TKPRPGP raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-07-27. Anything still debated is marked as such rather than presented as settled.
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.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
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.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
== History == Protein rich in phosphate was discovered early on. In 1906, Levene and Alsberg studied cleavage products of yolk vitellin, and showed that a phosphorus-rich proteinaceous fraction could be obtained from it. In 1933, Fritz Lipmann detected phosphoserine in casein. In 1948, a particularly phosphate-rich protein was isolated from yolk, and it was named phosvitin. Phosphorylase enzymes were discovered later. The first phosphorylase enzyme was discovered by Carl and Gerty Cori in the late 1930s. Carl and Gerty Cori found two forms of glycogen phosphorylase which they named A and B but did not correctly understand the mechanism of the B form to A form conversion. In 1954, another enzyme was discovered, which transfers phosphate from ATP onto a protein. Its physiological function was still not known. Glycogen phosphorylation was better understood later. The interconversion of phosphorylase b to phosphorylase a was described by Edmond Fischer and Edwin Krebs involving a phosphorylation/dephosphorylation mechanism. It was found that an enzyme named phosphorylase kinase and Mg-ATP were required to phosphorylate glycogen phosphorylase by assisting in the transfer of the γ-phosphoryl group of ATP to a serine residue on phosphorylase b. Protein phosphatase 1 is able to catalyze the dephosphorylation of phosphorylated enzymes by removing the phosphate group. Sutherland and Coris discovered epinephrine acts by activating phosphorylase, which leads to the formation of glucose from glycogen.
He concluded his speech by saying that "great rejuvenation of the Chinese nation and making America great again can go hand in hand" and that "Let us meet the people's expectations and show our historical initiative, let us keep advancing the cause of friendship between our two peoples and work together to build a better world".
== Alumni == Donna Feigley Barbisch (MPH), U.S. Army major general Francis Collins - director of the NIH, and head of the Human Genome Project J. Larry Jameson- interim President of the University of Pennsylvania J. Charles Jennette - physician and nephropathologist Ken Jeong - actor and comedian Christopher W. Lentz - U.S. Air Force Brigadier General Norman Sharpless - director of the National Cancer Institute (NCI)
EDC couples primary amines, and other nucleophiles, to carboxylic acids by creating an activated ester leaving group. First, the carbonyl of the acid attacks the carbodiimide of EDC, and there is a subsequent proton transfer. The primary amine then attacks the carbonyl carbon of the acid which forms a tetrahedral intermediate before collapsing and discharging the urea byproduct. The desired amide is obtained.
Arketamine (developmental code names PCN-101, HR-071603), also known as (R)-ketamine or (R)-(−)-ketamine, is the (R)-(−) enantiomer of ketamine. Similarly to racemic ketamine and esketamine, the (S)-(+) enantiomer of ketamine, arketamine is biologically active; however, it is less potent as an NMDA receptor antagonist and anesthetic and thus has never been approved or marketed for clinical use as an enantiopure drug. Arketamine is currently in clinical development as a novel antidepressant. Relative to esketamine, arketamine possesses 4 to 5 times lower affinity for the PCP site of the NMDA receptor. In accordance, arketamine is significantly less potent than racemic ketamine and especially esketamine in terms of anesthetic, analgesic, and sedative-hypnotic effects. Racemic ketamine has weak affinity for the sigma receptor, where it acts as an agonist, whereas esketamine binds negligibly to this receptor, and so the sigma receptor activity of racemic ketamine lies in arketamine. It was suggested that this action of arketamine may play a role in the hallucinogenic effects of racemic ketamine and that it may be responsible for the lowering of the seizure threshold seen with racemic ketamine. However several subsequent studies have indicated that esketamine is more likely to induce dissociative events, while studies in patients undergoing electroconvulsive therapy suggested that esketamine is a potent inducer of seizures.
Sources: en.wikipedia.org
=== Ancient era (pre-17th century) === An understanding of the inner workings of human tissues may date back further than most would expect. As early as the Neolithic period, sutures were being used to close wounds and aid in healing. Later on, societies such as ancient Egypt developed better materials for sewing up wounds such as linen sutures. Around 2500 BC in ancient India, skin grafts were developed by cutting skin from the buttock and suturing it to wound sites in the ear, nose, or lips. Ancient Egyptians often would graft skin from corpses onto living humans and even attempted to use honey as a type of antibiotic and grease as a protective barrier to prevent infection. In the 1st and 2nd centuries AD, Gallo-Romans developed wrought iron implants and dental implants could be found in ancient Mayans.
Mergny and Lacroix determined that the addition of a bulky methyl group had a destabilizing effect on the i-motif formation when they compared phosphorothioate, the natural phosphodiester, methylphosphonate, and peptide linkages and determined that only phosphodiester and phosphorothioate oligodeoxynucleotides were capable of forming stable i-motifs.
The efficacy of quinacrine was assessed in a rigorous clinical trial in the UK and the results were published in Lancet Neurology, and concluded that quinacrine had no measurable effect on the clinical course of CJD. Astemizole, a medication approved for human use, has been found to have anti-prion activity and may lead to a treatment for Creutzfeldt–Jakob disease. A monoclonal antibody (code name PRN100) targeting the prion protein (PrP) was given to six people with Creutzfeldt–Jakob disease in an early-stage clinical trial conducted from 2018 to 2022. The treatment appeared to be well-tolerated and was able to access the brain, where it might have helped to clear PrPC. While the treated patients still showed progressive neurological decline, and while none of them survived longer than expected from the normal course of the disease, the scientists at University College London who conducted the study see these early-stage results as encouraging and suggest conducting a larger study, ideally at the earliest possible intervention.
In this case, once the vapor layer is established, cooling never collapses the layer, and no nucleate boiling occurs; the layer instead slowly relaxes until the surface is cooled. Droplets of different liquids with different boiling temperatures will also exhibit a Leidenfrost effect with respect to each other and repel each other. The Leidenfrost effect has been used for the development of high sensitivity ambient mass spectrometry. Under the influence of the Leidenfrost condition, the levitating droplet does not release molecules, and the molecules are enriched inside the droplet. At the last moment of droplet evaporation, all the enriched molecules release in a short time period and thereby increase the sensitivity. A heat engine based on the Leidenfrost effect has been prototyped; it has the advantage of extremely low friction. The effect also applies when the surface is at room temperature but the liquid is cryogenic, allowing liquid nitrogen droplets to harmlessly roll off exposed skin. Conversely, the inverse Leidenfrost effect lets drops of relatively warm liquid levitate on a bath of liquid nitrogen.
The three substrates of this enzyme are saccharopine, oxidised nicotinamide adenine dinucleotide (NAD+), and water. Its products are L-lysine, reduced NADH, α-ketoglutaric acid, and a proton. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is N6-(L-1,3-dicarboxypropyl)-L-lysine:NAD+ oxidoreductase (L-lysine-forming). Other names in common use include lysine-2-oxoglutarate reductase, dehydrogenase, saccharopine (nicotinamide adenine dinucleotide,, lysine forming), epsilon-N-(L-glutaryl-2)-L-lysine:NAD oxidoreductase (L-lysine, forming), N6-(glutar-2-yl)-L-lysine:NAD oxidoreductase (L-lysine-forming), 6-N-(L-1,3-dicarboxypropyl)-L-lysine:NAD+ oxidoreductase, and (L-lysine-forming). This enzyme participates in lysine biosynthesis and lysine degradation.
Sources: en.wikipedia.org
Besides recommendations for infant vaccinations and boosters, many specific vaccines are recommended for other ages or for repeated injections throughout life – most commonly for measles, tetanus, influenza, and pneumonia. Pregnant women are often screened for continued resistance to rubella. As of 2011, the human papillomavirus vaccine was recommended in the US, and, as of 2009, in the UK. Vaccine recommendations for the elderly concentrate on pneumonia and influenza, which are more deadly to that group. In 2006, a vaccine was introduced against shingles, a disease caused by the chickenpox virus, which usually affects the elderly. Scheduling and dosing of a vaccination may be tailored to the level of immunocompetence of an individual and to optimize population-wide deployment of a vaccine when its supply is limited, e.g. in the setting of a pandemic.
WHO referred to the incident as one of the largest food safety events it has had to deal with, and stated it would be difficult to restore the confidence of Chinese consumers in baby formula. It saw regulation failing to keep pace with the rapid development of the food and industrial production as opening the gates to all types of misbehaviour and malfeasance. The spokesman said the scale of the problem proved it was "clearly not an isolated accident, [but] a large-scale intentional activity to deceive consumers for simple, basic, short-term profits". WHO Director-General Margaret Chan reminded Chinese mothers that breastfeeding was the best way to provide nutrition to infants while avoiding a risk of melamine exposure. She noted that the scandal showed "the impact and power of globalisation" in food distribution and highlighted "the importance of seamless cooperation from farm to consumer".
==== Determination by genetics or the environment ==== Behaviors can be either innate or learned from the environment, or both, dependent on the organism. The more complex nervous systems (or brains) are, the more influence learning has on behavior. However, even in mammals, a large fraction of behavior is genetically determined. For instance, prairie voles tend to be monogamous, while meadow voles are more promiscuous, a difference that is strongly determined by a single gene, Avpr1a, encoding a receptor for the peptide hormone Vasopressin.
AZX + e− → AZ−1X′ + νe Capture of a free electron is allowed, but physical conditions make this generally negligible outside stars. An example of electron capture is one of the decay modes of krypton-81 into bromine-81:
Sources: en.wikipedia.org
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.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.