Everything below concerns peptidase. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
| 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 |
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.
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.
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.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Clinical example: Diazepam has long been a drug of choice for status epilepticus; its high lipid solubility means it gets absorbed with equal speed whether given orally, or rectally (nonintravenous routes are convenient outside of hospital settings), but diazepam's high lipid solubility also means it does not remain in the vascular space, but soon redistributes into other body tissues. So, it may be necessary to repeat diazepam doses to maintain peak anticonvulsant effects, resulting in excess body accumulation. Lorazepam is a different case; its low lipid solubility makes it relatively slowly absorbed by any route other than intravenously, but once injected, it will not get significantly redistributed beyond the vascular space. Therefore, lorazepam's anticonvulsant effects are more durable, thus reducing the need for repeated doses. If a person is known to usually stop convulsing after only one or two diazepam doses, it may be preferable because sedative after effects will be less than if a single dose of lorazepam is given (diazepam anticonvulsant/sedative effects wear off after 15–30 minutes, but lorazepam effects last 12–24 hours). The prolonged sedation from lorazepam may, however, be an acceptable trade-off for its reliable duration of effects, particularly if the person needs to be transferred to another facility. Although lorazepam is not necessarily better than diazepam at initially terminating seizures, lorazepam is, nevertheless, replacing diazepam as the intravenous agent of choice in status epilepticus.
== Metabolism == In plants and microorganisms, aspartate is the precursor to several amino acids, including four that are essential for humans: methionine, threonine, isoleucine, and lysine. The conversion of aspartate to these other amino acids begins with reduction of aspartate to its semialdehyde, O2CCH(NH2)CH2CHO. Asparagine is derived from aspartate via transamidation:
=== Abuse of Coalition POWs === During the conflict, coalition aircrew shot down over Iraq were displayed as prisoners of war on TV, most with visible signs of abuse. Amongst several testimonies to poor treatment, USAF Captain Richard Storr was allegedly tortured by Iraqis during the Persian Gulf War. Iraqi secret police broke his nose, dislocated his shoulder and punctured his eardrum. Royal Air Force Tornado crew John Nichol and John Peters have both alleged that they were tortured during this time. Nichol and Peters were forced to make statements against the war on television. Members of British Special Air Service Bravo Two Zero were captured while providing information about an Iraqi supply line of Scud missiles to coalition forces. Only one, Chris Ryan, evaded capture while the group's other surviving members were violently tortured. Flight surgeon (later General) Rhonda Cornum was sexually assaulted by one of her captors after the Black Hawk helicopter in which she was riding was shot down while searching for a downed F-16 pilot.
==== Detection ==== Cabbage loopers possess olfactory receptor neurons on their antennae for detecting pheromones. The neurons are specifically located on two sensory structures called sensilla that differ in length and pore density. Male loopers have two types of neurons, and depending on which sensilla that are present, the neurons will detect female pheromones at varying sensitivities to each of the six pheromones. The neurons are most sensitive to the main component of the female pheromone blend, cis-7-dodecenyl acetate, and the male inhibitory signal, cis-7-dodecenol. The presence of cis-7-dodecenyl acetate is crucial for male response to female pheromones, as it is 80% of the entire blend. The base region of the antennae, where receptor neurons for this pheromone are located, has more sensory structures than the ends. The base region is also less likely to experience damage, showing the importance of detecting the pheromone. It is not clear why male neurons detect the inhibitory compound, as there is no evidence showing that females produce this compound. One possibility is that its presence in the female pheromone blend may be too small to be detected by scientific equipment. The inhibitory signal only elicits a response when delivered alongside female pheromones to avoid mixing signals from other species, suggesting that while it cannot be detected in the female pheromone blend, it has an important role in female detection. These neurons are also capable of recognizing and responding to cis-7-tetradecenyl acetate and cis-9-tetradecenyl acetate.
To minimize this problem, commercial supplies of THF are often stabilized with butylated hydroxytoluene (BHT). Distillation of THF to dryness is unsafe because the explosive peroxides can concentrate in the residue.
Sources: en.wikipedia.org
==== Class A sub-family ==== Class A enzymes methylate specific adenosine residues on rRNA and/or tRNA. In other words, they are RNA base-modifying radical SAM enzymes. The most mechanistically well-characterized are enzymes RlmN and Cfr. Both enzymes methylates substrate by adding a methylene fragment originating from SAM molecule. Therefore, RlmN and Cfr are considered methyl synthases instead of methyltransferases.
== Laboratory scale == Centrifugal partition chromatography has been extensively used for isolation and purification of natural products for 40 years. Due to the ability to get very high selectivity, and the ability to tolerate samples containing particulated matter, it is possible to work with direct extracts of biomass, opposed to traditional liquid chromatography, where impurities degrade the solid stationary phase so that separation become impossible. There are numerous laboratory scale centrifugal partition chromatography manufacturers around the world, like Gilson (Armen Instrument), Kromaton (Rousselet Robatel), and AECS-QUIKPREP. These instruments operate at flow rates of 1–500 mL/min. with stationary phase retentions of 40–80%. With the new rotor system created after 2022, LiLiChro was able to create a truly analytical instrument (miniLiLi) with a rotor internal volume of only 34ml, which means it can operate at a flow rate of 1ml/min. On the other hand, both the miniLiLi and the 140ml midiLiLi can operate with 90+% stationary phase retention.
=== Malaysia === Secretary General of the Malaysian United Indigenous Party, Azmin Ali said that the operation "amounted to a unilateral and unlawful use of armed force under international law, in violation of Article 2(4) of the Charter of the United Nations" and called for the Malaysian government to "strengthen the Global South through the Non-Aligned Movement and enhance cross-regional cooperation, while lending support to international accountability mechanisms addressing violations of international law." The chairman of the People's Justice Party's International Affairs Bureau, Maszlee Malik, urged the US to halt all military actions against Venezuela, respect Venezuela's sovereignty and political freedom fully aligned with the Charter of the United Nations and demanded the international community to "preserve peace and prioritize diplomatic solutions through dialogue and multilateral forums".
In South Africa, methamphetamine is called "tik" or "tik-tik". Known locally as "tik", the substance was virtually unknown as late as 2003. Now, it is the country's main addictive substance, even when alcohol is included. Children as young as eight are abusing the substance, smoking it in crude glass vials made from light bulbs. Since methamphetamine is easy to produce, the substance is manufactured locally in staggering quantities. The government of North Korea currently operates methamphetamine production facilities. There, the drug is used as medicine because no alternatives are available; it also is smuggled across the Chinese border. The Australian Crime Commission's illicit drug data report for 2011–2012 stated that the average strength of crystal methamphetamine doubled in most Australian jurisdictions within a 12-month period, and the majority of domestic laboratory closures involved small "addict-based" operations.
However, by careful optimization of instrument parameters which cause ion heating, hydrogen scrambling can be minimized to a degree which preserves the solution phase isotopic labeling until fragmentation can be performed using a technique where scrambling does not occur. More recently, ultraviolet photodissociation (UVPD) has also been investigated as a possible fragmentation technique to localize deuterium within peptides and proteins. In this regard, the conclusions have been mixed, while it is possible to obtain UVPD fragments which has not undergone scrambling under certain conditions, others have shown that scrambling can occur for both peptides and proteins during the UVPD fragmentation step itself. The theory consolidating these apparent contradictions has to do with the dual fragmentation pathway that may arise from UV irradiation of peptides and proteins, i.e. direct and statistical dissociation. That is, if experimental conditions favor direct dissociation and the precursor ion is kept at low internal energies before and during fragmentation the deuterium level of the resulting fragments will correspond to the non-scrambled precursor. However, experimental conditions may favor statistical dissociation during UV irradiation, especially at long irradiation times and low gas pressure, leading to internal conversion of the electronic excitation energy contributed by the UV photons. The result is vibrational excitation of the irradiated molecule which in turn undergo scrambling.
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.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.