Everything below concerns prohibited list. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-02-16. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Purity is normally assessed by reversed-phase HPLC, with the main peak reported as a percentage of total peak area, while identity is confirmed by mass spectrometry. Electrospray and MALDI-TOF instruments are both used, and the observed mass is compared with the value calculated from the stated sequence. Ion-exchange or size-exclusion methods appear where aggregation or charge variants are of interest. Water content, counter-ion content and residual trifluoroacetate from purification are separate variables that can shift the measured mass and should be weighed when reading a certificate of analysis.
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 |
|---|---|---|
| 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 |
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 heptapeptide with the sequence Ac-LKKTETQ. It corresponds to a short N-terminal region of thymosin beta-4, a 43-amino-acid protein found in many cell types. The fragment contains an actin-binding motif, which is one reason it appears in laboratory studies of cell migration and cytoskeletal dynamics. TB-500 is not the full-length protein and is produced as a research chemical rather than an approved therapeutic agent. Its molecular weight is approximately 889 Da.
Several names appear in scientific and commercial contexts for this peptide. The label TB-500 is informal and does not follow standard biochemical nomenclature. Research articles more often describe the compound as a thymosin beta-4 fragment, Tβ4 fragment, or by its sequence Ac-LKKTETQ. Confusing TB-500 with full-length thymosin beta-4 can lead to incorrect assumptions about activity because the fragment lacks the remaining residues of the parent protein. The relationship between fragment and parent protein remains an active area of study.
parvum seine Aktivität und geht in ein Ruhestadium („Zyste“, englisch “cyst”, dormant/resting stage) über (im modernen Sprachgebrauch bezeichnet bei Mikroorganismen der Begriff Zyste eine Dauerform ohne Stoffwechsel, insbesondere auch ohne Photosynthese; andernfalls liegt lediglich ein unbegeißeltes, nicht-motiles Stadium vor – was im früheren Sprachgebrauch nicht unterschieden wurde). In der neueren Literatur ist beispielsweise die Rede von „stationären Wachstums-/Todphasen“ (englisch stationary growth/death phases). Auf die produzierten Toxine (Prymnesine) wird weiter unten noch gesondert eingegangen.
== Vorkommen und Algenblüten == P. parvum wächst in einem Salzgehalt (Salinität) im Bereich von 0,5–30 psu (Practical Salinity Unit) mit einem Optimum bei 15 psu. Allerdings scheinen Stämme, die an verschiedenen Orten gesammelt wurden, unterschiedliche Salzgehaltstoleranzen zu haben. Ein Stamm namens LB 2797 (isoliert aus dem Colorado River in Texas) zeigt ein biphasisches Wachstumsmuster, d. h., die maximalen Zelldichten nahmen mit steigendem Salzgehalt von 5 bis 15 psu zu, nahmen aber bei höheren Werten in der Laborkultur wieder ab. Während Blüten von P. parvum in der östlichen Hemisphäre bereits seit den frühen 1900er Jahren dokumentiert sind, hat sich die Art seitdem weit verbreitet. Es wurden Blüten überall im Süden der USA sowie in einigen nördlichen Regionen beobachtet. Diese in Flussmündungen sehr häufige Art lebt normalerweise nur im Brackwasser, wird aber zunehmend auch im Süßwasser gefunden, darunter in den Vereinigten Staaten (z. B. in Texas seit 1985), im Lunzer See (Niederösterreich 2016) und in der Oder und angrenzenden Gewässern (Deutschland und Polen 2022/2024, s. u.). Dies gilt als besorgniserregend, insbesondere bei Fischern, die in bestimmten Seen und Flüssen bereits Fischsterben beobachtet haben. Sie kommt in der Natur in hellen, offenen Umgebungen vor, aber im Labor kann ihr Wachstum durch zu viel Licht gehemmt werden (Photoinhibition). Algenblüten treten in der Regel vom Spätwinter bis zum Sommer auf. Sie führen dazu, dass sich das Wasser grün bis gelblich verfärbt und sich Schaum bildet, wenn das Wasser aufgewühlt wird (an Wehren, Dämmen, Ufern).
Die Algenblüten bilden sich besonders leicht im Brackwasserbereich, so dass die von P. parvum gebildeten Toxine dort leichter kritische Konzentrationen erreichen können. Im letzten Jahrhundert haben zunehmend saisonale Fischsterben in Verbindung mit den toxischen Algenblüten von P. parvum weltweit Aquakulturen und einheimische Fisch-, Schalentier- und Molluskenpopulationen zerstört. Langanhaltende Blüten von P. parvum können zu großen Störungen der lokalen Ökologie und hohen finanziellen Verlusten führen.
=== Fischsterben in Florida in den 2000er Jahren === In Florida wurde in den 2000er Jahren auch beobachtet, dass Fische durch Blüten dieser Alge in Hinterhof- und Golfplatzteichen, oft in Küstenregionen, getötet wurden.
Sources: de.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.
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.