This is a working overview of Thymosin fraction 5, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-12. Anything still debated is marked as such rather than presented as settled.
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。
20世纪70年代，研究者从胸腺提取物中纯化出多种小肽，Tα1是其中被较早表征的一种。最初的制备依赖组织匀浆和层析步骤，产量低且成分复杂。随着固相肽合成技术成熟，实验室和工业界能够生产与天然序列一致的合成版本。合成肽的纯度可达95%以上，并可通过反相高效液相色谱和质谱进行鉴定。这一转变使研究不再依赖动物胸腺来源。
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。
Thymosin alpha 1 is a 28-amino-acid peptide first isolated from thymosin fraction 5, a bovine thymic extract. Its sequence begins with an acetylated serine residue and carries a high proportion of acidic residues, so the molecule has a net negative charge near neutral pH. Despite the shared name, it is unrelated in sequence to the thymosin beta family. Synthetic material prepared by solid-phase peptide synthesis is identical in sequence to the natural peptide.
Several names appear in the literature for this peptide, including thymalfasin and the abbreviation T-alpha-1. Naming conventions differ among research articles, regulatory documents, and supplier catalogs, which complicates literature searches. Both synthetic and recombinant production routes yield a peptide with the same 28-residue sequence as the thymic isolate. Because the thymosin label also covers unrelated peptides, sources should be compared by sequence rather than by name alone.
The peptide occurs naturally in thymic tissue and has been detected in serum and other biological fluids. Reported concentrations are low, and reliable measurement generally requires immunoassay or mass spectrometry with an enrichment step. It is released from a larger precursor, prothymosin alpha, by proteolytic cleavage, although the enzymes involved are not fully characterized. Whether circulating levels reflect thymic output specifically remains an open question.
| Property | Value | Notes |
|---|---|---|
| 化学分类 | 线性肽 | 由28个氨基酸组成 |
| 分子量 | 约3108 Da | 合成版本一致 |
| 外观 | 白色至类白色粉末 | 冻干品 |
| 溶解度 | 易溶于水 | 微溶于有机溶剂 |
| 储存温度 | -20°C（冻干） | 溶解后2-8°C |
Thymosin alpha-1 is a synthetic peptide of 28 amino acid residues that corresponds to a naturally occurring fragment first isolated from thymus tissue. Its chain is acetylated at the amino terminus, a modification that shields the peptide from rapid cleavage by aminopeptidases. The molecule carries a net negative charge at physiological pH and dissolves freely in water. Researchers classify it as an immune-modulating agent rather than a classical hormone, because it acts on several cell types of both the innate and the adaptive immune system.
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.
Identity and purity testing for thymosin alpha 1 relies mainly on reversed-phase high-performance liquid chromatography and mass spectrometry. Chromatography separates the parent peptide from truncated or modified variants, while mass spectrometry confirms the expected molecular mass. Amino acid analysis and peptide mapping provide additional sequence confirmation. Counterion content, water content, and residual solvents are measured separately as part of specification testing. No single method captures every attribute, so laboratories combine several techniques.
The peptide lacks cysteine, methionine, and tryptophan, so disulfide scrambling and sulfur oxidation are not major degradation routes. Instead, aspartate residues can undergo isomerization or cyclization to succinimide intermediates, generating isoaspartate variants. Hydrolysis of peptide bonds also occurs slowly in solution. These changes may reduce biological activity even when the main peak remains detectable. Stability studies therefore track both potency and the appearance of related substances.
== Function == Thymosin α1 is an agonist for toll-like receptor 2 and toll-like receptor 9 on both myeloid and dendritic antigen-presenting cells, thereby stimulating the adaptive immune response. Thymosin α1 is believed to be a major component of Thymosin Fraction 5 responsible for the activity of that preparation in restoring immune function in animals lacking thymus glands. It has been found to enhance cell-mediated immunity in humans as well as experimental animals.
Drug harmfulness is defined as the degree to which a psychoactive drug has the potential to cause harm to the user and is measured in several ways, such as by addictiveness and the potential for physical harm. More objectively harmful drugs may be colloquially referred to as "hard drugs", and less harmful drugs as "soft drugs". The term "soft drug" is considered controversial by critics as it may imply the false belief that soft drugs cause lesser or insignificant harm.
Unlike traditional techniques such as embryo gene editing, which directly alter the genome of an existing embryo and are therefore person-affecting, these synthetic gametes are built de novo and give rise to individuals who would not have existed otherwise, making the intervention non-person-affecting in the sense of Parfit. Gametes produced in this way, which are distinct from artificial gametes obtained through in vitro–derived gametogenesis, raise ethical questions regarding reproductive autonomy, identity, and the design of human traits without impacting pre-existing persons.
Sources: en.wikipedia.org
=== Cervical dystonia === Botulinum toxin type-A is used to treat cervical dystonia, but it can become ineffective after a time. Botulinum toxin type B received FDA approval for treatment of cervical dystonia in December 2000. Brand names for botulinum toxin type-B include Myobloc in the United States and Neurobloc in the European Union.
On 16 May 2023, three weeks after Tangaraju was put to death, 36-year-old Muhammad Faizal Mohd Shariff, a Singaporean who was found guilty in 2019 of trafficking 1.5 kg of marijuana was reported to have lost his final appeal to commute his sentence. A day after losing his appeal, Muhammad Faizal was hanged at dawn on 17 May 2023, with the authorities confirming his execution despite not naming Muhammad Faizal out of consideration for his family's need for privacy. Two executions of a 56-year-old man and 45-year-old woman (both convicted of drug offences) were scheduled to take place on 26 July and 28 July 2023 respectively; the female offender Saridewi Djamani was believed to be the first woman to be executed in 19 years, as the last known execution of a woman took place on 19 March 2004, when 37-year-old Yen May Woen was put to death for diamorphine trafficking. The 56-year-old male drug offender Mohd Aziz Hussain, as well as Saridewi, were both hanged as scheduled, becoming the third and fourth persons respectively to be executed in Singapore in the year of 2023. On 3 August 2023, Singapore carried out the hanging of Mohamed Shalleh Abdul Latiff, a 39-year-old Singaporean and former delivery driver found guilty of trafficking 54.04g of diamorphine in 2016. In total, five executions, all once again for drug trafficking, took place in the year 2023. When 35-year-old Ahmed Salim was hanged on 28 February 2024 for murdering his former fiancée, he was the first criminal hanged in Singapore in that year.
==== Slide preparation ==== This section refers to the preparation of standard cytogenetic preparations The slide is aged using a salt solution usually consisting of 2X SSC (salt, sodium citrate). The slides are then dehydrated in ethanol, and the probe mixture is added. The sample DNA and the probe DNA are then co-denatured using a heated plate and allowed to re-anneal for at least 4 hours. The slides are then washed to remove the excess unbound probe, and counterstained with 4',6-Diamidino-2-phenylindole (DAPI) or propidium iodide.
Sources: en.wikipedia.org
Many foods are rich in the amino acids and nucleotides imparting umami. Naturally occurring glutamate can be found in meats and vegetables. Inosine (IMP) comes primarily from meats and guanosine (GMP) from vegetables. Mushrooms, especially dried shiitake, are rich sources of umami flavor from guanylate. Smoked or fermented fish are high in inosinate, and shellfish in adenylate. Protein in food is tasteless, however processes such as fermentation, curing, or heat treatment release glutamate and other amino acids. Generally, umami taste is common to foods that contain high levels of L-glutamate, IMP and GMP, most notably in fish, shellfish, cured meats, meat extracts, mushrooms, vegetables (e.g., ripe tomatoes, Chinese cabbage, spinach, celery, etc.), green tea, hydrolyzed vegetable protein, and fermented and aged products involving bacterial or yeast cultures, such as cheeses, shrimp pastes, fish sauce, soy sauce, natto, nutritional yeast, and yeast extracts such as Vegemite and Marmite. Studies have shown that the amino acids in breast milk are often the first encounter humans have with umami. Glutamic acid makes up half of the free amino acids in breast milk.
== Vein == The middle coat is composed of a thick layer of connective tissue with elastic fibers, intermixed, in some veins, with a transverse layer of muscular tissue. The white fibrous element is in considerable excess, and the elastic fibers are in much smaller proportion in the veins than in the arteries.
=== Organic nitrogen compounds === Nitrogen is one of the most important elements in organic chemistry. Many organic functional groups involve a carbon–nitrogen bond, such as amides (RCONR2), amines (R3N), imines (RC(=NR)R), imides (RCO)2NR, azides (RN3), azo compounds (RN2R), cyanates (ROCN), isocyanates (RNCO), nitrates (RONO2), nitriles (RCN), isonitriles (RNC), nitrites (RONO), nitro compounds (RNO2), nitroso compounds (RNO), oximes (RC(=NOH)R), and pyridine derivatives. C–N bonds are strongly polarised towards nitrogen. In these compounds, nitrogen is usually trivalent (though it can be tetravalent in quaternary ammonium salts, R4N+), with a lone pair that can confer basicity on the compound by being coordinated to a proton. This may be offset by other factors: for example, amides are not basic because the lone pair is delocalised into a double bond (though they may act as bases at very low pH, being protonated at the oxygen), and pyrrole is not basic because the lone pair is delocalised as part of an aromatic ring. The amount of nitrogen in a chemical substance can be determined by the Kjeldahl method. In particular, nitrogen is an essential component of nucleic acids, amino acids and thus proteins, and the energy-carrying molecule adenosine triphosphate and is thus vital to all life on Earth.
== Reaction mechanism == In the first part of the reaction process, the carbonyl is converted to an iminium, to which a cyanide ion adds. First, the carbonyl oxygen of an aldehyde is protonated, followed by a nucleophilic attack of ammonia to the carbonyl carbon. After subsequent proton exchange, water is cleaved to form the iminium ion intermediate. A cyanide ion then attacks the iminium carbon yielding an aminonitrile.
Sources: en.wikipedia.org
它不是经典的内分泌激素，而是一种免疫调节肽。其作用主要通过局部免疫细胞间的信号传递实现，而非经血液循环作用于远隔器官。
天然胸腺素α1主要从胸腺组织提取，也可在脾脏和淋巴结中检出。目前研究和临床使用的多为化学合成版本，不再依赖动物组织。
胸腺素组分5是牛胸腺提取物的粗组分，包含多种肽。胸腺素α1是其中一种被纯化和表征的单一肽，具有明确的28个氨基酸序列。
It is a 28-amino-acid peptide originally purified from a bovine thymic extract and later produced synthetically. It is studied mainly for its effects on immune cell function.