The short version of Peptidase stability 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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
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.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
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.
==== Electoral environment ==== According to Gallup, most factors with respect to the electoral environment favored Republicans and Trump. These included low confidence in the economy, Republicans outnumbering Democrats in party affiliation (48–45%), low national satisfaction, Republicans being favored to address the economy and immigration, and Biden's low job approval rating. Harris was viewed more favorably on character and had an advantage on some issues. No incumbent party has won when a president had below a 45% approval rating, either losing reelection (Jimmy Carter in 1980, George H. W. Bush in 1992, and Trump himself in 2020) or the incumbent party lost the White House (Hubert Humphrey in 1968). According to exit polls, voters disapproved of Biden's performance 59–39%, and disapproved of how things were going in the United States 73–25%. Also, voters judged the economy negatively 68–32%, and said that inflation had caused them hardship 75–24%. A YouGov poll conducted from November 6–7, 2024 found that if Biden had been the Democratic nominee, Trump would have won the popular vote 49–42%. Nonpartisan election forecasters, including The Cook Political Report and Sabato's Crystal Ball, stated before the election that Biden would have been almost certain to lose. Harris did improve compared to Biden among voters making over $100,000 a year. NBC News found that Trump made larger gains in counties with tougher housing markets.
=== EC 1.7.99 With other acceptors === EC 1.7.99.1: hydroxylamine reductase EC 1.7.99.2: deleted: reaction may have been due to the combined action of EC 1.7.99.6 nitrous-oxide reductase and EC 1.7.99.7 nitric-oxide reductase EC 1.7.99.3: Now included with EC 1.7.2.1, nitrite reductase (NO-forming) EC 1.7.99.4: Now EC 1.7.1.1, nitrate reductase (NADH), EC 1.7.1.2, nitrate reductase [NAD(P)H], EC 1.7.1.3, nitrate reductase (NADPH), EC 1.7.5.1, nitrate reductase (quinone), EC 1.7.7.2, nitrate reductase (ferredoxin) and EC 1.9.6.1, nitrate reductase (cytochrome) EC 1.7.99.5: Now included with EC 1.5.1.20, methylenetetrahydrofolate reductase [NAD(P)H] EC 1.7.99.6: Now EC 1.7.2.4 nitrous-oxide reductase EC 1.7.99.7: Now EC 1.7.2.5 nitric oxide reductase (cytochrome c) EC 1.7.99.8: hydroxylamine oxidoreductase EC 1.7.99.8: Now classified as EC 1.7.2.8, hydrazine dehydrogenase
=== Resistance === Resistance to colistin is rare, but has been described. As of 2017, no agreement exists about how to define colistin resistance. The Société Française de Microbiologie uses a MIC cut-off of 2 mg/L, whereas the British Society for Antimicrobial Chemotherapy sets a MIC cutoff of 4 mg/L or less as sensitive, and 8 mg/L or more as resistant. No standards for describing colistin sensitivity are given in the United States. The first known colistin-resistance gene in a plasmid which can be transferred between bacterial strains is mcr-1. It was found in 2011 in China on a pig farm where colistin is routinely used and became publicly known in November 2015. The presence of this plasmid-borne gene was confirmed starting December 2015 in South-East Asia, several European countries, and the United States. It is found in certain strains of the bacteria Paenibacillus polymyxa. India reported the first detailed colistin-resistance study, which mapped 13 colistin-resistant infections recorded over 18 months. It concluded that pan-drug-resistant infections, particularly those in the bloodstream, have a higher mortality. Multiple other cases were reported from other Indian hospitals. Although resistance to polymyxins is generally less than 10%, it is more frequent in the Mediterranean and South-East Asia (Korea and Singapore), where colistin resistance rates are increasing. Colistin-resistant E. coli was identified in the United States in May 2016. Multiple mobile colistin resistance (mcr) genes have been identified since the discovery of mcr-1.
== Chemistry == Kurtoxin is a protein containing 63 amino acid residues with a mass of 7386.1 daltons. Its formula is C324H478N94O90S8. It can be isolated from the venom of Parabuthus transvaalicus by high-performance liquid chromatography (HPLC). Kurtoxin is closely related to α-scorpion toxins, a family of toxins that slow inactivation of voltage-gated sodium channels. The complete primary amino-acid sequence of kurtoxin is: KIDGYPVDYW NCKRICWYNN KYCNDLCKGL KADSGYCWGW TLSCYCQGLP DNARIKRSGR CRA.
inosine (I, Ino) A naturally occurring, non-canonical nucleoside consisting of a hypoxanthine base with its N9 nitrogen bonded to the C1 carbon of a ribose sugar. Inosine may be incorporated into certain RNA molecules such as the anticodons of some transfer RNAs, and occurs as an intermediate in the breakdown of adenosine to uric acid and in the recycling of adenosine by salvage pathways.
Sources: en.wikipedia.org
subsequently found that HClO destroys cytochromes and iron-sulfur clusters and observed that oxygen uptake is abolished by HClO and adenine nucleotides are lost. It was also observed that irreversible oxidation of cytochromes paralleled the loss of respiratory activity. One way of addressing the loss of oxygen uptake was by studying the effects of HClO on succinate-dependent electron transport. Rosen et al. found that levels of reductable cytochromes in HClO-treated cells were normal, and these cells were unable to reduce them. Succinate dehydrogenase was also inhibited by HClO, stopping the flow of electrons to oxygen. Later studies revealed that Ubiquinol oxidase activity ceases first, and the still-active cytochromes reduce the remaining quinone. The cytochromes then pass the electrons to oxygen, which explains why the cytochromes cannot be reoxidized, as observed by Rosen et al. However, this line of inquiry was ended when Albrich et al. found that cellular inactivation precedes loss of respiration by using a flow mixing system that allowed evaluation of viability on much smaller time scales. This group found that cells capable of respiring could not divide after exposure to HClO.
Ernest William Beckett (1856–1917), who became the 2nd Baron Grimthorpe. Helen Louisa Beckett-Denison (1858–1935). Adeline Gertrude Beckett-Denison (1859–1902), who married Sir Frederick Milner, 7th Baronet. Violet Katharine Beckett-Denison (1860–1883), who married Reginald Walkeline Chandos-Pole, grandson of Leicester Stanhope, 5th Earl of Harrington. Maud Augusta Beckett-Denison (1864–1927), who married Lord Henry Nevill (later 3rd Marquess of Abergavenny). William Gervase Beckett (1866–1937), who became Sir Gervase Beckett, 1st Baronet of Kirkdale Manor. Hon. Rupert Evelyn Beckett (1870–1955), who married Muriel Helen Florence Paget, granddaughter of Henry Paget, 2nd Marquess of Anglesey. Beckett died at the age of 64 when he fell under a train at Wimborne. He had arrived at Wimborne railway station to change trains for Bournemouth, and while waiting, he went for a walk. He was walking beside the track on the way back to the station when a strong wind blew his hat off, and he fell almost immediately under the train. His body was cut to pieces and carried some 56 feet. Following his death, Mrs. Gertrude Beatrice Brinkworth alleged she was his mistress and mother of his adopted children and sued his executors. Some money was paid, but the case came before the court, and the jury declared Mrs. Brinkworth's case to be a 'swindle' and rejected her claims even before the evidence in the case had been completed.
== Further reading == Lamarck, J.B.P.; De Monet, Comte De (1815) [1814]. "Suite des polypiers empâtés". Mémoires du Muséum d'Histoire Naturelle. 1: 69–80, 162–168, 331–340. Hooper, J.N.A.; Wiedenmayer, F. (1994). "Porifera". In Wells, A. (ed.). Zoological Catalogue of Australia. Vol. 12. pp. 1–620.
=== Block === In most US cities, a city block is between 1⁄16 and 1⁄8 mi (100 and 200 m). In Manhattan, the measurement "block" usually refers to a north–south block, which is 1⁄20 mi (80 m). Sometimes people living in places (like Manhattan) with a regularly spaced street grid will speak of long blocks and short blocks. Within a typical large North American city, it is often only possible to travel along east–west and north–south streets, so travel distance between two points is often given in the number of blocks east–west plus the number north–south (known to mathematicians as the Manhattan distance).
The EU adopted the listing of PFOA in Annex A of the Stockholm Convention with Commission Delegated Regulation (EU) 2020/784 of 8 April 2020 and introduced a limit value of 0,025 mg/kg for PFOA including its salts, and at 1 mg/kg for the individual PFOA-related compounds or a combination of those compounds. They also included some specific exemptions. Among them is a time-bound exemption for PFOA in fire-fighting foam.
Sources: en.wikipedia.org
An extension of a one-page handout that Lappé had circulated among her fellow improvisors in Berkeley, Diet for a Small Planet (1971) soon became the vegetarian text of the ecology movement, selling in the next ten years almost two million copies in three editions and six languages. Lappé wrote:
Guest speakers that term included Rajani Palme Dutt, Lady Violet Bonham Carter, his old headmaster John Wolfenden and Jacob Bronowski, whilst Aneurin Bevan addressed a packed meeting of the University Labour Club, chaired by Anthony Howard, in the Union Chamber.
=== Imprinting === Molecular imprinting describes a process by which a host is constructed from small molecules using a suitable molecular species as a template. After construction, the template is removed leaving only the host. The template for host construction may be subtly different from the guest that the finished host binds to. In its simplest form, imprinting uses only steric interactions, but more complex systems also incorporate hydrogen bonding and other interactions to improve binding strength and specificity.
=== Boat length === In rowing races such as the Oxford and Cambridge Boat Race, the margin of victory or defeat is expressed in fractions and multiples of boat lengths. The length of a rowing eight is about 62 feet (19 m). This is also commonly expressed in time i.e. 3 or 3.5 seconds. A shorter distance is the canvas, which is the length of the covered part of the boat between the bow and the bow oarsman, and equivalent to less than one second. The Racing Rules of Sailing also makes heavy use of boat lengths.
Sources: en.wikipedia.org
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
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.