pharmacokinetics raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-03-07. Anything still debated is marked as such rather than presented as settled.
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.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
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.
Ambient ionization is a form of ionization in which ions are formed in an ion source outside the mass spectrometer without sample preparation or separation. Ions can be formed by extraction into charged electrospray droplets, thermally desorbed and ionized by chemical ionization, or laser desorbed or ablated and post-ionized before they enter the mass spectrometer.
The first clinical study of vosilasarm, a small (n=22) phase 1 study in women with metastatic breast cancer, was started in 2017 and completed in 2020, with results published in 2019, 2020, and 2022. As of March 2023, vosilasarm is in phase 1/2 clinical trials for the treatment of breast cancer. Aside from its development as a potential pharmaceutical drug, vosilasarm is on the World Anti-Doping Agency list of prohibited substances and is sold for physique- and performance-enhancing purposes by black-market Internet suppliers. Vosilasarm is often used in these contexts at doses that have not been evaluated in clinical trials, with unknown effectiveness and safety. Many products sold online that are purported to be a specific SARM either contain none or contain other unrelated substances. Social media has played an important role in facilitating the widespread non-medical use of SARMs.
Chell is the player-character in both Portal games. She is a silent protagonist outside of small grunts during physical tasks. Very little truthful information is known about Chell; while GLaDOS makes many statements to Chell's background and history, GLaDOS herself admits she is unreliable. The only consistent fact that is used through the series is that Chell's parents gave her away. Whether they did it intentionally or not is unknown. Chell's appearance is modeled after Alésia Glidewell
"Mr Pace said the Ministry of the Interior was 'acting as a rogue element within the government'. It was controlled by the main Shia party, the Supreme Council for Islamic Revolution in Iraq (SCIRI); the Interior Minister, Baqir Jabr al-Zubeidi, is a former leader of SCIRI's Badr Brigade militia, which was one of the main groups accused of carrying out sectarian killings. Another was the Mahdi Army of the young cleric Muqtada al-Sadr, who is now part of the Shia coalition seeking to form a government after winning the mid-December election. Many of the 110,000 policemen and police commandos under the ministry's control are suspected of being former members of the Badr Brigade. Not only counterinsurgency units such as the Wolf Brigade, the Scorpions, and the Tigers, but the commandos and even the highway patrol police were accused of acting as death squads during this period over a decade ago.
Sources: en.wikipedia.org
==== Gas samples ==== Gaseous samples require a sample cell with a long pathlength to compensate for the diluteness. The pathlength of the sample cell depends on the concentration of the compound of interest. A simple glass tube with length of 5 to 10 cm equipped with infrared-transparent windows at both ends of the tube can be used for concentrations down to several hundred ppm. Sample gas concentrations well below ppm can be measured with a White's cell in which the infrared light is guided with mirrors to travel through the gas. White's cells are available with optical pathlength starting from 0.5 m up to hundred meters.
Although hot dogs are cooked during manufacture, it is still recommended that packaged hot dogs be heated to an internal temperature of at least 165 °F (75 °C) before consumption. Hot dogs are a form of processed meat. According to the International Agency for Research on Cancer (IARC), processed meat causes cancer, particularly colorectal cancer. Most hot dogs contain nitrite and/or nitrate preservatives, which react with amines in meat to form carcinogenic N-nitroso compounds. Hot dogs are also high in fat and salt. An American Institute for Cancer Research (AICR) report found that consuming one daily 50-gram serving of processed meat—about one hot dog—increases long-term risk of colorectal cancer by 20%. Thus, eating a hot dog every day would increase the probability of developing colorectal cancer by 5.8–7%. The AICR's warning campaign has been criticized as being "attack ads" by conservative news organization Fox News. The Cancer Project group filed a class-action lawsuit demanding warning labels on packages and at sporting events. Due to their size, shape, and ubiquitous consumption, hot dogs present a significant choking risk, especially for children. A study in the US found that 17% of food-related asphyxiations among children younger than 10 years of age were caused by hot dogs. The risk of choking on a hot dog is greatly reduced by slicing it. It has been suggested that redesigning the size, shape, and texture of hot dogs would reduce the risk of choking.
== Industrial sources == The majority of l-cysteine is obtained industrially by hydrolysis of animal materials, such as poultry feathers or hog hair. Despite widespread rumor, human hair is rarely a source material. Indeed, food additive or cosmetic product manufactures may not legally source from human hair in the European Union. Some animal-originating sources of l-cysteine as a food additive contravene kosher, halal, vegan, or vegetarian diets. To avoid this problem, synthetic l-cysteine, compliant with Jewish kosher and Muslim halal laws, is also available, albeit at a higher price. The typical synthetic route involves fermentation with an artificial E. coli strain. Alternatively, Evonik (formerly Degussa) introduced a route from substituted thiazolines. Pseudomonas thiazolinophilum hydrolyzes racemic 2‑amino-Δ2‑thiazoline-4‑carboxylic acid to l‑cysteine.
Mutagenesis and selection has been performed on an RNA ligase ribozyme from a large pool of random RNA sequences, resulting in isolation of the improved "Round-18" polymerase ribozyme in 2001 which could catalyze RNA polymers now up to 14 nucleotides in length. Upon application of further selection on the Round-18 ribozyme, the B6.61 ribozyme was generated and was able to add up to 20 nucleotides to a primer template in 24 hours, until it decomposes by cleavage of its phosphodiester bonds. The rate at which ribozymes can polymerize an RNA sequence multiples substantially when it takes place within a micelle. The next ribozyme discovered was the "tC19Z" ribozyme, which can add up to 95 nucleotides with a fidelity of 0.0083 mutations/nucleotide. Next, the "tC9Y" ribozyme was discovered by researchers and was further able to synthesize RNA strands up to 206 nucleotides long in the eutectic phase conditions at below-zero temperature, conditions previously shown to promote ribozyme polymerase activity. The RNA polymerase ribozyme (RPR) called tC9-4M was able to polymerize RNA chains longer than itself (i.e. longer than 177 nt) in magnesium ion concentrations close to physiological levels, whereas earlier RPRs required prebiotically implausible concentrations of up to 200 mM. The only factor required for it to achieve this was the presence of a very simple amino acid polymer called lysine decapeptide.
Nor-LSD, or norLSD, also known as N,N-diethyl-6-norlysergamide or as N-desmethyllysergic acid diethylamide (N-desmethyl-LSD), is a serotonin receptor modulator and putative psychedelic of the lysergamide family related to lysergic acid diethylamide (LSD). It is the analogue of LSD in which the methyl group at the 6 position of the ergoline ring system has been removed.
Sources: en.wikipedia.org
== Mechanism == The mechanism of the Hofmeister series is not entirely clear, but does not seem to result from changes in general water structure, instead more specific interactions between ions and proteins and ions and the water molecules directly contacting the proteins may be more important. Simulation studies have shown that the variation in solvation energy between the ions and the surrounding water molecules underlies the mechanism of the Hofmeister series. A quantum chemical investigation suggests an electrostatic origin to the Hofmeister series. This work provides site-centred radial charge densities of the ions' interacting atoms (to approximate the electrostatic potential energy of interaction), and these appear to quantitatively correlate with many reported Hofmeister series for electrolyte properties, reaction rates and macromolecular stability (such as polymer solubility, and virus and enzyme activities). Early members of the series increase solvent surface tension and decrease the solubility of nonpolar molecules ("salting out"); In effect, they strengthen the hydrophobic interaction. By contrast, later salts in the series increase the solubility of nonpolar molecules ("salting in") and decrease the order in water; in effect, they weaken the hydrophobic effect. The salting out effect is commonly exploited in protein purification through the use of ammonium sulfate precipitation.
==== K/R ==== There is a K to R substitution at amino acid position 95. The editing complementary sequence (ECS) is located in a region within the coding sequence about 200 base pairs upstream from the editing sites. The ECS forms 140 bp duplex structure. The A to G discrepancies for these two editing sites were confirmed experimentally to be RNA editing by analyzing matched cDNA and genomic dna sequences from the same tissue sample. Intriguingly, those RNAs that do not need an intron sequence to pair with could, in theory, continue to undergo editing as mature mRNA. A third candidate editing site did not show evidence of RNA editing in sequence analysis, which may be an indication that either the RNA editing process is tissue specific, or editing occurs at a low frequency. One other possible explanation is that these edits are related to specific genomic polymorphisms. The editing site also overlaps with an antisense transcript which could also form a double stranded RNA structure creating a suitable substrate for ADARs.
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According to these rules, compounds with the most ionic character will have large positive ions with a low charge, bonded to a small negative ion with a high charge. More generally HSAB theory can be applied, whereby the compounds with the most ionic character are those consisting of hard acids and hard bases: small, highly charged ions with a high difference in electronegativities between the anion and cation. This difference in electronegativities means that the charge separation, and resulting dipole moment, is maintained even when the ions are in contact (the excess electrons on the anions are not transferred or polarized to neutralize the cations). Although chemists classify idealized bond types as being ionic or covalent, the existence of additional types such as hydrogen bonds and metallic bonds, for example, has led some philosophers of science to suggest that alternative approaches to understanding bonding are required. This could be by applying quantum mechanics to calculate binding energies.
CDR2 is thought to recognize the MHC. HV4 of the β-chain is not thought to participate in antigen recognition as in classical CDRs, but has been shown to interact with superantigens. The constant domain of the TCR consists of short connecting sequences in which a cysteine residue forms disulfide bonds, which form a link between the two chains. The TCR is a member of the immunoglobulin superfamily, a large group of proteins involved in binding, recognition, and adhesion; the family is named after antibodies (also called immunoglobulins). The TCR is similar to a half-antibody consisting of a single heavy and single light chain, except the heavy chain is without its crystallizable fraction (Fc). The two main subunits of TCR (α- and β-chains) are twisted together. CD3 and zeta subunits are required to carry out the signal transduction. The MHC-TCR-CD3 interaction for T cells is functionally similar to the antigen(Ag)-immunoglobulin(Ig)-FcR interaction for myeloid leukocytes, and Ag-Ig-CD79 interaction for B cells.
Sources: en.wikipedia.org
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.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.