actin binding comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-03-18. 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.
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.
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.
| 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 |
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.
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.
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.
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.
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.
The designation TB-500 circulates in laboratory and catalog contexts without a single agreed definition. Most product listings apply it to an N-terminally acetylated seven-residue fragment of thymosin beta-4, while other listings attach the same label to the full 43-residue protein. Because the term is commercial rather than systematic, two entries bearing identical names may describe different molecules. Any documentation should therefore state which sequence a given sample is claimed to contain.
=== Primary Sources === Banks, Iain M. (1987), Consider Phlebas, Orbit, ISBN 1-85723-138-4. Banks, Iain M. (1988), The Player of Games, Orbit, ISBN 1-85723-146-5. Banks, Iain M. (1990), Use of Weapons, Orbit, ISBN 9780356191607. Banks, Iain M. (1991). The State of the Art. Orbit. ISBN 0-356-19669-0.. Banks, Iain M. (10 August 1994). "A Few Notes on the Culture". Newsgroup: rec.arts.sf.written. Retrieved 3 August 2021.. Banks, Iain M. (1996), Excession, Orbit, ISBN 1-85723-457-X. Banks, Iain M. (1998), Inversions, Orbit, ISBN 1-85723-763-3. Banks, Iain M. (2000), Look to Windward, Orbit, ISBN 1-85723-969-5. Banks, Iain M. (2008), Matter, Orbit, ISBN 978-1-84149-417-3. Banks, Iain M. (2010), Surface Detail, Orbit, p. 400, ISBN 978-1-84149-893-5. Banks, Iain M. (2012), The Hydrogen Sonata, Orbit, ISBN 978-0356501505. Banks, Iain M. (n.d.), "A few Notes on Marain", Trevor Hopkins Homepage, retrieved 9 August 2021.
Heat is transported between blood vessels flowing in opposite directions (countercurrent exchange) and is retained within the body rather than exiting via the gills. Warm blood can also be redirected from the liver to the body core. In addition, the species has an enlarged, thickened heart, and its blood contains more red blood cells and oxygen-carrying hemoglobin than most mammals and birds. One study found that stomach temperatures ranged from 24.7–26.8 °C (76–80 °F) in waters 12.9–16.1 °C (55–61 °F).
Chain brake A chain brake activator is located forward of the upper handle and is activated by a kickback event. When triggered, it tensions a band around the clutch drum, stopping the chain within milliseconds. A chain catcher is located between the saw body and the clutch cover. In most cases, it resembles a hook made of aluminum. It is used to stop the chain when it derails from the bar and shortens the length of the chain. When derailing, the chain swings from underneath the saw towards the operator. This prevents the chain from hitting the operator, which hits the rear handle guard instead. A rear handle guard protects the hand of the operator when the chain derails. Some chains have safety links, as on micro chisel saws. These links keep the saw close to the gap between two cutting links and lift the chain when the space at the safety link is full with saw chips, which lifts the chain and lets it cut slower. Nonprofessional chains have less aggressive teeth, by having shallower depth gauges.
== Personal life == Sherman met and married Hildegard Schroeder while they were both graduate students at the University of Iowa, and they had three children: Karen, Marc, and Keith. In addition to his professional activities, he has participated in organizations such as the Boy Scouts of America, the Jewish War Veterans organization, and the Lions Club. Sherman died on December 1, 2023, at the age of 98.
=== Effects of the WldS mutation === The mutation causes no harm to the mouse. The only known effect is that the Wallerian degeneration is delayed by up to three weeks on average after injury of a nerve. At first, it was suspected that the Wlds mutation slows down the macrophage infiltration, but recent studies suggest that the mutation protects axons rather than slowing down the macrophages. The process by which the axonal protection is achieved is poorly understood. However, studies suggest that the Wlds mutation leads to increased NMNAT1 activity, which leads to increased NAD+ synthesis. This in turn activates SIRT1-dependent process within the nucleus, causing changes in gene transcription. NAD+ by itself may provide added axonal protection by increasing the axon's energy resources. More recent work, however, raises doubt that either NMNAT1 or NAD+ can substitute for the full length Wlds gene. These authors demonstrated by both in vitro and in vivo methods that the protective effect of overexpression of NMNAT1 or the addition of NAD+ did not protect axons from degeneration. However, later studies showed that NMNAT1 is protective when combined with an axonal targeting peptide, suggesting that the key to the protection provided by WldS was the combination of NMNAT1's activity and the axonal localization provided by the N-terminal domain of the chimeric protein. The provided axonal protection delays the onset of Wallerian degeneration. Schwann cell activation should therefore be delayed, as they would not detect axonal degradation signals from ErbB2 receptors.
Sources: en.wikipedia.org
transcription The first step in the process of gene expression, in which an RNA molecule, known as a transcript, is synthesized by enzymes called RNA polymerases using a gene or other DNA sequence as a template. Transcription is a critical and fundamental process in all living organisms and is necessary in order to make use of the information encoded within a genome. All classes of RNA must be transcribed before they can exert their effects upon a cell, though only messenger RNA (mRNA) proceeds to translation to produce a functional protein, whereas the many types of non-coding RNA fulfill their duties without being translated. Transcription is also not always beneficial for a cell: when it occurs at the wrong time or at a functionless locus, or when mobile elements or infectious pathogens utilize the host's transcription machinery, the resulting transcripts (not to mention the waste of valuable energy and resources) are often harmful to the host cell or genome.
=== Biomedical applications === Because of their relatively large surface area, CNTs are capable of interacting with a wide variety of therapeutic and diagnostic agents (drugs, genes, vaccines, antibodies, biosensors, etc.). This can be utilized to assist in drug delivery directly into cells. In addition, CNTs have recently been used as reinforcements in implants and scaffolds due to their suitable reaction area, high elastic modulus, and load transfer capability.
=== Fish === A University of Florida scientist reports that male sand gobies work harder at building nests and taking care of eggs when females are present – the first time such "courtship parental care" has been documented in any species. In the cichlid species Tropheus moorii, a male and female will form a temporary monogamous pair bond and spawn; after which, the female leaves to mouthbrood the eggs on her own. T. moorii broods exhibit genetic monogamy (all eggs in a brood are fertilized by a single male). Another mouth brooding cichlid – the Lake Tanganyika cichlid (Xenotilapia rotundiventralis) has been shown that mating pairs maintain pair bonds at least until the shift of young from female to male. More recently the Australian Murray cod has been seen maintaining pair bonds over 3 years. Pair bonding may also have non-reproductive benefits, such as assisted resource defense. Recent study comparing two species of butterflyfishes, C. baronessa and C. lunulatus, indicate increase in food and energy reserves compared to individual fish.
Latin America (via IIAA). India, Pakistan, and Ceylon. The U.S. also participated in post-1945 UN initiatives for technical assistance to developing countries. Through a series of actions in 1948 and 1949, the UN's General Assembly and Economic and Social Council (ECOSOC) created the Expanded Programme of Technical Assistance (EPTA). The U.S. provided 60% of EPTA's financing. By 1955, EPTA adopted a country-led approach where the UN's TA in each country was programmed according to a plan drawn up by the receiving country in consultation with the UN. ECOSOC also created a new Technical Assistance Board, which (similarly to the United States' wartime Interdepartmental Committee) coordinated the TA being provided to low-income countries by various individual UN agencies.
Most aptamers are based on a specific oligomer sequence of 20-100 bases and 3-20 kDa. Some have chemical modifications for functional enhancements or compatibility with larger engineered molecular systems. DNA, RNA, XNA, and peptide aptamer chemistries can each offer distinct profiles in terms of shelf stability, durability in serum or in vivo, specificity and sensitivity, cost, ease of generation, amplification, and characterization, and familiarity to users. Typically, DNA- and RNA-based aptamers exhibit low immunogenicity, are amplifiable via Polymerase Chain Reaction (PCR), and have complex secondary structure and tertiary structure. DNA- and XNA-based aptamers exhibit superior shelf stability. XNA-based aptamers can introduce additional chemical diversity to increase binding affinity or greater durability in serum or in vivo. As 22 genetically encoded and over 500 naturally occurring amino acids exist, peptide aptamers, as well as antibodies, have much greater potential combinatorial diversity per unit length relative to the 4 nucleic acids in DNA or RNA. Chemical modifications of nucleic acid bases or backbones increase the chemical diversity of standard nucleic acid bases. Split aptamers are composed of two or more DNA strands that are pieces of a larger parent aptamer that has been broken in two by a molecular nick. The ability of each component strand to bind targets will depend on the location of the nick, as well as the secondary structures of the daughter strands. The presence of a target molecule supports the joining of DNA fragments.
Sources: en.wikipedia.org
Polymer–polymer systems. In a Polymer–polymer system, both phases are generated by a dissolved polymer. The heavy phase will generally be a polysaccharide, and the light phase is generally Polyethylene glycol (PEG). Traditionally, the polysaccharide used is dextran. However, dextran is relatively expensive, and research has been exploring using less expensive polysaccharides to generate the heavy phase. If the target compound being separated is a protein or enzyme, it is possible to incorporate a ligand to the target into one of the polymer phases. This improves the target's affinity to that phase, and improves its ability to partition from one phase into the other. This, as well as the absence of solvents or other denaturing agents, makes polymer–polymer extractions an attractive option for purifying proteins. The two phases of a polymer–polymer system often have very similar densities, and very low surface tension between them. Because of this, demixing a polymer–polymer system is often much more difficult than demixing a solvent extraction. Methods to improve the demixing include centrifugation, and application of an electric field. Polymer–salt systems. Aqueous two-phase systems can also be generated by generating the heavy phase with a concentrated salt solution. The polymer phase used is generally still PEG. Generally, a kosmotropic salt, such as Na3PO4 is used, however PEG–NaCl systems have been documented when the salt concentration is high enough. Since polymer–salt systems demix readily they are easier to use.
=== 1989 === 9 July Moving Pictures, with Sir Jonathan Miller, the documentary explains how the brain sees images, with relation to television; Gotthold Ephraim Lessing and his work Laocoön; animator Sergio Simonetti; the National Science and Media Museum in Bradford; the Asteroid theme of Pearl & Dean; cognitive scientist Jerome Lettvin; John Grover and the 1989 film Licence to Kill; with the documentary editor Simon Rose. Produced by Patrick Uden, directed by Michael Proudfoot, made by Uden Associates 23 July The Bicycle: The Green Machine, Columbus of Italy that made cycle steel tubing from 130 kg steel billets; Cinelli of Milan; sports scientist Adrienne Hardman of Loughborough University; cycle chains were mostly made in Japan; 2m would be sold in UK - 700k by Raleigh. Narrated by the Radio 4 newsreader John Hedges, produced by Jeremy Llewellyn-Jones, made by Chrysalis Television 30 July Earth Calling Basingstoke, about Guy Hurst, who collates sightings for The Astronomer (BAA); Dave Graham from Brompton-on-Swale; John Wall, known for his Crayford focuser; the documentary was filmed around April 1989, and the astronomers in County Durham saw the effects of the March 1989 geomagnetic storm.
In another study with escitalopram citalopram, metabolomic analysis of plasma from patients with MDD revealed that variations in glycine metabolism were negatively associated with patient outcome upon treatment with selective serotonin reuptake inhibitors (SSRIs), an important drug class involved in the treatment of this disease.
The dynamics of an epidemic, for example, the flu, are often much faster than the dynamics of birth and death, therefore, birth and death are often omitted in simple compartmental models. The SIR system without so-called vital dynamics (birth and death, sometimes called demography) described above can be expressed by the following system of ordinary differential equations:
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.
The lyophilised powder is typically held at -20 C or lower in a dry, dark place. Reconstituted solutions are aliquoted and frozen to avoid repeated freeze-thaw cycles.