Everything below concerns freeze-thaw. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-28. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
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.
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.
=== Co-flowing droplet formation === Co-flowing is a passive droplet formation method where the dispersed phase channel is enclosed inside a continuous phase channel. At the end of the dispersed phase channel, the fluid is stretched until it breaks from shear forces and forms droplets either by dripping or jetting. Dripping occurs when capillary forces dominate the system and droplets are created at the channel endpoint. Jetting occurs, by widening or stretching, when the continuous phase is moving slower, creating a stream from the dispersed phase channel opening. Under the widening regime, the dispersed phase is moving faster than the continuous phase causing a deceleration of the dispersed phase, widening the droplet and increasing the diameter. Under the stretching regime, viscous drag dominates causing the stream to narrow creating a smaller droplet. The effect of the continuous phase flow rate on the droplet size depends on whether the system is in a stretching or widening regime thus different equations must be used to predict droplet size. Droplet size is usually around several hundred nanometers with a CV of less than 5% and a rate of up to tens of kHz.
=== Ribbon machine === Corning continued developing automated bulb-production machines, installing the Ribbon Machine in 1926 in its Wellsboro, Pennsylvania, factory. The Ribbon Machine surpassed any previous attempts to automate bulb production and was used to produce incandescent bulbs into the 21st century. The inventor, William Woods, along with his colleague at Corning Glass Works, David E. Gray, had created a machine that by 1939 was producing 1,000 bulbs per minute. The Ribbon Machine works by passing a continuous ribbon of glass along a conveyor belt, heated in a furnace, and then blown by precisely aligned air nozzles through holes in the conveyor belt into molds. Thus the glass bulbs or envelopes are created. A typical machine can produce 50,000 to 120,000 bulbs per hour, depending on the size of the bulb. By the 1970s, 15 ribbon machines installed in factories around the world produced the entire supply of incandescent bulbs. The filament and its supports are assembled on a glass stem, which is then fused to the bulb. The air is pumped out of the bulb, and the evacuation tube in the stem press is sealed by a flame. The bulb is then inserted into the lamp base, and the whole assembly tested. The 2016 closing of Osram-Sylvania's Wellsboro, Pennsylvania plant meant that one of the last remaining ribbon machines in the United States was shut down.
==== Juan Alberto Kessel Linares elected as Grand Master ==== Late in the day on March 24, Juan Alberto Kessel Linares was elected as the new Grand Master of the Grand Lodge of Cuba to replace Urquía Carreño. On March 30, a week after his appointment as Grand Master, Kessel Linares accused Urquía Carreño of having stolen an additional $2,360 in August 2023. The money, according to Kessel Linares, had been given to him by the serving Grand Treasurer at the time, Salvador Orestes Arango Troncoso. When Urquía Carreño was eventually asked about the money by Grand Secretary Misiel Hernández Peraza, Urquía Carreño allegedly informed him that the money was in the possession of the recently elected Grand Treasurer, Airam Cervera. Kessel Linares then revealed that the Grand Lodge had filed an official complaint with the National Revolutionary Police at the Zapata Police Station in Havana.
==== Prerequisites for applying to a specialist training program ==== A physician practicing in Sweden may apply to a specialist training program (Swedish: Specialisttjänstgöring) after being licensed as a physician by The National Board of Health and Welfare. To obtain a license through the Swedish education system a candidate must go through several steps. First the candidate must successfully finish a five-and-a-half-year undergraduate program, made up of two years of pre-clinical studies and three and a half years of clinical postings, at one of Sweden's seven medical schools—Uppsala University, Lund University, The Karolinska Institute, The University of Gothenburg, Linköping University, Umeå University, or Örebro University—after which a degree of Master of Science in Medicine (Swedish: Läkarexamen) is awarded. The degree makes the physician eligible for an internship (Swedish: Allmäntjänstgöring) ranging between 18 and 24 months, depending on the place of employment. The internship is regulated by the National Board of Health and Welfare and regardless of place of employment it is made up of four main postings with a minimum of nine months divided between internal medicine and surgery—with no less than three months in each posting—three months in psychiatry, and six months in general practice. It is customary for many hospitals to post interns for an equal amount of time in surgery and internal medicine (e.g. six months in each of the two).
The first fully synthetic opioid was meperidine (Demerol), found serendipitously by German chemist Otto Eisleb (or Eislib) at IG Farben in 1932. Meperidine was the first opioid to have a structure unrelated to morphine, but with opioid-like properties. Its analgesic effects were discovered by Otto Schaumann in 1939. Gustav Ehrhart and Max Bockmühl, also at IG Farben, built on the work of Eisleb and Schaumann. They developed "Hoechst 10820" (later methadone) around 1937. In 1959 the Belgian physician Paul Janssen developed fentanyl, a synthetic opioid with 30 to 50 times the potency of heroin. Nearly 150 synthetic opioids are now known.
Sources: en.wikipedia.org
== Medical uses == Moxetumomab pasudotox as monotherapy is indicated for the treatment of adults with relapsed or refractory hairy cell leukemia (HCL) after receiving at least two prior systemic therapies, including treatment with a purine nucleoside analogue (PNA).
== Pathway systems == The vast size of the Inca empire made it essential that efficient and effective transportation systems were created and built to assist in the exchanging of goods, services, people, etc. At one point, "their (the Inca) empire eventually extended across western South America from Quito in the north to Santiago in the south, making it the largest empire ever seen in the Americas and the largest in the world at that time (between c. 1400 and 1533 CE)." It is known to have "extended some 3500-4000 km along the mountainous backbone of South America." The trails, roads, and bridges were designed not only to link the empire physically, but these structures also helped the empire to maintain communication.
== See also == Avogadro's law – Relationship between volume and amount of a gas at constant temperature and pressure Boyle's law – Relation between gas pressure and volume Charles's law – Relationship between volume and temperature of a gas at constant pressure Combined gas law – Combination of Charles', Boyle's and Gay-Lussac's gas laws
As a hormone, adrenaline acts on nearly all body tissues by binding to adrenergic receptors. Its effects on various tissues depend on the type of tissue and expression of specific forms of adrenergic receptors. For example, high levels of adrenaline cause smooth muscle relaxation in the airways but causes contraction of the smooth muscle that lines most arterioles. Adrenaline is a nonselective agonist of all adrenergic receptors, including the major subtypes α1, α2, β1, β2, and β3. Adrenaline's binding to these receptors triggers a number of metabolic changes. Binding to α-adrenergic receptors inhibits insulin secretion by the pancreas, stimulates glycogenolysis in the liver and muscle, and stimulates glycolysis and inhibits insulin-mediated glycogenesis in muscle. β adrenergic receptor binding triggers glucagon secretion in the pancreas, increased adrenocorticotropic hormone (ACTH) secretion by the pituitary gland, and increased lipolysis by adipose tissue. Together, these effects increase blood glucose and fatty acids, providing substrates for energy production within cells throughout the body. Binding of β adrenergic receptor also increases the production of cyclic AMP. Adrenaline causes liver cells to release glucose into the blood, acting through both alpha and beta-adrenergic receptors to stimulate glycogenolysis. Adrenaline binds to β2 receptors on liver cells, which changes conformation and helps Gs, a heterotrimeric G protein, exchange GDP to GTP. This trimeric G protein dissociates to Gs alpha and Gs beta/gamma subunits.
Sources: en.wikipedia.org
== Selected bibliography == Banday Khalid M, Pasikanti KK, Chan EC, Singla R, Rao KV, Chauhan VS, Nanda RK. (July 2011). "Use of urine volatile organic compounds to discriminate tuberculosis patients from healthy subjects". Anal Chem. 83 (14): 5526–34. doi:10.1021/ac200265g. PMID 21619052.{{cite journal}}: CS1 maint: multiple names: authors list (link) Rao KV, Konar S, Gangadharan J, Vikas V, Sampath S (October 2015). "A pure non-gestational ovarian choriocarcinoma with delayed solitary brain metastases: Case report and review of the literature". J Neurosci Rural Pract. 6 (4): 578–81. doi:10.4103/0976-3147.169869. PMC 4692019. PMID 26752905. Jamwal SV, Mehrotra P, Singh A, Siddiqui Z, Basu A, Rao KV (March 2016). "Mycobacterial escape from macrophage phagosomes to the cytoplasm represents an alternate adaptation mechanism". Sci. Rep. 6 (23089) 23089. Bibcode:2016NatSR...623089J. doi:10.1038/srep23089. PMC 4793295. PMID 26980157. Ghosh AK1, Reddy BS, Yen YC, Cardenas E, Rao KV, Downs D, Huang X, Tang J, Mesecar AD (May 2016). "Design of Potent and Highly Selective Inhibitors for Human β-Secretase 2 (Memapsin 1), a Target for Type 2 Diabetes". Chem. Sci. 1 (7): 3117–3122. doi:10.1039/C5SC03718B. PMC 4916918. PMID 27347366.{{cite journal}}: CS1 maint: multiple names: authors list (link) CS1 maint: numeric names: authors list (link)
=== Bullhead sharks === Bullhead shark egg cases are shaped like an auger, with two spiral flanges. This allows the egg cases to become wedged in the crevices of rocky sea floors, where the eggs are protected from predators; however, some bullhead sharks deposit their eggs on sponges or seaweed. Hatchlings are considered large for sharks, reaching over 14 cm in length by the time they leave the egg case. Bullhead shark eggs typically hatch after 7 to 12 months, depending on the species. The female Japanese bullhead shark has been known to deposit their eggs in one location along with other females, called a "nest". The egg case of the Mexican hornshark features a tendril and more rigid flanges, suggesting that egg case design of this species is evolving towards anchoring with tendrils and away from wedging into crevices. As a member of the order Heterodontiformes, the whitespotted bullhead sharks is thought to be oviparous, but egg cases have never been observed.
Primer and bonding resin are applied to etched dentin, they penetrate the intertubular dentin, forming hybrid layer. They also penetrate and polymerize in open dentinal tubules, forming resin tags. Moist bonding technique has been shown repeatedly to enhance bond strengths of etch-and-rinse adhesives because water preserves the porosity of collagen network for monomer interdiffusion.
=== Bulk metal preparation === In order to characterize chemical and physical properties of solid berkelium and its compounds, a program was initiated in 1952 at the Material Testing Reactor, Arco, Idaho, US. It resulted in preparation of an eight-gram plutonium-239 target and in the first production of macroscopic quantities (0.6 micrograms) of berkelium by Burris B. Cunningham and Stanley Gerald Thompson in 1958, after a continuous reactor irradiation of this target for six years. This irradiation method was and still is the only way of producing weighable amounts of the element, and most solid-state studies of berkelium have been conducted on microgram or submicrogram-sized samples. The world's major irradiation sources are the 85-megawatt High Flux Isotope Reactor at the Oak Ridge National Laboratory in Tennessee, USA, and the SM-2 loop reactor at the Research Institute of Atomic Reactors (NIIAR) in Dimitrovgrad, Russia, which are both dedicated to the production of transcurium elements (atomic number greater than 96). These facilities have similar power and flux levels, and are expected to have comparable production capacities for transcurium elements, although the quantities produced at NIIAR are not publicly reported. In a "typical processing campaign" at Oak Ridge, tens of grams of curium are irradiated to produce decigram quantities of californium, milligram quantities of berkelium-249 and einsteinium, and picogram quantities of fermium. In total, just over one gram of berkelium-249 has been produced at Oak Ridge since 1967.
The HER2 gene (also known as HER2/neu and ErbB2 gene) is amplified in 20–30% of early-stage breast cancers. Trastuzumab is a monoclonal antibody targeting HER2, inducing an immune-mediated response that causes internalization and recycling of HER2. It may also upregulate cell cycle inhibitors such as p21Waf1 and p27Kip1. The HER2 pathway promotes cell growth and division when it is functioning normally; however, when it is overexpressed, cell growth accelerates beyond its normal limits. In some types of cancer, the pathway is exploited to promote rapid cell growth and proliferation and hence tumor formation. The EGF pathway includes the receptors HER1 (EGFR), HER2, HER3, and HER4; the binding of ligands (e.g. EGF etc.) to HER receptors is required to activate the pathway. The pathway initiates the MAP kinase pathway as well as the PI3 kinase/AKT pathway, which in turn activates the NF-κB pathway. In cancer cells the HER2 protein can be expressed up to 100 times more than in normal cells (2 million versus 20,000 per cell). The HER receptors are proteins that are embedded in the cell membrane and communicate molecular signals from outside the cell (molecules called EGFs) to inside the cell, and turn genes on and off. The HER (human epidermal growth factor receptor) protein, binds to human epidermal growth factor, and stimulates cell proliferation. In some cancers, notably certain types of breast cancer, HER2 is over-expressed and causes cancer cells to reproduce uncontrollably. HER2 is localized at the cell surface, and carries signals from outside the cell to the inside.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
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.