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Peptide Identity And Structure — What the Evidence Shows

By Editorial Desk · published 2025-11-24 · last reviewed 2025-12-12 · Wiki

elevated plus maze 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 2025-12-12. Numbers and descriptions here follow the published literature rather than marketing material.

Peptide Identity and Structure

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.

Selank Background and Peptide Chemistry

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.

Selank at a glance

PropertyValueNotes
Peptide sequenceThr-Lys-Pro-Arg-Pro-Gly-ProSeven residues; tuftsin plus a Pro-Gly-Pro tail
Molecular formulaC33H57N11O9Commonly reported value for the free peptide
Monoisotopic massRoughly 751.4 DaAverage molecular mass near 751.9 Da
AppearanceWhite to off-white powderTypically supplied as a lyophilized solid
Solubility classFreely soluble in waterAlso dissolves in saline and other polar solvents

Background and Peptide Identity

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.

Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.

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Proposed Mechanisms and Research Endpoints

Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.

Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.

Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.

Background and Molecular Identity

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.

Identity and Structural Background

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.

Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.

Supporting material

=== Enols and enolates === The α-carbon is important for enol- and enolate-based carbonyl chemistry as well. Chemical transformations affected by the conversion to either an enolate or an enol, in general, lead to the α-carbon acting as a nucleophile, becoming, for example, alkylated in the presence of primary haloalkane. An exception is in reaction with silyl chlorides, bromides, and iodides, where the oxygen acts as the nucleophile to produce silyl enol ether.

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Multi/minicore myopathy is a congenital myopathy usually caused by mutations in either the SELENON and RYR1 genes. It is characterised the presence of multifocal, well-circumscribed areas with reduction of oxidative staining and low myofibrillar ATPase on muscle biopsy. It is also known as Minicore myopathy, Multicore myopathy, Multiminicore myopathy, Minicore myopathy with external ophthalmoplegia, Multicore myopathy with external ophthalmoplegia and Multiminicore disease with external ophthalmoplegia.

== Definition == Polycythemia is defined as serum hematocrit (Hct) or hemoglobin (HgB) exceeding normal ranges expected for age and gender, typically Hct >49% in healthy adult men and >48% in women, or HgB >16.5 g/dL in men or >16.0 g/dL in women. The definition is different for neonates and varies by age in children.

Once the cell has received a non-trivial load, and has expended the phosphocreatine reserve, a small quantity of ATP will become discharged down to AMP. AMP will instantly up-regulate myophosphorylase, which will start liberating glucose from glycogen and make it available to the glycolytic pathway, producing pyruvate and recharging AMP back to ATP. Due to the greater availability of pyruvate as a substrate, and pyruvate also contributing a citric acid cycle intermediate, α-ketoglutarate, while consuming glutamate, the citric acid cycle will also speed up. The combination of glycolysis and the citric acid cycle now balances ATP production with ATP demand and the pool of AMP does not grow further. Because all pyruvate is not burned down in the citric acid cycle—a consequence of the pyruvate's concentration regulating its burning at this moment—the excess is converted to lactate and passed into blood as lactic acid. In muscle cells with normal AMPD activity, the purine nucleotide cycle would now start to gradually add fumarate to the pool of the citric acid cycle intermediates. This would decrease the excess rate of pyruvate production by increasing its consumption, increase the rate of AMP recharge to ATP by the citric acid cycle, and consequently reduce liberation of glucose from glycogen, until increased supply of blood-borne fuels allows to shut down glycogenolysis completely. In muscle cells with AMPD deficiency, ATP production rate of the citric acid cycle will not be synchronized with ATP demand.

Sources: en.wikipedia.org

Notes from published material

Cèpe bronzé ("dark cep"; Boletus aereus), much rarer than B. edulis, is more highly regarded by gourmets and consequently more expensive. Usually smaller than B. edulis, it is also distinctively darker in colour. It is especially suited to drying. Cèpe des pins ("pine tree cep"; Boletus pinophilus or Boletus pinicola) grows among pine trees. Rarer than B. edulis, it is less appreciated by gourmets than the two other kinds of porcini, but remains a mushroom rated above most others. Cèpe d'été ("summer cep"; Boletus reticulatus), also less common and found earlier. Molecular phylogenetic analyses have proven these three are all distinctive and separate species; other taxa formerly believed to be unique species or subspecies, such as B. betulicola, B. chippewaensis, B. persoonii, B. quercicola and B. venturii, are now known to be part of a B. edulis species complex with a wide morphological, ecological and geographic range, and that the genetic variability in this complex is low. Similar molecular technology has been developed to rapidly and accurately identify B. edulis and other commercially important fungi. Three divergent lineages found in Yunnan province in China that are commonly marketed and sold as B. edulis (and are actually more closely related to B. aereus) were described in 2013 as B. bainiugan, B. meiweiniuganjun and B. shiyong. The classification has since been updated and expanded. All lineages are still members of Boletus sect. Boletus, the sensu stricto "porcini clade" of the genus.

The strength of venom differs markedly between species and even more so between families, as measured by median lethal dose (LD50) in mice. Subcutaneous LD50 varies by over 140-fold within elapids and by more than 100-fold in vipers. The amount of venom produced also differs among species, with the Gaboon viper able to potentially deliver from 450 to 600 milligrams of venom in a single bite, the most of any snake. Opisthoglyphous colubrids have venom ranging from life-threatening (in the case of the boomslang) to barely noticeable (as in Tantilla).

Vaccines are examples of antigens in an immunogenic form, which are intentionally administered to a recipient to induce the memory function of the adaptive immune system towards antigens of the pathogen invading that recipient. The vaccine for seasonal influenza is a common example.

In women, the breasts overlie the pectoralis major muscles and extend on average from the level of the second rib to the level of the sixth rib in the front of the rib cage; thus, the breasts cover much of the chest area and the chest walls. At the front of the chest, the breast tissue can extend from the clavicle (collarbone) to the middle of the sternum (breastbone). At the sides of the chest, the breast tissue can extend into the axilla (armpit), and can reach as far to the back as the latissimus dorsi muscle, extending from the lower back to the humerus bone (the bone of the upper arm). As a mammary gland, the breast is composed of differing layers of tissue, predominantly two types: adipose tissue; and glandular tissue, which affects the lactation functions of the breasts. The natural resonant frequency of the human breast is about 2 hertz. Morphologically, the breast is tear-shaped. The superficial tissue layer (superficial fascia) is separated from the skin by 0.5–2.5 cm of subcutaneous fat (adipose tissue). The suspensory Cooper's ligaments are fibrous-tissue prolongations that radiate from the superficial fascia to the skin envelope. The female adult breast contains 14–18 irregular lactiferous lobes that converge at the nipple. The 2.0–4.5 mm milk ducts are immediately surrounded with dense connective tissue that support the glands. Milk exits the breast through the nipple, which is surrounded by a pigmented area of skin called the areola. The size of the areola can vary widely among women. The areola contains modified sweat glands known as Montgomery's glands.

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Sources: en.wikipedia.org

Frequently asked questions

What is the primary sequence of Selank?

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.

Is Selank found naturally in the body?

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.

Why does the peptide contain three proline residues?

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.

What is selank?

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.

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