Is TB-500 hard to dissolve?

No. It is small, highly charged and strongly hydrophilic. Adsorption to container surfaces is the more likely practical problem.

Does it need a reducing agent?

No. There is no cysteine in the sequence.

How is concentration measured without aromatic residues?

Not by 280 nm absorbance. Gravimetric preparation from a certified peptide content, or another analytical method, is required.

TB-500 Molecular Structure and Properties

The short answer

TB-500 is C38H68N10O14 at 889.0 Da: seven residues, net positively charged, highly water-soluble and conformationally flexible. It carries none of the residues that usually dictate peptide handling (no cysteine, no methionine, no aromatic).

Key facts

Formula: C38H68N10O14
Molecular weight: 889.0 Da
PubChem CID: 62707662
Net charge: Positive at physiological pH
Basic residues: Two lysines
Acidic residues: One glutamate
Solubility: Readily water-soluble

Charge and solubility

Two lysines against one glutamate gives a net positive charge at physiological pH. Combined with two threonine hydroxyls and a glutamine amide, and with no hydrophobic core to bury, the peptide is strongly hydrophilic and dissolves readily in aqueous buffer. Solubility is rarely the limiting factor with this compound.

Adsorption is the practical issue instead

Small, highly charged peptides adsorb to glass and plastic surfaces, and at low concentrations the fraction lost to the container can be significant. This is the physical loss mechanism most likely to matter here, rather than degradation, which the composition largely rules out. Low-binding tubes and avoiding unnecessary transfers address it.

Research material referenced

TB-500 5mg, third-party HPLC tested

Buy TB-500 · £23.99

Flexibility

Seven residues with no proline and no disulfide constraint is about as unstructured as a peptide gets. It samples many conformations in solution, which has two consequences: no defined structure to solve, and an entropic penalty on binding that a constrained peptide would not pay.

The absent residues

No cysteine means no disulfide bonds and no reducing agent required. No methionine means no thioether oxidation and no +16 Da satellite on a mass spectrum. No asparagine means no deamidation at the usual hotspot. Between them these account for most peptide degradation in practice, and TB-500 is subject to none of them.

No spectroscopic handle

The absence of tryptophan, tyrosine and phenylalanine means almost no absorbance near 280 nm. The standard spectrophotometric method for peptide quantification does not work, and concentration must be established gravimetrically or by another analytical route. This is a real inconvenience rather than a trivial one.

How it compares within the library

TB-500 shares its no-cysteine, no-methionine, no-aromatic profile with Selank, and for the same practical reasons: chemically robust, physically prone to adsorption, and awkward to quantify. Semax and MOTS-c sit at the other end, carrying methionines that dominate their handling.

Quick reference

Property	Value
Sequence	Ac-LKKTETQ
Molecular weight	889.0 Da
Formula	C38H68N10O14
PubChem CID	62707662
Cysteine	None
Methionine	None
Aromatic residues	None

Frequently asked questions

Is TB-500 hard to dissolve?: No. It is small, highly charged and strongly hydrophilic. Adsorption to container surfaces is the more likely practical problem.
Does it need a reducing agent?: No. There is no cysteine in the sequence.
How is concentration measured without aromatic residues?: Not by 280 nm absorbance. Gravimetric preparation from a certified peptide content, or another analytical method, is required.

Extended research context

The TB-500 (Thymosin β4 fragment) deep dive

Deep dive: TB-500 vs full-length Thymosin Beta-4

'TB-500' is a synthetic peptide corresponding to the active 17-amino-acid actin-binding region of the endogenous 43-residue Thymosin Beta-4 protein. The two are not identical. TB-500 lacks the flanking sequence that gives full-length TB-4 additional binding partners. In the research literature, papers use 'Thymosin β4' when they mean the full protein and 'TB-500' or 'AcSDKP fragment' when they mean the shorter synthetic peptide. Reading a CoA carefully to see which molecule is in the vial matters. Mass spec is the definitive check.

Actin-binding as the core mechanism

The N-terminal region of TB-4 (and TB-500 by inheritance) contains the canonical actin-binding motif. This motif sequesters G-actin monomers, modulating the G:F actin equilibrium in cell cultures. That mechanism is why almost every mechanistic paper on TB-500 traces back to cytoskeletal reorganisation, cell migration, and models of tissue repair.

Handling considerations unique to TB-500

TB-500 is a 17-residue peptide with modest amphipathicity; it reconstitutes cleanly in bacteriostatic water but is sensitive to repeated freeze/thaw. Aliquoting into single-use volumes on first reconstitution preserves potency across a batch. HPLC on the batch CoA should show a single dominant peak; a doublet suggests deamidation.

Research applications

▸In vitro actin-polymerisation assays (G:F actin ratio measurement)
▸Cell-migration and wound-scratch assays in fibroblast lines
▸Angiogenesis models: tube-formation and endothelial migration assays
▸Analytical method development for short peptides on RP-HPLC
▸Reference-material comparisons against endogenous Thymosin β4

Handling checklist

✓Store lyophilised vials at −20 °C long-term
✓Reconstitute with bacteriostatic water (0.9% benzyl alcohol)
✓Aliquot immediately to avoid freeze/thaw cycles
✓Refrigerate reconstituted aliquots at 2–8 °C; use within 28 days
✓Confirm mass (~4,963 Da for TB-500) via CoA before study use

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Assuming TB-500 = full Thymosin β4

Fix: TB-500 is the 17-residue actin-binding fragment; check the CoA sequence.

✗ Repeated freeze/thaw

Fix: Aliquot at first reconstitution; each cycle degrades yield.

✗ Using tap water

Fix: Use bacteriostatic or sterile water only.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

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Written and reviewed by

The UK Peptides Editorial Team · Research library, UK Peptides

The editorial team is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate. Corrections are made in place and the review date updated.

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TB-500 Molecular Structure and Physical Properties