freeze-thaw 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.
Last reviewed on 2026-06-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For lyophilized powder, long term |
| Common analytical method | Reverse-phase HPLC | Usually paired with mass spectrometry |
| Typical reported purity | At or above 95 percent by area | Research-grade material |
| Aqueous solubility | High | Solutions used in laboratory assays |
| Moisture sensitivity | Hydrolyzes in solution | Aseptic handling reduces degradation |
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
== Education == Source: While curriculum may vary somewhat from program to program, all accredited pathologists' assistants programs are two-year masters degrees that include didactic and clinical training, similar to physician associate programs. The didactic year includes education in surgical and autopsy pathology, anatomy, histology, and laboratory operations. Students are then placed in a clinical setting with affiliated hospitals and/or medical examiner's offices to learn surgical and autopsy dissection. Pathologists' assistant programs are accredited by NAACLS and attending an accredited program is the only route to certification by the ASCP-BOC. Pathologists' assistants that have passed the ASCP certification exam use the post-nominal letters "PA(ASCP)". PA programs collectively graduate approximately 245 students a year. As of 2024, over 3000 pathologists’ assistants have been certified. Universities offering pathologists' assistant degrees include:
Bottromycins contain a C-terminal decarboxylated thiazole in addition to a macrocyclic amidine. There are currently six known bottromycin compounds, which differ in the extent of side chain methylation, an additional characteristic of the bottromycin class. The total synthesis of bottromycin A2 was required to definitively determine the structure of the first bottromycin. Thus far, gene clusters predicted to produce bottromycins have been identified in the genus Streptomyces. Bottromycins differ from other RiPPs in that there is no N-terminal leader peptide. Rather, the precursor peptide has a C-terminal extension of 35-37 amino acids, hypothesized to act as a recognition sequence for posttranslational machinery.
==== Elimination ==== Atomoxetine and its metabolites are eliminated mainly via excretion into urine. Less than 3% of atomoxetine is excreted unchanged in urine regardless of CYP2D6 status, indicating extensive metabolism. In CYP2D6 extensive metabolizers, who are considered to have normal CYP2D6 activity, more than 96% of a dose of radiolabeled atomoxetine is excreted in urine within 24 hours and 1 to 2% is excreted in feces. Conversely, in CYP2D6 poor metabolizers, excretion is slower, with only 27% excreted after 24 hours, a majority of radioactivity excreted within 72 hours, and ~144 hours required for full excretion. In addition, only 80% of radioactivity is excreted in urine while 13 to 22% is excreted in feces in CYP2D6 poor metabolizers. The major excreted metabolite of atomoxetine is 4-hydroxyatomoxetine glucuronide, which accounts for >80% of the dose in urine but <17% of the dose in feces. The fractions excreted in urine as 4-hydroxyatomoxetine and 4-hydroxyatomoxetine glucuronide account for 86% of a dose in CYP2D6 extensive metabolizers, but only 40% in CYP2D6 poor metabolizers. CYP2D6 poor metabolizers excrete greater amounts of minor atomoxetine metabolites, namely N-desmethylatomoxetine and 2-hydroxymethylatomoxetine and their conjugates, than extensive metabolizers. The elimination half-life of atomoxetine is 4.5 to 5.3 hours in CYP2D6 extensive metabolizers. However, in CYP2D6 poor metabolizers, the half-life of atomoxetine is 19 to 21.6 hours, or about 4-fold longer in comparison.
== January 11, 1982 (Monday) == The lowest temperature ever recorded in England was measured at Newport, Shropshire, where the thermometer reading was −26.1 °C (−15.0 °F). Filming began on Return of the Jedi, the third film in the Star Wars franchise, and the conclusion of the original trilogy, with production starting at sound stages the Elstree Studios in England at Borehamwood, Hertfordshire. Born: Denis Kolodin, Russian footballer with 23 caps for the Russia national team; in Kamyshin, Russian SFSR, Soviet Union Blake Heron, American actor known for his starring role in the 1996 film Shiloh; in Rockville Centre, New York (d. from a drug overdose, 2017) Died: Jiro Horikoshi, Japanese aeronautical engineer who designed the Zero fighter. A. W. Haydon, 75, American inventor wand specialist in miniaturization, known for his invention of 82 devices and innovations, including the microswitch used in computers, as well other devices for use by the general public, by the U.S. military and by NASA Sir Kenneth Strong, 81, British Army Major General and advisor of the Normandy Landings on D-Day in 1944, as well as negotiating the surrender of both Italy and Japan Carl M. Voyles, 83, American Canadian football head coach for the Hamilton Tiger-Cats, known for guiding the team to winning the 1953 Grey Cup Manya Surve, 37, Indian gangster, suspected in multiple murders and robberies, became the first of 622 criminals in Bombay to die in an "encounter killing" by police in the Maharashtra state.
== Future projections == Studies based on historical trends project a continued increase in obesity prevalence in Brazil. A modelling study published in Scientific Reports estimated that nearly 30% of Brazilian adults could be living with obesity by 2030 if existing trends continue. Projections presented at the International Congress on Obesity in 2024 suggested that approximately 48% of Brazilian adults could have obesity by 2044. According to the World Obesity Federation, obesity is expected to generate substantial healthcare and economic burdens in Brazil unless effective prevention and treatment strategies are expanded.
Sources: en.wikipedia.org
== Sources == Foods high in threonine include cottage cheese, poultry, fish, meat, lentils, black turtle bean and sesame seeds. Racemic threonine can be prepared from crotonic acid by alpha-functionalization using mercury(II) acetate.
Many of Pauling's critics, including scientists who appreciated the contributions that he had made in chemistry, disagreed with his political positions and saw him as a naïve spokesman for Soviet communism. In 1960, he was ordered to appear before the Senate Internal Security Subcommittee, which termed him "the number one scientific name in virtually every major activity of the Communist peace offensive in this country". A headline in Life magazine characterized his 1962 Nobel Prize as "A Weird Insult from Norway". Pauling was a frequent target of the National Review magazine. In an article entitled "The Collaborators" in the magazine's July 17, 1962, issue, Pauling was referred to not only as a collaborator, but as a "fellow traveler" of proponents of Soviet-style communism. In 1963, Pauling sued the magazine, its publisher William Rusher, and its editor William F. Buckley, Jr for $1 million. He lost both his libel suits and the 1968 appeal (unlike his earlier 1963 libel case against the Hearst Corporation), because in the meantime the landmark case New York Times Co. v. Sullivan had established the actual malice standard for libel lawsuits by public figures, requiring that not only falsehood but deliberate lying should be proved by the plaintiff in such cases. His peace activism, his frequent travels, and his enthusiastic expansion into chemical-biomedical research all aroused opposition at Caltech. In 1958, the Caltech Board of Trustees demanded that Pauling step down as chairman of the Chemistry and Chemical Engineering Division.
Adults typically range from 120 to 188 cm (47 to 74 in) in head-and-body length, and 63 to 103.5 cm (24.8 to 40.7 in) in shoulder height. Although the American black bear is the smallest bear species in North America (smaller than the brown and polar bears), large males exceed the size of other bear species in other continents. Weight tends to vary according to age, sex, health and season. Adult males typically weigh between 60–300 kg (130–660 lb) with females averaging between 33% and 50% less at 40–150 kg (88–331 lb). Seasonal variation in weight is very pronounced: in autumn, their pre-den weight tends to be 30% higher than in spring, when black bears emerge from their dens. Bears on the East Coast tend to be heavier on average than their West Coast counterparts, although they typically follow Bergmann's rule regarding average size being inversely correlated with environment temperature, and bears from the northwest are often slightly heavier than the bears from the southeast. In California, studies indicate that the average adult mass is 86 kg (190 lb) in males and 58 kg (128 lb) in females. Adults in Yukon Flats National Wildlife Refuge in east-central Alaska were found to average 87.3 kg (192 lb) in males and 63.4 kg (140 lb) in females, whereas on Kuiu Island in southeastern Alaska (where nutrient dense salmon are readily available) adults averaged 115 kg (254 lb). In Great Smoky Mountains National Park, adult males averaged 112 kg (247 lb) and adult females averaged 47 kg (104 lb) per one study.
Under circumstances in which CENPA is lost from a chromosome a fail-safe mechanism has been described in human cells in which CENPB recruits CENPA via a satellite DNA binding domain to repopulate the centromere with CENPA nucleosomes. CENPA interacts directly with the inner kinetochore through proteins including CENPC and CENPN. Through this interaction the microtubules are able to accurately segregate chromosomes during mitosis.
Darkling Beetle/Mealworm Information. Center for Insect Science Education Outreach. University of Arizona. Mealworms and Darkling Beetles (Tenebrio beetle). Archived 2021-04-26 at the Wayback Machine FOSSweb.
Sources: en.wikipedia.org
=== ICD-11 === The ICD-11 defines catatonia as a syndrome of psychomotor disturbances, characterized by the co-occurrence of several symptoms such as stupor, catalepsy, waxy flexibility, mutism, negativism, posturing, mannerisms, stereotypies, psychomotor agitation, grimacing, echolalia, and echopraxia. Catatonia may occur in the context of specific mental disorders, including mood disorders, schizophrenia or other primary psychotic disorders, and neurodevelopmental disorders. It may also be induced by psychoactive substances, including medications, or caused by a medical condition not classified under mental, behavioral, or neurodevelopmental disorders.
At this point, a fully working vaccine has not been created, and it is therefore decided that the best thing for the Syndicate to do is to comply with the original deal and turn over the hybrid to the Colonists in the hope that they are spared the resulting takeover. Before this can be done, however, the Rebels kill all but a few members of the Syndicate in addition to Cassandra, the only living successful alien-human hybrid, before the Syndicate is able to send a signal to the Colonists. Without a successful hybrid, the timetable for the Colonist invasion will not be advanced and the date set for colonization remains December 22, 2012.
=== Acidity === Thiols are easily deprotonated. Relative to the alcohols, thiols are more acidic. The conjugate base of a thiol is called a thiolate. Butanethiol has a pKa of 10.5 vs 15 for butanol. Thiophenol has a pKa of 6, versus 10 for phenol. A highly acidic thiol is pentafluorothiophenol (C6F5SH) with a pKa of 2.68. Thus, thiolates can be obtained from thiols by treatment with alkali metal hydroxides.
Legumin is family of globular proteins obtained from beans, peas, lentils, vetches, hemp and other leguminous seeds. Garden peas are a common nutritional source for humans that contains legumin. Legumin is similar to the casein of mammalian milk and was called "vegetable casein" since it was considered analogous to the mammalian protein. The primary function of the legumin protein in seeds is storage. Legumin proteins are one of the main storage proteins of angiosperms and gymnosperms. Legumin is an insoluble hexameric conjugated protein with a high concentration of carbon and oxygen.
Sources: en.wikipedia.org
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.
Lyophilized powder is usually kept frozen and protected from moisture. Solutions are less stable and are often used promptly or divided into aliquots to avoid repeated freeze-thaw cycles. Exact shelf-life values depend on purity and handling.
No. A purity figure derived from chromatographic area does not prove the amino acid sequence. Identity requires an orthogonal method such as mass spectrometry or sequencing. Truncated or isomerized peptides can co-elute with the target compound.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.