TB-500

TB-500 is a synthetic peptide reproducing the actin-binding stretch of thymosin β4, a 43-residue protein present in almost every mammalian cell type and found at high levels in platelets and wound fluid. This fragment covers residues 17 to 23 — the LKKTETQ sequence — responsible for the parent protein’s interaction with G-actin, and consequently the focus of most cytoskeletal research involving the molecule.

This listing is 10 mg of lyophilised TB-500 acetate at 96.8% HPLC purity with LC–MS identity confirmation, supplied with a lot-specific certificate of analysis and shipped cold-chain from Dublin.

Thymosin β4, the LKKTETQ sequence, and what TB-500 is

Thymosin β4 is the main protein responsible for sequestering monomeric G-actin in most cells. By holding actin in reserve, it lets a cell release building blocks quickly for filament assembly whenever it needs to change shape, move, or close a wound. That one function underlies a surprisingly broad set of observed effects, since almost every mechanical activity a cell performs depends on the state of its actin supply.

The seven-residue LKKTETQ fragment keeps actin-binding activity on its own, which is why it became the tool of choice for labs wanting to probe the actin-related side of thymosin β4 biology without synthesising the entire 43-residue protein. It’s worth being precise about naming here, since catalogues often blur the line: TB-500 is not thymosin β4 — it is a short fragment derived from it. Treating the two as interchangeable in a protocol or citation makes an assumption the data may not support, and reviewers do notice.

What researchers use it to study

Most published research focuses on cell migration and wound-closure models. Scratch assays and Boyden-chamber migration studies using keratinocytes, endothelial cells and fibroblasts are the standard readouts, together with imaging of actin filament organisation. A second area is angiogenesis, tracked through endothelial tube formation and vessel sprouting. A third covers cardiac and corneal repair models, where the parent protein has drawn the most interest and the fragment is used as a mechanistic tool.

Because the sequence is short, water-soluble and cheap to make well, TB-500 also serves as a positive control in migration assays — a reference stimulus that a novel compound’s effect can be scaled against. That role only holds if the material itself is well defined, since a control with an uncertain impurity profile undermines every comparison built on it.

As with everything in this catalogue, the evidence base is preclinical. TB-500 has no medicinal authorisation in Ireland or the EU and is supplied here strictly for laboratory research.

Working with TB-500 at the bench

TB-500 is among the easier peptides in this range to handle. It’s highly water-soluble, dissolves within a minute or two, and holds up across a wide pH range. A 10 mg vial mixed with 2 mL of bacteriostatic water gives a 5 mg/mL stock, roughly 6 mM, which dilutes comfortably down into the micromolar range typically used in migration and tube-formation assays.

In scratch-wound assays, the peptide is usually applied as soon as the monolayer is scratched, with images taken at set intervals over eight to twenty-four hours. Two controls are worth building in: a vehicle-only well matched for bacteriostatic water content, and a proliferation-inhibited arm using mitomycin C or reduced serum, so wound closure due to migration can be separated from closure due to cell division. Leaving out the second control is a common weak point in published scratch-assay work.

For analytical characterisation, the peptide runs cleanly on a standard C18 gradient. Its N-terminal acetylation is worth confirming by mass rather than assumed — the de-acetylated form differs by 42 daltons and is a known synthesis impurity that can elute very close by under shallow gradients.

• 10 mg + 2 mL bacteriostatic water = 5 mg/mL (~6 mM)
• Dissolves quickly; tolerates a wide pH range
• Pair scratch assays with a proliferation-inhibited control arm
• Confirm N-terminal acetylation by mass (+42 Da difference)

Storage, reconstitution and bench handling

A lyophilised vial arrives sealed under vacuum. If it isn’t going to be reconstituted within a few days, put it in a −20 °C freezer as soon as it’s unpacked. In powder form the peptide copes reasonably well with transit: the 2–8 °C gel-pack chain used for An Post and DPD delivery within Ireland, plus a short spell at room temperature while you unpack, won’t do it meaningful harm. What does harm it is moisture. Let the vial warm to room temperature before you crack the seal, or airborne water will settle on the cold glass and the cake, and slow hydrolysis starts from that moment.

Reconstitute using bacteriostatic water for injection, or plain sterile water if the solution will be used the same day. Run the diluent gently down the inside of the vial rather than firing it straight at the cake — a fine mist thrown up by a hard stream is peptide lost to the walls. Swirl the vial by hand, or simply let it stand for ten to fifteen minutes and allow the powder to go into solution unassisted. Do not vortex or shake it: shear forces at the surface of the liquid unfold peptide chains, and this is the single most frequent reason a solution that assays fine still performs erratically at the bench.

Once dissolved, keep the vial at 2–8 °C out of the light and use it within the window given on that lot’s certificate of analysis. For anything longer, split the stock into single-use volumes in low-binding polypropylene tubes and freeze at −20 °C or colder. Thawing and refreezing repeatedly works against you: every cycle concentrates dissolved material at the advancing ice edge and pushes the peptide toward aggregation, so material drawn from the same vial the twentieth time is not really the same as material drawn the first time.

• Lyophilised: −20 °C, kept dry and dark
• Reconstituted: 2–8 °C, single-use aliquots recommended
• Warm to room temperature before opening to stop condensation forming
• Swirl by hand — never vortex or shake
• Label each aliquot with the lot number and the reconstitution date

Reading this lot’s certificate of analysis

At 96.8%, this lot falls within the usual range for a short acetylated peptide, and the certificate identifies what makes up the remainder. For LKKTETQ, the typical related substances are the de-acetylated form and single-residue deletion sequences, each reported separately once they exceed the reporting threshold rather than being lumped into a total.

Because this peptide is quite hygroscopic, pay attention to the water content figure — a cake that has picked up moisture in storage will weigh more but deliver less peptide. If your protocol needs an absolute rather than relative concentration, dissolve the full vial contents in a measured diluent volume rather than weighing out part of the powder, and check the resulting stock by UV or amino-acid analysis.

Paperwork, compliance and shipping from Ireland

Every box leaving our Dublin site comes with a certificate of analysis tied to that specific lot. It records the HPLC assay result together with the method used to obtain it, identity confirmation by LC–MS against a reference standard, residual solvent levels, Karl Fischer water content, and endotoxin limits. Any purity figure quoted without the method behind it tells you very little, and it’s usually the first thing a knowledgeable buyer wants to see when weighing up suppliers. Certificates are kept on file by lot, so a reorder can always be checked against the data generated for the original batch.

Orders are priced in euro, dispatched from Dublin under a recorded 2–8 °C cold chain, and reach addresses within Ireland the next working day via An Post or DPD. Northern Ireland and the rest of the EU take two to three days. Because shipments stay within a domestic network, there’s no customs clearance, no surprise import VAT, and no multi-day hold at a border post — which does more for peptide integrity than any figure printed on the box.

This material is intended solely for in-vitro laboratory research and analytical reference purposes. It is not a medicine, not a food supplement, and it is not cleared for use in humans or animals. Buyers are responsible for handling, containing and disposing of it in line with their institution’s rules and with Irish and EU law.

Frequently asked questions

Is TB-500 the same as thymosin β4?

No. TB-500 is a synthetic seven-residue fragment (LKKTETQ, residues 17–23) of the 43-amino-acid thymosin β4 protein. It carries the actin-binding motif but is not the same as the full-length protein.

How soluble is TB-500?

Very soluble. It dissolves readily in bacteriostatic or sterile water; 10 mg in 2 mL gives a 5 mg/mL stock within a couple of minutes of gentle swirling.

What purity and documentation are supplied?

96.8% by reverse-phase HPLC with LC–MS identity confirmation, plus a lot-specific certificate of analysis covering assay, identity, water content, residual solvents and endotoxin.

Where does the order ship from?

From our Dublin facility, priced in euro, with An Post or DPD delivery within Ireland under a 2–8 °C gel-pack cold chain. Domestic Irish orders face no customs delay.

For laboratory research use only. Not for human or veterinary use, not a medicinal product, not a food supplement.