This is a working overview of freeze-thaw, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-06-25 and is reviewed periodically as new material appears.
Identity and purity are usually checked by reverse-phase high-performance liquid chromatography, which separates the intact chain from truncated products, together with mass spectrometry for confirmation of the expected mass. Peptide mapping after enzymatic digestion and amino acid analysis add sequence-level evidence. Release testing also covers water content, residual solvents, and counter-ions, all of which influence measured mass and stability. Related-peptide limits are commonly expressed as a percentage of total peak area, with individual unspecified impurities held below a lower threshold.
The lyophilized peptide is a white to off-white powder that dissolves freely in water and in aqueous buffers near neutral pH. Because the molecule carries a net negative charge under physiological conditions, saline and phosphate solutions are the usual vehicles, while strongly acidic media are avoided. Stock solutions are commonly divided into small aliquots so that repeated freezing and thawing can be limited, since cycling may encourage aggregation. Solubility in organic solvents is poor and those solvents are seldom used as primary diluents.
Practical handling focuses on limiting adsorption and contamination. The peptide dissolves readily in water, and dilute solutions tend to adhere to plastic and glass surfaces, so an inert carrier protein or a defined buffer can reduce losses in laboratory work. Workers also record the counter-ion form, since an acetate or trifluoroacetate salt changes the mass balance of the weighed powder. Documentation of lot number, purity value, and storage history supports reproducibility when results from different laboratories are compared.
Lyophilized material is generally held at reduced temperature to slow degradation, and storage at minus twenty degrees Celsius or lower is common practice for long-term retention. Short-term working portions are often kept between two and eight degrees Celsius. Once dissolved, the peptide is less stable than the dry powder, and repeated freeze-thaw cycles are associated with loss of material and with aggregate formation. Vials are usually allowed to reach room temperature before opening so that condensation does not introduce moisture, and solutions are protected from light where practical.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography, which separates the peptide from closely related impurities and from truncated or oxidized variants. Mass spectrometry supplies the molecular mass and confirms the expected sequence length, while amino acid analysis can be used to check composition. Because the molecule has no chromophore beyond the peptide backbone, ultraviolet detection is typically performed at a low wavelength, where baseline interference from solvents and buffers is a practical concern. Water content and counter-ion content are often reported alongside purity.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Assessed by visual inspection at release |
| Solubility class | Freely soluble in water | Aqueous buffers near neutral pH |
| Typical storage temperature | Minus 20 degrees Celsius | Lyophilized, desiccated, protected from light |
| Typical analytical method | Reverse-phase HPLC with mass spectrometry | Used together for purity and identity |
| Common synonyms | T-alpha-1; thymalfasin | Older reports use several designations |
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.
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.
Identity and purity are normally assessed by reversed-phase high-performance liquid chromatography, which separates the peptide from related impurities and truncation products. Mass spectrometry confirms molecular mass and detects modifications such as deamidation or oxidation. Amino acid analysis and peptide mapping provide additional sequence-level confirmation. For research material, a certificate of analysis typically reports these results together with water content and counter-ion identity, since the lyophilized powder is often supplied as an acetate or trifluoroacetate salt.
Several factors accelerate degradation: alkaline pH, elevated temperature, exposure to oxidants, and the presence of residual moisture. Deamidation of asparagine residues and oxidation of methionine are the most commonly reported degradation routes. Because the peptide lacks disulfide bonds, it does not undergo the thiol-related aggregation seen in some other biologics, but physical aggregation can still occur at high concentration. Stability data are product-specific, and extrapolating shelf life between formulations is not reliable.
Lyophilized thymosin alpha-1 is generally stored at or below minus twenty degrees Celsius, protected from moisture and light. Short-term handling at ambient temperature is possible for dry powder, but reconstituted solutions degrade faster and are usually kept at two to eight degrees Celsius with a defined expiry of days rather than weeks. Repeated freeze-thaw cycles should be avoided because they promote aggregation and loss of potency. Exact limits depend on the formulation and should follow the supplier's documentation.
胸腺素α1对免疫系统的影响涉及多种细胞类型。研究表明，它可促进未成熟T细胞向成熟T细胞分化，并增强T细胞对抗原刺激的增殖反应。树突状细胞在Tα1存在下表达更高水平的共刺激分子，从而更有效地呈递抗原。此外，自然杀伤细胞的活性也观察到上升。这些效应并非直接杀伤病原体，而是调节宿主免疫应答的强度与方向。
在信号层面，Tα1可能通过Toll样受体等模式识别受体发挥作用。部分实验显示，它能激活髓样分化因子88依赖的通路，进而促进核因子κB进入细胞核。这导致白细胞介素2、干扰素γ和白细胞介素12等细胞因子的转录增加。这些细胞因子偏向辅助性T细胞1型应答，有助于细胞免疫。然而，具体受体和结合位点尚未完全确定，不同实验模型的结果存在差异。
Atmosphere of the Sun: in detectable trace amounts Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere Atmosphere of Venus: 0.002% Earth's atmosphere: ≈0.40% over full atmosphere, typically 1–4% at surface Atmosphere of the Moon: in trace amounts Atmosphere of Mars: 0.03% Atmosphere of Ceres Atmosphere of Jupiter: 0.0004% – in ices only; and that of its moon Europa Atmosphere of Saturn – in ices only; Enceladus: 91% and Dione (subsurface ocean) Atmosphere of Uranus – in trace amounts below 50 bar Atmosphere of Neptune – found in the deeper layers Extrasolar planet atmospheres: including those of HD 189733 b and HD 209458 b, Tau Boötis b, HAT-P-11b, XO-1b, WASP-12b, WASP-17b, and WASP-19b. Stellar atmospheres: not limited to cooler stars and even detected in giant hot stars such as Betelgeuse, Mu Cephei, Antares and Arcturus. Circumstellar disks: including those of more than half of T Tauri stars such as AA Tauri as well as TW Hydrae, IRC +10216 and APM 08279+5255, VY Canis Majoris and S Persei.
== Biography == David Colin Sherrington was born at Webster Street, Litherland, Liverpool on 5 March 1945, the second child of Alfred George Sherrington, a dock labourer, and Lucy Gladys Sherrington, née Pyke. He attended two primary/junior schools before passing the eleven-plus exam, enabling him to go to Waterloo Grammar School. Crosby. His A-Level results were good enough for him to by-pass the first year of the chemistry degree course at the University of Liverpool and enter the second year in 1963. He graduated first-class in 1966. Sherrington stayed at Liverpool for his PhD, under Anthony Ledwith, and then continued as a research assistant in the same department so that he could help his recently widowed mother. In 1971 he applied for two fellowships: at Heriot-Watt University and at the University of Strathclyde. He was successful with the second, and took up a post in Alastair M. North’s department of pure and applied chemistry. Before moving north, David Sherrington married Valerie Vinnicombe at County Road Methodist Church, Walton in June 1972. They had met at the university tennis club, where she was secretary and he was trying to lose weight. By 1975 his researches in Scotland had become focused on polymer-supported reactions. In 1984 Sherrington accepted a three-year contract at Unilever’s Port Sunlight laboratory under its research director Sir Geoffrey Allen, FRS. His job was to build and lead the Polymer Science Area. He worked in fields that had practical value – always his wish – such as biodegradable polymers and molecular imprinting.
== External links == Austrian Centre of Industrial Biotechnology official website The Centre of Excellence for Biocatalysis - CoEBio3 The University of Exeter - Biocatalysis Centre Center for Biocatalysis and Bioprocessing - The University of Iowa TU Delft - Biocatalysis & Organic Chemistry (BOC) KTH Stockholm - Biocatalysis Research Group Institute of Technical Biocatalysis at the Hamburg University of Technology (TUHH) Biocascades Project
=== Knight Bachelor === Alan Ayckbourn, , Playwright. For services to The Theatre. Jack Mervyn Frank Baer. For services to the Art Trade. Nicholas Brian Baker, , Member of Parliament for Dorset North. For political service. Alec Victor Bedser, . For services to Cricket. Thomas Leon Blundell, . For services to the Biotechnology and Biological Sciences Research Council and to Scientific Research. Alan Peter Budd, Chief Economic Adviser to Her Majesty's Treasury and Head, Government Economic Service. Peter John Davis, Chairman, National Advisory Council for Education and Training Targets. For services to Training and to Industry. Simon James Day. For political and public service. Geoffrey James Dear, , Her Majesty's Inspector of Constabulary. For services to the Police. Richard Charles Hastings Eyre, , Artistic Director, Royal National Theatre. For services to Drama. David Harrison, , Master, Selwyn College, University of Cambridge. For services to Education and to Nuclear Safety. John Smith Harvie, . For political and public service. Robert Baynes Horton, Chairman, Railtrack plc. For services to the Railway Industry. Gordon Minto Hourston, Chairman, Armed Forces' Pay Review Body. For services to the Armed Forces and to Industry. Michael Nicholas Howard Jenkins, , Chairman, Futures and Options Association and the London Clearing House. For services to the Finance Industry. John Martin Kirby Laing, , Chairman, John Laing plc. For services to the Construction Industry. James Paul McCartney, , Musician. For services to Music. Professor Samuel Roy Meadow.
Nicotine, which is contained in cigarettes and other smoked tobacco products, is a stimulant and is one of the main factors leading to continued tobacco smoking. Nicotine is a highly addictive psychoactive chemical. When tobacco is smoked, most of the nicotine is pyrolyzed; a dose sufficient to cause mild somatic dependency and mild to strong psychological dependency remains. The amount of nicotine absorbed by the body from smoking depends on many factors, including the type of tobacco, whether the smoke is inhaled, and whether a filter is used. There is also a formation of harmane (a MAO inhibitor) from the acetaldehyde in cigarette smoke, which seems to play an important role in nicotine addiction probably by facilitating dopamine release in the nucleus accumbens in response to nicotine stimuli. According to studies by Henningfield and Benowitz, nicotine is more addictive than cannabis, caffeine, alcohol, cocaine, and heroin when considering both somatic and psychological dependence. However, due to the stronger withdrawal effects of alcohol, cocaine and heroin, nicotine may have a lower potential for somatic dependence than these substances. About half of Canadians who currently smoke have tried to quit. McGill University health professor Jennifer O'Loughlin stated that nicotine addiction can occur as soon as five months after the start of smoking.
Sources: en.wikipedia.org
=== 4 April === The United States government announced a $2.6 billion (USD) aid package to Ukraine which includes ammunition for HIMARS, air defense interceptors, artillery rounds, small arms ammunition, and anti-drone systems.
The company was founded in Pittsburgh, Pennsylvania, in 1902 by Chester Garfield Fisher (1881–1965), originally called the "Scientific Materials Co.". After obtaining his degree in engineering at Western University of Pennsylvania (now University of Pittsburgh), C.G. Fisher purchased the stockroom of the Pittsburgh Testing Laboratory. Fisher became a supplier of lab equipment and reagents for the area's industrial research. Early products included microscopes, burets, pipettes, litmus, balances, colorimeters, dissecting kits, and anatomical models. The first catalog, the 400 page Scientific Materials Co. Catalog of Laboratory Apparatus & Supplies, was published in 1904. Fisher established an R&D lab at his company in 1915. Edwin Fisher, Chester's brother, developed the Meker-Fisher burner in 1921, an advancement on the design of the Bunsen burner. The company manufactured an electric-combustion furnace and combustion train for analyzing carbon levels in steel, and an electrically heated and thermostatically controlled bacteriological incubator. In 1925, the company purchased Montreal-based Scientific Supplies, Ltd. The same year, the company was renamed Fisher Scientific. In 1940, Fisher Scientific acquired the New York supply company Eimer & Amend, which was founded in 1851 by Bernard G. Amend. Aiken Fisher, Chester's oldest son, became president of the company in 1949. In 1955, Fisher established a chemical manufacturing facility in Fair Lawn, New Jersey. In 1957, the company purchased the New York–based medical apparatus supply company E. Machlett & Sons.
Helen Jill Cooper is a British chemist who is Professor of mass spectrometry at the University of Birmingham. She serves as Deputy Head of the School of Chemistry and holds an Engineering and Physical Sciences Research Council Established Career Fellowship. Her research considers the development of native ambient mass spectrometry to enable direct analysis of intact proteins and protein assemblies from tissue.
The EP features Cantrell on lead vocals on the opening track, "Brother", and guest vocals by Ann Wilson from the band Heart, who joined Staley and Cantrell for the choruses of "Brother" and "Am I Inside". The EP also features Mark Arm of Mudhoney and Chris Cornell of Soundgarden, who shared vocals with Staley and Cantrell on the song "Right Turn", credited to "Alice Mudgarden" in the liner notes. In 1992, Alice in Chains appeared in the Cameron Crowe film Singles, performing their song "It Ain't Like That" while portraying an unnamed bar band. The band also contributed the song "Would?" to the film's soundtrack, whose video received an award for Best Video from a Film at the 1993 MTV Video Music Awards.
On June 28, 2007, the FARC suddenly reported the death of 11 of the 12 kidnapped provincial deputies from Valle del Cauca Department. The Colombian government accused the FARC of executing the hostages and stated that government forces had not made any rescue attempts. FARC claimed that the deaths occurred during a crossfire, after an attack on one of its camps by an "unidentified military group". FARC did not report any other casualties on either side. In 2007, Venezuelan President Hugo Chávez and Colombian Senator Piedad Córdoba were acting as authorised mediators in the ongoing humanitarian exchange between the FARC and the government of Colombia. Colombian President Álvaro Uribe had given Chávez permission to mediate under the conditions that all meetings with the FARC would take place in Venezuela and that Chávez would not contact members of the Colombian military directly but instead would go through proper diplomatic channels. However, President Uribe abruptly terminated Chávez's mediation efforts on November 22, 2007, after Chávez personally contacted General Mario Montoya Uribe, the Commander of the Colombian National Army. In response, Chávez said that he was still willing to mediate, but had withdrawn Venezuela's ambassador to Colombia and placed Colombian-Venezuelan relations "in a freezer". President Uribe responded by accusing Chávez of legitimizing terrorism and pursuing an expansionist project on the continent.
Sources: en.wikipedia.org
Reconstituted solutions are typically kept refrigerated at two to eight degrees Celsius when used within a short window, or frozen in aliquots for longer periods. Repeated freeze-thaw cycles are avoided because they can reduce recovery of intact peptide.
It establishes that the measured mass matches the expected value for the intact molecule. It also helps detect modifications such as oxidation or truncation that shift the mass by a known amount.
Cycling between frozen and liquid states can promote aggregation and adsorption to container walls. Dividing a stock into single-use aliquots limits the number of cycles a given vial undergoes.
Cool storage below freezing is usual for long-term retention, with a desiccant and protection from light. Portions are often split before first use to avoid repeated handling.