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.
Updated 2025-11-03. Numbers and descriptions here follow the published literature rather than marketing material.
The compound is most often distributed as a lyophilized powder, appearing white to off-white and forming a loose cake or fluffy solid. It is hygroscopic to some degree, so brief exposure to humid air can add water weight and complicate weighing. The peptide dissolves readily in water and in neutral aqueous buffers, and aqueous solubility is generally described as high, well above the concentrations used in typical assays. Some polar organic solvents are also usable, which matters when a concentrated stock is prepared before dilution into buffer.
Storage recommendations center on keeping the dry powder cold, dry, and dark. A freezer at -20 degrees Celsius or below is conventional, and desiccant is often included to limit moisture uptake. Once dissolved, the peptide is less stable, and solutions are typically kept frozen and thawed only once. Repeated freeze-thaw cycles are a common source of losses because they promote aggregation and adsorption to container surfaces. Working aliquots are therefore prepared in advance, and glass or low-binding plastic is usually preferred over ordinary laboratory plastic.
Identity and purity are assessed with a small set of standard techniques. Reverse-phase high-performance liquid chromatography gives a purity estimate from peak area, usually recorded at 214 or 220 nanometers, where the peptide bond absorbs. Mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidized species. Amino acid analysis or tandem mass spectrometry sequencing can verify the sequence itself. Additional quality attributes include water content, residual trifluoroacetic acid carried over from purification, and endotoxin where the material is intended for biological work.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized cake or fluffy solid |
| Water solubility | High | Dissolves in water and neutral buffers |
| Dry storage | -20 °C or below | Dry, dark, desiccated |
| Reconstituted storage | Frozen, single thaw | Repeated freeze-thaw promotes loss |
| Purity method | Reverse-phase HPLC | Peak area read at 214 or 220 nm |
Lyophilised material is stable for extended periods when kept dry and cold, and suppliers typically recommend storage well below freezing. Once dissolved, the peptide is handled at refrigeration temperatures and used within a short period, because peptide bonds and the acetylated terminus can be affected by repeated freeze-thaw cycles, proteases, or extreme pH. Bacteriostatic water and saline are both described as solvents, although preservatives can interfere with some analytical workflows. Reconstituted solutions are inspected for particulates before use.
Sports authorities classify the peptide as a prohibited substance, and it appears on the World Anti-Doping Agency list under peptide hormones, growth factors, and related substances. Racing jurisdictions for horses and dogs have issued separate restrictions, and several national bodies treat it as a controlled or prescription-only item. As a research chemical it is sold without a therapeutic indication, and labels usually state that the product is not for human or veterinary use. Regulatory treatment therefore varies by country.
Lyophilised peptide powders are hygroscopic, and the fragment absorbs atmospheric moisture when a vial is opened at room temperature. Weighing and aliquoting are normally done quickly in a dry environment, and stock solutions are divided into single-use portions before freezing. Repeated freeze-thaw cycles are avoided because they promote aggregation and can shift the measured content of a vial. These practices are general to synthetic peptides rather than unique to this sequence, but they matter more for short chains kept for long periods.
The seven-residue chain carries several polar and charged side chains, so it dissolves readily in water and in aqueous buffers near neutral pH. No cysteine is present, so disulphide formation is not a concern and reducing agents are unnecessary. Dilute ammonium hydroxide or acetonitrile-water mixtures are sometimes used for stock solutions when initial dissolution is slow. Strongly alkaline conditions and prolonged contact with oxidising agents are avoided because they can modify lysine-containing stretches, and haze in solution usually signals incomplete dissolution or aggregated material.
Identity and purity are checked with reversed-phase high-performance liquid chromatography, which separates the target sequence from truncated or deletion analogues, and with mass spectrometry, which confirms the expected molecular mass. Amino acid analysis and peptide mapping give orthogonal confirmation but are used less often outside specialist laboratories. Counter-ion content varies: material purified on trifluoroacetic acid gradients retains trifluoroacetate, and ion exchange can convert the salt form. Residual water and solvent are measured by Karl Fischer titration or thermogravimetric analysis, and any purity figure should be read together with the method used to obtain it.
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.
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.
=== Gold Cup runners-up and the 2001 Copa América (2000–2001) === Colombia made their first appearance at the CONCACAF Gold Cup as invited guests in 2000, beating Jamaica 1–0 through Gonzalo Martínez and losing 2–0 to Honduras in a three-team group, both matches played at the Miami Orange Bowl. In the quarter-final on 19 February they twice came from behind against the hosts the United States — Faustino Asprilla cancelling out Brian McBride and Gerardo Bedoya equalising in the 81st minute after Chris Armas had scored — to draw 2–2 after extra time, then won the shootout 2–1 in a sequence in which six of the nine attempts failed. A 2–1 semi-final win over Peru at Qualcomm Stadium followed, an own goal by Marcial Salazar and a Víctor Bonilla strike putting Colombia through before a crowd of 3,402. In the final at the Los Angeles Memorial Coliseum on 27 February, Canada won 2–0 through a Jason de Vos header in first-half stoppage time and a Carlo Corazzin penalty, before 6,197 spectators.
== Ecological lifetime == A poison which enters the food chain—whether of industrial, agricultural, or natural origin—might not be immediately toxic to the first organism that ingests the toxin, but can become further concentrated in predatory organisms further up the food chain, particularly carnivores and omnivores, especially concerning fat soluble poisons which tend to become stored in biological tissue rather than excreted in urine or other water-based effluents. Apart from food, many poisons readily enter the body through the skin and lungs. Hydrofluoric acid is a notorious contact poison, in addition to its corrosive damage. Naturally occurring sour gas is a fast-acting atmospheric poison, which can be released by volcanic activity or drilling rigs. Plant-based contact irritants, such as that possessed by poison ivy, are often classed as allergens rather than poisons; the effect of an allergen being not a poison as such, but to turn the body's natural defenses against itself. Poison can also enter the body through faulty medical implants, or by injection (which is the basis of lethal injection in the context of capital punishment). In 2013, 3.3 million cases of unintentional human poisonings occurred. This resulted in 98,000 deaths worldwide, down from 120,000 deaths in 1990. In modern society, cases of suspicious death elicit the attention of the Coroner's office and forensic investigators.
Izmaylovsky Park, created in 1931, is one of the world's largest urban parks, along with Richmond Park in London. With an area of 15.34 square kilometers (5.92 sq mi), Izmaylovsky Park is six times larger than Central Park in New York. Bauman Garden, officially founded in 1920 and renamed in 1922 after the Bolshevik Nikolay Bauman, is one of the oldest parks in Moscow. It lies on the site of the former Golitsyn estate and eighteenth-century public garden.
Sources: en.wikipedia.org
In hepatocellular carcinoma models, O-GlcNAc is associated with activating phosphorylation of HDAC1, which in turn regulates expression of the cell cycle regulator p21Waf1/Cip1 and cell motility regulator E-cadherin. OGT has been found to stabilize SREBP-1 and activate lipogenesis in breast cancer cell lines. This stabilization was dependent on the proteasome and AMPK. OGT knockdown resulted in decreased nuclear SREBP-1, but proteasomal inhibition with MG132 blocked this effect. OGT knockdown also increased the interaction between SREBP-1 and the E3 ubiquitin ligase FBW7. AMPK is activated by T172 phosphorylation upon OGT knockdown, and AMPK phosphorylates SREBP-1 S372 to inhibit its cleavage and maturation. OGT knockdown had a diminished effect on SREBP-1 levels in AMPK-null cell lines. In a mouse model, OGT knockdown inhibited tumor growth but SREBP-1 overexpression partly rescued this effect. These results contrast from those of a previous study which found that OGT knockdown/inhibition inhibited AMPK T172 phosphorylation and increased lipogenesis. In breast and prostate cancer cell lines, high levels of OGT and O-GlcNAc have been associated both in vitro and in vivo with processes associated with disease progression, e.g., angiogenesis, invasion, and metastasis. OGT knockdown or inhibition was found to downregulate the transcription factor FoxM1 and upregulate the cell-cycle inhibitor p27Kip1 (which is regulated by FoxM1-dependent expression of the E3 ubiquitin ligase component Skp2), causing G1 cell cycle arrest.
== History == Frank Berger was working in a laboratory of a British drug company, looking for a preservative for penicillin, when he noticed that a compound called mephenesin (or myanesin) calmed laboratory rodents without actually sedating them. Berger subsequently referred to this “tranquilizing” effect in a now-historic article, published by the British Journal of Pharmacology in 1946. However, three major drawbacks existed to the use of mephenesin as a tranquilizer: a very short duration of action, greater effect on the spinal cord than on the brain (resulting in a very low therapeutic index), and a weak activity.
==== United States ==== In the United States, immediate-release injectable nalmefene was approved in 1995, as an antidote for opioid overdose. It was sold under the brand name Revex. The product was discontinued by its manufacturer around 2008. A generic version was approved for medical use in the United States in February 2022. In May 2023, the Food and Drug Administration (FDA) approved a nalmefene hydrochloride nasal spray, under the brand name Opvee, for the emergency treatment of opioid overdose in people aged twelve years of age and older. In August 2024, the FDA approved a nalmefene hydrochloride auto-injector (Zurnai) for the emergency treatment of known or suspected opioid overdose in people aged twelve years of age and older. The FDA granted the application for the nalmefene hydrochloride auto-injector fast track and priority review designations. The FDA granted approval of Zurnai to Purdue Pharma L.P. As of 2012, nalmefene in pill form, used for the treatment of alcohol dependence and other addictive behaviors, is not available in the United States.
Structural effects can also be important. The difference between fumaric acid and maleic acid is a classic example. Fumaric acid is (E)-1,4-but-2-enedioic acid, a trans isomer, whereas maleic acid is the corresponding cis isomer, i.e. (Z)-1,4-but-2-enedioic acid (see cis-trans isomerism). Fumaric acid has pKa values of approximately 3.0 and 4.5. By contrast, maleic acid has pKa values of approximately 1.5 and 6.5. The reason for this large difference is that when one proton is removed from the cis isomer (maleic acid) a strong intramolecular hydrogen bond is formed with the nearby remaining carboxyl group. This favors the formation of the maleate H+, and it opposes the removal of the second proton from that species. In the trans isomer, the two carboxyl groups are always far apart, so hydrogen bonding is not observed.
Sources: en.wikipedia.org
== Function == The product of this gene, P2Y1 belongs to the family of G-protein coupled receptors. This family has several receptor subtypes with different pharmacological selectivity, which overlaps in some cases, for various adenosine and uridine nucleotides. This receptor functions as a receptor for extracellular ATP and ADP. In platelets binding to ADP leads to mobilization of intracellular calcium ions via activation of phospholipase C, a change in platelet shape, and probably to platelet aggregation.
This has reduced the risk of occupationally induced cancer from radon, although health issues may persist for those who are currently employed in affected mines and for those who have been employed in them in the past. As the relative risk for miners has decreased, so has the ability to detect excess risks among that population.
== Clinical significance == The Wnt signaling pathway was first linked to bone development when a loss-of-function mutation in LRP5 was found to cause osteoporosis-pseudoglioma syndrome. Shortly thereafter, two studies reported that gain-of-function mutations in LRP5 caused high bone mass. Many bone density related diseases are caused by mutations in the LRP5 gene. There is controversy whether bone grows through Lrp5 through bone or the intestine. The majority of the current data supports the concept that bone mass is controlled by LRP5 through the osteocytes. Mice with the same Lrp5 gain-of-function mutations also have high bone mass. The high bone mass is maintained when the mutation only occurs in limbs or in cells of the osteoblastic lineage. Bone mechanotransduction occurs through Lrp5 and is suppressed if Lrp5 is removed in only osteocytes. There are promising osteoporosis clinical trials targeting sclerostin, an osteocyte-specific protein which inhibits Wnt signaling by binding to Lrp5. An alternative model that has been verified in mice and in humans is that Lrp5 controls bone formation by inhibiting expression of TPH1, the rate-limiting biosynthetic enzyme for serotonin, a molecule that regulates bone formation, in enterochromaffin cells of the duodenum and that excess plasma serotonin leads to inhibition in bone. Another study found that a different Tph1-inhibitor decreased serotonin levels in the blood and intestine, but did not affect bone mass or markers of bone formation.
Sources: en.wikipedia.org
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.
Suppliers typically quote a percentage derived from reverse-phase HPLC peak area. That figure reflects the relative amount of the main peak and does not by itself confirm identity or exclude related impurities. Mass spectrometry is commonly paired with it for confirmation.
Peptides purified by reverse-phase chromatography often carry trifluoroacetate as a counter-ion, which adds mass and can affect solubility and apparent behavior in assays. Acetate and hydrochloride forms are also offered. Knowing which form is present matters when calculating how much peptide a given weight contains.
Sealed, desiccated and protected from light, at -20 °C or lower for long-term storage. Short-term storage at refrigerator temperature is common in working laboratories.