A practical reference on lyophilization: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-09-11 and is reviewed periodically as new material appears.
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。
Quality control for thymosin alpha-1 focuses on identity, purity, and potency. Identity is confirmed by mass spectrometry and amino acid analysis, while purity is assessed by chromatography with limits on related substances and residual solvents. Potency assays may use cell-based immune readouts, but these are not standardized across laboratories. Regulatory status differs by jurisdiction; no product is approved in the United States for clinical use, whereas some other countries register injectable forms for specific indications.
Quantifying thymosin alpha-1 in a sample usually relies on reverse-phase high-performance liquid chromatography. The peptide lacks strong chromophores, so detection often occurs at 214 nm, where the peptide backbone absorbs. Mass spectrometry provides confirmatory identification and can detect sequence variants or truncations. Immunoassays have been used in biological matrices, but they may cross-react with related fragments. For purity assessment, chromatographic peak area gives the main component percentage, while mass accuracy verifies molecular identity.
The lyophilized peptide is generally stable for extended periods when kept cold and dry. Once dissolved, aqueous solutions are less stable; hydrolysis, oxidation, and aggregation can degrade the material. Storage at -20 °C or lower slows these processes. Repeated freeze-thaw cycles are best avoided because they can promote aggregation. The exact shelf life depends on formulation, pH, and concentration, so stability studies are typically performed for each specific product.
| 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 |
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.
Like most short peptides, thymosin alpha-1 is susceptible to hydrolysis under strongly acidic or basic conditions and to oxidation when exposed to air over long periods. The acetylated amino terminus blocks one common degradation route, which contributes to the molecule's relative robustness in solution. Lyophilized material generally retains potency for extended periods when kept cold and dry. Once reconstituted, aqueous solutions are less stable and are typically used within a defined window rather than held indefinitely at ambient temperature.
Routine handling calls for storage of the lyophilized powder at refrigerated temperatures, away from light, in a sealed container. Working solutions are often prepared in sterile water or buffer and kept cold between uses. Repeated freeze-thaw cycles are generally avoided because they can promote aggregation and loss of material. Laboratories usually record lot number, reconstitution date, and storage conditions so that any change in behavior can be traced to a specific preparation.
=== Plants, climate and environmental change === Plant responses to climate and other environmental changes can inform one's understanding of how these changes affect ecosystem function and productivity. For example, plant phenology can be a useful proxy for temperature in historical climatology, and the biological impact of climate change and global warming. Palynology, the analysis of fossil pollen deposits in sediments from thousands or millions of years ago allows the reconstruction of past climates. Estimates of atmospheric CO2 concentrations since the Palaeozoic have been obtained from stomatal densities and the leaf shapes and sizes of ancient land plants. Ozone depletion can expose plants to higher levels of ultraviolet radiation-B (UV-B), resulting in lower growth rates. Moreover, information from studies of community ecology, plant systematics, and taxonomy is essential to understanding vegetation change, habitat destruction and species extinction.
The forced sterilization policy under Peruvian president Alberto Fujimori affected almost exclusively Quechua and Aymara women, a total of about 270,000 (and 22,000 men) according to official figures. The sterilization program lasted for over five years between 1996 and 2001. During this period, women were coerced into forced sterilization. Sterilizations were often performed under dangerous and unsanitary conditions, as the doctors were pressured to perform operations under unrealistic government quotas, which made it impossible to properly inform women and receive their consent. The Bolivian film director Jorge Sanjinés dealt with the issue of forced sterilization in 1969 in his Quechua-language feature film Yawar Mallku. Quechuas have been left out of their nation's regional economic growth in recent years. The World Bank has identified eight countries on the continent to have some of the highest inequality rates in the world. The Quechuas have been subject to these severe inequalities, as many of them have a much lower life expectancy than the regional average, and many communities lack access to basic health services. Perceived ethnic discrimination continues to play a role at the parliamentary level. When the newly elected Peruvian members of parliament Hilaria Supa Huamán and María Sumire swore their oath of office in Quechua—for the first time in the history of Peru in an Indigenous language—the Peruvian parliamentary president Martha Hildebrandt and the parliamentary officer Carlos Torres Caro refused their acceptance.
Closely monitoring a patient's condition but withholding treatment until symptoms appear or change. Also called watchful waiting, active surveillance, and expectant management. (NCI) Observational study
"The soy foods movement began in small pockets of the counterculture, notably the Tennessee commune named simply The Farm, but by the mid-1970s a vegetarian revival helped it gain momentum and even popular awareness through books such as The Book of Tofu." Although practically unseen in 1900, by 2000 soybean plantings covered more than 70 million acres, second only to corn, and it became America's largest cash crop. In 2021, 87,195,000 acres were planted, with the largest acreage in the states of Illinois, Iowa, and Minnesota.
Parasitic infections include trichomoniasis, pediculosis pubis, and scabies. Trichomoniasis is transmitted by a parasitic protozoan and is the most common non-viral STI. Most cases are asymptomatic but may present symptoms of irritation and a discharge of unusual odor. Pediculosis pubis, commonly called crabs, is a disease caused by the crab louse an ectoparasite. When the pubic hair is infested, the irritation produced can be intense. Scabies, also known as the "seven year itch", is caused by another ectoparasite, the mite Sarcoptes scabiei, giving intense irritation.
Sources: en.wikipedia.org
They drove into the camp past FRELIMO guards to the parade ground where many were assembled before the attack commenced. The head of the Selous Scouts, Ronald Francis Reid-Daly, claimed that captured ZANLA documents showed that the people killed in the raid were either trained guerrillas or were undergoing guerrilla instruction and training. Paul L. Moorcraft and Peter McLaughlin wrote in 1982, that "although the camp did contain trained guerrillas and young recruits, many of its inhabitants were old people, women and young children who had fled from Rhodesia as refugees". They further wrote in 2010, that "although nearly all the personnel in the camp were unarmed, many were trained guerillas or undergoing instruction" and that documents captured from ZANLA, revealed more than 1,028 were killed in the operation. A 1994 Amnesty International publication described the operation as a massacre and stated that the camp at Nyadzonya housed refugees, and that a soldier who participated in the raid later stated: "We were told that Nyadzonia was a camp containing several thousand unarmed refugees who could be recruited to join the guerrillas. It would be easier if we went in and wiped them out while they were unarmed and before they were trained rather than waiting for the possibility of them being trained and sent back armed into Rhodesia". According to Amnesty International, 1,000 people were killed and the operation was "a gross human rights violation and a war crime".
Selenium forms several allotropes that interconvert with temperature changes, depending somewhat on the rate of temperature change. When prepared in chemical reactions, selenium is usually an amorphous, brick-red powder. When rapidly melted, it forms the black, vitreous form, usually sold commercially as beads. The structure of black selenium is irregular and complex and consists of polymeric rings with up to 1000 atoms per ring. Black selenium is a brittle, lustrous solid that is slightly soluble in CS2. Upon heating, it softens at 50 °C and converts to gray selenium at 180 °C; the transformation temperature is reduced by presence of halogens and amines. The red α, β, and γ forms are produced from solutions of black selenium by varying the evaporation rate of the solvent (usually CS2). They all have a relatively low, monoclinic crystal symmetry (space group 14) and contain nearly identical puckered cyclooctaselenium (Se8) rings as in sulfur. The eight atoms of a ring are not equivalent (i.e. they are not mapped one onto another by any symmetry operation), and in fact in the γ-monoclinic form, half the rings are in one configuration (and its mirror image) and half in another. The packing is most dense in the α form. In the Se8 rings, the Se–Se distance varies depending on where the pair of atoms is in the ring, but the average is 233.5 pm, and the Se–Se–Se angle is on average 105.7°. Other selenium allotropes may contain Se6 or Se7 rings.
The poly-Pro I helix is much denser than the PPII helix due to the cis isomers of its peptide bonds. It is also rarer than the PPII conformation because the cis isomer is higher in energy than the trans. Its typical dihedral angles (-75°, 160°) are close, but not identical to, those of the PPII helix. However, the PPI helix is a right-handed helix and more tightly wound, with roughly 3.3 residues per turn (rather than 3). The rise per residue in the PPI helix is also much smaller, roughly 1.9 Å. Again, there is no internal hydrogen bonding in the poly-Pro I helix, both because an H-bond donor atom is lacking and because the amide nitrogen and oxygen atoms are too distant (roughly 3.8 Å again) and oriented incorrectly.
Most species are generalist predators, eating microalgae, sponges, bivalves, snails and other small animals. The crown-of-thorns starfish consumes coral polyps, while other species are detritivores, feeding on decomposing organic material and faecal matter. A few are suspension feeders, gathering in phytoplankton; Henricia and Echinaster often feed with sponges, taking advantage of the water current they produce. Various species can absorb organic nutrients from the surrounding water, and this may form a significant portion of their diet. The processes of feeding and capture may be aided by special parts; Pisaster brevispinus, the short-spined pisaster from the West Coast of America, can use a set of specialized tube feet to dig itself deep into the soft substrate to extract prey (usually clams). Grasping the shellfish, the starfish slowly pries open the prey's shell, overcoming the clam's adductor muscle, and inserts its everted stomach into the crack to digest the soft tissues. The gap between the clam's valves need only be a fraction of a millimetre wide for the stomach to gain entry.
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。
Reverse-phase HPLC with ultraviolet detection at 214 nm is common. Mass spectrometry is used to confirm molecular identity and detect modifications. Immunoassays exist but may not distinguish the intact peptide from fragments.