The questions below are the ones researchers ask most about storing, mixing and handling TB-500. Each answer reflects the peptide’s sequence, Ac-Leu-Lys-Lys-Thr-Glu-Thr-Gln, the acetylated 17 to 23 fragment of thymosin beta-4, and links to the fuller page where there is one.
How long does TB-500 last in the fridge after mixing?
Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, TB-500 lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. No published stability study covers TB-500 in solution over weeks, so the window is general guidance that its chemistry supports. The full table is on how long TB-500 lasts.
How long does unmixed TB-500 powder last?
A sealed lyophilised vial keeps for the weeks it is in use at 2 to 8 °C and for months at minus 20 °C. The dry cake has almost no water, so the chemistry and enzyme activity that affect TB-500 in solution have little to work with. Days at room temperature in transit do not harm it, so it ships without an ice pack.
Is TB-500 the same as thymosin beta-4?
No. Thymosin beta-4 is a 43-residue protein. TB-500 is Ac-LKKTETQ, the acetylated 17 to 23 fragment of it, identified in TB-500 products by mass spectrometry (Esposito et al., Drug Testing and Analysis, 2012). The full protein has a methionine at position 6 that oxidises; the fragment does not. More in TB-500 vs thymosin beta-4.
Why is TB-500 so stable?
Its seven residues include no methionine, cysteine, tryptophan, histidine, tyrosine, asparagine or aspartic acid, so the main oxidation, deamidation and isomerisation routes are absent (Manning et al., Pharmaceutical Research, 2010). Its N-terminus is acetylated, which rules out pyroglutamate formation, and it is too short and polar to aggregate readily.
What does TB-500 break down into?
The mapped route is enzymatic. In serum and enzyme systems it is cut next to its lysines into shorter acetylated pieces, mainly Ac-LK, with Ac-LKK lasting longest (Rahaman et al., Journal of Chromatography B, 2024). These fragments are colourless and soluble, which is why a clear vial is not on its own proof of full strength. Sterile access keeps those enzymes out of a mixed vial.
What do you mix TB-500 with?
Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol so a refrigerated vial can be accessed more than once. TB-500 is short, polar and free of aromatic residues, so it dissolves fully without acid or other solvents. The reasons are on the TB-500 solubility guide.
How much bacteriostatic water goes in a 10 mg TB-500 vial?
There is no single correct volume. With 2 mL a 10 mg vial gives 5 mg/mL; with 1 mL it gives 10 mg/mL. More water spreads the same amount of peptide through a larger volume, so write the chosen concentration on the vial. The tables and calculator are on the TB-500 reconstitution page.
Why is my TB-500 cloudy after mixing?
Brief cloudiness that clears within 10 to 15 minutes is usually trapped air from adding water too fast or shaking. Haze that persists, strands, particles or a tint that appears later point to warm storage, freezing or contamination, and the solution is discarded. More in why peptides gel or go cloudy.
Can you freeze mixed TB-500?
Not a vial that will be opened again, because repeated freezing and thawing promotes aggregation in peptide solutions. Laboratories that need frozen solution divide it into single-use aliquots and thaw each one once. Sealed powder can be frozen at minus 20 °C without concern.
Does TB-500 need to be kept out of the light?
It is less light-sensitive than most peptides because it has no tryptophan, tyrosine or phenylalanine, the residues that absorb ultraviolet light and start photo-oxidation. Keeping the vial boxed in the dark is still standard practice. It also keeps the vial away from warmth, which matters more for this peptide.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
