A practical reference on Ac-SDKP: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-03-05 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | Approximately 0.9 kDa | Depends on exact fragment sequence and counterion |
| Amino acid sequence | LKKTETQ (commonly cited) | Short actin-binding motif from thymosin beta-4 |
| Common salt form | Acetate salt | Trifluoroacetate also reported in research material |
| Reconstitution solvent | Sterile water or buffer | Gentle mixing; avoid vigorous agitation |
| Solution storage | -20 °C or lower | Aliquot to avoid repeated freeze-thaw cycles |
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.
Material is normally supplied as a lyophilised powder in a sealed vial. The powder is hygroscopic, so exposure to humid air leads to water uptake, caking and gradual loss of the fluffy texture that indicates a good freeze-dry. Vials are best kept sealed with desiccant, protected from light and stored cold. Letting a cold vial warm to room temperature before opening reduces condensation on the contents. Purity is normally reported from a chromatographic run, and that figure applies to the batch as tested rather than to the vial after repeated opening.
TB-500 is a catalogue name applied to a synthetic peptide related to thymosin beta-4, an actin-binding protein found in most mammalian cells. Suppliers do not use the label consistently: some describe it as the full 43-residue protein, others as a short fragment from the actin-binding region, and others as a related tetrapeptide. Because the name is commercial rather than chemical, two products sold under it may not contain the same molecule. This naming ambiguity is the first point to check in any description of the material.
The most frequently cited identity is a seven-residue fragment with the sequence LKKTETQ, taken from the actin-binding domain of the parent protein. A separate molecule, N-acetyl-seryl-aspartyl-lysyl-proline, often shortened to Ac-SDKP, derives from the same protein's N-terminal region and appears in overlapping literature. Reported molecular masses therefore differ between sources, and a mass value on its own does not establish which fragment is present. Confirmation requires a defined sequence rather than a single number.
Research interest in thymosin beta-4 fragments centres on actin sequestration, cell migration and tissue repair models. Most published work uses cultured cells or animal wound and cardiac preparations, and findings are generally described as preliminary. No fragment of this protein has been approved as a therapeutic product by major regulators. Reviews of the field note inconsistent dosing, delivery routes and outcome measures across studies, which complicates direct comparison. The material is best understood as a laboratory reagent with an active but unresolved research literature.
Aleme Eshete observes that “the ‘Mahal Safari’ movement may be taken as the first signal that alerted the Ethiopian Government of a Bolshevik-type popular movement,” indicating that the term later took on broader political connotations.
Polystyrene packing peanuts are inexpensive, readily available, and have excellent drainage. However, they can be too lightweight for some uses. They are used mainly in closed-tube systems. Note that non-biodegradable polystyrene peanuts must be used; biodegradable packing peanuts will decompose into a sludge. Plants may absorb styrene and pass it to their consumers; this is a possible health risk.
== Research == Although primarily known for the development of computational methods for predicting and designing the structures and functions of proteins, Baker maintains an active experimental biochemistry group. He has authored over 600 scientific papers. Baker's group developed the Rosetta algorithm for ab initio protein structure prediction, which has been extended into a tool for protein design, a distributed computing project called Rosetta@home, and the computer game Foldit. Baker served as the director of the Rosetta Commons, a consortium of labs and researchers that develop biomolecular structure prediction and design software. His group has regularly competed in the CASP structure prediction competition, specializing in ab initio methods, including both manually assisted and automated variants of the Rosetta protocol. Using artificial intelligence, his group has developed later a newer version of the program known as RoseTTAFold. Baker's group is also active in the field of protein design; they are noted for designing Top7, the first artificial protein with a novel fold. In 2017, Baker's Institute for Protein Design received over $11 million from Open Philanthropy, followed by an additional $3 million donation in 2021. In April 2019, Baker gave a TED talk titled "5 challenges we could solve by designing new proteins" at TED2019 in Vancouver, Canada.
Sources: en.wikipedia.org
== Potential drug interactions == CoQ10 taken as a pharmacological substance has potential to inhibit the effects of theophylline as well as the anticoagulant warfarin; CoQ10 may interfere with warfarin's actions by interacting with cytochrome p450 enzymes thereby reducing the INR, a measure of blood clotting. The structure of CoQ10 is similar to that of vitamin K, which competes with and counteracts warfarin's anticoagulation effects. CoQ10 is not recommended in people taking warfarin due to the increased risk of clotting.
== Comparison to other assays == While the colloidal gold assay is the most sensitive in-solution colorimetric protein assay, it may be equally sensitive or surpassed in sensitivity by fluorescent protein assays such as the CBQCA, FQ, NanoOrange, Quant-iT, and EZQ assays.
is the total length of the capillary. Since only charged ions are affected by the electric field, neutral analytes are poorly separated by capillary electrophoresis. The velocity of migration of an analyte in capillary electrophoresis will also depend upon the rate of electroosmotic flow (EOF) of the buffer solution. In a typical system, the electroosmotic flow is directed toward the negatively charged cathode so that the buffer flows through the capillary from the source vial to the destination vial. Separated by differing electrophoretic mobilities, analytes migrate toward the electrode of opposite charge. As a result, negatively charged analytes are attracted to the positively charged anode, counter to the EOF, while positively charged analytes are attracted to the cathode, in agreement with the EOF as depicted in figure 3.
Pseudouridine is an RNA modification that is introduced post-translationally, meaning after the RNA is transcribed. The proteins that facilitate this are called pseudouridine synthases (PUS) and are found in all kingdoms of life. Most research has been conducted on how PUS modify tRNA, so mechanisms involving snRNA and mRNA are not clearly defined. PUS can vary on RNA specificity, structure, and isomerization mechanisms. PUS enzymes are divided into five families which share an active sequence and important structural motifs.
Sources: en.wikipedia.org
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.
Reversed-phase liquid chromatography separates components and reports purity from peak area. Mass spectrometry confirms the molecular mass expected for the sequence. Additional approaches such as peptide mapping or amino acid analysis provide independent confirmation.
Reported percentages depend on the analytical method, the detection wavelength, and whether salts and water are counted. A value above ninety-five percent by chromatography does not by itself establish a correct sequence. Different suppliers also calculate purity against different reference standards.
No. TB-500 is a short synthetic peptide matching residues 17 to 23 of thymosin beta-4, while the parent protein contains 43 residues. The fragment lacks the rest of the protein sequence, so the two are related but not identical.