Preloaded Autoinjector | TB-500 | 3ml Pen | 5mg/ml

The TB-500 autoinjector is a preloaded 3ml research device containing thymosin β4 in solution at 5mg/ml, giving 15mg of total peptide. Thymosin β4 is a 43-residue peptide, CAS 77591-33-4, molecular weight 4963.55, whose defining property is high-affinity binding to monomeric globular actin.

Specification Table

What Is the TB-500 Autoinjector Used For in Research?

The honest framing is that the compound is a tool for studying actin dynamics, and everything else follows from that.

Actin exists in two interconverting states. Globular actin, G-actin, is the free monomer. Filamentous actin, F-actin, is the polymer built from those monomers. Cells continuously shift the balance between them, and that shifting is what drives cell shape change, migration and division.

Thymosin β4 binds G-actin with high affinity and holds it in the monomeric state. It is the principal G-actin sequestering protein in mammalian cells, present at high intracellular concentration, and its function is to maintain a reservoir of unpolymerised actin available for rapid filament assembly when signalling demands it.

Research applications follow directly. Anything concerning cell migration, cytoskeletal remodelling, or the regulation of the monomer pool can use this peptide as an intervention. Huff and colleagues reviewed the actin biology in detail (Huff et al., International Journal of Biochemistry and Cell Biology, 2001), and Goldstein and colleagues covered the wider research context (Goldstein et al., 2012).

What Does the LKKTETQ Motif Do?

Actin binding localises to a specific seven-residue stretch, LKKTETQ, occupying positions 17 to 23 of the 43-residue sequence. Identifying it was significant because it separated the functional core from the rest of the molecule.

The motif is what physically contacts actin, and synthetic peptides consisting of the motif alone retain measurable actin-binding activity. That has practical consequences for anyone comparing preparations, because fragments containing only this region have been sold under the TB-500 name historically, and they are not the same molecule as the full 43-residue peptide.

The distinction matters for interpretation. A fragment binds actin, but it lacks whatever contribution the remaining 36 residues make to binding kinetics, cellular uptake and stability. Findings generated with one should not be assumed to transfer to the other.

For a preparation like this one, confirm from the certificate of analysis that the material is full-length thymosin β4 at 4963.55 daltons rather than a motif-containing fragment. The mass difference is large enough that no ambiguity should survive a mass spectrometry check.

Why Is an Unstructured Peptide Harder to Characterise?

Thymosin β4 is intrinsically disordered in free solution. It adopts no stable fold, existing instead as a flexible chain sampling many conformations, and it becomes ordered only on binding actin.

That behaviour has real analytical consequences. Circular dichroism, which reports secondary structure content, gives a spectrum characteristic of a random coil rather than the defined helix or sheet signatures used to confirm folding in structured proteins. A disordered spectrum is the correct finding here, not evidence of denaturation.

Size-exclusion chromatography also behaves unexpectedly. A disordered chain occupies a larger hydrodynamic volume than a folded protein of the same mass, so the peptide elutes earlier than its molecular weight would predict. Calibrating against globular standards and reading the answer literally will overestimate the mass.

The practical upshot is that standard protein characterisation methods need interpreting differently for this molecule, and a finding that looks anomalous against globular-protein expectations may be entirely normal.

What Does the Preloaded Format Change?

Device-oriented queries dominate the demand reaching the TB-500 autoinjector page, which says the audience is evaluating format as much as compound.

A preloaded pen removes the reconstitution step and the variability it introduces. For a 43-residue peptide that variability is not trivial: incomplete dissolution of a large lyophilized cake, shear from over-agitation, adsorptive loss during transfer, and inconsistent time between reconstitution and use all affect delivered concentration invisibly.

Against that, solution-state supply means the peptide has been in aqueous conditions since manufacture. For an intrinsically disordered peptide, aggregation is the principal concern, since disordered chains have exposed hydrophobic surface that a folded protein would bury. Aggregated material is inactive and can interfere with the assay it enters.

At 5 mg/ml the solution is approximately 1.0 millimolar, which is a convenient starting point for most cell-based work and requires fewer dilution steps than the picomolar arithmetic some peptides in this catalogue demand.

How Should the Device Be Verified?

Gravimetric checking of the TB-500 autoinjector is the direct method and takes minutes. Actuate onto a tared weighing vessel, record delivered mass, convert through solution density, and repeat across several actuations to capture accuracy against nominal volume and precision between draws.

Perform the check at the temperature of intended use rather than straight from refrigeration, since cold solution is more viscous and viscosity affects delivery in a spring-driven mechanism.

Inspect the solution before each draw, against both light and dark backgrounds. Aggregation in a disordered peptide frequently appears first as faint opalescence rather than obvious turbidity, and a dark background makes that early stage visible when a light one will not.

Treat the first actuation after a rest period as suspect. Air ingress into the delivery path and seal relaxation both cause under-delivery on first use, and unless a priming step is specified and followed, the first draw should not be trusted until gravimetric data says otherwise.

How Is Actin Binding Measured?

Several established methods report on the G-actin sequestration the TB-500 autoinjector is used to study, and they answer subtly different questions.

The pyrene-actin polymerisation assay is the workhorse. Actin labelled with pyrene at cysteine 374 shows a large fluorescence increase on incorporation into filaments, so polymerisation can be followed in real time. A sequestering agent reduces the rate and the plateau, and the concentration dependence of that reduction gives an apparent affinity.

The critical concentration assay measures the same underlying property differently. At steady state, free monomer concentration sits at a fixed value determined by filament thermodynamics. A sequestering protein raises the apparent critical concentration, because some monomer is held unavailable, and the shift quantifies how much.

Direct binding measurement by isothermal titration calorimetry or surface plasmon resonance gives the affinity without inferring it from polymerisation behaviour. These are more demanding and more definitive.

One methodological caution applies across all of them. Thymosin β4 binds ATP-actin considerably more tightly than ADP-actin, so nucleotide state changes the measured affinity. An assay that does not control the nucleotide state is measuring an average across whatever mixture happens to be present, which is why published affinity values vary more than they should.

What the 43-Residue Length Implies

Thymosin beta 4 sits at an awkward size for peptide chemistry, long enough to raise synthesis difficulty and short enough that recombinant expression is often not worth the setup.

Solid-phase synthesis efficiency compounds across couplings. Even at 99.5 percent per step, a 43-residue chain accumulates measurable deletion sequences, and those deletion products differ from the target by a single residue, which makes them hard to resolve chromatographically.

That has a direct implication for purity interpretation. A 98 percent purity figure on a 43-residue peptide means something different from the same figure on a tripeptide, because the impurity profile of the longer peptide is dominated by closely related sequences rather than by unrelated material.

For actin-binding work the practical question is whether deletion products retain activity. A sequence missing a residue outside the LKKTETQ motif may bind normally, while one missing a residue inside it may not, and a bulk purity figure cannot distinguish those cases.

Where the work depends on precise stoichiometry, mass spectrometry showing the impurity distribution is more informative than a single purity percentage.

Handling the Device in Laboratory Practice

Store at 2-8°C protected from light, returning the device to its packaging between sessions rather than leaving it out on a bench.

Record device lot number, date of first actuation, storage conditions and volume drawn at each session. Because solution-state stability over shelf life is not published for this format, the interval between first use and each later draw is an experimental variable that belongs in the record.

Where the solution enters a downstream actin assay, remember that the peptide is being added to a system whose entire readout concerns the monomer-polymer balance. Vehicle controls matter more than usual, because excipients in an unpublished formulation could themselves affect actin dynamics, and nobody has ruled that out for this product.

What Does the Preclinical Record Report?

The literature here divides cleanly into two halves, and keeping them apart is what makes any statement about this compound defensible.

One half is actin biology, which is settled science about a real endogenous protein and is described above.

The other half is injury-model work, and that is where every claim attached to the market name comes from.

Reported findings across those models cover wound healing in dermal injury, tissue repair in tendon and muscle, and angiogenesis in ischaemic tissue.

Cardiac work is the most substantial part. Thymosin beta-4 has been studied in myocardial infarction models, where reported effects include cardiac repair and improved cell survival after ischaemia, and it reached early-phase clinical trials on that basis.

Corneal and dermal wound trials also ran, which makes this compound unusual among research peptides in having reached human studies at all.

Those trials studied thymosin beta-4 itself, given by defined routes at defined doses. This product is a fragment sold under a market name, which is a distinction the next section takes up.

Reported reduced inflammation and tissue regeneration in the animal work are the origin of the recovery language attached to this compound.

What does not exist is any trial in tendon injuries, ligament injuries, joint pain, muscle recovery or post-surgical recovery in humans. Those are the uses the market sells and the ones with no evidence behind them.

Cell differentiation is reported as part of the mechanism in the cardiac work, where progenitor cells are described as migrating and differentiating after treatment.

Is TB-500 the Same as Thymosin Beta-4?

No, and this is the single most misunderstood point about the compound.

Thymosin beta-4 is a 43-residue protein found naturally in most cells. TB-500 as sold in this market is generally a shorter synthetic fragment built around the actin-binding motif rather than the full sequence.

A thymosin beta 4 fragment and the intact protein are not interchangeable, and a study of one does not establish anything about the other.

That matters because almost all the clinical work cited for TB-500 was done with the full protein. Anyone citing the cardiac trials in support of the fragment is citing a different molecule.

Confirming which one is actually in a given device is a certificate question. The mass difference is large and any competent analysis resolves it, so the answer is available to anyone who asks.

This page states the sequence and length in the specification table above so that the question does not have to be inferred.

What Is the Regulatory and Anti-Doping Position?

Two facts attach here and both are worth stating plainly.

The compound holds no approval anywhere. The FDA has placed it among substances presenting significant safety risks for compounding, so it does not appear on the 503A bulks list and compounding pharmacies in the United States cannot lawfully compound it for patients.

Anti-doping is the second. WADA prohibits it in and out of competition, and a tested athlete using it is committing an anti-doping rule violation whatever the route of administration.

The theoretical concern most often raised is cancer risk, on the reasoning that a compound promoting angiogenesis and cell migration is promoting them indiscriminately.

No study has examined that in humans over any meaningful period, which makes it an open question rather than either a known risk or a cleared one.

This device is supplied for laboratory research only. It is not injectable peptide therapy, not a treatment, and not for administration to humans or animals.

What Do the Circulating Dosing Protocols Actually Represent?

Dosing figures for this compound circulate widely, and their provenance is worth understanding before any of them is repeated.

The usual pattern quoted is a loading phase of several weekly administrations followed by a maintenance phase at lower frequency, expressed in milligrams per week.

Those TB-500 dosage figures do not come from a published human study. They come from vendor sheets and forum consensus, and they have propagated by repetition rather than by measurement.

No pharmacokinetic study of this fragment in humans has been published, so no dosing interval can be derived from a half-life that nobody has measured.

A loading and maintenance structure is borrowed from drugs where it has a pharmacokinetic rationale. Applying it here is analogy rather than reasoning.

Where dosing is discussed for research use, the only defensible basis is the concentration used in the specific published model being replicated, stated in molar terms and matched to the assay.

Subcutaneous injection and intramuscular administration are what the market uses. Neither is validated for this compound in humans and this product is not for injection into anyone.

Injection-site reactions are the local effect most often reported anecdotally, which is unsurprising for any unbuffered peptide solution given subcutaneously.

What Is the Wolverine Stack?

Search traffic for this compound is dominated by one phrase and it deserves a direct answer.

The wolverine stack is a market nickname for combining this compound with BPC-157, on the reasoning that two compounds with reported tissue repair activity should combine well. GHK-Cu and KPV sometimes join it.

No controlled study has tested that combination in anything. The wolverine stack is a marketing construct and the name comes from a comic-book character.

BPC-157 is the compound most often paired here. BPC-157 and this one share a market rather than a mechanism. One is a gastric protein fragment acting through VEGFR2 signalling; this one sequesters actin monomers.

Those are unrelated pathways, so a BPC-157 result transfers to this compound no better than a result for any other peptide would. A wolverine stack pairs them anyway, on the strength of the pairing rather than of either mechanism.

Compounding pharmacies once supplied both, which is where much of the peptide therapy framing around a wolverine stack originated, and that route is now closed in the United States for both compounds.

Therapeutic peptides as a category do contain approved drugs with real evidence. Neither compound in this pairing is among them.

The vocabulary around it is unusually loose. This compound is sold as a recovery peptide, a regenerative peptide and the wolverine peptide, and BPC-157 is sold on gut health alongside everything else, none of which corresponds to a defined claim.

Stack guides widen further still, folding in growth hormone secretagogues such as sermorelin and GLP-1 drugs such as semaglutide, which share no mechanism with either compound here.

What TB-500 peptide therapy means in practice is peptide injections assembled from vendor listings, and enhanced recovery is the promise attached rather than a measured outcome.

Reduced pro-inflammatory cytokines appear in the animal injury work and are the closest thing to a mechanistic basis for that promise.

Published Literature

Confirmed against publisher records or primary indexes before inclusion. The entries cover actin biology rather than this device format, which has no published data behind it.

1. Huff T, Müller CS, Otto AM, Netzker R, Hannappel E. International Journal of Biochemistry and Cell Biology. 2001;33(3):205-220.
2. Goldstein AL, Hannappel E, Sosne G, Kleinman HK. Expert Opinion on Biological Therapy. 2012;12(1):37-51.
3. Safer D, Elzinga M, Nachmias VT. Journal of Biological Chemistry. 1991;266(7):4029-4032.
4. Sosne G, Qiu P, Goldstein AL, Kurpakus-Wheater M. FASEB Journal. 2010;24(7):2144-2151.
5. Hannappel E. Annals of the New York Academy of Sciences. 2010;1194:27-35.

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