Heptapeptide comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-06-13. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
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.
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.
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.
The resin beads can then be returned to the ion-exchange facility, where they are reused. The ion-exchange process is also used to separate other sets of very similar chemical elements, such as zirconium and hafnium, which incidentally is also very important for the nuclear industry. Zirconium is practically transparent to free neutrons, used in building reactors, but hafnium is a very strong absorber of neutrons, used in reactor control rods.
chemical decomposition The breakdown of a single particle or entity (such as a molecule or reactive intermediate) into two or more fragments, or a chemical reaction in which two or more products are formed from a single reactant. Contrast chemical synthesis.
Aminopeptidases are enzymes that catalyze the cleavage of amino acids from the N-terminus (beginning), of proteins or peptides. They are found in many organisms; in the cell, they are found in many organelles, in the cytosol (internal cellular fluid), and as membrane proteins. Aminopeptidases are used in essential cellular functions, and are often zinc metalloenzymes, containing a zinc cofactor. Aminopeptidases occur in both water-soluble and membrane-bound forms and can be found both in various cellular compartments and in the extracellular environment (outside of cells). Their broad substrate specificity, their ability to strongly bind to their targets, allows them to remove beginning N-terminal amino acids from almost all unsubstituted oligopeptides. For instance, Aminopeptidase N (AP-N) is particularly abundant in the brush border membranes of the kidney, the small intestine, and the placenta, and is also found in the liver. AP-N is involved in the final digestion of peptides generated from the hydrolysis (cleaving) of proteins by gastric and pancreatic proteases. Some aminopeptidases are monomeric, and others are found as assemblies of relatively high mass (50 kDa) subunits. cDNA sequences are available for several aminopeptidases and a crystal structure of the open state of human endoplasmic reticulum aminopeptidase 1 is available.
Elements are known with up to the first seven shells occupied. The first shell contains only one orbital, a spherical s orbital. As it is in the first shell, this is called the 1s orbital. This can hold up to two electrons. The second shell similarly contains a 2s orbital, and it also contains three dumbbell-shaped 2p orbitals, and can thus fill up to eight electrons (2×1 + 2×3 = 8). The third shell contains one 3s orbital, three 3p orbitals, and five 3d orbitals, and thus has a capacity of 2×1 + 2×3 + 2×5 = 18. The fourth shell contains one 4s orbital, three 4p orbitals, five 4d orbitals, and seven 4f orbitals, thus leading to a capacity of 2×1 + 2×3 + 2×5 + 2×7 = 32. Higher shells contain more types of orbitals that continue the pattern, but such types of orbitals are not filled in the ground states of known elements. The subshell types are characterized by the quantum numbers. Four numbers describe an orbital in an atom completely: the principal quantum number n, the azimuthal quantum number ℓ (the orbital type), the orbital magnetic quantum number mℓ, and the spin magnetic quantum number ms.
Sources: en.wikipedia.org
=== Regulation === Production, which is otherwise freerunning, is suppressed/regulated by amylin, a peptide hormone co-secreted with insulin from the pancreatic β cells. As plasma glucose levels recede, the subsequent reduction in amylin secretion alleviates its suppression of the α cells, allowing for glucagon secretion. Secretion of glucagon is stimulated by:
Sun tea is frequently brewed in temperate areas by placing tea and room-temperature water together in a glass jar left outdoors in direct sunlight. Steeping times are necessarily long, two to four hours. Tea may also be brewed with no heat at all by simply immersing the tea bags or infuser in room-temperature water and allowing a period of several hours (typically overnight) for steeping. Since sun brewing occurs in a temperature range that can promote the development of bacteria, particularly Alcaligenes viscolactis, the Centers for Disease Control and the Tea Association of the U.S.A. Inc. suggest storing sun-brewed tea in the refrigerator and discarding it after 24 hours.
== Relationship with humans == The chain catshark is not currently fished for human consumption. The chain catshark has been described as "gorgeous", and this, combined with its small size, makes it a popular cold-water aquarium fish. It is frequently displayed and bred at public aquariums. Research in shark behavior, including reproduction, has been done in chain catsharks kept in public aquariums or laboratories.
== Discovery == Before the discovery of the ubiquitin–proteasome system, protein degradation in cells was thought to rely mainly on lysosomes, membrane-bound organelles with acidic and protease-filled interiors that can degrade and then recycle exogenous proteins and aged or damaged organelles. However, work by Joseph Etlinger and Alfred L. Goldberg in 1977 on ATP-dependent protein degradation in reticulocytes, which lack lysosomes, suggested the presence of a second intracellular degradation mechanism. This was shown in 1978 to be composed of several distinct protein chains, a novelty among proteases at the time. Later work on modification of histones led to the identification of an unexpected covalent modification of the histone protein by a bond between a lysine side chain of the histone and the C-terminal glycine residue of ubiquitin, a protein that had no known function. It was then discovered that a previously identified protein associated with proteolytic degradation, known as ATP-dependent proteolysis factor 1 (APF-1), was the same protein as ubiquitin. The proteolytic activities of this system were isolated as a multi-protein complex originally called the multi-catalytic proteinase complex by Sherwin Wilk and Marion Orlowski. Later, the ATP-dependent proteolytic complex that was responsible for ubiquitin-dependent protein degradation was discovered and was called the 26S proteasome.
=== Differential diagnosis === The major differential diagnosis is diabetic ketoacidosis (DKA). In contrast to DKA, serum glucose levels in HHS are extremely high, usually greater than 40-50 mmol/L (600 mg/dL). Metabolic acidosis is absent or mild. A temporary state of confusion (delirium) is also more common in HHS than DKA. HHS also tends to affect older people more. DKA may have fruity breath, and rapid and deep breathing. DKA often has serum glucose level greater than 300 mg/dL (HHS is >600 mg/dL). DKA usually occurs in type 1 diabetics whereas HHS is more common in type 2 diabetics. DKA is characterized by a rapid onset, and HHS occurs gradually over a few days. DKA also is characterized by ketosis due to the breakdown of fat for energy. Both DKA and HHS may show symptoms of dehydration, increased thirst, increased urination, increased hunger, weight loss, nausea, vomiting, abdominal pain, blurred vision, headaches, weakness, and low blood pressure with standing.
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.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.