Where to Buy TB-500 2 mg Fragment (17-23): Vendor Comparison & Research Info

TB-500 Fragment (17–23) is a synthetic, -acetylated heptapeptide derived directly from the central functional domain of Thymosin Beta-4 (), a naturally occurring 43-amino-acid peptide expressed in most human tissue types. Encompassing amino acid residues 17 through 23, the sequence—Ac-LKKTETQ—represents the core, highly conserved actin-binding motif of the parent protein.

While full-length Thymosin Beta-4 serves multi-faceted intracellular and extracellular roles, the 17–23 fragment was engineered specifically to isolate the localized biochemical interactions between this essential sequence and globular actin (G-actin). By isolating this active binding cassette, researchers can examine cytoskeletal regulation, actin polymerization dynamics, cell migration pathways, focal adhesion remodeling, and localized tissue repair mechanisms without the confounding effects of secondary functional domains present in the full-length parent protein.

Supplied as a highly stable, lyophilized powder at  analytical purity, TB-500 Fragment (17–23) serves as a precision research tool for in vitro, ex vivo, and preclinical laboratory studies across regenerative biology, molecular pharmacology, cellular physiology, and bio-engineering.

Structural Engineering & Molecular Biochemistry

To evaluate the utility of TB-500 Fragment (17–23), researchers must distinguish between the truncated 7-amino-acid fragment and the native, full-length 43-amino-acid Thymosin Beta-4 polypeptide.

1. The Active Actin-Binding Motif (LKKTETQ)

Native Thymosin Beta-4 acts as the primary intracellular actin-sequestering protein in eukaryotic cells. The specific heptapeptide sequence spanning residues 17–23 (Leu-Lys-Lys-Thr-Glu-Thr-Gln) forms the primary contact surface that interacts directly with the cleft between subdomains 1 and 3 of monomeric .

2. N-Terminal Acetylation (Ac-)

In its synthetic form, the N-terminal leucine residue is modified with an acetyl group (Ac-). This modification protects the peptide against rapid degradation by N-terminal aminopeptidases, enhancing chemical stability in aqueous solutions during laboratory assays and extending its functional half-life during experimental incubations.

3. Molecular Weight & Structural Conformational Flexibility

With a molecular mass of approximately  (compared to  for native ), the reduced steric footprint of the 17–23 fragment allows for distinct diffusion kinetics across cellular membranes and extracellular matrix environments. This smaller size facilitates targeted structural studies investigating direct protein-peptide binding without steric interference from neighboring polypeptide regions.

Mechanism of Action & Cellular Dynamics

The primary biochemical role of the  sequence centers on its capacity to interact with the cytoskeletal network. Actin dynamics govern fundamental cellular processes, including cell shape maintenance, lamellipodia formation, focal adhesion assembly, directional motility, and cytokinesis.

1. Regulation of G-Actin Sequestration & F-Actin Polymerization

In resting cells,  monomers are maintained in a dynamic equilibrium with filamentous actin (). Upon binding to , the  motif inhibits spontaneous nucleotide exchange and prevents premature assembly into filaments. By regulating the pool of available , the peptide modulates the rate and spatial orientation of filament assembly at the leading edge of migrating cells.

2. Induction of Cell Motility & Chemotaxis

Cellular migration is a multi-step cycle involving membrane protrusion, adhesion, cell body contraction, and rear detachment. The 17–23 sequence promotes localized actin treadmilling, driving the formation of filopodia and lamellipodia. Experimental observations indicate that exposure to the fragment enhances directional movement in several key regenerative cell populations:

• Fibroblasts: Accelerating matrix deposition and mechanical tension generation during structural tissue repair models.

• Keratinocytes: Facilitating epithelial re-sheathing and border closure in scratch-wound assays.

• Endothelial Cells: Supporting capillary sprout formation, directional alignment, and early-stage angiogenic responses.

3. Extracellular Matrix (ECM) Interactions & Remodeling

Beyond direct cytoskeletal interactions, research indicates that the presence of the active actin-binding motif influences downstream gene expression and protein secretion profiles. Laboratory models demonstrate alterations in matrix metalloproteinase (MMP) activity, collagen alignment, and fibronectin expression, contributing to structural matrix organization during tissue remodeling phases.

Primary Laboratory Research Domains

1. Wound Healing & Epithelial Regeneration

A major area of scientific investigation focuses on cutaneous and mucosal wound-healing models. Researchers employ scratch assays and 3D organotypic culture systems to evaluate how TB-500 Fragment (17–23) accelerates cell migration into denuded areas. While full-length Tbeta4  exhibits broader anti-inflammatory and anti-apoptotic signaling, comparative studies aim to determine how much of the accelerated re-epithelialization rate is driven purely by LKKTETQ-mediated motility versus secondary anti-inflammatory cascades.

2. Angiogenesis & Endothelial Cell Biology

Blood vessel growth (angiogenesis) relies on coordinated endothelial cell proliferation, migration, and lumen formation. The 17–23 fragment is routinely studied in tube-formation assays on basement membrane matrices (Matrigel) to determine its capacity to stimulate endothelial cell alignment into microvascular structures. Understanding these capillary sprouting mechanisms provides insights into tissue vascularization during repair.

3. Musculoskeletal & Tendon Repair Models

Connective tissue injury models—such as tendon, ligament, and skeletal muscle micro-trauma—frequently evaluate cell responses to actin-modulating mimetics. Investigators evaluate how the fragment influences tenocyte proliferation, collagen type I and III synthesis ratios, and biomechanical strength recovery in experimental models of mechanical overload.

4. Cardiovascular & Ischemic Tissue Research

Following ischemic injury, cardiac myofibroblasts and endothelial progenitor cells undergo significant cytoskeletal reorganization. Research protocols explore whether exposure to the isolated actin-binding motif can support cellular survival, attenuate fibrotic scar tissue formation, or promote local vascular remodeling in cultured cardiomyocytes and endothelial networks.

Comparative Analysis: Parent Protein vs. Fragment

Because published literature frequently references "TB-500" or "Thymosin Beta-4" interchangeably, researchers must carefully distinguish between the full-length protein and the isolated 17–23 fragment when interpreting experimental data.

Product Characteristics & Quality Control

• High Analytical Purity: Every batch is subjected to Reverse-Phase High-Performance Liquid Chromatography (RP-HPLC) to ensure an analytical purity profile meeting or exceeding .

• Mass Spectrometry Verification: Electrospray Ionization Mass Spectrometry (ESI-MS) validates the exact molecular weight and confirms correct amino acid assembly.

• Controlled Lyophilization: Freeze-dried under nitrogen to yield a uniform cake that exhibits rapid reconstitution characteristics.

• Minimal Counter-Ion Residue: Processed to minimize residual salt and moisture content, ensuring baseline reproducibility across delicate cell culture protocols.

Reconstitution & Laboratory Handling Protocols

To ensure optimal stability and activity of TB-500 Fragment (17–23) during experimental procedures, adhere to standard peptide handling practices:

1. Equilibration: Prior to reconstitution, allow the frozen vial to warm to ambient room temperature (). This minimizes air intake and prevents condensation from contaminating the dried cake.

2. Reconstitution: Slowly add sterile, deionized water (ddH2O),  0.9% sterile sodium chloride solution, or sterile phosphate-buffered saline (PBS, pH 7.4) along the inner glass wall of the vial.

3. Mixing: Gently rotate or swirl the vial until the lyophilized powder completely dissolves. Do not vortex vigorously, as aggressive mechanical agitation can disrupt hydrogen bonding and cause peptide aggregation.

4. Storage & Aliquoting: For immediate use, store reconstituted solutions at 2C-8C for up to 7 days. For long-term storage, aliquot the solution into sterile, low-binding polypropylene tubes and freeze at -20C or -80C. Avoid repeated freeze-thaw cycles.