Written by the Core Power Peptides Research Team — biochemists and laboratory specialists compiling and verifying peptide research data. Learn about our quality standards →
TB-500 Fragment 17-23 (sequence LKKTETQ) is the minimal bioactive fragment of thymosin beta-4 (Tβ4) responsible for the parent molecule’s actin-binding and cell migration activity. Rather than using the full 43-amino acid Tβ4 protein, researchers investigating the specific actin-regulatory mechanism often use this smaller, more targeted fragment — making it a distinct research tool from full-length TB-500.
This guide covers what distinguishes Fragment 17-23 from full-length TB-500, its mechanism, and the research contexts where the fragment is the more appropriate choice.
What Is TB-500 Fragment 17-23?
Thymosin beta-4 is a 43-amino acid actin-sequestering protein expressed in nearly all human and animal cells. Structure-activity research identified that a specific 7-amino acid region — residues 17 through 23 (Leu-Lys-Lys-Thr-Glu-Thr-Gln, or LKKTETQ) — retains the core actin-binding and cell migration-promoting activity of the full protein. This discovery allowed researchers to work with a much smaller, more synthetically accessible peptide while retaining the mechanistically relevant activity for certain research applications.
Key Specifications
- Sequence: LKKTETQ (7 amino acids)
- Parent protein: Thymosin beta-4 (Tβ4), amino acids 17-23
- Molecular weight: ~847 Da (fragment) vs. ~4,921 Da (full-length Tβ4)
- Primary mechanism: Actin monomer binding / cell migration signaling
Mechanism of Action
- Actin Binding Domain: The LKKTETQ sequence is the core actin-binding motif within thymosin beta-4, responsible for sequestering G-actin monomers and regulating polymerization dynamics
- Cell Migration Signaling: This fragment retains the ability to promote directional cell migration in in vitro models, a property linked to actin cytoskeleton remodeling during cell movement
- Independent of Full-Length Tβ4 Domains: Full-length Tβ4 contains additional domains beyond the actin-binding region, including sequences implicated in anti-inflammatory signaling and cell survival pathways that the fragment does not include
Fragment 17-23 vs. Full-Length TB-500: Research Considerations
| Parameter |
Fragment 17-23 |
Full-Length TB-500 (Tβ4) |
| Size |
7 amino acids (~847 Da) |
43 amino acids (~4,921 Da) |
| Core actin-binding activity |
Retained |
Retained |
| Anti-inflammatory signaling (NF-κB) |
Not well characterized |
Documented |
| Cardiac progenitor cell activation |
Not established |
Documented (Bock-Marquette et al., Nature 2004) |
| Corneal wound healing data |
Not established |
Documented (Sosne et al.) |
| Cost / synthesis complexity |
Lower |
Higher |
| Best suited for |
Actin dynamics / cell motility-focused research |
Broader regenerative, cardiac, and anti-inflammatory research |
The key research decision point: full-length TB-500 has a substantially larger published data set covering cardiac regeneration, corneal healing, and systemic anti-inflammatory effects — properties tied to domains outside the minimal actin-binding fragment. Fragment 17-23 is appropriate when a study is specifically isolating the actin-regulatory mechanism and does not require the broader biological activity profile of the full protein.
Research Applications
Cell Migration and Cytoskeletal Studies
- Used in in vitro scratch/wound assays to isolate the actin-binding contribution to cell migration, separate from other Tβ4-mediated signaling pathways
- Valuable as a mechanistic control when comparing full-length Tβ4 effects against the isolated actin-binding domain
Structure-Activity Relationship Research
- Serves as a reference compound in studies mapping which regions of thymosin beta-4 are responsible for which biological effects
- Used alongside full-length Tβ4 and other fragments to build a complete picture of the protein’s functional domains
Comparative Peptide Research
- Frequently used in side-by-side protocols with full-length TB-500 to determine whether an observed effect requires the complete protein or can be reproduced with the minimal actin-binding sequence alone
Dosage Reference for Research
| Context |
Dose |
Route |
Notes |
| In vitro (cell migration assays) |
1–100 ng/mL |
Culture media |
Scratch assay / transwell migration protocols |
| In vitro actin polymerization assays |
0.1–10 µM |
Cell-free assay buffer |
Biochemical characterization |
| Rodent models (exploratory) |
Comparable to full-length Tβ4 molar equivalents |
SC or IP |
Limited published in vivo data specific to fragment |
Research reference only. Not dosing guidance for human use.
Where to Buy TB-500 Fragment 17-23 for Research
Sourcing criteria for research-grade Fragment 17-23:
- HPLC purity ≥99% with published certificate of analysis
- Mass spectrometry confirmation of the exact 7-amino acid sequence (LKKTETQ)
- Lyophilized format for long-term stability at −20°C
- Clear labeling distinguishing fragment from full-length TB-500 — the two are not interchangeable in protocols requiring specific domain activity
HPLC Verified
TB-500 Fragment 17-23 (10mg)
Purity: 99%+ HPLC
Sequence: LKKTETQ
Testing: Third-Party COA
$70
Buy Now
HPLC Verified
TB-500 (Full-Length) 10mg
Purity: 99%+ HPLC
Sequence: Full 43-aa Tβ4
Testing: Third-Party COA
$75
Buy Now
Frequently Asked Questions
Is TB-500 Fragment 17-23 the same as regular TB-500?
No. Fragment 17-23 is a 7-amino acid piece of the full 43-amino acid thymosin beta-4 protein. It retains the core actin-binding activity but does not include the domains associated with full-length Tβ4’s broader documented effects on cardiac progenitor cells, corneal healing, and anti-inflammatory signaling. Researchers should choose based on which mechanism their protocol requires.
Why would a researcher choose the fragment over full-length TB-500?
The fragment is useful when a study specifically wants to isolate the actin-regulatory mechanism without the broader biological activity of the full protein — for example, in structure-activity relationship studies or cell migration assays where actin dynamics are the variable of interest. It’s also lower cost due to simpler synthesis.
What does “frag 17-23” mean?
“Frag 17-23” is shorthand commonly used in the research community for TB-500 Fragment 17-23 — referring to amino acid positions 17 through 23 of the thymosin beta-4 sequence, which correspond to the LKKTETQ actin-binding motif.
Compiled for educational and scientific reference. TB-500 Fragment 17-23 is not approved for human use; material from Core Power Peptides is supplied strictly for in vitro and laboratory research, and researchers are responsible for compliance with applicable local regulations.
