freeze-thaw cycling raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-07-17 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Amino acid length | 28 residues | Single chain with an acetylated N-terminus |
| Molecular mass | Approximately 3,108 Da | Small shifts occur with counter-ion and water content |
| Isoelectric point | Around 3.5 | Low value follows from the many acidic residues |
| Parent molecule | N-terminal region of prothymosin alpha | Free circulating form in humans is not firmly established |
| Common synonyms | Thymalfasin; T alpha 1 | Older literature also uses the full spelled-out form |
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.
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.
Laboratory work indicates that the peptide acts on cells of both the innate and adaptive immune systems. Reported effects include signalling through Toll-like receptors on dendritic cells, enhanced T-cell maturation, and increased natural killer cell activity. These actions are described largely from cell-culture and animal experiments, and the precise receptor-level events remain incompletely defined. Studies in humans have generally measured immune markers rather than a single defined molecular target. The resulting picture remains partly descriptive.
Clinical research has examined the peptide in chronic hepatitis B and C, as a vaccine adjuvant, and in sepsis and oncology settings. Results across trials have been mixed, and several studies were small or conducted under differing protocols. Regulatory status varies by country, and the compound is not approved in every jurisdiction where it is studied. Evidence for any single indication should be read with attention to sample size and endpoint choice.
Thymosin alpha-1 is a 28-residue peptide first isolated from thymus tissue in the 1970s. It corresponds to the N-terminal portion of thymosin beta-4, from which it is cleaved in vivo. The peptide carries an acetyl group at its N-terminus, a modification that affects its charge and stability. Synthetic material produced by solid-phase peptide synthesis is chemically identical to the natural fragment and is the form used in research and clinical studies.
The monoepoxide of treosulfan (EBDM) exhibited greater brain penetration than the parent compound, with tissue-to-plasma ratios of 0.25 in young adult rats and 0.50 in juvenile rats. The elimination half-life of treosulfan in patients is short, averaging 1.5–2.0 h. The apparent elimination half-life of the biologically active epoxides is similar to that of treosulfan, reflecting the phenomenon of formation rate-limited elimination. The most common side effects include infections, nausea (feeling sick), stomatitis (inflammation of the lining of the mouth), vomiting, diarrhea, and abdominal pain (belly ache). Tiredness, febrile neutropenia (low white blood cell counts with fever) and high blood levels of bilirubin (a breakdown product of red blood cells) are also seen in more than 1 in 10 adults, and rash also affects more than 1 in 10 children. The most common adverse reactions include musculoskeletal pain, stomatitis, pyrexia, nausea, edema, infection, and vomiting. Selected grade 3 or 4 nonhematological laboratory abnormalities include increased GGT, increased bilirubin, increased ALT, increased AST, and increased creatinine. Treosulfan was authorized for medical use in the European Union in June 2019, and approved for medical use in the United States in January 2025.
==== Countries ==== The Netherlands has the lowest rate of antibiotic prescribing in the OECD, at a rate of 11.4 defined daily doses (DDD) per 1,000 people per day in 2011. DDD is a statistical measure of drug consumption, defined by the World Health Organization (WHO). • Germany and Sweden also have lower prescribing rates, with Sweden's rate having been declining since 2007. • Greece, France and Belgium have high prescribing rates.
There are some 5,000 potato varieties worldwide, 3,000 of them in the Andes alone — mainly in Peru, Bolivia, Ecuador, Chile, and Colombia. Over 100 cultivars might be found in a single valley, and a dozen or more might be maintained by a single agricultural household. The European Cultivated Potato Database is an online collaborative database of potato variety descriptions updated and maintained by the Scottish Agricultural Science Agency within the framework of the European Cooperative Programme for Crop Genetic Resources Networks—which is run by the International Plant Genetic Resources Institute. Around 80 varieties are commercially available in the UK. For culinary purposes, varieties are often differentiated by their waxiness: floury or mealy baking potatoes have more starch (20–22%) than waxy boiling potatoes (16–18%). The distinction may also arise from variation in the comparative ratio of two different potato starch compounds: amylose and amylopectin. Amylose, a long-chain molecule, diffuses from the starch granule when cooked in water, and lends itself to dishes where the potato is mashed. Varieties that contain a slightly higher amylopectin content, which is a highly branched molecule, help the potato retain its shape after being boiled in water. Potatoes that are good for making potato chips or potato crisps are sometimes called "chipping potatoes", which means they meet the basic requirements of similar varietal characteristics, being firm, fairly clean, and fairly well-shaped.
=== North America === Tim Hortons originally was concentrated in Ontario and Atlantic Canada. However, the chain has expanded its presence into Quebec and western Canada. Its location in Iqaluit, Nunavut, was the northernmost store as of 2010. Its location in Pond Inlet, Nunavut is the northernmost store as of 2023.
=== As a food product === Fresh açaí has been consumed as a dietary staple in the region around the Amazon river delta for centuries. The fruit is processed into pulp for supply to food product manufacturers or retailers, sold as frozen pulp, juice, or an ingredient in various products from beverages, including grain alcohol, smoothies, foods, cosmetics and supplements. In Brazil, it is commonly eaten as açaí na tigela. In a study of three traditional Caboclo populations in the Brazilian Amazon, açaí palm was described as the most important plant species because the fruit makes up a major component of their diet, up to 42% of the total food intake by weight.
Sources: en.wikipedia.org
All medal achievements listed below are based only on the statistics up to the end of the 2018 Vietnam National Games. The three-code abbreviation for the names of participating sports delegations only began to be used on the system starting from the 2022 Vietnam National Games, so sports delegations that ceased to exist before that time will not have an abbreviation.
==== In midlife ==== The midlife crisis may mark the first reliable drop in happiness during an average human's life. Evidence suggests most people generally become happier with age, with the exception of the years 40 – 50, which is the typical age at which a crisis might occur. Researchers specify that people in both their 20s and 70s are happier than during midlife, although the extent of happiness changes at different rates. For example, feelings of stress and anger tend to decline after age 20, worrying drops after age 50, and enjoyment very slowly declines in adulthood but finally starts to rise after age 50. Well-being in late life is more likely to be related to other contextual factors including proximity to death. However, most of this terminal decline in well-being could be attributed to other changes in age-normative functional declines including physical health and function. Also, there is growing debate that assumptions that a single population estimate of age-related changes in well-being truly reflects the lived experiences of older adults has been questioned. The use of growth mixture modelling frameworks has allowed researchers to identify homogenous groups of individuals who are more similar to each other than the population based on their level and change in well-being and has shown that most report stable well-being in their late life and in the decade prior to death.
Reptiles interaction also contribute to chemical ecology via bioaccumulation or neutralization of toxic compounds. Diablito poison frog (Oophaga sylvatica) which feeds on leaf litter arthropods sequesters the poison cardenolides with no self harm. Species of dart frogs have evolved in similar fashion to the insects they consume via modification to their Na+/K+-ATPase. Again, similar to the insects they prey upon, the dart frog physiology has changed to allow for secretion of toxic chemicals such as batrachotoxins found on the skin of certain neotropical dendrobatid frogs. Modification to the Na+/K+-ATPase illustrates a co-evolution based on a predator-prey arms race where each must keep evolving to survive. Another example is the interactions between the horned lizards (Phrynosoma spp.) and harvester ants (Pogonomyrmex spp.). Horned lizards evolution has shown the blood contains a factor that metabolizes toxins produced by harvester ants. The metabolized poison is broken down and used in a specialized blood squirting defensive mechanism to defend the horned lizard against predators.
Lisa Sanders then questions if the episodes could be caused by an increase in stress, rooted by a traumatic stress episode within his early childhood involving custody actions between his mother and father. To help Matt out with the stress and psychological aspect of his illness, he was referred to a psychiatrist at Johns Hopkins that started him on cognitive behavioral therapy. While the cognitive therapy would help Matt out with his internal stress it might also help alleviate the severity of his episode until he is able to secure a valid diagnosis.
Sources: en.wikipedia.org
=== Electron transfer reactions === Cytochrome P450 type enzymes that catalyze monooxygenase (hydroxylation) reactions are dependent on the transfer of two electrons from FAD to the P450. Two types of P450 systems are found in eukaryotes. The P450 systems that are located in the endoplasmic reticulum are dependent on a cytochrome P-450 reductase (CPR) that contains both an FAD and an FMN. The two electrons on reduced FAD (FADH2) are transferred one at a time to FMN and then a single electron is passed from FMN to the heme of the P450. The P450 systems that are located in the mitochondria are dependent on two electron transfer proteins: An FAD containing adrenodoxin reductase (AR) and a small iron-sulfur group containing protein named adrenodoxin. FAD is embedded in the FAD-binding domain of AR. The FAD of AR is reduced to FADH2 by transfer of two electrons from NADPH that binds in the NADP-binding domain of AR. The structure of this enzyme is highly conserved to maintain precisely the alignment of electron donor NADPH and acceptor FAD for efficient electron transfer. The two electrons in reduced FAD are transferred one a time to adrenodoxin which in turn donates the single electron to the heme group of the mitochondrial P450. The structures of the reductase of the microsomal versus reductase of the mitochondrial P450 systems are completely different and show no homology.
=== RNA genomes === Like DNA, RNA can carry genetic information. RNA viruses have genomes composed of RNA that encodes a number of proteins. The viral genome is replicated by some of those proteins, while other proteins protect the genome as the virus particle moves to a new host cell. Viroids are another group of pathogens, but they consist only of RNA, do not encode any protein and are replicated by a host plant cell's polymerase.
During his mayoralty, Sanders called himself a socialist and was described as such in the press. During his first term, his supporters, including the first Citizens Party city councilor Terry Bouricius, formed the Progressive Coalition, the forerunner of the Vermont Progressive Party. The Progressives never held more than six seats on the 13-member city council, but they had enough to keep the council from overriding Sanders's vetoes. Under his leadership, Burlington balanced its city budget; attracted a minor league baseball team, the Vermont Reds, then the Double-A affiliate of the Cincinnati Reds; became the first US city to fund community-trust housing; and successfully sued the local cable television franchise, thereby winning reduced rates for customers. Sanders led downtown revitalization projects, including the improvement of Burlington's Lake Champlain waterfront. In 1981, he campaigned against the unpopular plans by Burlington developer Tony Pomerleau to convert the then-industrial waterfront property owned by the Central Vermont Railway into expensive condominiums, hotels, and offices. He ran under the slogan "Burlington is not for sale" and successfully supported a plan that redeveloped the waterfront area into a mixed-use district featuring housing, parks, and public spaces. Sanders was a consistent critic of US foreign policy in Latin America throughout the 1980s. In 1985, Burlington City Hall hosted a foreign policy speech by Noam Chomsky.
Sources: en.wikipedia.org
It is usually described as an immunomodulatory peptide rather than a classic circulating hormone. No endocrine gland is known to release it as a primary secretory product, and its measured presence in blood is not firmly established.
Prothymosin alpha is a much larger acidic protein, roughly 111 to 113 residues long, and the thymosin alpha-1 sequence matches its N-terminal region. The small peptide is therefore best understood as a fragment of that parent protein rather than a separate gene product.
Trials and clinical reports have examined chronic hepatitis B and C, use as a vaccine adjuvant, and supportive treatment in some immunodeficiency and oncology settings. Results vary by indication, and regulatory approval differs between countries.
It corresponds to a fragment of the larger protein prothymosin alpha, which is present in many tissues. The isolated 28-amino-acid peptide was originally obtained from thymus preparations, and the pharmaceutical product is synthesized rather than extracted. The term therefore describes both a natural fragment and a manufactured drug substance.