The short version of actin binding fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-03-25 and is reviewed periodically as new material appears.
Once dissolved, the peptide is far less stable than the dry powder. Aqueous solutions are subject to hydrolysis, oxidation at susceptible residues and gradual loss of material through adsorption onto glass and plastic surfaces. Terminal glutamine can cyclise under some conditions, producing a related species that complicates purity assessment. Dilute solutions tend to lose a larger fraction of material to surfaces than concentrated ones. Buffers, pH and ionic strength all influence the rate of change, so stability figures are only meaningful when those parameters are stated alongside the storage interval.
Detection in biological samples relies on mass spectrometry, typically liquid chromatography coupled to tandem mass spectrometry after peptide extraction and enrichment. Intact peptides can also be confirmed by high-resolution mass measurement together with fragmentation data. Detection windows in urine are short because the peptide is degraded by proteases and cleared quickly, and concentrations are low. Many jurisdictions treat the compound as a prohibited substance in sport, grouped with peptide hormones and related factors, while it is not an approved therapeutic product. Identity and purity statements therefore rest on certificates of analysis, ideally issued by an independent laboratory.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or powder |
| Solubility class | Freely soluble in water | Aqueous buffers also used |
| Typical storage temperature | About -20 degrees Celsius | Dry, sealed and protected from light |
| Typical analytical method | Reversed-phase HPLC or LC-MS/MS | Used for purity, identity and quantification |
| Common synonyms | Thymosin beta-4 fragment | Also listed under fragment-based descriptions |
Interest in the peptide grew during the 2000s and 2010s, when studies of tendon and ligament injuries in horses reported changes in lesion size after treatment. Those reports circulated widely outside the scientific literature and shaped much of the current online discussion. Subsequent reviews noted inconsistent study design, small groups, and a shortage of independent replication. Popular descriptions often blur the line between the fragment, the complete protein, and unrelated growth factors, which complicates comparisons across sources.
TB-500 is a synthetic peptide whose sequence corresponds to a short fragment near the N-terminus of thymosin beta-4, a small protein present in most mammalian cells. The fragment is commonly cited as containing the actin-binding region of the parent molecule, which is why it appears in laboratory work on cell migration and tissue repair. Suppliers distribute it as a lyophilised powder intended for research use. Its identity is defined by amino acid sequence and by the presence of an acetyl group on the N-terminal residue.
Animal work has examined the peptide in models of cardiac injury, skin wounding, and corneal repair, with reported outcomes covering cell migration, inflammatory cell influx, and tissue remodeling. Several of those experiments used the full-length protein or longer fragments instead of the seven-residue sequence, which makes direct comparison between reports difficult. Results are generally described as tissue-dependent, and effect sizes vary considerably across laboratories. Independent replication is uneven, so the overall picture is incomplete rather than settled.
Controlled human trials of the short fragment are scarce. Much of what appears in review articles is extrapolated from animal models or from studies of the parent protein, and literature searches return a larger body of cardiac and ophthalmic work on thymosin beta-4 than on the abbreviated peptide. Regulatory treatment differs by jurisdiction, and in several countries the material is handled as a research chemical rather than an approved therapeutic. Statements about human benefit should be read as provisional.
Biological interest in this peptide centers on its relationship to actin dynamics. Thymosin beta-4 binds monomeric actin through an LKKTET motif, and a short sequence carrying that motif can compete with other actin-binding proteins in cell-free preparations. Investigators propose that such competition shifts the balance between filament assembly and disassembly, which in turn affects how readily a cell extends protrusions and migrates. Most of the supporting observations come from cultured cells and purified protein systems rather than from intact organisms.
=== Chromatography === Stein and Moore developed a method to quantify and separate amino acids with column chromatography, using potato starch as the stationary phase. The fractions, originally collected manually, were collected in their newly developed automated fraction collector, and the amount of each amino acid was determined by an adjusted color reaction with ninhydrin. They began testing other methods of separation, such as ion exchange chromatography, to reduce the analysis time, as it took two weeks to analyze one protein using the starch columns. Ion exchange chromatography reduced the time to 5 days during initial experiments, and eventually Stein and Moore whittled the process down even further with the help of Daryl Spackman, which resulted in the first automatic amino acid analyzer. Along with their well-known work in protein sequences, this automatic amino acid analyzer was also utilized in Stein's study of amino acids in human urine and blood plasma.
==== GBA gene ==== The GBA gene is associated with lysosome storage and autophagy. GBA encodes the enzyme glucocerebrosidase (GCase), necessary for breaking down glucosylceramide (GlcCer). Mutations in GBA can cause modifications in GCase protein structure, decreases in GCase activity and protein levels, and the accumulation of GlcCer in the cell. Approximately 5–15% of PD patients have mutations in the GBA gene. Mendelian genetics are not strictly observed in GBA mutations in PD. Both gain-of-function and loss-of-function GBA mutations are associated with increased risk of PD. GBA is one of a number of pleiotropic genes which have multiple effects in the body, that have been linked to PD risk. Mutations in GBA1 can cause either complete loss‐of‐function and the lysosomal disorder Gaucher's disease, or partial loss‐of‐function with an increased risk for PD. Mutations in EPG5 are implicated in a range of dysfunctions, from severe (Vici syndrome), to moderate (atypical parkinsonism) and mild (typical PD). Microdeletions at 22q11.2 have been variously linked to PD, schizophrenia, and DiGeorge syndrome.
Paraherbalism is the pseudoscientific use of extracts of plant or animal origin as supposed medicines or health-promoting agents. Phytotherapy differs from plant-derived medicines in standard pharmacology because it does not isolate and standardize the compounds from a given plant believed to be biologically active. It relies on the false belief that preserving the complexity of substances from a given plant with less processing is safer and potentially more effective, for which there is no evidence either condition applies. Phytochemical researcher Varro Eugene Tyler described paraherbalism as "faulty or inferior herbalism based on pseudoscience", using scientific terminology but lacking scientific evidence for safety and efficacy. Tyler listed ten fallacies that distinguished herbalism from paraherbalism, including claims that there is a conspiracy to suppress safe and effective herbs, herbs cannot cause harm, whole herbs are more effective than molecules isolated from the plants, herbs are superior to drugs, the doctrine of signatures (the belief that the shape of the plant indicates its function) is valid, dilution of substances increases their potency (a doctrine of the pseudoscience of homeopathy), astrological alignments are significant, animal testing is not appropriate to indicate human effects, anecdotal evidence is an effective means of proving a substance works and herbs were created by God to cure disease. Tyler suggests that none of these beliefs have any basis in fact.
=== DNA repair and replication === In chloroplasts of the moss Physcomitrella patens, the DNA mismatch repair protein Msh1 interacts with the recombinational repair proteins RecA and RecG to maintain chloroplast genome stability. In chloroplasts of the plant Arabidopsis thaliana the RecA protein maintains the integrity of the chloroplast's DNA by a process that likely involves the recombinational repair of DNA damage.
Cream can be skimmed from whey. Whey cream is saltier, tangier, and "cheesier" than ("sweet") cream skimmed from milk, and can be used to make whey butter. Due to the low fat content of whey, the yield is low, with typically two to five parts of butter manufactured from the whey of 1,000 parts milk. Whey cream and butter are suitable for making butter-flavoured food, as they have a stronger flavour of their own. They are also cheaper to manufacture than sweet cream and butter.
Sources: en.wikipedia.org
In the field of engineering, the hydrophobicity (or dewetting ability) of a flat surface (e.g., a counter top in kitchen or a cooking pan) can be measured by the contact angle of water droplet. A University of Nebraska–Lincoln team devised a computational approach that can relate the molecular hydrophobicity scale of amino-acid chains to the contact angle of water nanodroplet. The team constructed planar networks composed of unified amino-acid side chains with native structure of the beta-sheet protein. Using molecular dynamics simulation, the team is able to measure the contact angle of water nanodroplet on the planar networks (caHydrophobicity). On the other hand, previous studies show that the minimum of excess chemical potential of a hard-sphere solute with respect to that in the bulk exhibits a linear dependence on cosine value of contact angle. Based on the computed excess chemical potentials of the purely repulsive methane-sized Weeks–Chandler–Andersen solute with respect to that in the bulk, the extrapolated values of cosine value of contact angle are calculated(ccHydrophobicity), which can be used to quantify the hydrophobicity of amino acid side chains with complete wetting behaviors.
=== N-degrons === Proteolytic cleavage can lead to exposure of residues at the N-terminus of a protein. According to the N-end rule, different N-terminal amino acids (or N-degrons) are recognized to a different extent by their appropriate ubiquitin ligase (N-recognin), influencing the half-life of the protein. For instance, positively charged (Arg, Lys, His) and bulky hydrophobic amino acids (Phe, Trp, Tyr, Leu, Ile) are recognized preferentially and thus considered destabilizing degrons since they allow faster degradation of their proteins.
{\displaystyle \left(\mathbf {w} _{i},{\frac {\partial \mathbf {u} _{j}}{\partial t}}\right)=-{\bigl (}\mathbf {w} _{i},\left(\mathbf {u} \cdot \nabla \right)\mathbf {u} _{j}{\bigr )}-\nu \left(\nabla \mathbf {w} _{i}:\nabla \mathbf {u} _{j}\right)+\left(\mathbf {w} _{i},\mathbf {f} ^{S}\right).}
=== Electronics === Thermal evaporation has been investigated for the production of organic light-emitting diodes (OLEDs) and organic photovoltaic cells. In organic photovoltaic cells, the purity of the organic semiconductor layers influences the device's energy conversion efficiency and stability.
=== Fatty acids and insulin secretion === Fatty acids also affect insulin secretion. In type 2 diabetes, fatty acids are able to potentiate insulin release to compensate the increment need of insulin. It was found that the β-cells express free fatty acid receptors at their surface, through which fatty acids can impact the function of β-cells. Long-chain acyl-CoA and DAG are the metabolites resulting from the intracellular metabolism of fatty acids. Long-chain acyl-CoA has the ability to acylate proteins that are essential in the insulin granule fusion. On the other hand, DAG activates PKC that is involved in the insulin secretion.
Sources: en.wikipedia.org
A total synthesis of progesterone was reported in 1971 by William S. Johnson. The synthesis begins with reacting the phosphonium salt 7 with phenyl lithium to produce the phosphonium ylide 8. The ylide 8 is reacted with an aldehyde to produce the alkene 9. The ketal protecting groups of 9 are hydrolyzed to produce the diketone 10, which in turn is cyclized to form the cyclopentenone 11. The ketone of 11 is reacted with methyl lithium to yield the tertiary alcohol 12, which in turn is treated with acid to produce the tertiary cation 13. The key step of the synthesis is the π-cation cyclization of 13 in which the B-, C-, and D-rings of the steroid are simultaneously formed to produce 14. This step resembles the cationic cyclization reaction used in the biosynthesis of steroids and hence is referred to as biomimetic. In the next step the enol orthoester is hydrolyzed to produce the ketone 15. The cyclopentene A-ring is then opened by oxidizing with ozone to produce 16. Finally, the diketone 17 undergoes an intramolecular aldol condensation by treating with aqueous potassium hydroxide to produce progesterone.
UK-414,495 is a drug developed by Pfizer for the treatment of female sexual arousal disorder. UK-414,495 acts as a potent, selective inhibitor of the enzyme neutral endopeptidase, which normally serves to break down the neuropeptide VIP. The consequent increase in VIP activity alters blood flow to the genital region leading to increased lubrication and muscle relaxation.
Johnson meets with Soviet Premier Alexei Kosygin in Glassboro, New Jersey for a three-day summit. July 1: Beginning of the War of Attrition. July 6: The Nigerian Civil War begins in response to Biafra's declaration of independence. August 8: Bangkok Declaration is established to quell the communist threat in Southeast Asia. This creates ASEAN. October 8: Che Guevara is captured in Bolivia by U.S. trained Bolivian rangers. October 9: Che Guevara is executed after being captured the day before. November 29: Robert McNamara announces that he will resign as U.S. Secretary of Defense to become President of the World Bank.
Aragonite occurs in majority when the reaction conditions inhibit the formation of calcite and/or promote the nucleation of aragonite. For example, the formation of aragonite is promoted by the presence of magnesium ions, or by using proteins and peptides derived from biological calcium carbonate. Some polyamines such as cadaverine and Poly(ethylene imine) have been shown to facilitate the formation of aragonite over calcite. Solid‑state NMR analysis has revealed that poly‑aspartate-stabilized ACC contains water molecules that undergo millisecond-timescale flips, illustrating dynamic hydration as a key factor in delaying crystallization.
Sources: en.wikipedia.org
Sealed, dry and protected from light at reduced temperature is the usual laboratory convention. Allowing a cold vial to reach room temperature before opening limits condensation. Repeated opening exposes the powder to moisture and should be minimised.
Reported purity reflects the batch tested, the chromatographic method used and whether an independent laboratory performed the work. Values quoted without method detail or a traceable certificate are difficult to compare directly.
Short peptides are rapidly broken down by proteases and appear at low concentrations in urine, so the detection window is narrow. Sensitive extraction combined with tandem mass spectrometry is typically required.
Not necessarily. TB-500 is a commercial label that suppliers apply to synthetic peptides described as thymosin beta-4 or a fragment of it. Published research most often studies the full-length protein, so statements about one do not automatically transfer to the other.