TB-500 Molecular Weight, Sequence & CAS Reference

Chemical Overview & Nomenclature of TB-500

TB-500 is a synthetic peptide derivative based on the active functional domain of naturally occurring Thymosin Beta-4 (Tβ4), a 43-amino acid G-actin sequestering protein. In published biochemical literature, the designation TB-500 is frequently used interchangeably with the full-length synthetic 43-amino acid sequence of Thymosin Beta-4, as well as specific short-chain active fragments containing the actin-binding motif (LKKTETQ). When evaluating commercial reference material or preparing assays, laboratory investigators must distinguish between full-length synthetic Thymosin Beta-4 and truncated sequence variants.

As a primary regeneration peptide, TB-500 has been extensively investigated in preclinical literature for its capacity to influence cellular motility, cytoskeletal remodeling, and extracellular matrix organization. Research models utilize high-purity synthetic material to isolate the exact molecular mechanisms driving actin polymerization and cellular migration without the confounding background of endogenously expressed mammalian tissue extracts. For laboratory testing requiring quantified molecular standards, researchers can consult our full catalog of all peptides for analytical specification sheets.

Primary Amino Acid Sequence & Domain Structure

The primary amino acid sequence of full-length synthetic Thymosin Beta-4 (commonly supplied under the research name TB-500) consists of 43 residues with an N-terminal acetylation. The single-letter amino acid code sequence is established as follows:

Ac-SDKPDMAEIEKFDKSKLKKTETQEKNPLPSKETIEQEKQAGES-OH

The three-letter amino acid sequence representation is written as: Ac-Ser-Asp-Lys-Pro-Asp-Met-Ala-Glu-Ile-Glu-Lys-Phe-Asp-Lys-Ser-Lys-Leu-Lys-Lys-Thr-Glu-Thr-Gln-Glu-Lys-Asn-Pro-Leu-Pro-Ser-Lys-Glu-Thr-Ile-Glu-Gln-Glu-Lys-Gln-Ala-Gly-Glu-Ser-OH.

Within this 43-residue structure, the region spanning residues 17 through 23 (Leu-Lys-Lys-Thr-Glu-Thr-Gln, or LKKTETQ) represents the essential actin-binding domain. In vitro binding studies indicate that this specific hexapeptide-to-heptapeptide motif is primarily responsible for sequestering monomeric G-actin and preventing spontaneous polymerization into F-actin filaments until regulated signaling events occur. Some research literature isolated this truncated sequence (Ac-LKKTETQ-NH2) for targeted domain analysis, whereas full-length TB-500 encompasses the complete 43-residue sequence to preserve secondary structure and native solubility profiles.

Molecular Weight, Empirical Formula & Mass Spectrometry Data

Determining the exact molecular weight of synthetic TB-500 depends strictly on whether the research material represents the full 43-amino acid sequence or the truncated active domain. Analytical data for both entities are standard reference parameters in chemical identification:

Full-Length Synthetic Thymosin Beta-4 (43 Amino Acids): • Empirical Formula: C212H350N56O78S • Monoisotopic Mass: ~4963.50 Da • Molecular Weight (Average): 4963.49 g/mol

Truncated Actin-Binding Fragment (Ac-LKKTETQ, Residues 17–23): • Empirical Formula: C38H68N10O14 • Monoisotopic Mass: ~888.49 Da • Molecular Weight (Average): ~889.01 g/mol

In high-performance liquid chromatography coupled with mass spectrometry (HPLC/MS) analysis, full-length TB-500 yields characteristic multiply-charged ion states due to the presence of multiple basic residues (lysines). Typical electrospray ionization (ESI-MS) spectra display prominent peaks corresponding to [M+4H]4+, [M+5H]5+, and [M+6H]6+ charge distributions. Laboratory personnel validating analytical identity should compare observed m/z spectra against theoretical isotope distributions calculated from the primary empirical formula.

CAS Registry Numbers & Chemical Taxonomy

Chemical abstracts assign specific CAS Registry Numbers based on exact sequence length and structural modifications. Investigators citing technical literature or preparing institutional chemical safety protocols should reference the appropriate CAS identifier:

• CAS Registry Number for Full-Length Synthetic Thymosin Beta-4: 77591-33-4 • CAS Registry Number for Acetylated Domain Fragment (Ac-LKKTETQ): 885340-86-7 (when assigned under specific chemical inventories) • IUPAC Name (Full-Length): N-acetyl-L-seryl-L-aspartyl-L-lysyl-L-prolyl-L-aspartyl-L-methionyl-L-alanyl-L-glutamyl-L-isoleucyl-L-glutamyl-L-lysyl-L-phenylalanyl-L-aspartyl-L-lysyl-L-seryl-L-lysyl-L-leucyl-L-lysyl-L-lysyl-L-threonyl-L-glutamyl-L-threonyl-L-glutaminyl-L-glutamyl-L-lysyl-L-asparaginyl-L-prolyl-L-leucyl-L-prolyl-L-seryl-L-lysyl-L-glutamyl-L-threonyl-L-isoleucyl-L-glutamyl-L-glutaminyl-L-glutamyl-L-lysyl-L-glutaminyl-L-alanyl-glycyl-L-glutamyl-L-serine

Where specific salt forms or stereo-isomeric variants are not assigned unique CAS entries in public databases, chemical taxonomy relies on the primary sequence designation and salt stoichiometry documented in lot-specific documentation.

Counterion Chemistry: Trifluoroacetate (TFA) vs. Acetate Salt Forms

During solid-phase peptide synthesis (SPPS), basic amino acid residues—particularly the nine lysine (Lys) residues present in full-length TB-500—form ionic bonds with acid cleaving reagents. Consequently, raw synthetic peptides are typically isolated as trifluoroacetate (TFA) salts. The presence of residual TFA counterions alters the gross formula weight and impacts gross mass measurements during laboratory preparation.

Net peptide content (NPC) reflects the actual proportion of pure peptide mass relative to total dry powder weight, which includes bound salt counterions and residual hydration water. A typical lyophilized TB-500 preparation may have a net peptide content ranging between 75% and 88%. For sensitive cell culture or enzymatic in vitro assays where TFA might induce cellular toxicity or alter pH dynamics, researchers frequently utilize acetate salt exchange. When conducting precision stoichiometry, laboratory protocols must calculate final working concentrations using the lot-specific net peptide content provided on the manufacturer's analytical certificate, rather than relying solely on gross balance mass.

Net Peptide Content & Reconstitution Calculations

Accurate concentration calculations require accounting for net peptide percentage and reconstitution volume. For example, if a laboratory vial contains 10 mg of gross lyophilized powder with a verified net peptide content of 82%, the actual mass of active TB-500 peptide present is 8.2 mg.

To achieve a target stock concentration of 2.0 mg/mL of net active compound, the required volume of sterile laboratory solvent (such as bacteriostatic water or phosphate-buffered saline) is calculated as: Volume (mL) = Net Mass (mg) / Target Concentration (mg/mL) Volume = 8.2 mg / 2.0 mg/mL = 4.10 mL solvent

Laboratory researchers requiring rapid, standard solvent-to-mass calculations for experimental design can utilize our interactive reconstitution calculator to determine dilution parameters across varying mass and purity specifications.

Biological Mechanisms Investigated in Preclinical Models

In preclinical research models, TB-500 (Thymosin Beta-4) is studied primarily as a key regulatory molecule in actin dynamics and tissue remodeling. Monomeric G-actin binding by the LKKTETQ domain maintains an intracellular pool of unpolymerized actin monomers, facilitating rapid cytoskeletal rearrangement in response to chemotactic signals. Preclinical studies suggest that this intracellular mechanism is fundamental to cell migration, endothelial cell differentiation, and capillary morphogenesis.

In vitro assays and animal models demonstrate that exogenous administration of research-grade TB-500 promotes cell migration into damaged cellular matrices, accelerates blood-vessel formation (angiogenesis), and enhances structural flexibility during soft-tissue and muscle-fiber recovery. Furthermore, preclinical investigations highlight the peptide's capacity to downregulate specific pro-inflammatory cytokines and reduce focal fibrosis by modulating transforming growth factor-beta (TGF-β) signaling cascades. These mechanisms make TB-500 a subject of active research in musculoskeletal repair, corneal wound healing, and dermal tissue regeneration models.

Comparative Analysis: TB-500 vs. BPC-157 vs. GHK-Cu

Within preclinical tissue repair and regenerative signaling research, several distinct peptide compounds are evaluated for complementary or distinct mechanisms of action. A comparative analysis of these compounds clarifies structural and functional differences:

While TB-500 acts predominantly through actin sequestering, cellular motility, and blood-vessel formation, BPC-157 is a 15-amino acid pentadecapeptide (MW ~1419.5 g/mol) investigated for its modulation of the VEGFR2 pathway, nitric oxide synthesis, and tendon-to-bone junction recovery. Conversely, GHK-Cu is a small tripeptide-copper complex (MW ~403.9 g/mol) studied for gene expression regulation, collagen synthesis, and extracellular matrix remodeling. In specialized multi-factorial research designs, investigators frequently compare these distinct molecular pathways to analyze synergistic mechanisms involved in soft-tissue remodeling.

Researchers managing larger studies or sourcing high-volume research inventories can review enterprise supply options via our wholesale lab account portal.

Analytical Quality Control & PX1 Research Verification

Analytical precision and lot-to-lot consistency are essential for reproducible laboratory experiments. PX1 Research subjects every batch of synthetic peptide to rigorous quality control standards in ISO 17025 accredited testing facilities operating under GMP-compliant guidelines.

Analytical verification includes high-performance liquid chromatography (HPLC) to confirm chemical purity (exceeding 99.0%), mass spectrometry (MS) to verify precise molecular weight and identity, and chromogenic LAL assays to ensure endotoxin levels remain strictly below baseline laboratory limits (<0.01 EU/mg). Every shipment includes full batch documentation; researchers can inspect lot-specific analytical data directly by accessing our public Certificate of Analysis (COA) repository. All products are manufactured in the USA and dispatched directly from our California and Arizona logistics facilities.

Laboratory Storage & Handling Guidelines

To maintain structural integrity and prevent hydrolytic degradation or oxidation of sensitive residues (such as methionine at position 6 in the full sequence), synthetic TB-500 must be stored under controlled conditions:

• Lyophilized Powder: Store at -20°C for long-term stability (up to 24 months). Protect from moisture desiccants and direct light exposure. • Reconstituted Solution: After reconstitution in sterile, buffered aqueous media (pH 6.5–7.4), store stock solutions at 2°C to 8°C for short-term experimental procedures (up to 30 days). For extended liquid storage, store aliquots at -80°C to minimize freeze-thaw degradation cycles. • Solvent Compatibility: Soluble in sterile water, normal saline (0.9% NaCl), and standard PBS buffers. Avoid vigorous mechanical vortexing during dissolution to prevent peptide aggregation.

To purchase highly verified material for ongoing in vitro and preclinical research applications, view our TB-500 (Thymosin Beta-4) 10mg product reference page. For broader literature context on structural modeling, visit our centralized research library hub.