A practical reference on heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-31 and is reviewed periodically as new material appears.
Thymosin beta-4 is a naturally occurring protein of 43 amino acids found in most mammalian cells, where it binds actin monomers and influences filament dynamics. It was first isolated from thymus tissue in the early 1980s, and its actin-binding activity was later mapped to a short region near the N-terminus. The synthetic fragment sold as TB-500 was designed to reproduce that region rather than the full protein. Whether a short fragment reproduces the behavior of the intact molecule remains an open question, since the parent protein carries additional structural elements outside the binding region.
Published research on the intact protein is substantial, covering actin regulation, cell migration, and wound models. Research using the heptapeptide fragment specifically is far smaller, and much of the circulating material originates in supplier documentation rather than peer-reviewed reports. Where fragment studies do exist, they often employ different sequences, chain lengths, or terminal modifications, which complicates direct comparison across papers. Readers encountering claims about TB-500 should therefore separate evidence about thymosin beta-4 from evidence about the fragment itself.
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.
| Property | Value | Notes |
|---|---|---|
| Reported sequence | Ac-LKKTETQ | Described in most listings as the actin-binding region of thymosin beta-4 |
| Reported molecular weight | Approximately 889 Da | Value shifts with the stated sequence; compare against the certificate of analysis |
| Parent protein length | 43 amino acids | Thymosin beta-4; the fragment covers only a small part of it |
| Common synonyms | TB4 fragment; thymosin beta-4 fragment | Trade-style names rather than formal nomenclature |
| Formal monographs | Not established | Labeling conventions differ by supplier and region |
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.
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.
Reconstitution of a lyophilized peptide is normally done with sterile water or a suitable buffer under aseptic conditions. Adding solvent down the vial wall and allowing gentle dissolution instead of vigorous vortexing reduces the chance of aggregation, which can lower the effective concentration of the resulting solution. Concentrated stocks are usually diluted into working buffer shortly before use. Because no standard preparation protocol exists for TB-500 specifically, laboratories adapt general peptide handling practice, and reported results may reflect differing preparation choices.
Dry peptide powder is commonly kept at −20 °C in a desiccated container away from light, a practice that limits moisture uptake and oxidation. Once dissolved, solutions are generally held at 2–8 °C for short periods or frozen at −20 °C or lower for longer storage, with repeated freeze-thaw cycles avoided. Hydrolysis and oxidation are the main degradation routes for peptides in solution, and both accelerate at higher temperature or extreme pH. Published stability data specific to TB-500 are limited, so shelf life should be treated as uncertain.
== External links == Official website Indian Council of Historical Research - Sudhir Chandra - Economic and Political Weekly, Vol. 7, No. 28 (Jul. 8, 1972), pp. 1311-1313 Society Name Search at www.delhi.gov.in
According to the 2011 census, the literacy rate in Jammu and Kashmir was 67.17%, male literacy was 75%, while female literacy was at 56.43%. University of Kashmir located in Srinagar is the main university in the territory. Other universities include University of Jammu, Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir, Shri Mata Vaishno Devi University, Islamic University of Science & Technology, etc. Major institutions of higher education are NIT Srinagar, IIT Jammu, IIM Jammu, NIFT Srinagar and IHM Srinagar. Medical colleges include SKIMS, and the Government Medical College in Srinagar and All India Institute of Medical Sciences, Vijaypur, Jammu.
The extreme pressure of 2,500 m of water (approximately 25 megapascals or 250 atmospheres) is thought to play a role in stabilizing iron sulfide for biological purposes. This armor plating probably serves as a defense against the venomous radula (teeth) of predatory snails in that community. In March 2017, researchers reported evidence of possibly the oldest forms of life on Earth. Putative fossilized microorganisms were discovered in hydrothermal vent precipitates in the Nuvvuagittuq Belt of Quebec, Canada, that may have lived as early as 4.280 billion years ago, not long after the oceans formed 4.4 billion years ago, and not long after the formation of the Earth 4.54 billion years ago.
Sources: en.wikipedia.org
=== Progression free survival === The Progression Free Survival is usually used in analysing the results of the treatment for the advanced disease. The event for the progression free survival is that the disease gets worse or progresses, or the patient dies from any cause. Time to Progression is a similar endpoint that ignores patients who die before the disease progresses.
=== Signal transduction === GHRH binding to GHRHR results in increased GH production mainly by the cAMP-dependent pathway, but also by the phospholipase C pathway (IP3/DAG pathway), and other minor pathways. The cAMP-dependent pathway is initiated by the binding of GHRH to its receptor, causing receptor conformation that activates Gs alpha subunit of the closely associated G-Protein complex on the intracellular side. This results in stimulation of membrane-bound adenylyl cyclase and increased intracellular cyclic adenosine monophosphate (cAMP). cAMP binds to and activates the regulatory subunits of protein kinase A (PKA), allowing the free catalytic subunits to translocate to the nucleus and phosphorylate the transcription factor cAMP response element-binding protein (CREB). Phosphorylated CREB, together with its coactivators, p300 and CREB-binding protein (CBP) enhances the transcription of GH by binding to CREs cAMP-response elements in the promoter region of the GH gene. It also increases transcription of the GHRHR gene, providing positive feedback. In the phospholipase C pathway, GHRH stimulates phospholipase C (PLC) through the βγ-complex of heterotrimeric G-proteins. PLC activation produces both diacylglycerol (DAG) and inositol triphosphate (IP3), the latter leading to release of intracellular Ca2+ from the endoplasmic reticulum, increasing cytosolic Ca2+ concentration, resulting in vesicle fusion and release of secretory vesicles containing premade growth hormone.
== History == Tacrolimus was discovered in 1987 by a Japanese team led by pharmacologist Tohru Kino; it was among the first macrolide immunosuppressants discovered, preceded by the discovery of rapamycin (sirolimus) on Rapa Nui (Easter Island) in 1975. It is produced by a soil bacterium, Streptomyces tsukubensis. The name tacrolimus is derived from "Tsukuba macrolide immunosuppressant". The early development (investigational new drug phase) of tacrolimus, called at the time by the development code FK-506, happened in the next several years. A firsthand account of that process is given in Thomas Starzl's 1992 memoir. Tacrolimus was first approved by the US Food and Drug Administration (FDA) in 1994, for use in liver transplantation; the indications were extended to include kidney transplants. The first generic version of tacrolimus (capsule for oral route) was approved in the US in 2009. A generic version of tacrolimus for injection was approved in the US in 2017. Tacrolimus was approved for medical use in the European Union in 2002, for the treatment of moderate to severe atopic dermatitis. In 2007, the indications were expanded to include the prophylaxis of transplant rejection in adult kidney or liver allograft recipients and the treatment of allograft rejection resistant to treatment with other immunosuppressive medicinal products in adults.
Sources: en.wikipedia.org
Most listings describe it as a short acetylated peptide with the sequence Ac-LKKTETQ, presented as a region of thymosin beta-4. The label is a trade-style name rather than a standardized chemical name, so the exact content of a given vial depends on the supplier.
No. Thymosin beta-4 is a protein of 43 amino acids, while TB-500 is described as a short fragment of it. The two differ in size, structure, and the range of interactions each can support.
Naming for research peptides is not centrally coordinated, so vendors set their own labels and specifications. Differences in stated sequence, molecular weight, or purity documentation usually trace back to those independent labeling choices.
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.