prohibited list 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.
Last reviewed on 2026-06-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized cake or fluffy solid |
| Water solubility | High | Dissolves in water and neutral buffers |
| Dry storage | -20 °C or below | Dry, dark, desiccated |
| Reconstituted storage | Frozen, single thaw | Repeated freeze-thaw promotes loss |
| Purity method | Reverse-phase HPLC | Peak area read at 214 or 220 nm |
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.
TB-500 is a synthetic peptide preparation marketed under a name derived from thymosin beta-4, a 43-residue actin-binding protein first isolated from thymus tissue. The full-length protein has a reported molecular mass near 4963 Da, while material sold as TB-500 is often described as a fragment containing the actin-binding motif LKKTETQ. Because suppliers use the name inconsistently, published sources sometimes refer to the same label as a fragment, a synthetic copy, or a related analog. This naming ambiguity complicates direct comparison of reports across studies.
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.
Lignans and lignin differ in their molecular weight, the former being small and soluble in water, the latter being high polymers that are undigestable. Both are polyphenolic substances derived by oxidative coupling of monolignols. Thus, most lignans feature a C18 cores, resulting from the dimerization of C9 precursors. The coupling of the lignols occurs at C8. Eight classes of lignans are: "furofuran, furan, dibenzylbutane, dibenzylbutyrolactone, aryltetralin, arylnaphthalene, dibenzocyclooctadiene, and dibenzylbutyrolactol." Many lignans are metabolized by mammalian gut microflora, producing so-called enterolignans.
SSRIs prevent 5-HT from binding to SERT which prevents absorption of 5-HT back into the presynapse terminal, where it is metabolized by monoamine oxidase or stored in secretory vesicles. As a result, the 5-HT concentration increases at the somatodendritic area of the 5-HT neuron but not so much at the axon terminal area (demonstrated in figure 2). This increase in 5-HT concentration causes desensitization of somatodendritic 5-HT1A autoreceptors. When these 5-HT1A autoreceptors have been downregulated, they will no longer restrict the impulse flow of the 5-HT neuron. The impulse flow is turned on and as a result 5-HT is released at the axon terminal. However, this increase of 5-HT does not happen quickly compared to the increase of 5-HT at the somatodendritic area of the 5-HT neuron. This delay is caused by the time it takes 5-HT to downregulate 5-HT1A autoreceptors and turn on the neuro impulse flow of the 5-HT neuron. This delay can explain the reason why antidepressants do not have effect on depression immediately. This can also be the reason why the antidepressant mechanisms can be connected to the increasing neuro impulse flow from 5-HT neurons, where as the concentration of 5-HT increases at the axon terminal before SSRIs start to work properly. When SSRIs have (1) inhibited the re-uptake pump, (2) increased somatodendritic 5-HT, (3) desensitized somatodendritic 5-HT1A autoreceptors, (4) turned on the impulse flow and (5) increased the release of 5-HT from axon terminal, the last step might be desensitization of postsynaptic 5-HT receptors.
== Chemistry == 1,2-Diarylethylamines contain the substructure ArCH2CH(Ar')NRR', where Ar, Ar' = aryl and R, R' = H or organyl. A chiral center exists at the ethylamine carbon atom bearing the two aryl groups. The enantiomers often have a large difference in pharmacological activity. For example, (+)-(S)-diphenidine has 40 times higher affinity than (−)-(R)-form for the NMDA receptor. According to a review by Jason Wallach and Simon Brandt (2018), most psychoactive 1,2-diarylethylamines reported in the scientific literature contain non-heteroaromatic aryl groups (i.e., both rings are carbocyclic). Some exceptions include lanicemine and an analogue N-ethyl-lanicemine, which feature a heteroaromatic pyridyl ring. Additional heteroaromatic analogues have been disclosed in the patent literature.
Sources: en.wikipedia.org
== External links == AGSD. - Association for Glycogen Storage Disease. A US-based non-profit, parent and patient oriented support group dedicated to promoting the best interest of all the different types of glycogen storage disease. AGSD-UK - Association for Glycogen Storage Disease (UK). A UK-based charity which helps individuals and families affected by Glycogen Storage Disease by putting people in contact, providing information and support, publishing a magazine and holding conferences, workshops, courses and family events. IamGSD - International Association for Muscle Glycogen Storage Disease. A non-profit, patient-led international group encouraging efforts by research and medical professionals, national support groups and individual patients worldwide. IPA - International Pompe Association. (Pompe Disease is also known as GSD-II). A non-profit, federation of Pompe disease patient's groups world-wide. It seeks to coordinate activities and share experience and knowledge between different groups. EUROMAC - EUROMAC is a European registry of patients affected by McArdle Disease and other rare neuromuscular glycogenoses. CoRDS - Coordination of Rare Diseases at Sanford (CoRDS) is a centralized international patient registry for all rare diseases. They work with patient advocacy groups, including IamGSD, individuals and researchers. CORD - Canadian Organization for Rare Disorders (CORD) is a Canadian national network for organizations representing all those with rare disorders.
=== Scientific === Radon emanation from the soil varies with soil type and with surface uranium content, so outdoor radon concentrations can be used to track air masses to a limited degree. Because of radon's rapid loss to air and comparatively rapid decay, radon is used in hydrologic research that studies the interaction between groundwater and streams. Any significant concentration of radon in a river may be an indicator that there are local inputs of groundwater. Radon soil concentration has been used to map buried close-subsurface geological faults because concentrations are generally higher over the faults. Similarly, it has found some limited use in prospecting for geothermal gradients. Some researchers have investigated changes in groundwater radon concentrations for earthquake prediction. Increases in radon were noted before the 1966 Tashkent and 1994 Mindoro earthquakes. Radon has a half-life of approximately 3.8 days, which means that it can be found only shortly after it has been produced in the radioactive decay chain. For this reason, it has been hypothesized that increases in radon concentration is due to the generation of new cracks underground, which would allow increased groundwater circulation, flushing out radon. The generation of new cracks might not unreasonably be assumed to precede major earthquakes. In the 1970s and 1980s, scientific measurements of radon emissions near faults found that earthquakes often occurred with no radon signal, and radon was often detected with no earthquake to follow.
Granulocyte colony-stimulating factor (G-CSF or GCSF), also known as colony-stimulating factor 3 (CSF 3), is a glycoprotein that stimulates the bone marrow to produce granulocytes and stem cells and release them into the bloodstream. Functionally, it is a cytokine and hormone, a type of colony-stimulating factor, and is produced by a number of different tissues. The pharmaceutical analogs of naturally occurring G-CSF are called filgrastim and lenograstim. G-CSF also stimulates the survival, proliferation, differentiation, and function of neutrophil precursors and mature neutrophils.
=== Built under license === Focke-Wulf C.19 – license-built (autogyro)– licence-built version of the Cierva C.19, with Siemens Sh 14 engine. (one prototype, converted from Cierva C.19 Mk.IV) Focke-Wulf C.30 Heuschrecke (Grasshopper) – licence-built version of the Cierva C.30, with Siemens Sh 14 engine. Focke-Wulf FWP.149D – license-built Piaggio P.149
Sources: en.wikipedia.org
== Honors and awards == Pauling received numerous honorary degrees (around 47 by his death), starting with his alma mater in 1933, and including prestigious institutions like Cambridge University, Oxford University, Princeton University, Reed College, and Yale University. Awards and honors received during his career include the following:
=== Depression and bipolar depression === Candesartan is currently being investigated as a potential adjunct therapy for both depression and bipolar depression in the CADET (Candesartan Adjunctive Trials) clinical trials. These studies—one for major depressive disorder and one for bipolar depression—are double-blind, placebo-controlled clinical trials. The proposed mechanism of action is via antagonism of the AT-1 receptor, which a 2017 meta-analysis indicated may have effects on mental health. As Candesartan is a strong AT-1 receptor antagonist, it was selected for the clinical trial.
Thermodynamic stability of proteins represents the free energy difference between the folded and unfolded protein states. This free energy difference is very sensitive to temperature, hence a change in temperature may result in unfolding or denaturation. Protein denaturation may result in loss of function, and loss of native state. The free energy of stabilization of soluble globular proteins typically does not exceed 50 kJ/mol. Taking into consideration the large number of hydrogen bonds that take place for the stabilization of secondary structures, and the stabilization of the inner core through hydrophobic interactions, the free energy of stabilization emerges as small difference between large numbers.
Sources: en.wikipedia.org
Short transit at ambient temperature is generally tolerated, but long-term storage at room temperature is not recommended. Heat, moisture, and light all accelerate degradation. Cold, dry, dark storage is the conventional choice.
Suppliers typically quote a percentage derived from reverse-phase HPLC peak area. That figure reflects the relative amount of the main peak and does not by itself confirm identity or exclude related impurities. Mass spectrometry is commonly paired with it for confirmation.
Peptides purified by reverse-phase chromatography often carry trifluoroacetate as a counter-ion, which adds mass and can affect solubility and apparent behavior in assays. Acetate and hydrochloride forms are also offered. Knowing which form is present matters when calculating how much peptide a given weight contains.
TB-500 is a name used for a short synthetic peptide fragment taken from the actin-binding region of thymosin beta-4. Material sold under this label is usually a lyophilized powder supplied for laboratory research rather than a licensed medicine. The commonly cited sequence is LKKTETQ.