If you have been reading about actin binding and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-03-31. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Lyophilized peptide arrives as a dry cake that should stay sealed until use. Reconstitution is generally performed with sterile water or a buffered solution, and the resulting liquid should be handled gently to limit mechanical stress. Repeated freeze-thaw cycles are widely described as harmful to short peptides, so dividing a reconstituted batch into single-use portions is a common practice. Laboratories also record the solvent, concentration, and date of preparation on the vial label to keep later measurements traceable.
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.
| 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 |
Proposed activity centers on actin sequestration and on the movement of cells during repair processes. In cell culture and animal models, the fragment has been associated with migration, tube formation, and tissue remodeling. These observations are frequently described as preliminary, because most published work uses rodent or in vitro systems rather than controlled human trials. Whether the short fragment reproduces the effects of the full protein remains an open question, and the relationship between dose, route, and measured outcome is not well characterized.
The compound circulates in the literature as a research reagent rather than an approved therapeutic. Regulatory agencies in several countries have not authorized it for medical use, and sporting bodies list related thymosin beta-4 peptides among prohibited substances. Suppliers typically market it with a purity figure and a certificate of analysis, while peer-reviewed clinical reports remain sparse. Discussions therefore often separate laboratory findings from anecdotal reports, and reviewers tend to note the small size and methodological limits of the available studies.
TB-500 refers to a synthetic peptide fragment derived from the actin-binding region of thymosin beta-4, a protein present in most mammalian cells. The full protein contains forty-three amino acids, while the commonly sold fragment is a much shorter acetylated sequence, often cited as LKKTETQ. The fragment retains part of the actin-binding motif but lacks the remainder of the parent protein. Material sold under this name is usually lyophilized powder intended for laboratory research, and it is not a finished pharmaceutical product.
Lyophilised peptide is normally reconstituted with sterile water or a neutral buffer shortly before use. Because repeated freeze-thaw cycles can degrade the material, dividing a reconstituted solution into single-use aliquots is a common practice. Working solutions are usually kept cold and protected from light. The exact shelf life depends on concentration, buffer composition, and handling, so it is often determined empirically rather than assumed.
Peptide bonds are susceptible to hydrolysis under extreme pH and to enzymatic cleavage if proteases are present. Heat, oxidising agents, and prolonged exposure to light also contribute to loss of material. Aggregation can occur at high concentrations or in certain buffer systems, and it may not be visible to the eye. Storage at -20 C or below is typical for both powder and aliquoted solutions, and desiccation of the powder is preferred.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography together with mass spectrometry. The chromatogram provides a purity estimate as a percentage of total peak area, while the mass spectrum confirms that the observed mass matches the expected value. Amino acid analysis or tandem mass spectrometry sequencing can provide additional confirmation. Reported purity figures depend on the column, gradient, and detection wavelength, so values from different laboratories are not directly comparable without method details.
TB-500 is a synthetic seven-amino-acid peptide with the sequence LKKTETQ, corresponding to residues 17 through 23 of the protein thymosin beta-4. The N-terminus is typically acetylated in the described form, giving a monoisotopic mass near 888.5 Da and an average mass of about 889 Da. The designation TB-500 is a catalogue label rather than a formal chemical name, and the same sequence appears in the literature under several alternative abbreviations. It is handled as a research reagent rather than a pharmaceutical product.
Thymosin beta-4 is a 43-residue actin-binding protein found in most mammalian cell types, where it participates in cytoskeletal regulation and cell migration. TB-500 represents only a short fragment of that protein and does not include the remaining residues. Whether the isolated fragment reproduces the full range of activities reported for the intact protein remains an open question. Researchers commonly treat the two as related but distinct entities when comparing results.
Published work involving this sequence spans actin-binding assays, cell-migration studies, wound-healing models, and cardiovascular or musculoskeletal experiments. Much of the biological rationale derives from in vitro systems and animal models, and the number of controlled human studies is small. Reported outcomes vary across preparations, doses, and routes, which complicates comparison between studies. Reviews generally describe the evidence base as preliminary rather than settled. Mechanistic explanations are often proposed by analogy to the parent protein rather than demonstrated directly.
=== Metabolism === The alkaloids are organic nitrogenous compounds, derivatives of secondary metabolism, synthesised through the metabolic pathway of benzylisoquinoline. First, the amino acid phenylalanine, through the enzyme phenylalanine hydroxylase, is transformed into tyrosine. Tyrosine can follow two different routes: by tyrosine hydroxylase it can form L-dopamine (L-DOPA), or it can be reduced to form 4-phenylhydroxyacetaldehyde (4-HPAA). Subsequently, L-DOPA reacts with 4-HPAA and, through a series of reactions, forms (S) -norcoclaurine, which carries the benzylisoquinoline skeleton that gives its name to this pathway. The conversion of (S) -norcoclaurin to (S) -reticuline is one of the key points, since from (S) -reticuline morphine can be formed through the morphinan route, noscapine through the path of the noscapina or berberina.
The biosynthetic machinery of an NRPS system is composed of multimodular enzymatic assembly lines that contain one module for each amino acid monomer incorporated. Within each module are catalytic domains that carry out the elongation of the growing peptidyl chain. The growing peptide is covalently tethered to a thiolation domain; here it is termed the peptidyl carrier protein, as it carries the growing peptide from one catalytic domain to the next. Again, the apo-T domain must be primed to the holo-T domain by a PPTase, attaching a flexible phosphopantetheine arm to a conserved serine residue. An adenylation domain selects the amino acid monomer to be incorporated and activates the carboxylate with ATP to make the aminoacyl-AMP. Next, the A domain installs an aminoacyl group on the thiolate of the adjacent T domain. The condensation (C) domain catalyzes the peptide bond forming reaction, which elicits chain elongation. It joins an upstream peptidyl-S-T to the downstream aminoacyl-S-T (Figure 7). Chain elongation by one aminoacyl residue and chain translocation to the next T domain occurs in concert. The order of these domains is C-A-T. In some instances, an epimerization domain is necessary in those modules where L-amino acid monomers are to be incorporated and epimerized to D-amino acids. The domain organization in such modules is C-A-T-E. The first module has a three-domain C-A-T organization; these often occur in assembly lines that make N-acylated peptides. The first C domain catalyzes N-acylation of the initiating amino acid (tryptophan) while it is installed on T.
== Pharmacology == Several classes of drugs target the serotonin system, including some antidepressants, anxiolytics, antipsychotics, analgesics, antimigraine drugs, oxytocics, antiemetics, appetite suppressants, and anticonvulsants, as well as psychedelics and entactogens.
Sources: en.wikipedia.org
== Health effects == Due to the elevated levels of nitrites, consuming salted fish increases risk of stomach cancer and nasopharyngeal cancer. The International Agency for Research on Cancer classify salted fish (Chinese-style) as a Group 1 carcinogen.
== June 8, 1915 (Tuesday) == Battle of Hébuterne — The Germans regrouped to slow the French advance and recaptured their second line by the end of the day. Born: Kayyar Kinhanna Rai, Indian poet, known for his poems and activism work for an independent India; in Kayyar, British India (present-day India) (d. 2015) Ruth Stone, American poet, recipient of 2002 National Book Award and 2002 Wallace Stevens Award for the poetry collection In the Galaxy; in Roanoke, Virginia, United States (d. 2011)
TATA box Also Goldberg-Hogness box. A highly conserved non-coding DNA sequence containing a consensus of repeating T and A base pairs that is commonly found in promoter regions of genes in archaea and eukaryotes. The TATA box often serves as the site of initiation of transcription or as a binding site for transcription factors.
CBC Digital Archives. "Chasing a Cure for Diabetes". Accessed 16 June 2008. Dr. Charles Best Secondary School. Accessed 16 June 2008. Ontario Plaques, "The Discovery of Insulin". Accessed 16 June 2008. Order of Canada citation (archived) University of Toronto. Banting and Best Department of Medical Research "Charles Herbert Best". Accessed 16 June 2008. "Rewriting Medical History: Charles Best and the Banting and Best Myth by Michael BLiss". Accessed 23 July 2011. Charles Best Papers (Archived 2016-03-03 at the Wayback Machine), Thomas Fisher Rare Book Library. Charles H. Best Foundation archival papers held at the University of Toronto Archives and Records Management Services
Sources: en.wikipedia.org
== Prognosis == Long-term outcomes for people with sCSFLS remain poorly studied. Symptoms may resolve in as little as two weeks as the dura mater lining heals naturally, or they can persist for months. Less commonly, patients may have unremitting symptoms for many years. People with chronic sCSFLS may be disabled and unable to work. Recurrent CSF leak at an alternate site after recent repair is common.
Creatine kinase S-type, mitochondrial is an enzyme that in humans is encoded by the CKMT2 gene. Mitochondrial creatine kinase (MtCK) is responsible for the transfer of high energy phosphate from mitochondria to the cytosolic carrier, creatine. The "energy-rich" gamma-phosphate group of ATP that is generated by oxidative phosphorylation inside mitochondria is trans-phosphorylated to creatine (Cr) to give phospho-creatine (PCr), which then is exported from the mitochondria into the cytosol, where it is made available to cytosolic creatine kinases (CK) for in situ regeneration of the ATP that has been used for cellular work. Cr then is returning to the mitochondria where it stimulates mitochondrial respiration and again is charged-up by mitochondrial ATP via MtCK. This process is termed the PCr/Cr-shuttle or circuit. MtCK belongs to the creatine kinase (CK) isoenzyme family. It exists as two isoenzymes, sarcomeric MtCK and ubiquitous MtCK, encoded by separate genes. Mitochondrial creatine kinase occurs in two different oligomeric forms: dimers and octamers, in contrast to the exclusively dimeric cytosolic creatine kinase isoenzymes. Sarcomeric mitochondrial creatine kinase has 80% homology with the coding exons of ubiquitous mitochondrial creatine kinase. This gene contains sequences homologous to several motifs that are shared among some nuclear genes encoding mitochondrial proteins and thus may be essential for the coordinated activation of these genes during mitochondrial biogenesis.
=== May 2009 === On 18 May 2009, the SENSEX surged up 2,110.79 points to close at 14,285.21, from its previous closing of 12,174.42, for its largest single day rally. Less than a month later, on 4 June 2009, the SENSEX would cross the 15,000 mark. However, the SENSEX remained volatile during the summer of 2009. The SENSEX plunged by 869.65 points on 6 July 2009, the day of Union Budget presentation in Parliament on concerns over high fiscal deficit. This was the biggest Budget-day loss for the index. On 17 August 2009, the SENSEX lost 626.71 points. Once again, the SENSEX would recover from the volatility. On 7 September 2009, the SENSEX crossed the 16,000 mark, closing at 16,016.32 points. The index would gain 3,000 points over the next 12 months, as the SENSEX crossed the 19,000 mark on 13 September 2010, closing at 19,208.33 points.
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.
Dry lyophilized powder is usually kept frozen, desiccated, and out of direct light. Sealed vials are not opened until needed, because moisture uptake can degrade short peptides. Longer archival storage is often done at lower temperatures than routine working stock.