Thymosin beta-4 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-03-01 and is reviewed periodically as new material appears.
The fragment most often associated with the name carries the sequence Ac-LKKTETQ, matching residues 17 through 23 of thymosin beta-4. That region holds the actin-binding motif responsible for much of the parent protein's biochemical activity. Apart from N-terminal acetylation the peptide is unmodified and contains no disulfide bonds, so it shows little ordered secondary structure in solution. Full-length thymosin beta-4 is instead a 43-residue polypeptide of roughly 4.9 kDa found widely across mammalian cell types.
Material sold under this label typically arrives as a freeze-dried powder in a sealed vial with a certificate of analysis. Such certificates usually report reversed-phase chromatography purity plus a mass confirmation, and stated purities commonly sit between 95 and 99 percent. Counter-ion identity, residual trifluoroacetate, water content, and peptide net weight are separate specifications that a certificate may or may not include. A purity figure alone does not establish sequence identity, so independent mass verification remains the practical check.
TB-500 is a synthetic heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | ≈889 Da for the 7-residue fragment | Full-length thymosin beta-4 is ≈4.9 kDa; catalogs differ |
| Appearance | White to off-white powder | Hygroscopic; weight shifts with residual moisture |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers; poorly soluble in nonpolar solvents |
| Typical storage temperature | −20 °C, desiccated, protected from light | Once rehydrated, short-term holding at 2-8 °C |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity by UV absorbance; identity by ESI-MS or MALDI-TOF |
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
Laboratory work on thymosin beta-4 describes binding to monomeric actin and effects on cell migration, angiogenesis, and inflammatory signaling in cultured cells. Animal models have examined skin, corneal, and cardiac repair after injury, with outcomes reported mainly in preclinical literature. Most of that evidence concerns the parent protein rather than preparations labelled TB-500, so extrapolation from animal findings to a specific commercial product remains uncertain. Whether the two behave identically in living systems has not been established in controlled human studies.
No major regulatory agency has approved TB-500 for therapeutic use, and it holds no pharmacopoeial monograph. The name appears on the World Anti-Doping Agency prohibited list within the class covering peptide hormones, growth factors, and related substances. Detection in doping control relies on mass spectrometric methods applied to urine, often after preparation steps that concentrate the analyte. Discussion of TB-500 therefore clusters in biochemistry, sports medicine, and anti-doping literature rather than in registered clinical trials.
Research peptides are typically supplied as a white to off-white lyophilised powder in a sealed vial. The dry solid is more stable than a solution and is normally kept refrigerated or frozen until use. Dissolution is usually done in water, phosphate-buffered saline or a similar aqueous medium, depending on the assay. Because the material is hygroscopic and easily contaminated, opening vials in a low-humidity environment and recording the lot number before use are standard laboratory practices.
Once in solution, short peptides are generally less stable than the dry powder, and repeated freeze-thaw cycles are a common cause of loss. Laboratory guidance usually calls for aliquoting on first dissolution and storing aliquots at -20 °C or below, away from light. Adsorption to plastic and glass surfaces can lower measured concentration, particularly at low concentrations, so container material and buffer choice can affect results. Visible cloudiness, colour change or unexpected precipitate is a signal to re-check the material.
Dry powder is commonly held at minus twenty degrees Celsius, with some suppliers recommending lower temperatures for long-term archival storage. Once dissolved, solutions are typically kept cold and protected from light, since aqueous peptide solutions can lose integrity through hydrolysis or oxidation over time. Stability data specific to this fragment are limited in the public literature, and much of the guidance comes from general peptide handling practice rather than from controlled degradation studies. Users therefore treat stated shelf lives as approximate rather than fixed.
Identity and purity are normally assessed with reversed-phase high-performance liquid chromatography, paired with mass spectrometry to confirm molecular mass. A certificate of analysis reports a purity percentage, usually derived from chromatographic peak area, but that figure does not by itself prove a correct sequence or the absence of counterions. Independent verification may include amino acid analysis or peptide mapping. Batch-to-batch variation is a documented concern in the research chemical market, and the gap between a quoted purity value and actual peptide content can be substantial when the material is a salt or retains residual water.
=== 5 January === Ten people were killed in an SAF airstrike in Khartoum. The SAF and the JDF claimed to have deflected an RSF assault on El Fasher that came from the east and southeast of the city. The JDF also intercepted a weapons convoy for the RSF, arresting both Sudanese and Libyan nationals.
Themed core specialties (A&E, Intensive Therapy Unit [ITU] and anaesthetics) Surgical specialties Medical specialties Psychiatry Run-through specialties (e.g., general practice, clinical radiology, pathology, paediatrics) The first four categories all run on a similar structure: the Trainee first completes a two-year structured and broad-based core training programme in that field (e.g., core medical training), which makes them eligible for competitive entry into an associated specialty training scheme (e.g., gastroenterology if core medical training has been completed). The Core training years are referred to as CT1 and CT2, and the specialist years are ST3 onwards until completing training. Core training and the first year or two of speciality training are equivalent to the old Senior House Officer jobs. It is customary for trainees in these areas to sit their Membership examinations (e.g., Royal College of Physicians (MRCP), Royal College of Surgeons (MRCS)) in order to progress and compete for designated sub-specialty training programmes that attract a national training number as specialty training year 3 (ST3) and beyond – up to ST9 depending on the particular training specialty. In the fifth category, the trainee immediately starts specialty training (ST1 instead of CT1) progressing up to Consultant level without break or further competitive application process (run-through training).
Baran began his independent career at the Scripps Research Institute in the summer of 2003, and received tenure just three years later. In the 20 years since then, he has supervised over 300 graduate students, post-doctoral scholars, visiting scholars and interns. He is currently the Dr. Richard A. Lerner Endowed Chair at Scripps Research
Sources: en.wikipedia.org
==== On Unnatural Amino Acids ==== Pd-mediated Sonogashira, Heck, and Suzuki-Miyaura cross-coupling reactions have been applied widely to modify peptides and proteins, where diverse Pd reagents have been developed for the application in aqueous solutions. Those reactions require the protein or peptide substrate bearing unnatural functional groups such as alkyne, aryl halides, and aryl boronic acids, which can be achieved through genetic code expansion or post-translational modifications.
=== Derivation === This section presents a derivation of the equation above for electrons. A similar derivation can be found for the equation for holes. Consider the fact that the number of electrons is conserved across a volume of semiconductor material with cross-sectional area, A, and length, dx, along the x-axis. More precisely, one can say:
=== Follicular phase === GnSAF prevents a pre-ovulatory surge in LH during this time, allowing sufficient time for the dominant follicle to mature before ovulation. At the start of the follicular phase, high serum FSH concentrations stimulate the development and proliferation of the granulosa cells of the small antral follicles, resulting in a steady increase in GnSAF biosynthesis. The relatively high GnSAF bioactivity dampens the response of the pituitary gland to GnRH by antagonising the sensitising effects of estradiol on the pituitary gland. The GnRH pulse, in the presence of GnSAF, is not frequent or potent enough to stimulate LH secretion from the anterior pituitary above basal levels.
Sources: en.wikipedia.org
Usually not, though usage overlaps. The label most often refers to a short acetylated fragment of the parent protein, while thymosin beta-4 itself is the full 43-residue molecule. Because suppliers vary, a sequence statement is needed to settle the question for any particular lot.
The name is a commercial label rather than a systematic chemical designation, so different vendors and papers attach it to different sequences. Some treat it as a fragment and others as the whole protein. Comparing two reports therefore requires checking what each one actually analyzed.
Typically it reflects the relative area of the main peak in a reversed-phase chromatogram at a given wavelength. It does not confirm the amino acid sequence, the counter-ion, or the amount of peptide by mass. Identity is normally established by a separate mass measurement.
TB-500 is a synthetic heptapeptide corresponding to a fragment of thymosin beta-4. It is used in laboratory research and is not an approved drug.