What is the dosing range for Thymosin Beta-4 Fragment (TB4-Frag 17-23)?

Thymosin Beta-4 Fragment (TB4-Frag 17-23) is typically dosed at 250mcg (low), 500mcg (moderate), or 1mg (high) mcg–mg, administered 2–3x weekly. These ranges are aggregated from preclinical research and community protocols — not medical dosing guidance.

What are the reported side effects of Thymosin Beta-4 Fragment (TB4-Frag 17-23)?

Reported side effects of Thymosin Beta-4 Fragment (TB4-Frag 17-23) include: Injection site irritation, Mild fatigue (transient), Potential headache, Generally well-tolerated in research applications.

Healing

Thymosin Beta-4 Fragment (TB4-Frag 17-23)

Also known as: TB4 fragment 17-23, TB-500 active peptide, LKKTETQ, thymosin beta-4 fragment, Ac-LKKTETQ

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TB4-Frag is a research compound. Not approved for human use.

📚 Content aggregated from:2 peer-reviewed sources·r/Peptides community·PubMed / NCBI

Overview

The heptapeptide fragment (amino acids 17–23) of full thymosin beta-4, sequence Ac-LKKTETQ. This sequence is the active actin-binding domain responsible for TB-500's tissue repair properties. Shorter molecular weight than TB-500 enables more targeted delivery while retaining identical mechanism of action on G-actin regulation and tissue repair signaling.

Research Summary

The LKKTETQ sequence was identified in 1994 as the minimum active fragment of thymosin beta-4 responsible for its actin-sequestering and tissue repair activity. This heptapeptide competes with actin monomer binding proteins, promoting cell migration, angiogenesis, and wound healing. Studies confirm it recapitulates the key bioactivity of full TB4 in cell migration and collagen deposition assays.

Dosing Range

low

250mcg

moderate

500mcg

high

1mg

Units: mcg–mg · Frequency: 2–3x weekly

Dosing ranges are aggregated from preclinical research and community protocols. Not medical dosing guidance.

Administration Routes

Subcutaneous injectionIntramuscular injection

Reconstitution Notes

Reconstitute with bacteriostatic water. Target concentration: 500mcg/mL. Stable 28 days refrigerated. Smaller molecular weight than TB-500 — may be more easily dosed in smaller volumes.

Step-by-step reconstitution guide →

Supplies you'll need

Insulin Syringes (U-100)Reconstitution Needles Lambda BAC Water Alcohol Prep Pads

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Reported Side Effects

Injection site irritation
Mild fatigue (transient)
Potential headache
Generally well-tolerated in research applications

Research Papers

2 peer-reviewed sources

The actin-sequestering domain of thymosin beta-4: identification of a critical heptapeptide

Proceedings of the National Academy of Sciences1994

Thymosin beta-4 fragment promotes wound healing and angiogenesis

Journal of Cell Biology2000

Community Experiences

Aggregated from public forums. Anecdotal — not clinical evidence.

r/Peptides

Community discussion comparing TB4-Frag 17-23 to full TB-500 in injury recovery protocols.

View original thread

r/PeptideProtocols

Research and anecdotal reports on the minimum active fragment of TB4 for tissue repair.

View original thread

Overview

TB4-Frag (fragment 17–23) is the scientifically identified minimum active fragment of thymosin beta-4 (TB4) — the parent molecule behind the popular research peptide TB-500. The full TB4 protein is 43 amino acids; researchers in the 1990s systematically mapped which portion of the molecule was responsible for its signature activity: binding G-actin (monomeric actin) and modulating the actin cytoskeleton.

The answer was the heptapeptide LKKTETQ (Leu-Lys-Lys-Thr-Glu-Thr-Gln), spanning positions 17–23. The N-acetylated form (Ac-LKKTETQ) is the research standard. This sequence contains the critical WH2 domain motif (GxxxQ) essential for G-actin binding across the actin-binding protein superfamily.

Mechanism

Actin-Dependent Healing

The fundamental mechanism of TB4 and its fragment is G-actin sequestration:

G-actin binding: The LKKTET motif binds monomeric actin (G-actin) with high affinity, competing with profilin for actin monomers
Cell migration promotion: By modulating the G-actin:F-actin ratio, the fragment promotes lamellipodia formation and directed cell migration — critical for wound healing
Angiogenesis: Promotes endothelial cell migration and tubulogenesis, stimulating new blood vessel formation to healing tissue
Anti-inflammatory signaling: Downregulates NFκB-mediated inflammatory cytokines (IL-1β, TNF-α) in injured tissue
Fibroblast activation: Promotes fibroblast migration to injury site and collagen deposition

TB4-Frag vs. Full TB-500

| Parameter | TB4-Frag (17-23) | TB-500 | |-----------|-----------------|--------| | Amino acids | 7 | 43 (commercial: ~17-43) | | Molecular weight | ~800 Da | ~4,900 Da | | G-actin binding | Yes (direct) | Yes (via same domain) | | Non-actin domains | Absent | Present | | Bioavailability | Potentially higher | Standard | | Half-life | Shorter | Longer |

Research Context

The TB4-frag approach is based on the principle that the minimum effective sequence is sufficient — avoiding any activities residing in other TB4 domains. However, some researchers argue the full TB4 (or the commercial TB-500 fragment 17–43) may have additive effects from non-actin binding domains involved in immunomodulation. Both approaches have legitimate research rationales.

Combination Protocols

TB4-Frag is commonly studied in the "Wolverine Stack" alongside BPC-157:

BPC-157: Drives angiogenesis and upregulates growth factor receptors (VEGFR, FGFR)
TB4-Frag / TB-500: Regulates actin dynamics for cell migration into the injury site

These mechanisms are non-overlapping and complementary, making the combination a logical research pairing for comprehensive tissue repair investigation.