trifluoroacetate 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 2026-06-27. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular mass | ≈889 Da for the 7-residue fragment | Full-length thymosin beta-4 is ≈4.9 kDa; catalogs differ |
| Appearance | White to off-white powder | Hygroscopic; weight shifts with residual moisture |
| Solubility class | Freely soluble in water | Also dissolves in aqueous buffers; poorly soluble in nonpolar solvents |
| Typical storage temperature | −20 °C, desiccated, protected from light | Once rehydrated, short-term holding at 2-8 °C |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity by UV absorbance; identity by ESI-MS or MALDI-TOF |
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.
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.
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.
The figures provided in this section on epidemiology all refer to undernutrition even if the term malnutrition is used which, by definition, could also apply to too much nutrition. The Global Hunger Index (GHI) is a multidimensional statistical tool used to describe the state of countries' hunger situation. The GHI measures progress and failures in the global fight against hunger. The GHI is updated once a year. The data from the 2015 report shows that Hunger levels have dropped 27% since 2000. Fifty two countries remain at serious or alarming levels. In addition to the latest statistics on Hunger and Food Security, the GHI also features different special topics each year. The 2015 report include an article on conflict and food security.
The further decline of Byzantine state-of-affairs paved the road to a third attack in 1185, when a large Norman army invaded Dyrrachium, owing to the betrayal of high Byzantine officials. Some time later, Dyrrachium—one of the most important naval bases of the Adriatic—fell again to Byzantine hands.
== Medical use of synthetic selenium compounds == The substance loosely called selenium sulfide (with the approximate formula SeS2) is the active ingredient in some anti-dandruff shampoos. The selenium compound kills the scalp fungus Malassezia, which causes shedding of dry skin fragments. The ingredient is also used in body lotions to treat Tinea versicolor due to infection by a different species of Malassezia fungus. Several clinical trials have assessed the use of selenium supplements in critically ill adults; however, the effectiveness and potential benefits of selenium supplementation in this context is not well understood.
Hypnotica was a class of somniferous drugs and substances tested in medicine of the 1890s and later. These include urethan, acetal, methylal, sulfonal, paraldehyde, amylenhydrate, hypnon, chloralurethan, ohloralamid, or chloralimid. Research about using medications to treat insomnia evolved throughout the last half of the 20th century. Treatment for insomnia in psychiatry dates back to 1869, when chloral hydrate was first used as a soporific. Barbiturates emerged as the first class of drugs in the early 1900s, after which chemical substitution allowed derivative compounds. Although they were the best drug family at the time (with less toxicity and fewer side effects), they were dangerous in overdose and tended to cause physical and psychological dependence. During the 1970s, quinazolinones and benzodiazepines were introduced as safer alternatives to replace barbiturates; by the late 1970s, benzodiazepines emerged as the safer drug. Benzodiazepines are not without their drawbacks; substance dependence is possible, and deaths from overdoses sometimes occur, especially in combination with alcohol or other depressants. Questions have been raised as to whether they disturb sleep architecture. Nonbenzodiazepines or Z-drugs like zolpidem were introduced in the 1980s and 1990s. Although it is clear that they are less toxic than barbiturates, their predecessors, comparative efficacy over benzodiazepines has not been established. Such efficacy is hard to determine without longitudinal studies.
Sources: en.wikipedia.org
Peptides and proteins are often described by the number of amino acids in their chain, e.g. a protein with 158 amino acids may be described as a "158 amino-acid-long protein". Peptides of specific shorter lengths are named using IUPAC numerical multiplier prefixes:
Feline cutaneous asthenia is a rare inheritable skin disease of cats characterised by abnormal elasticity, stretching, and improper healing of the skin. Pendulous wing-like folds of skin form on the cat's back, shoulders and haunches. Even stroking the cat can cause the skin to stretch and tear. A recessive autosomal (non-sex linked) form of feline cutaneous asthenia has been identified in Siamese cats and related breeds. In the homozygous state, it is apparently lethal. Feline cutaneous asthenia is similar to the Ehlers–Danlos syndrome of humans. Cats with cutaneous asthenia cannot be grasped by the scruff, as this may tear away. Cats may also have slipping joints, as in human Ehlers-Danlos syndrome. Dietary supplements may be needed to promote skin healing and regrowth.
== Personal life == While a model, Larter moved to Los Angeles to pursue acting. In 2002, she moved to New York City for three years. In an interview with Phillymag, she gave reason for the move: I took some time off to define myself outside the pressures of the industry. Part of me really needed to know if this is what I wanted to do with the rest of my life. In January 2005, she went back to living in Los Angeles for a role in Heroes. In December 2007, Larter and her longtime boyfriend, Hayes MacArthur were engaged. They had met on the set of National Lampoon's Homo Erectus. In a 2007 interview with Cosmopolitan, Larter said: "I told my boyfriend after three weeks that I wanted to marry him and that we could do it tomorrow." On August 1, 2009, Larter and MacArthur married at MacArthur's parents' estate in Kennebunkport, Maine. Among the wedding guests was Larter's close friend and fellow actress Amy Smart. Larter and MacArthur purchased a three-story home in the Hollywood Hills for $2.9 million in 2012. During the COVID-19 pandemic, they moved to Sun Valley, Idaho. On July 20, 2010, Larter announced that she and MacArthur were expecting their first child and on the September 10 episode of Late Night with Jimmy Fallon, announced that she was expecting a boy. Larter gave birth to their son in 2010. In August 2014, Larter confirmed that she and MacArthur were expecting their second child that winter and she had a girl in 2015. As of 2013, Larter had two dogs, Jackpot, a German Shepherd and Ella, a Wheaten terrier.
Sources: en.wikipedia.org
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.
The name is a commercial label rather than a systematic chemical designation, so different vendors and papers attach it to different sequences. Some treat it as a fragment and others as the whole protein. Comparing two reports therefore requires checking what each one actually analyzed.
Typically it reflects the relative area of the main peak in a reversed-phase chromatogram at a given wavelength. It does not confirm the amino acid sequence, the counter-ion, or the amount of peptide by mass. Identity is normally established by a separate mass measurement.
TB-500 is a trade-style label for a synthetic peptide connected to thymosin beta-4. It is sold mainly through research-chemical channels and is not a single chemically defined product across suppliers.