TB-500 5mg

What TB-500 is

TB-500 is a laboratory designation rather than a systematic chemical name. This product is cataloged as a synthetic fragment of thymosin beta-4, built around the six-residue LKKTET motif through which that 43-residue protein contacts monomeric actin. A fragment of this kind is a short linear peptide, not an excised folded domain: thymosin beta-4 has no stable fold of its own and becomes helical only when it binds actin.

The name is applied loosely across the market. Some sellers use it for a short fragment, usually given as residues 17 to 23 (LKKTETQ) and often N-terminally acetylated; others use it for the full-length protein. Those materials differ several-fold in mass and behave very differently on a column. TB-500 should also be kept apart from thymosin alpha-1, an unrelated 28-residue peptide that shares nothing with it beyond a historical naming convention.

TB-500 5mg specification

How TB-500 is analyzed

A fragment from this region is dominated by lysine, threonine, glutamate and glutamine, which makes it strongly hydrophilic. It retains weakly on C18 and can elute near the solvent front, so a gradient that opens at very low organic strength does most of the work of pulling it away from polar synthesis by-products. With no tryptophan, tyrosine or phenylalanine present, a 280 nm trace is uninformative and purity is read at about 214 nm. N-terminal acetylation adds 42 Da and removes a positive charge, moving both mass and retention time, so acetylated and free-amine versions are separate species. Deletion sequences one residue short elute close to the main peak and are the impurity class to watch.

Two lysines in so short a chain also mean a relatively large counter-ion share, which widens the gap between chromatographic purity and net peptide content. The independent HPLC run for TB-500 5mg is published here on the product page, and because the vial has no lot code, its crimp and cap color is how it is paired with that run.

Research contexts for TB-500

• Cell-free G-actin binding assays, including pyrene-actin polymerization and sedimentation
• Binding-affinity measurement by isothermal titration calorimetry or fluorescence anisotropy
• Circular dichroism of the disorder-to-helix transition on actin binding
• Scratch and transwell migration assays in cultured cell lines
• Literature sorting that separates fragment studies from full-length thymosin beta-4 work

Our TB-500 exists for actin biochemistry, cell-culture assays and analytical comparison at the bench; it is not made for any living subject.

TB-500 questions

Is TB-500 the same molecule as thymosin beta-4?

No. Thymosin beta-4 is a 43-residue protein, while TB-500 names a short synthetic peptide based on its actin-binding region. A result reported for one cannot be carried over to the other.

Why do TB-500 products from different sources show different masses?

The name does not fix a sequence, so vendors differ in fragment length and in whether the N-terminus is acetylated. Comparing an observed mass against the mass calculated for a stated sequence is the only dependable identity check.

What is the LKKTET motif?

It is the six-residue stretch in the central part of thymosin beta-4 that makes contact with monomeric actin, and it is the element a TB-500 fragment is designed to carry.