TB-500 vs Thymosin Beta-4: What's the Difference?

Two names, different scopes

Thymosin beta-4 is a 43-amino-acid peptide with an approximate molecular mass of 4.9 kDa. TB-500 is a synthetic short fragment name used in research catalogs. The terms therefore do not describe interchangeable sequence lengths: one refers to the full peptide, while the other is used for a shorter defined fragment. Clear technical writing should retain that distinction whenever a product name, sequence, or analytical result is reported.

The catalog specification for TB-500 identifies the synthetic fragment Ac-LKKTETQ. “Ac” denotes an acetylated N-terminus, and LKKTETQ gives the residue sequence in one-letter notation. This fragment comprises seven amino-acid residues plus the N-terminal acetyl group. Its stated formula is C38H68N10O14, with a molecular weight of 889.0 g/mol. These data identify the catalogued fragment; they are not a description of the entire 43-residue thymosin beta-4 molecule.

Sequence notation

One-letter sequence notation is compact, but every symbol must be interpreted in its stated context. In Ac-LKKTETQ, the initial “Ac” is a chemical terminal modification, not an amino-acid residue. The residue letters that follow identify leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine. Written-out notation can reduce transcription errors when records are compared across labels, COAs, and analytical files.

The full thymosin beta-4 designation concerns a much longer amino-acid chain. Its approximate 4.9 kDa mass is consequently not the mass of the seven-residue TB-500 fragment. Comparisons should pair each mass with the structure it describes and should not carry a value from one name to the other. Likewise, fragment nomenclature should not be expanded into an unverified claim that a vial contains the full-length peptide.

Formula and molecular mass

A molecular formula counts the atoms in a defined molecular structure, while molecular mass summarizes their contribution using atomic masses. For the catalogued TB-500 fragment, the stated formula is C38H68N10O14 and the stated molecular weight is 889.0 g/mol. Formula and mass are complementary identifiers, not alternatives to sequence information. Terminal modifications matter in both: the N-terminal acetyl group is part of the named structure and should be retained when comparing formula or mass records.

Thymosin beta-4 is described here as a 43-amino-acid peptide of approximately 4.9 kDa. Because this is an approximate mass for the full peptide, it is best presented at that precision. Reporting excessive decimal places would imply a level of definition not supplied by the catalog specification. Comparisons across sources should preserve units and clarify whether a reported mass is calculated, nominal, or derived by an analytical method.

Catalog identity

The TB-500 item is specified as 10 mg. Product amount and molecular identity are separate fields: the amount states the vial’s listed content, whereas sequence, formula, and mass identify the named chemical structure. A well-formed inventory entry includes both. The catalog description should call TB-500 a synthetic short fragment name used in research catalogs and give Ac-LKKTETQ explicitly, avoiding wording that conflates it with the full-length 43-amino-acid peptide.

For comparison tasks, first capture the exact label text, then consult the lot-matched COA. If another record uses “thymosin beta-4” as a broad heading, do not assume that heading proves the full-length sequence is present. Preserve distinctions between product title, stated sequence, and analytical identity. This approach supports precise discussion of nomenclature while leaving no ambiguity about which structure the specified formula and mass describe.

Analytical confirmation

HPLC provides chromatographic separation and a profile that can be used to assess reported purity. LC-MS provides mass-based data that can support an identity assessment. A COA should be read for the specific lot, including the method, result, and product identifier; the presence of an instrument or method name alone is not evidence of a particular outcome. The reported analytical data should correspond to the same defined structure and lot as the vial label.

A lot-matched COA can be checked on the site’s Verify a lot page. Keep a copy or reference with receiving and inventory documents, together with the vial’s lot number. For a fragment, sequence and mass information make an especially useful cross-check, but no single field replaces the full document review. Record any differences in spelling, formatting, or product naming, and resolve them using the specific lot’s label and analytical documentation.

Fragment identity records

Terminal notation deserves particular attention when fragment names are compared. The acetyl prefix in Ac-LKKTETQ is part of the written identity, whereas the seven letters after the prefix describe residue order. Omitting the prefix during data entry can make two records appear equivalent when their stated structural notation differs. Preserve punctuation consistently, and include a plain-language note that identifies the terminal modification.

A comparison worksheet can place sequence, formula, stated molecular weight, product amount, and lot identifier in separate columns. This simple layout prevents a vial quantity from being mistaken for a structure-level mass and keeps the fragment distinct from the longer name sometimes used in catalog discussions. If two documents disagree, quote both values with their source and revision date, then seek a lot-specific clarification rather than selecting one silently.

A controlled vocabulary can index both the fragment label and its sequence while retaining the source’s exact term. Such indexing improves retrieval without treating related names as structural synonyms.

Storage and shipping

TB-500 is supplied as a lyophilized material in a sealed glass vial. Store the sealed vial at 2–8 °C, protect it from light, and keep it dry. These are the stated storage conditions for the sealed lyophilized presentation. Keep lot identification legible and maintain the link between the vial and its COA throughout storage and inventory handling.

Shipping is US-only with cold-chain handling. Receiving records should connect the shipment to the lot number, product label, and COA, and can document the package condition when received. For nomenclature purposes, retain the description “synthetic short fragment” and the specified Ac-LKKTETQ sequence. That language distinguishes TB-500 from full-length thymosin beta-4 while keeping the item’s stated formula and mass tied to the correct structure.