Everything below concerns thymosin beta-4. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-01-10. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C38H68N10O14 | Acetylated heptapeptide form |
| Monoisotopic mass | 888.5 Da | Average mass about 889 Da |
| Appearance | White to off-white solid | Usually supplied as lyophilised powder |
| Solubility class | Highly water soluble | Also dissolves in aqueous buffers |
| Common synonyms | Tbeta4 fragment, thymosin beta-4 (17-23) | Refer to the same sequence |
Interest in the compound comes largely from studies of the parent protein, which participates in actin sequestration, cell migration and tissue repair processes. Whether a short fragment reproduces those activities is a separate question that remains open in the published record. Many summaries describe mechanisms by analogy to thymosin beta-4 rather than from direct measurements on the fragment. Claims about activity should be treated as provisional unless a cited study specifies the exact peptide, its purity and the assay used.
TB-500 is a laboratory label applied to a short synthetic peptide that is widely described as a fragment of thymosin beta-4, an actin-binding protein present in most mammalian cells. Suppliers and review articles usually present TB-500 as the N-terminal region of that protein, but the exact sequence attached to the name is not consistent across sources. Some product descriptions list a seven-residue chain; others use the label loosely for the parent protein itself. Because of that variation, any technical discussion of TB-500 needs to state which sequence is meant.
Thymosin beta-4 was isolated from calf thymus in the early 1980s and later characterised as an abundant intracellular actin-sequestering protein. Interest in short synthetic fragments grew once the actin-binding motif had been mapped to the middle of the sequence. TB-500 came out of that line of work as a truncated analogue rather than a natural isolate, and it is now sold mainly to laboratories. Published studies on the fragment have been largely in vitro or in animal models, and controlled human trials remain sparse, so claims about effects in people rest on extrapolation.
Literature and online discussion often conflate TB-500 with full-length thymosin beta-4, even though the two differ in size and are not interchangeable in analytical terms. The fragment is produced by solid-phase peptide synthesis, and the product is a defined seven-residue chain rather than a biological extract. Because the term is a trade-style label, two vendors may supply materials of the same nominal sequence but different counter-ion content, purity, or water content. Comparisons across studies are therefore difficult unless the exact sequence and purity are reported.
==== Competitive assays ==== Competitive assays are generally used for smaller analytes since smaller analytes have fewer binding sites. The sample first encounters antibodies to the target analyte labelled with a visual tag (colored particles). The test line contains the target analyte fixed to the surface. When the target analyte is absent from the sample, unbound antibody will bind to these fixed analyte molecules, meaning that a visual marker will show. Conversely, when the target analyte is present in the sample, it binds to the antibodies to prevent them binding to the fixed analyte in the test line, and thus no visual marker shows. This differs from sandwich assays in that no band means the analyte is present.
Refers to the testing of experimental drugs in the test tube or in animals - the testing that occurs before trials in humans may be carried out. (NLM) Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done. (NCI) Predictive factor
=== Christian Science Monitor libel case === The Christian Science Monitor also published a story on 25 April 2003, stating that it had documentary evidence that he had received "more than ten million dollars" from the Iraqi government. On 20 June 2003, the Monitor reported that its own investigation had concluded that the documents were sophisticated forgeries. Galloway sued The Christian Science Monitor for libel. In March 2004, he accepted damages and a public apology from the Monitor.
== Strengths == Simple, fast and inexpensive: In COBRA, DNA methylation levels are easily and quickly measured without the need for laborious sub-cloning and sequencing, as with bisulfite sequencing. The assay is straightforward and can be done with standard inexpensive molecular biology reagents. High compatibility: Due to the PCR and purification steps, the method not only works with very small amounts of genomic DNA, but also samples that have been treated with paraffin, both of which can be problems in other DNA methylation quantification protocols such as Southern blotting and methylation-sensitive restriction enzyme digestion followed by PCR. Quantitative: This is in contrast to methylation-specific PCR, which is qualitative. With COBRA, DNA methylation levels can be directly quantified at a given locus, yielding more information per assay. Scalability for high-throughput sample processing: With COBRA, many regions of interest can be processed in parallel in separate samples digested with the same restriction enzyme. This is in contrast to bisulfite sequencing analysis, where each region needs to be examined rigorously by sequencing many clones per locus, costing more time. Multiple queries per assay: Methylation status can be interrogated at multiple CpG-containing restriction sites in a single digestion assay.
Sources: en.wikipedia.org
The parties of the Weimar Coalition (Social Democrats, Centre and the left-liberal German Democratic Party (DDP)) were the base of the Weimar Republic but lost their majority in the 1920 elections. After this, majority governments were rare as they required the support of the Weimar Coalition and the national liberal German People's Party (DVP). Social Democrats and DVP found it hard to agree on economic policy while Social Democrats disagreed with the Centre Party on issues like religious schools or a nationwide Concordat with the Holy See. Following the 1920 elections, the Centre's Constantin Fehrenbach formed a minority government in a coalition with the DDP and the DVP. In May 1921 the Weimar Coalition once again joined forces with the Centre's Joseph Wirth as Chancellor, but this minority government collapsed again in November 1922. After this, the Centre participated in the non-affiliated Wilhelm Cuno's "government of the economy", together with both liberal parties and the Bavarian People's Party (BVP). In August 1923, the DVP's Gustav Stresemann formed a Grand Coalition administration, comprising the Centre, both Liberal parties and the Social Democrats, which lasted until November, when the Social Democrats left the coalition and the Centre's Wilhelm Marx became chancellor of a cabinet of the remaining parties. In January 1925 the non-affiliated Hans Luther was appointed chancellor and formed a coalition between the Centre, both Liberal parties, the BVP and, for the first time, the right-wing German National People's Party (DNVP).
=== Optogenetics === Optogenetics allows control of biological events in a non-invasive manner. The field has advanced in recent years with a number of new tools, including those to trigger light sensitivity, such as the Blue-Light-Utilizing FAD domains (BLUF). BLUFs encode a 100 to 140 amino acid sequence that was derived from photoreceptors in plants and bacteria. Similar to other photoreceptors, the light causes structural changes in the BLUF domain that results in disruption of downstream interactions. Current research investigates proteins with the appended BLUF domain and how different external factors can impact the proteins.
Messenger RNA (mRNA) is the type of RNA that carries information from DNA to the ribosome, the sites of protein synthesis (translation) in the cell cytoplasm. The coding sequence of the mRNA determines the amino acid sequence in the protein that is produced. However, many RNAs do not code for protein (about 97% of the transcriptional output is non-protein-coding in eukaryotes). These so-called non-coding RNAs ("ncRNA") can be encoded by their own genes (RNA genes), but can also derive from mRNA introns. The most prominent examples of non-coding RNAs are transfer RNA (tRNA) and ribosomal RNA (rRNA), both of which are involved in the process of translation. There are also non-coding RNAs involved in gene regulation, RNA processing and other roles. Certain RNAs are able to catalyse chemical reactions such as cutting and ligating other RNA molecules, and the catalysis of peptide bond formation in the ribosome; these are known as ribozymes. According to the length of RNA chain, RNA includes small RNA and long RNA. Usually, small RNAs are shorter than 200 nt in length, and long RNAs are greater than 200 nt long. Long RNAs, also called large RNAs, mainly include long non-coding RNA (lncRNA) and mRNA. Small RNAs mainly include 5.8S ribosomal RNA (rRNA), 5S rRNA, transfer RNA (tRNA), microRNA (miRNA), small interfering RNA (siRNA), small nucleolar RNA (snoRNAs), Piwi-interacting RNA (piRNA), tRNA-derived small RNA (tsRNA) and small rDNA-derived RNA (srRNA).
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Sources: en.wikipedia.org
=== Demineralization === In the strict sense, the term demineralization should imply removing all dissolved "mineral species" from water. Thus not only removing dissolved salt as obtained by simple deionization, but also neutral dissolved "Mineral species" such as dissolved iron hydroxides (Fe(OH)3) or dissolved silica (Si(OH)4), two solutes often present in water. In this way, demineralized water has the same electrical conductivity as deionized water, but is purer because it does not contain non-ionized substances, i.e. neutral solutes. However, demineralized water is often used interchangeably with deionized water and can be also confused with softened water, depending on the exact definition used: removing only the cations susceptible to precipitate as insoluble minerals (from there, "demineralization"), or removing all the "mineral species" present in water, and thus not only dissolved ions but also neutral solute species. So, the term demineralized water is vague and deionized water or softened water should often be preferred in its place for more clarity.
=== Decoding by high throughput sequencing === According to the complexity of the DNA encoded chemical library (typically between 103 and 106 members), a conventional Sanger sequencing based decoding is unlikely to be usable in practice, due both to the high cost per base for the sequencing and to the tedious procedure involved. High throughput sequencing technologies exploited strategies that parallelize the sequencing process displacing the use of capillary electrophoresis and producing thousands or millions of sequences at once. In 2008 was described the first implementation of a high-throughput sequencing technique originally developed for genome sequencing (i.e. "454 technology") to the fast and efficient decoding of a DNA encoded chemical library comprising 4000 compounds. This study led to the identification of novel chemical compounds with submicromolar dissociation constants towards streptavidin and definitely shown the feasibility to construct, perform selections and decode DNA-encoded libraries containing millions of chemical compounds. Now decoding of DNA-encoded libraries using commercial next-generation DNA sequencing platforms (e.g. Illumina) is the standard approach.
=== Size === The smallest bat, and one of the smallest mammals, is Kitti's hog-nosed bat (Craseonycteris thonglongyai), which is 29–33 mm (1+1⁄8–1+1⁄4 in) long with a 150-millimetre (6 in) forearm and weighs 2 oz (56+11⁄16 g). The largest species is the giant golden-crowned flying fox (Acerodon jubatus), which can weigh 1.5 kg (3+1⁄4 lb) with a wingspan of 1.6 m (5 ft 3 in). Larger bats tend to use lower frequencies and smaller bats higher for echolocation; high-frequency echolocation is better at detecting smaller prey. Small prey may be absent in the diets of large bats as they are unable to detect them.
== Clinical significance == Collagen XXIII plays a role as a biomarker for detection and recurrence of NCLSC cells (non-small cell lung carcinoma) and the reappearance of prostate cancer. Some experiments suggest that collagen XXIII influences cellular adhesion and stimulates metastasis development by facilitating cancer cells growth and survival when they are rounded and not able to spread. It has been shown that loss of collagen XXIII may complicate cellular adhesion and reduce lung cancer cell retention.
Sources: en.wikipedia.org
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.
It consists of leucine, lysine, lysine, threonine, glutamic acid, threonine, and glutamine in that order. The N-terminal leucine is usually acetylated in the forms described in catalogues.
Controlled human data is limited, and most published findings come from cell culture or animal work. This makes it difficult to state clinical effects with confidence.
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.