Tb4 is actin sequestration. G-actin is the globular, unassembled form of actin. Actin must assemble into F-actin (filamentous actin) to form the cell skeleton. Tb4 binds G-actin and holds it in a pool. This pool is released when the cell needs to move or change shape.
Tb4 is studied in cell models for effects on the G-actin to F-actin ratio. A change in this ratio affects how the cell moves and how strong its internal skeleton is. These are in vitro findings only.
What Is the Actin-Binding Region of Thymosin Beta-4?
The actin-binding region of Tb4 is located at residues 17 to 23. The sequence is Leu-Lys-Lys-Thr-Glu-Thr-Gln (LKKTETQ). Some studies use the shorter LKKTET sequence (residues 17 to 22).
This region is called the WH2 (Wiskott-Aldrich Syndrome protein Homology 2) domain. WH2 domains are found in many proteins that bind G-actin. The WH2 domain in Tb4 has a high affinity for G-actin.
When the LKKTETQ sequence binds G-actin, it sequesters (holds back) actin from assembling into filaments. This changes the balance of free actin in the cell. The cell uses this actin pool when it needs to move.
According to Safer D et al. (1991) (PMID 2002545), thymosin beta-4 sequesters G-actin at micromolar concentrations in cell models. This established the WH2 domain as the primary actin-binding region of Tb4. These are in vitro findings only.
What Is TB-500 in Research?
TB-500 is a research label used for synthetic peptide fragments from the thymosin beta-4 sequence. The most common form is the 17-23 fragment (LKKTETQ). Some formulations use a slightly extended sequence. The term TB-500 does not refer to a single exact sequence, so researchers must specify which fragment they are using.
In research protocols, TB-500 (the 17-23 fragment) is added to cell cultures. Scientists then measure cell migration speed and direction. Scratch assay is a common method. A scratch is made in a cell monolayer. The rate at which cells fill the scratch is measured.
Animal models also use TB-500. Rodent models track tissue repair markers and gene expression changes after injury. Results from treated groups are compared to control groups. These are animal model findings only.
TB-500 is available at Next Level Pharm as a COA-verified research compound. Every lot is tested by HPLC and mass spec. Each vial ships with a COA and lot number.
How Is Thymosin Beta-4 Studied in Animal Models?
In animal models, Tb4 is studied for effects on cell migration and tissue gene markers after injury. Scientists administer the compound and then measure repair markers in the target tissue. Markers include CD34 (stem cell marker), PCNA (cell division marker), and collagen gene expression.
According to Bock-Marquette I et al. (2004) (PMID 15181200), thymosin beta-4 activated integrin-linked kinase (ILK) and promoted cell migration and survival signals in cardiac cell models. Tb4-treated animals showed different cardiac gene marker profiles than control groups. These are animal model findings only.
Some models track blood vessel marker density after Tb4 treatment. VEGF gene expression and vessel-forming assays are used. All data come from cell and animal studies.
How Do Full Tb4 and the 17-23 Fragment Differ?
Full thymosin beta-4 is 43 amino acids long. It has the actin-binding region (residues 17 to 23) plus other regions that interact with different proteins. The full protein may act on integrin-linked kinase (ILK) through regions outside the actin-binding site.
The 17-23 fragment (LKKTETQ) contains only the actin-binding region. It shows actin sequestration effects in cell models but may lack the full range of effects seen with the complete protein.
Researchers compare the full protein and the fragment in the same cell assays to identify which regions are responsible for specific gene marker changes. Both are for lab research use only.
Frag 17-23 is available at Next Level Pharm as a COA-verified research compound. Every lot is tested to ≥99% purity. Each vial ships with a COA and lot number.
What Assays Are Used in Thymosin Beta-4 Research?
Thymosin beta-4 research uses several assay types. The scratch assay (wound closure assay) measures cell migration speed. A scratch is made in a cell layer. The time for cells to fill the scratch is tracked.
Actin polymerization assays measure the ratio of G-actin to F-actin in treated cells. Fluorescent probes mark each actin form. A shift from G to F indicates more actin assembly.
Gene expression assays measure RNA for actin-related genes and ILK pathway markers. Western blot confirms protein level changes. All assays are run in cell models.
| Feature | Full Thymosin Beta-4 | TB-500 (17-23 Fragment) |
| Sequence length | 43 amino acids | 7 amino acids (LKKTETQ) |
| Molecular weight | ~4,921 daltons | ~835 daltons |
| Actin-binding region | Yes (residues 17-23) | Yes (entire sequence) |
| ILK interactions | Yes (via other regions) | Not confirmed in fragment alone |
| Research model | Cell and animal models | Cell and animal models |
| Purity standard | ≥99% HPLC + mass spec | ≥99% HPLC + mass spec |
| Application | Lab research only | Lab research only |
Frequently Asked Questions
What Is Thymosin Beta-4?
Thymosin beta-4 (Tb4) is a 43-amino acid protein found in many tissues in animals, including thymus, platelets, and wound fluid. Its main role is to bind G-actin (globular actin) and hold it in a cellular pool. This pool is used when cells need to move or change shape. Tb4 is also studied for effects on integrin-linked kinase and cell migration markers in cell and animal models. All data come from in vitro and animal studies. For lab research use only.
What Is TB-500?
TB-500 is a research label for synthetic peptide fragments derived from the thymosin beta-4 sequence. The most studied form is the 17-23 fragment (LKKTETQ), which is the actin-binding region of the full protein. TB-500 is added to cell cultures to study effects on actin dynamics and cell migration. Animal models also track tissue gene markers after TB-500 treatment. TB-500 is not a single defined compound, so researchers specify the exact fragment used. For lab research use only.
What Is the 17-23 Fragment of Thymosin Beta-4?
The 17-23 fragment of thymosin beta-4 has the amino acid sequence Leu-Lys-Lys-Thr-Glu-Thr-Gln (LKKTETQ). This 7-amino acid segment is the actin-binding region (WH2 domain) of the full protein. It binds G-actin and holds it in a pool that cells use for movement. Researchers study this fragment in cell assays to isolate the actin-binding function from other regions of the full Tb4 protein. For lab research use only.
What Is G-Actin?
G-actin (globular actin) is the single-molecule form of actin. Actin exists in two forms: G-actin (unassembled) and F-actin (filamentous, assembled). F-actin forms the structural network inside cells that gives them shape and allows them to move. G-actin must join F-actin filaments for the cell to change shape. Thymosin beta-4 binds G-actin to hold it in a pool. When cells need to move, they release G-actin to build new F-actin filaments.
What Is a Scratch Assay?
A scratch assay (wound closure assay) is a method used to measure cell migration in a cell culture dish. A straight scratch is made in a layer of cells. The gap is measured over time. Cells that migrate faster close the gap sooner. This method tests how a compound changes cell migration speed. In TB-500 research, scratch assays track whether cells with or without the fragment migrate at different rates. All data come from in vitro models.
What Is Integrin-Linked Kinase?
Integrin-linked kinase (ILK) is an enzyme inside cells that links integrins (surface receptor proteins) to the actin skeleton. When ILK is active, it changes how cells stick to surfaces and how they move. Full thymosin beta-4 has regions that interact with ILK. This is one difference between the full protein and the 17-23 actin-binding fragment. ILK activity is measured by protein phosphorylation assays. All data come from cell and animal models.
How Is Thymosin Beta-4 Different from BPC-157?
Both are studied in cell and animal models for effects on tissue gene markers, but they are distinct compounds with different mechanisms. Thymosin beta-4 (43 amino acids) works by binding G-actin and possibly activating ILK. BPC-157 (15 amino acids) is studied for effects on VEGF and growth factor signaling through receptor pathways. They target different steps in cell biology. They should not be treated as substitutes in research protocols. Both are for lab research use only.
What Does HPLC Confirm in TB-500 Research?
HPLC (high-performance liquid chromatography) separates compounds by size and charge. For TB-500 (the 17-23 fragment), HPLC confirms that the target peptide makes up ≥99% of the compound by area. Other peaks represent impurities. A COA (certificate of analysis) reports the HPLC result with a chromatogram. Mass spec confirms the molecular weight matches the expected fragment sequence. Both tests are run per batch before shipping.
What Animal Models Are Used in Tb4 Research?
Rodent models are most common in thymosin beta-4 research. Scientists administer the compound to the animal and then measure gene and protein markers in target tissues at set time points. Cardiac injury models track ILK activity and cell survival markers. Skin injury models track cell migration and collagen gene expression. Control groups receive vehicle only. Results from treated vs. control groups are compared by statistical analysis. All are animal model findings only.
Are These Compounds Verified for Research Use?
Research-grade TB-500 and Frag 17-23 are tested by HPLC and mass spec per batch. HPLC confirms ≥99% purity for the target compound peak. Mass spec confirms molecular weight matches the expected amino acid sequence (LKKTETQ or similar). A COA with lot number is provided per batch. All compounds are for lab research use only and are not for clinical or personal use of any kind.
Summary
Thymosin beta-4 is a 43-amino acid protein studied in cell and animal models for effects on actin dynamics and cell migration markers. TB-500 refers to synthetic fragments derived from the Tb4 sequence. The key fragment is residues 17 to 23 (LKKTETQ), the actin-binding domain of the full protein.
Both the full protein and the fragment are studied for effects on G-actin sequestration and cell migration in cell assays. All cited findings come from cell and animal research. These compounds are not approved for human use. They are for lab research only.
What Should You Do Next?
Researchers studying actin dynamics and cell migration biology should source verified compounds for lab protocols. Before any study, confirm HPLC purity is ≥99% and mass spec matches the expected molecular weight. Record the lot number from the COA for batch traceability.
Shop research peptides. TB-500 and Frag 17-23 are available with HPLC and mass spec data on every COA.
People Also Read
- BPC-157 vs TB-500: A Detailed Research Comparison Guide
- TB-500 Fragment 17-23 Research: LKKTET Actin Binding Studies
About the Author
Next Level Pharm Research Team
Alex M covers peer-reviewed findings in peptide science for Next Level Pharm, a US-based supplier of research-grade peptides verified to ≥99% purity via HPLC and mass spectrometry on every batch.
Disclaimer: The information provided on this page is for educational and research purposes only. Next Level Pharm products are intended for laboratory research use only. They are not intended for human consumption, diagnostic, therapeutic, or medicinal purposes. This content does not constitute medical advice. Always consult a licensed healthcare professional before making any health-related decisions.