Thymosin fraction 5 is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-07-18. Numbers and descriptions here follow the published literature rather than marketing material.
Lyophilized material is typically treated as a hygroscopic solid that should be brought to room temperature before the container is opened, which limits condensation on the powder. Reconstitution is commonly done with sterile water or a buffered diluent, and gentle mixing is preferred over vigorous agitation to reduce foaming and surface adsorption. Because peptides can bind to plastic and glass, diluents containing a small amount of carrier protein are sometimes used in laboratory work. Working solutions are generally aliquoted and prepared fresh rather than subjected to repeated freezing and thawing.
Stability depends on temperature, pH, and the number of freeze-thaw events the sample has experienced. Freeze-dried material is commonly held at -20 °C or colder, while reconstituted liquid is kept cold and used within a short window. Extreme pH and prolonged light exposure can promote deamidation, oxidation, or aggregation, particularly at asparagine and methionine positions. Adsorption to container walls can lower the measured concentration of a dilute solution even when the peptide molecules themselves remain intact.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or chemically modified byproducts. Mass spectrometry confirms the expected molecular mass and can indicate acetylation state or sequence errors. Amino acid analysis and peptide mapping supply complementary sequence-level information, while endotoxin testing is relevant for preparations intended for cell or animal work. Purity figures reported by suppliers refer to the method used and are not directly comparable across laboratories unless conditions are stated.
The peptide was identified during work in the 1970s on thymosin fraction 5, a partially purified extract of calf thymus. Investigators separated that mixture and characterized individual components, one of which they named thymosin alpha-1. The same compound later received the international nonproprietary name thymalfasin. Commercial material is produced by solid-phase peptide synthesis rather than by extraction, so synthetic and natural forms share an identical sequence. Naming conventions vary across the literature, and readers should distinguish the alpha-1 peptide from other thymosins that have unrelated sequences and functions.
Thymosin beta-4 is a separate 43-residue peptide that binds actin and participates in cell migration; it shares no sequence similarity with thymosin alpha-1 despite the common family name. Other preparative materials, such as thymosin fraction 5 and thymopoietin, contain distinct mixtures or peptides. The shared thymosin label reflects the tissue of origin used in early purification, not a common structural core. Treating these molecules as interchangeable is a frequent source of confusion in laboratory reports and in popular summaries alike.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Visual description varies by batch |
| Solubility | Freely soluble in water | Aqueous buffers are commonly used |
| Typical storage temperature | -20 °C or below for powder | Reconstituted liquid kept at 2-8 °C short term |
| Purity method | Reversed-phase HPLC | Value derived from peak area integration |
| Identity method | Mass spectrometry | Confirms mass and sequence integrity |
The peptide was described in the 1970s as a component of thymic extracts, and early research focused on restoring immune function in immunodeficiency states. A synthetic version entered clinical development in the 1980s and is approved as a drug in several countries for conditions such as chronic hepatitis B and certain immunodeficiencies. Approval status varies widely by jurisdiction, and in the United States it is not an approved therapeutic. Regulatory and clinical positions differ, so statements about efficacy should be tied to specific indications and studies.
Thymosin alpha-1 is a synthetic peptide of 28 amino acids, corresponding to the N-terminal fragment of prothymosin alpha. Its sequence begins with acetylation at the N-terminus, a modification that affects stability and receptor interaction. The peptide is acidic, with a calculated isoelectric point near 4.2, and carries no disulfide bonds, so its secondary structure is largely flexible in solution. Molecular mass is approximately 3108 daltons. The native form was first isolated from bovine thymus tissue, while pharmaceutical material is produced by solid-phase peptide synthesis.
Within the immune system, the peptide acts on several cell types rather than a single target. Reported activities include promotion of T-cell maturation, enhancement of natural killer cell activity, and modulation of cytokine production by dendritic cells and macrophages. Some of these effects appear to operate through toll-like receptor signaling, though the precise receptor-level mechanism remains debated. Whether the observed immune changes translate into clinical benefit is a separate question and depends on the indication studied.
Whether the free 28-residue peptide circulates in human tissue remains debated. The best-documented human source is prothymosin alpha, a larger acidic protein that carries the sequence at its N-terminus. Reports of measurable peptide levels in serum and lymphoid tissue exist, yet some of that signal may come from cross-reacting fragments or from the parent protein. Most reviews therefore treat prothymosin alpha as the established human molecule and describe independent circulation of the small peptide as an unresolved question.
Immunological studies connect the peptide to multiple parts of the immune response. It has been reported to engage Toll-like receptor signaling, to promote dendritic cell maturation, and to influence the balance of T helper cell subsets. Changes in natural killer cell activity and in cytokine release appear in cell culture and animal models. These observations describe broad immunomodulatory behavior rather than a single defined receptor target, and the primary molecular interaction has not been settled.
市售的胸腺素α1通常以冻干粉形式提供，溶解后用于注射。其氨基酸组成包括多个酸性残基，因此在中性pH下带负电荷。该肽可溶于水和生理盐水，但在有机溶剂中溶解度有限。储存条件通常为冻干状态下负20摄氏度，溶解后需冷藏并避免反复冻融。常见的同义词包括胸腺肽α1、thymalfasin和Tα1。
胸腺素α1（thymosin alpha 1，Tα1）是一种由28个氨基酸组成的酸性肽，N端被乙酰化，分子量约为3108道尔顿。该肽最早从牛胸腺组织提取物中分离，属于胸腺素组分5的一个成分。其序列在不同哺乳动物中高度保守，提示其具有基本的生物学功能。名称中的“α1”指其在电泳中的迁移位置，并非表示亚型编号。它既存在于胸腺，也存在于脾脏和淋巴结等免疫组织。
== Therapeutic drug monitoring == Plasma level monitoring of vancomycin is necessary due to the drug's biexponential distribution, intermediate hydrophilicity, and potential for ototoxicity and nephrotoxicity, especially in populations with poor renal function and/or increased propensity to bacterial infection. Vancomycin activity is considered time-dependent; that is, antimicrobial activity depends on how long the serum drug concentration exceeds the minimum inhibitory concentration of the target organism. Thus, peak serum levels have not been shown to correlate with efficacy or toxicity; indeed, concentration monitoring is unnecessary in most cases. Circumstances in which therapeutic drug monitoring is warranted include patients receiving concomitant aminoglycoside therapy, patients with (potentially) altered pharmacokinetic parameters, patients on haemodialysis, patients administered high-dose or prolonged treatment, and patients with impaired renal function. In such cases, trough concentrations are measured. Therapeutic drug monitoring is also used for dose optimization of vancomycin in treating children. Target ranges for serum vancomycin concentrations have changed over the years. Early authors suggested peak levels of 30 to 40 mg/L and trough levels of 5 to 10 mg/L, but current recommendations are that peak levels need not be measured and that trough levels of 10 to 15 mg/L or 15 to 20 mg/L, depending on the nature of the infection and the specific patient's needs, may be appropriate.
Hybrids are offspring resulting from the breeding of two genetically distinct individuals, which usually will result in a high degree of heterozygosity, though hybrid and heterozygous are not synonymous. The deliberate or accidental hybridizing of two or more species of closely related animals through captive breeding is a human activity which has been in existence for millennia and has grown for economic purposes. Hybrids between different subspecies within a species (such as between the Bengal tiger and Siberian tiger) are known as intra-specific hybrids. Hybrids between different species within the same genus (such as between lions and tigers) are known as interspecific hybrids or crosses. Hybrids between different genera (such as between sheep and goats) are known as intergeneric hybrids. Natural hybrids will occur in hybrid zones, where two populations of species within the same genera or species living in the same or adjacent areas will interbreed with each other. Some hybrids have been recognized as species, such as the red wolf (though this is controversial). Artificial selection, the deliberate selective breeding of domestic animals, is being used to breed back recently extinct animals in an attempt to achieve an animal breed with a phenotype that resembles that extinct wildtype ancestor. A breeding-back (intraspecific) hybrid may be very similar to the extinct wildtype in appearance, ecological niche and to some extent genetics, but the initial gene pool of that wild type is lost forever with its extinction.
Post-SSRI sexual dysfunction (PSSD) is an iatrogenic condition in which sexual side effects persist after discontinuation of serotonin reuptake inhibiting antidepressants, including venlafaxine. Characteristic symptoms include genital numbness, pleasureless or weak orgasm, loss of libido, and erectile dysfunction; non-sexual symptoms such as emotional blunting and cognitive impairment may also occur. The condition can arise after even brief exposure to a serotonin reuptake inhibitor and may persist indefinitely; there is currently no established treatment. A case study published in 2023 specifically documented PSSD symptoms—including low libido, delayed ejaculation, and erectile dysfunction—developing after discontinuation of venlafaxine, with 5-HT1A receptor downregulation proposed as a possible mechanism. A 2023 retrospective cohort study of over 12,000 males estimated the risk of irreversible sexual dysfunction (as measured by persistent need for phosphodiesterase inhibitors after antidepressant cessation) at approximately 0.46% of patients treated with serotonergic antidepressants, including SNRIs. The DSM-5 noted in 2013 that serotonin reuptake inhibitor–induced sexual dysfunction may persist after the agent is discontinued. In 2019, the European Medicines Agency's Pharmacovigilance Risk Assessment Committee recommended that product labels for all SSRIs and SNRIs, including venlafaxine, be updated to warn that sexual dysfunction may be long-lasting after treatment is stopped.
== Further reading == Scanga R, Scalise M, Marino N, Parisi F, Barca D, Galluccio M, et al. (October 2023). "LAT1 (SLC7A5) catalyzes copper(histidinate) transport switching from antiport to uniport mechanism". iScience. 26 (10) 107738. Bibcode:2023iSci...26j7738S. doi:10.1016/j.isci.2023.107738. PMC 10492218. PMID 37692288.
Sources: en.wikipedia.org
==== Sub-gingival margins ==== A gingivectomy can also be done to increase the clinical crown height of teeth. This is suitable in treatment planning for teeth with inadequate tissue for retention of prosthetic restorations as a result of subgingival carious lesions or coronal fractures. Surgical treatment resets the margin while maintaining the biological width and clinical attachment.
Any purchase using a reusable cup was to award three entries. On March 7, 2020, due to the COVID-19 pandemic, Tim Hortons announced that it had cancelled the distribution of physical cups for the promotion due to concerns that the virus could be spread by returned cups, and that the promotion would be conducted solely via the app. The chain had also joined others in temporarily prohibiting the use of reusable cups for similar reasons. The changes from 2020 remained in use through 2024, with the promotion therefore being renamed to "Roll Up to Win". In addition, Tim Hortons announced that every electronic entry would be guaranteed to win Tims Rewards points at a minimum. In February 2025, Tim Hortons announced that physical cups would return to the promotion alongside digital entries for a limited time.
With the widespread interest in birds, use of a large number of people to work on collaborative ornithological projects that cover large geographic scales has been possible. These citizen science projects include nationwide projects such as the Christmas Bird Count, Backyard Bird Count, the North American Breeding Bird Survey, the Canadian EPOQ or regional projects such as the Asian Waterfowl Census and Spring Alive in Europe. These projects help to identify distributions of birds, their population densities and changes over time, arrival and departure dates of migration, breeding seasonality, and even population genetics. The results of many of these projects are published as bird atlases. Studies of migration using bird ringing or colour marking often involve the cooperation of people and organizations in different countries.
=== EC 2.7.11: Protein-serine/threonine kinases === EC 2.7.11.1: non-specific serine/threonine protein kinase EC 2.7.11.2: [pyruvate dehydrogenase (acetyl-transferring)] kinase EC 2.7.11.3: dephospho-(reductase kinase) kinase EC 2.7.11.4: (3-methyl-2-oxobutanoate dehydrogenase (acetyl-transferring)) kinase EC 2.7.11.5: [isocitrate dehydrogenase (NADP+)] kinase EC 2.7.11.6: [tyrosine 3-monooxygenase] kinase EC 2.7.11.7: myosin-heavy-chain kinase EC 2.7.11.8: Fas-activated serine/threonine kinase EC 2.7.11.9: Goodpasture-antigen-binding protein kinase EC 2.7.11.10: IkB kinase EC 2.7.11.11: cAMP-dependent protein kinase EC 2.7.11.12: cGMP-dependent protein kinase EC 2.7.11.13: protein kinase C EC 2.7.11.14: rhodopsin kinase EC 2.7.11.15: β-adrenergic-receptor kinase EC 2.7.11.16: G-protein-coupled receptor kinase EC 2.7.11.17: Ca2+/calmodulin-dependent protein kinase EC 2.7.11.18: myosin-light-chain kinase EC 2.7.11.19: phosphorylase kinase EC 2.7.11.20: elongation factor 2 kinase EC 2.7.11.21: polo kinase EC 2.7.11.22: cyclin-dependent kinase EC 2.7.11.23: [RNA-polymerase]-subunit kinase EC 2.7.11.24: mitogen-activated protein kinase EC 2.7.11.25: mitogen-activated protein kinase kinase kinase EC 2.7.11.26: tau-protein kinase EC 2.7.11.27: [acetyl-CoA carboxylase] kinase EC 2.7.11.28: tropomyosin kinase EC 2.7.11.29: low-density-lipoprotein receptor kinase EC 2.7.11.30: receptor protein serine/threonine kinase EC 2.7.11.31: [hydroxymethylglutaryl-CoA reductase (NADPH)] kinase EC 2.7.11.32: [pyruvate, phosphate dikinase] kinase EC 2.7.11.33: [pyruvate, water dikinase] kinase
== See also == NMR spectroscopy Nuclear magnetic resonance Nuclear magnetic resonance spectroscopy of carbohydrates Nuclear magnetic resonance spectroscopy of nucleic acids Protein crystallization Protein dynamics Relaxation (NMR) X-ray crystallography
Sources: en.wikipedia.org
=== Potential technology === A new family of LEDs are based on the semiconductors called perovskites. In 2018, less than four years after their discovery, the ability of perovskite LEDs (PLEDs) to produce light from electrons already rivaled those of the best performing OLEDs. They have a potential for cost-effectiveness as they can be processed from solution, a low-cost and low-tech method, which might allow perovskite-based devices that have large areas to be made with extremely low cost. Their efficiency is superior by eliminating non-radiative losses, in other words, elimination of recombination pathways that do not produce photons; or by solving outcoupling problem (prevalent for thin-film LEDs) or balancing charge carrier injection to increase the EQE (external quantum efficiency). The most up-to-date PLED devices have broken the performance barrier by shooting the EQE above 20%. In 2018, Cao et al. and Lin et al. independently published two papers on developing perovskite LEDs with EQE greater than 20%, which made these two papers a mile-stone in PLED development. Their device have similar planar structure, i.e. the active layer (perovskite) is sandwiched between two electrodes. To achieve a high EQE, they not only reduced non-radiative recombination, but also utilized their own, subtly different methods to improve the EQE. In the work of Cao et al., researchers targeted the outcoupling problem, which is that the optical physics of thin-film LEDs causes the majority of light generated by the semiconductor to be trapped in the device.
Kevin Billings, Honorary Group Captain, 601 (County of London) Squadron, Royal Auxiliary Air Force. For services to the Royal Air Force in the United States of America and the UK. Paul Britton, Chair, Tate Americas Foundation. For services to the arts and to philanthropy. Kevin Burke, Arts Philanthropist and Board Member, BAFTA Hong Kong Advisory Board. For services to charity and to philanthropy. Philip Hugh Davies, Principal, Philip Davies (Heritage and Planning) Ltd. For services to UK and Commonwealth Heritage. Luke Dearden, lately Political Counsellor, UK Delegation to NATO, Brussels, Belgium. For services to British Foreign and Security Policy. Duncan Edwards, Chief Executive Officer, BritishAmerican Business, and Honorary Director, The St. George's Society, New York, United States of America. For services to UK/US Trade relations and to charity. Lieutenant Colonel (Rtd) Michael Edwards, lately Senior Reports Officer, Ceasefire and Transitional Security Arrangements Monitoring and Verification Mechanism, Juba, South Sudan. For services to peace in South Sudan. Brian Hancock, Surgeon, Wythenshaw Hospital; Founding Member and Trustee, Uganda Childbirth Injury Fund. For services to surgery in Sub-Saharan Africa. Susan Hannam, Vice President, CUDECA Hospice Foundation, Spain. For services to palliative care and volunteering services in Spain. Laura Hickey, lately Director Multilateral and Human Rights, Foreign, Commonwealth and Development Office. For services to crisis management and British Foreign Policy.
The different m/z separation elements of a hybrid mass spectrometer can be represented by a shorthand notation. The symbol Q represents a quadrupole mass analyzer, q is a radio frequency collision quadrupole, TOF is a time-of-flight mass spectrometer, B is a magnetic sector and E is an electric sector.
On 27 May 2021, Danish epidemiologist Tina Fischer spoke on the This Week in Virology podcast, advocating for a second phase of the study to audit blood samples for COVID-19 antibodies in China. WHO-convened study team member Marion Koopmans, on that same broadcast, advocated for WHO member states to make a decision on the second phase of the study, though she also cautioned that an investigatory audit of the laboratory itself may be inconclusive. In early July 2021, WHO emergency chief Michael Ryan said the final details of phase 2 were being worked out in negotiations between WHO and its member states, as the WHO works "by persuasion" and cannot compel any member state (including China) to cooperate. In July 2021 China rejected WHO requests for greater transparency, cooperation, and access to data as part of Phase 2. On 16 July 2021, Foreign Ministry spokesperson Zhao Lijian declared that China's position was that future investigations should be conducted elsewhere and should focus on cold chain transmission and the US military's labs. On 22 July 2021, the Chinese government held a press conference in which Zeng Yixin, Vice Health Minister of the National Health Commission (NHC), said that China would not participate in a second phase of the WHO's investigation, denouncing it as "shocking" and "arrogant". He elaborated "In some aspects, the WHO's plan for next phase of investigation of the coronavirus origin doesn't respect common sense, and it's against science.
Sources: en.wikipedia.org
Cold storage slows the chemical degradation reactions that occur in solution. Lyophilized powder is more stable than reconstituted liquid and tolerates longer storage periods. Repeated temperature cycling should still be avoided because it can drive aggregation and loss of material.
Mass spectrometry is the standard confirmation of molecular mass and acetylation state. Chromatography establishes purity but does not identify the molecule on its own. The two techniques are normally applied together during verification.
No, because the reported value reflects the detection method and wavelength used, which vary between laboratories. A number stated without method details cannot be compared directly with another supplier's figure. Requesting the chromatogram and the method conditions is a common way to interpret it.
It is a 28-residue synthetic peptide studied as an immune-modulating agent and approved as a drug in some countries. The sequence matches a naturally occurring fragment isolated from thymus tissue. It is not a hormone in the endocrine sense.