The short version of Pro-Gly-Pro fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
In cosmetic applications, botulinum toxin is considered relatively safe and effective for reduction of facial wrinkles, especially in the uppermost third of the face. Commercial forms are marketed under the brand names Botox Cosmetic/Vistabel from Allergan, Dysport/Azzalure from Galderma and Ipsen, Xeomin/Bocouture from Merz, Jeuveau/Nuceiva from Evolus, manufactured by Daewoong in South Korea. The effects of botulinum toxin injections for glabellar lines ("11's lines" between the eyes) typically last two to four months and in some cases, product-dependent, with some patients experiencing a longer duration of effect of up to six months or longer. Injection of botulinum toxin into the muscles under facial wrinkles causes relaxation of those muscles, resulting in the smoothing of the overlying skin. Smoothing of wrinkles is usually visible three to five days after injection, with maximum effect typically a week following injection. Muscles can be treated repeatedly to maintain the smoothed appearance. DaxibotulinumtoxinA (Daxxify) was approved for medical use in the United States in September 2022. It is indicated for the temporary improvement in the appearance of moderate to severe glabellar lines. DaxibotulinumtoxinA is an acetylcholine release inhibitor and neuromuscular blocking agent. The FDA approved daxibotulinumtoxinA based on evidence from two clinical trials (Studies GL-1 and GL-2), of 609 adults with moderate to severe glabellar lines. The trials were conducted at 30 sites in the United States and Canada.
Since the bacteriophage Phage Φ-X174 was sequenced in 1977, the DNA sequences of thousands of organisms have been decoded and stored in databases. This sequence information is analyzed to determine genes that encode proteins, RNA genes, regulatory sequences, structural motifs, and repetitive sequences. A comparison of genes within a species or between different species can show similarities between protein functions, or relations between species (the use of molecular systematics to construct phylogenetic trees). With the growing amount of data, it long ago became impractical to analyze DNA sequences manually. Computer programs such as BLAST are used routinely to search sequences—as of 2008, from more than 260,000 organisms, containing over 190 billion nucleotides.
Many buildings in the city are classified as "historical monuments", but the 2000s marked the real recognition of Le Havre's architectural heritage. The city received the label "City of Art and History" in 2001, then in 2005 UNESCO inscribed the city of Le Havre as a World Heritage Site. The oldest building still standing in Le Havre is the Graville Abbey. The other medieval building in the city is the Chapel of Saint-Michel of Ingouville. Because of the bombing in 1944, heritage from the modern era is rare: Le Havre Cathedral, the Church of Saint Francis, the Museum of the Hotel Dubocage of Bleville, the House of the ship-owner and the old palace of justice (now the Natural History Museum) are concentrated in the Notre-Dame and Saint-François areas. The buildings of the 19th century testify to the maritime and military vocations of the city: the Hanging Gardens, the Fort of Tourneville, Vauban docks, and the Maritime Villa. The heritage of the 1950s and 1960s which were the work of the Auguste Perret workshop forms the most coherent architecture: the Church of Saint Francis and the Town Hall are the centrepieces. The all curved architecture of the "Volcano", designed by Oscar Niemeyer, contrasts with that of the rebuilt centre. Finally, the reconstruction of many districts is a showcase for the architecture of the 21st century. Among the achievements by renowned architects are the Chamber of Commerce and Industry (René and Phine Weeke Dottelond), Les Bains Des Docks (Jean Nouvel). °
Sources: en.wikipedia.org
For centuries, naturalists treated lichens as self-contained, plant-like organisms distinguished only by outward appearance. Theophrastus (c. 300 BC) introduced the word lichen for crusty bark growths, yet offered little insight beyond the name. Until the mid-1700s, taxonomists lumped lichens with algae, mosses, or fungi in broad, pre-evolutionary schemes. A pivotal step came in 1700, when the French botanist Joseph Pitton de Tournefort erected the genus Lichen, acknowledging the group's distinctiveness—even while keeping it beside mosses and liverworts. Robert Morison's 1699 Herbarium, for instance, split lichens into five "Muscofungi" types, a purely morphological scheme that left little mark on later work. The Italian polymath Pier Antonio Micheli published the first recognizable lichen classification in his 1729 Nova plantarum genera. While he kept all species in the catch‑all genus Lichen—echoing Tournefort—Micheli organized them into several "orders" based on thallus texture and fruiting body form. Those informal groupings later became the nuclei of modern genera, and his morphological terminology laid the groundwork for subsequent binomial treatments. In 1753 Carl Linnaeus introduced the first coherent plant-classification scheme in Species Plantarum. He listed roughly 80 lichen species, grouping almost all under the single genus Lichen. Such compression mirrored 18th-century ignorance of lichen diversity: 'lichen' was little more than a catch-all for crusty or leafy growths on bark and stone.
Afucosylated antibodies are intensely used in the field of advanced medicine, also due to their high ADCC (antibody-dependent cellular cytotoxicity). This makes them effective in binding to specific targets while minimizing damage to surrounding tissue. Some of the fields in which afucosylated antibodies are used or considered for application are: cancer immunotherapy autoimmune diseases Infectious diseases Furthermore, afucosylated antibodies are used as diagnostic tools and play a role in the development of personalized medications.
Naked extracellular DNA (eDNA), most of it released by cell death, is nearly ubiquitous in the environment. Its concentration in soil may be as high as 2 μg/L, and its concentration in natural aquatic environments may be as high at 88 μg/L. Various possible functions have been proposed for eDNA: it may be involved in horizontal gene transfer; it may provide nutrients; and it may act as a buffer to recruit or titrate ions or antibiotics. Extracellular DNA acts as a functional extracellular matrix component in the biofilms of several bacterial species. It may act as a recognition factor to regulate the attachment and dispersal of specific cell types in the biofilm; it may contribute to biofilm formation; and it may contribute to the biofilm's physical strength and resistance to biological stress. Cell-free fetal DNA is found in the blood of the mother, and can be sequenced to determine a great deal of information about the developing fetus. Under the name of environmental DNA eDNA has seen increased use in the natural sciences as a survey tool for ecology, monitoring the movements and presence of species in water, air, or on land, and assessing an area's biodiversity.
226Ra occurs in the decay chain of uranium-238 (238U), which is the most common naturally occurring isotope of uranium. It undergoes alpha decay to radon-222, which is also radioactive; the decay chain ultimately terminates at lead-206. Because of its occurrence in the 238U decay chain, 226Ra exists naturally at low concentrations not only in uranium-containing minerals, but universally diffused in the environment (as also is uranium), as in soil and groundwater.
Sources: en.wikipedia.org
Woodhouse College is a single site selective state sixth form centre situated between North Finchley and Friern Barnet on the eastern side of the London Borough of Barnet in North London, England. It was formerly a state grammar school, known as Woodhouse Grammar School.
== Limitations == While mice are by far the most widely used animals in biomedical research, recent studies have highlighted their limitations. For example, the utility of rodents in testing for sepsis, burns, inflammation, stroke, ALS, Alzheimer's disease, diabetes, cancer, multiple sclerosis, Parkinson's disease, and other illnesses has been called into question by a number of researchers. Regarding experiments on mice, some researchers have complained that "years and billions of dollars have been wasted following false leads" as a result of a preoccupation with the use of these animals in studies. Mice differ from humans in several immune properties: mice are more resistant to some toxins than humans; have a lower total neutrophil fraction in the blood, a lower neutrophil enzymatic capacity, lower activity of the complement system, and a different set of pentraxins involved in the inflammatory process; and lack genes for important components of the immune system, such as IL-8, IL-37, TLR10, ICAM-3, etc. Laboratory mice reared in specific-pathogen-free (SPF) conditions usually have a rather immature immune system with a deficit of memory T cells. These mice may have limited diversity of the microbiota, which directly affects the immune system and the development of pathological conditions. Moreover, persistent virus infections (for example, herpesviruses) are activated in humans, but not in SPF mice with septic complications and may change the resistance to bacterial coinfections. "Dirty" mice are possibly better suitable for mimicking human pathologies.
The price of real estate in Moscow continues to increase. The expected price averages $4,000 per square meter (11 sq ft) near the perimeter of the city or $6,500–8,000 per square meter in a prestigious district. The price sometimes exceeds $40,000 per square meter for a flat. Renting costs about $1,200 per month for a one-bedroom apartment and about $1,000 per month for a studio in the city center. A typical one-bedroom apartment in Moscow is about 30 square meters (320 square feet) in area; a typical two-bedroom apartment is 45 square meters (480 square feet); and a typical three-bedroom apartment is 70 square meters (750 square feet). Many residents cannot move out of their apartments, especially if a family lives in a two-room apartment originally granted by the state during the Soviet era. Some city residents have attempted to cope with the cost of living by renting out their apartments while staying in dachas (country houses) outside the city. In 2006, Mercer Human Resources Consulting named Moscow the world's most expensive city for expatriate employees, ahead of recurring winner Tokyo, because of the stable Russian ruble as well as increasing housing prices. Moscow also ranked first in the 2007 edition and 2008 edition of the survey. However, in 2009, Tokyo overtook Moscow, which came in third after Osaka. In 2014, according to Forbes magazine, Moscow was ranked the world's ninth most expensive city. This magazine ranked Moscow the second most expensive city the previous year.
=== Reactivity === The reactivities of the alkali metals increase going down the group. This is the result of a combination of two factors: the first ionisation energies and atomisation energies of the alkali metals. Because the first ionisation energy of the alkali metals decreases down the group, it is easier for the outermost electron to be removed from the atom and participate in chemical reactions, thus increasing reactivity down the group. The atomisation energy measures the strength of the metallic bond of an element, which falls down the group as the atoms increase in radius and thus the metallic bond must increase in length, making the delocalised electrons further away from the attraction of the nuclei of the heavier alkali metals. Adding the atomisation and first ionisation energies gives a quantity closely related to (but not equal to) the activation energy of the reaction of an alkali metal with another substance. This quantity decreases going down the group, and so does the activation energy; thus, chemical reactions can occur faster and the reactivity increases down the group.
=== Lift-check valve === A lift-check valve is a check valve in which the disc, sometimes called a lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. A guide keeps motion of the disc on a vertical line, so the valve can later reseat properly. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.
Sources: en.wikipedia.org
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
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.