heptapeptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-11-04. 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.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
| 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 |
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.
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.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
== Biosynthesis == In humans, myo-Inositol is synthesized de novo but D-chiro-inositol is not. myo-Inositol is synthesized from glucose 6-phosphate (G6P) in two steps. First, G6P is isomerised by an inositol-3-phosphate synthase enzyme (for example, ISYNA1) to myo-inositol 1-phosphate, which is then dephosphorylated by an inositol monophosphatase enzyme (for example, IMPA1) to give free myo-inositol. In humans, most inositol is synthesized in the kidneys, followed by testicles, typically in amounts of a few grams per day. At the peripheral level, myo-inositol is converted to D-chiro-inositol by a specific epimerase. Only a minor fraction of myo-inositol is converted into D-chiro-inositol. The activity of this epimerase is insulin dependent, causing a reduction of D-chiro-inositol in muscle, fat, and liver when there is insulin resistance. D-chiro-inositol reduces the conversion of testosterone to estrogen, thereby increases the levels of testosterone and worsening PMOS.
== Further reading == De Iuliis, Gerardo; Pulerà, Dino (2019). "Vertebrates and Their Kin". The Dissection of Vertebrates. pp. 1–44. doi:10.1016/B978-0-12-410460-0.00001-2. ISBN 978-0-12-410460-0. Myomeres are the segmented paired muscular blocks that extend through the trunk and tail. Alternating contraction of the musculature of the right and left sides of the body exerts forces on the notochord, noted earlier as a laterally flexible rod, that allow the side-to-side locomotory movements characteristic of less derived chordates and vertebrates. Johnston, I.A. (2008). "The biological basis of variability in the texture of fish flesh". Improving Seafood Products for the Consumer. pp. 465–489. doi:10.1533/9781845694586.5.465. ISBN 978-1-84569-019-9. The fillet is made up of segmentally arranged structures called myotomes or myomeres, the shape of which varies along the length of the body. In three dimensions, the myomeres constitute a series of overlapping cones that are bounded by connective tissue sheets or myocommata called myosepta. Typically, a transverse steak through the fillet will cut through several myotomes at different levels. Each myotome contains a lateral superficial strip of dark muscle primarily composed of slow contracting fibre types that are used for sustained swimming activity (Johnston et al., 1977).
== Types == Metabolic myopathies are generally caused by an inherited genetic mutation, an inborn error of metabolism. (In livestock, an acquired environmental GSD is caused by intoxication with the alkaloid castanospermine.) Metabolic myopathies cause the underproduction of adenosine triphosphate (ATP) within the muscle cell. The genetic mutation typically has an autosomal recessive hereditary pattern making it fairly rare to inherit, and even more rarely it can be caused by a random de novo genetic mutation, or autosomal dominant, X-linked, or mitochondrial. Metabolic myopathies are categorized by the metabolic pathway to which the deficient enzyme or transport protein belongs. The main categories of metabolic myopathies are listed below:
== In popular culture == On 7 August 1980, Samora Machel made a famous speech involving the national flag of Zimbabwe, in which he said while holding the flag, "This flag covers everyone. There are no blacks in Zimbabwe, there are no whites, there are no mulattos and Indians, today there are just Zimbabweans." In Harare, Zimbabwe, in 2011, the Zimbabwean reported that many cars displayed one or multiple small flag icons. Sales of the national flag were extremely high in the country. According to Petina Gappah in The Guardian in 2010, the flag is a "reminder that the nation was born of pain".
Arsenic exposure plays a key role in the pathogenesis of vascular endothelial dysfunction as it inactivates endothelial nitric oxide synthase, leading to a reduction in the generation and bioavailability of nitric oxide. In addition, chronic arsenic exposure induces high oxidative stress, which may affect the structure and function of the cardiovascular system. Further, the arsenic exposure has been noted to induce atherosclerosis by increasing the platelet aggregation and reducing fibrinolysis. Moreover, arsenic exposure may cause arrhythmia by increasing the QT interval and accelerating the cellular calcium overload. The chronic exposure to arsenic upregulates the expression of tumor necrosis factor-α, interleukin-1, vascular cell adhesion molecule and vascular endothelial growth factor to induce cardiovascular pathogenesis. Arsenic has also been shown to induce cardiac hypertrophy by activating certain transcription factors involved in pathologically remodeling the heart. Tissue culture studies have shown that arsenic compounds block both IKr and Iks channels and, at the same time, activate IK-ATP channels. Arsenic compounds also disrupt ATP production through several mechanisms. At the level of the citric acid cycle, arsenic inhibits pyruvate dehydrogenase and by competing with phosphate it uncouples oxidative phosphorylation, thus inhibiting energy-linked reduction of NAD+, mitochondrial respiration, and ATP synthesis. Hydrogen peroxide production is also increased, which might form reactive oxygen species and oxidative stress.
Sources: en.wikipedia.org
== Repair == L-isoaspartyl methyltransferase repairs isoaspartate and D-aspartate residues by sticking a methyl group onto the side chain carboxyl group in the residue, creating an ester. The ester rapidly and spontaneously turns into the succinimide (red), and randomly turns back into normal aspartic acid (black) or isoaspartate again (green) for another attempt.
The word "GULAG" is an acronym for Glavnoe Upravlenie Lagerei, or Main Camp Administration, the institution which ran the Soviet camps. But over time, the word has also come to signify the system of Soviet slave labor itself, in all its forms and varieties: labor camps, punishment camps, criminal and political camps, women's camps, children's camps, transit camps. Even more broadly, "Gulag" has come to mean the Soviet repressive system itself, the set of procedures that Alexander Solzhenitsyn once called "our meat grinder": the arrests, the interrogations, the transport in unheated cattle cars, the forced labor, the destruction of families, the years spent in exile, the early and unnecessary deaths.
=== Dentin graft === Dentin bone, made from extracted teeth, comprises more than 85% of tooth structure, the enamel consists of HA mineral and comprises 10% of tooth structure. Dentin is similar to bone in its chemical composition, by volume 70–75% is HA mineral and 20% organic matrix, mostly fibrous type I collagen. Dentin, like bone, may release growth and differentiating factors while being resorbed by osteoclasts. In order to make the dentin graft usable and bacteria-free, some companies have developed clinical procedures which include grinding, sorting and cleaning of the teeth for immediate or future use. In Korea, the Korea Tooth Bank performed bio-recycling of 38 000 patients' own teeth from January 2009 until October 2012.
== Expert reviews of the evidence == Letby has maintained that she is innocent of the offences for which she was convicted. Following the trials, a number of medical, statistical and other scientific experts have criticised the prosecution's evidence. The defence have been criticised for failing to call any of their own expert witnesses at trial. In 2025, a panel of experts convened by neonatologist Shoo Lee, provided with the infants' records and other trial evidence by Letby's legal representatives, published an assessment of the cases which presented alternative explanations for all of the deaths and collapses. The infants' families and the prosecution's lead expert witness have disputed these findings. The Court of Appeal has previously rejected challenges to the safety of the convictions.
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.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.