A practical reference on Peptidase stability: 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.
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.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
| Property | Value | Notes |
|---|---|---|
| Typical purity specification | 95 percent or higher by RP-HPLC | Area percentage of the main peak |
| Identity confirmation | Electrospray ionization mass spectrometry | Observed mass compared with the theoretical value near 751.9 Da |
| Recommended dry storage | -20 °C, desiccated | -80 °C for multi-year archival material |
| Solution handling | Prepare fresh; avoid long storage | Sterile filtration reduces microbial load |
| Common synonyms | TKPRPGP; TP-7 | Sequence code and laboratory designation used interchangeably |
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
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.
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.
== In polymer physics == In some scientific areas such as polymer physics, one may consider a chain of points and links between consecutive points. If the points are sequentially numbered and located at positions r1, r2, r3, etc. then bond vectors are defined by u1=r2−r1, u2=r3−r2, and ui=ri+1−ri, more generally. This is the case for kinematic chains or amino acids in a protein structure. In these cases, one is often interested in the half-planes defined by three consecutive points, and the dihedral angle between two consecutive such half-planes. If u1, u2 and u3 are three consecutive bond vectors, the intersection of the half-planes is oriented, which allows defining a dihedral angle that belongs to the interval (−π, π]. This dihedral angle is defined by
Ottoman anti slavery laws where not enforced in the late 19th-century, particularly not in Hejaz; the first attempt to ban the Red Sea slave trade in 1857, the firman of 1857, resulted in a rebellion in the Hejaz Province, the Hejaz rebellion, which resulted in Hejaz being exempted from the ban. The Anglo-Ottoman Convention of 1880 formally banned the Red Sea slave trade, but it was not enforced in the Ottoman Provinces in the Arabian Peninsula. In the late 19th century, the Sultan of Morocco stated to Western diplomats that it was impossible for him to ban slavery because such a ban would not be enforceable, but the British asked him to ensure that the slave trade in Morocco would at least be handled discreet and away from the eyes of foreign witnesses. Chattel slavery lasted in most of the Middle East until the 20th century. The Red Sea slave trade still provided enslaved people from Africa to the Arabian Peninsula after World War II. As recently as the 1960s, Saudi Arabia's slave population was estimated at 300,000. Along with Yemen, the Saudis abolished slavery in 1962.
==== Slovak ==== First Catholic Slovak Ladies Association - Founded January 1, 1892, at St. Ladislaus Church in Cleveland as the First Catholic Slovak Ladies Union. Adopted the current name in the late 1960s. Absorbed some smaller fraternals over the years, including the Cleveland Slovak Union in 1945, the Slovak Catholic Cadets Union, the Catholic Slovak Benefit Organization of Cleveland, and the Catholic Slovak Brotherhood from Braddock, Pennsylvania. In 1969 it absorbed the Catholic Slovak Union, which had 1,500 members. Had 102,000 members in 1965, 95,000 in 1979 and 87,000 in 1994 Headquarters in Beachwood, Ohio. Locals called "Branches", present in 12 states and two Canadian provinces. National convention meets quadrennially. Gives aid to convents, monasteries, a theological seminary in Rome, and a "priest scholarship" underwritten by the Cleveland diocese. Awards $10,000 in nursing and college scholarships annually; maintains home for the aged in Beachwood. Organizes biannual youth conferences for people 16-20 which emphasizes the fraternal benefit system. Those who have been with the group for 25 years receive a pin, and 50 years a cash reward. First Catholic Slovak Union of the United States of America and Canada - Slovak name Prva Katolicka Slovenska Jednota Originally organized as the St. Joseph Society for Slovak Catholics in Cleveland, May 5, 1889. On April 9, 1890, they voted to form a union of all Slovak Catholic societies in the US. A union convention took place in Cleveland on September 4, 1890, and united seven Slovak Catholic societies.
Many canids feed opportunistically on carrion. Examples include foxes such as the Arctic fox, corsac fox, gray fox, kit fox and red fox, hyenas such as the brown hyena, spotted hyena and striped hyena, black-backed jackals and golden jackals, as well as coyotes, culpeos, dingoes, gray wolves, Pampas zorros, and raccoon dogs. Types of carrion fed upon ranges from dead wildlife and dead livestock to abandoned predator kills and hunting discards. Anatomically and immunologically, canids are well-adapted to carrion feeding. For example, gray wolves hold food in their stomachs for at least twice as long as humans and other primates. This gives their gastric acid longer to kill pathogens before they enter the small intestine. The intestinal tracts of canids are also much shorter than those of primates, so pathogens have less time to multiply and cause disease prior to their expulsion. Anti-botulinum antibodies are an additional antibacterial defense detected in coyotes.
Motorsport Space travel Sports equipment Sailing Orthopedic technology in orthotics as well as in prosthetics In electrical engineering as an "intermediate layer" in multilayer circuit boards and as insulating material for electrical machines and transformers Rotor blades in wind turbines
Sources: en.wikipedia.org
== Food processing level == Food processing level (FPL) is a parameter used for grouping of food processing according to physical and (bio)chemical changes taking place in food materials during processing. Definition of the extent of processing benefits from the use of an ordinal level of measurement. Arbitrary grouping of processed food using nominal scales, such as extent of change, nature of change, raw material sources, ingredients used, place of processing, purpose of processing, traditional, novel and other type of treatments is often criticised. Ranking of food processing at an ordinal scale at any stage from food production in agriculture to eating by consumer describes the extent of food processing using the order of the different levels of processing. Processed food classifications often identify processing as a criterion for the grouping of processed foods. Some processed food classifications, such as the Nova classification, emphasise the role of processing in the development of obesity and noncommunicable diseases. The public health interest is particularly in the Nova category of ultra-processed foods, a highly processed foods category, which often causes controversy on whether ingredients of processed foods or food processing relate to adverse health outcomes.
Pro-gastrin-releasing-peptide, also known as Pro-GRP, is a gastrin-releasing peptide (GRP) precursor, a neurotransmitter that belongs to the bombesin-related neuromedin B family. GRP stimulates the secretion of gastrin in order to increase the acidity of the gastric acid. Pro-GRP is a peptide composed of 125 amino acids, expressed in the nervous system and digestive tract. It is different from progastrin, consisting of 80 amino acids, precursor of gastrin in its intracellular version and oncogene in its extracellular version (hPG80). The presence of GRP in lung cancer samples was identified in 1983. In pathological situations, GRP has mitogenic activity in vitro in many cancers including pancreatic cancer, small cell lung carcinoma, prostate cancer, kidney cancer, breast and colorectal cancer. GRP could operate as an autocrine growth factor. In cancers, GRP induces cell growth and inhibits apoptosis by shutting down the endoplasmic reticulum stress pathway. The mechanisms of the impacted signal pathways have not been established. As early as 1994, research on Pro-GRP as a biomarker for small-cell lung carcinoma began. Because of the very short half-life of GRP (2 minutes), the Pro-GRP is used for measurements and analysis. Since then, Pro-GRP has been used as a tumor marker for patients with small-cell lung carcinoma in limited and extended stages.
While Compulsion Games are a Canadian studio based out of Montreal, many of them are fascinated by British television and film, which formed much of the influence on We Happy Few. The 1960s British setting was found to be ideal for the game and concept; according to Compulsion's COO Sam Abbott, this was "a great period with lots of relentless optimism about the future, while also at the same time ignoring a lot of actual problems that existed in the society of the time". Dystopic fiction was a common influence. Provost stated that a primary influence was the 1985 dystopian film Brazil. Other influential works include The Prisoner, A Clockwork Orange, Brave New World, V for Vendetta and Doctor Who, along with the humor of Monty Python and Blowup for the game's aesthetics. Some of the Compulsion team, including Provost, had been with Arkane Studios during a time where they were secretly developing an episode for the Half-Life series, also set in a dystopian world, which carried into We Happy Few. Provost felt the belief of citizens that they were in a utopia and the darker reality "under the hood" formed the "basis" of dystopian fiction. The idea of the Wellies wearing masks was seen as flipping around the use of Guy Fawkes masks in V for Vendetta, that instead of being a sign of resistance, they would be "a symbol of the psychological oppression", forcing their wearer to be smiling all the time, according to Provost.
==== Safety ==== The safety of red yeast rice (RYR) products has not been established. Some supplements have been found to contain high levels of citrinin, which can be toxic to the liver, kidneys, and cellular DNA. Commercial products also have highly variable amounts of monacolins and rarely declare this content on the label, making risk assessment difficult. Ingredient suppliers have been suspected of "spiking" red yeast rice preparations with purified lovastatin. One published analysis reported several commercial products as being almost entirely monacolin K—which would occur if the drug lovastatin was illegally added—rather than the expected composition of many monacolin compounds. There are reports in the literature of muscle myopathy and liver damage resulting from red yeast rice usage. From a review: "The potential safety signals of myopathies and liver injury raise the hypothesis that the safety profile of RYR is similar to that of statins. Continuous monitoring of dietary supplements should be promoted to finally characterize their risk profile, thus supporting regulatory bodies for appropriate actions." The European Food Safety Authority (EFSA) Panel on Food Additives and Nutrient Sources added to Food concluded that when red yeast rice preparations contained monacolins, the Panel was unable to identify an intake that it could consider as safe. The reason given was case study reports of severe adverse reactions to products containing monacolins at amounts as low as 3 mg/day. Red yeast rice is not recommended during pregnancy or breast-feeding.
Sources: en.wikipedia.org
== See also == Timeline of Knoxville, Tennessee History of Tennessee List of people from Knoxville, Tennessee National Register of Historic Places listings in Knox County, Tennessee East Tennessee Historical Society
== In cancer progression and metastasis == Initiation of metastasis requires invasion, which is enabled by EMT. Carcinoma cells in a primary tumor lose cell-cell adhesion mediated by E-cadherin repression and break through the basement membrane with increased invasive properties, and enter the bloodstream through intravasation. Later, when these circulating tumor cells (CTCs) exit the bloodstream to form micro-metastases, they undergo MET for clonal outgrowth at these metastatic sites. Thus, EMT and MET form the initiation and completion of the invasion-metastasis cascade. At this new metastatic site, the tumor may undergo other processes to optimize growth. For example, EMT has been associated with PD-L1 expression, particularly in lung cancer. Increased levels of PD-L1 suppresses the immune system which allows the cancer to spread more easily. EMT confers resistance to oncogene-induced premature senescence. Twist1 and Twist2, as well as ZEB1 protects human cells and mouse embryonic fibroblasts from senescence. Similarly, TGF-β can promote tumor invasion and evasion of immune surveillance at advanced stages. When TGF-β acts on activated Ras-expressing mammary epithelial cells, EMT is favored and apoptosis is inhibited. This effect can be reversed by inducers of epithelial differentiation, such as GATA-3. EMT has been shown to be induced by androgen deprivation therapy in metastatic prostate cancer. Activation of EMT programs via inhibition of the androgen axis provides a mechanism by which tumor cells can adapt to promote disease recurrence and progression.
The band had been using drum tapes on tour before Thomas. Their next release was the new recording "Sidewalking", released in March 1988, and backed by some of the live tracks, followed a month later by Barbed Wire Kisses. Later that year, they did a remix for the single "Birthday" by The Sugarcubes. In September 1989, The band provided backing vocals for the Erasure single "Drama!". The band's third studio album, Automatic, was released in October 1989, by which time Evans had been replaced by Ben Lurie. Boasting heavy use of synthesized bass and keyboards, the album was not received quite as well as its predecessors. It contained the singles "Head On" and "Blues from a Gun". By this time, the violence that was originally associated with the band was practically non-existent and the Reid brothers were less antagonistic and aggressive in general. The Rollercoaster EP (August 1990) would be their last release for over a year, the band undertaking a tour of the same name with My Bloody Valentine, Dinosaur Jr., and Blur.
Sources: en.wikipedia.org
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.
A reported purity value reflects the share of the main peak in one chromatographic run and says nothing about identity. Confirming that the expected sequence is present requires a separate measurement such as mass spectrometry. Purity and identity are distinct questions.
A mass spectrum reports the molecular masses present in a sample and shows whether they match the value expected for selank, near 751.9 Da. It also flags common artifacts such as truncation or adduct formation. It does not establish correct stereochemistry or complete sequence order on its own.
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.