The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-04-17 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| 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 |
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
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.
CPA is generally well-tolerated and has a mild side-effect profile regardless of dosage when it is used in combination with an estrogen in women. Side effects of CPA in general include hypogonadism (low sex-hormone levels) and associated symptoms such as demasculinization, sexual dysfunction, infertility, and osteoporosis (fragile bones); breast changes such as breast tenderness, breast enlargement, and gynecomastia (breasts in men); emotional changes such as fatigue and depression; and other side effects such as vitamin B12 deficiency, weak glucocorticoid effects, and elevated liver enzymes. Weight gain can occur with CPA when it is used at high doses. Some of the side effects of CPA can be improved or fully prevented if it is combined with an estrogen to prevent estrogen deficiency. Few quantitative data are available on many of the potential side effects of CPA. Pooled tolerability data for CPA is not available in the literature. Cyproterone is also known to suppress adrenocortical function. At very high doses in aged men with prostate cancer, CPA can cause cardiovascular side effects. Rarely, CPA can produce blood clots, liver toxicity (including hepatitis, liver failure, and liver cancer), excessively high prolactin levels, and certain benign brain tumors including meningiomas (tumors of the meninges) and prolactinomas (prolactin-secreting tumors of the pituitary gland). Upon discontinuation from high doses, CPA can produce adrenal insufficiency as a withdrawal effect.
Metofoline (INN), also known as methofoline (USAN), is an opioid analgesic drug discovered in the 1950s by a team of Swiss researchers at Hoffmann-La Roche. Methopholine is an isoquinoline derivative which is not structurally related to most other opioids. However, its structural similarity to the non-opioid alkaloid papaverine is notable. Metofoline has around the same efficacy as an analgesic as codeine, and was evaluated for the treatment of postoperative pain. Metofoline tablets were marketed in the United States under the brand name of Versidyne, but the drug was withdrawn from the market in 1965 due to the occurrence of ophthalmic side-effects alongside the discovery that the drug could produce cataracts in dogs. Metofoline has two enantiomers, with the levo (R) enantiomer being the active form, around 3x the potency of codeine, and the (S) enantiomer being inactive. Analogs where the 4'-chloro group has been replaced by other electron withdrawing groups have also been tested, the fluoro derivative being slightly more potent than chloro, and the nitro derivative being most potent of all, with the racemic 4'-nitromethopholine being around 20x the potency of codeine. Later research was carried out by Bristol-Myer in the 1960s and animal studies suggested derivatives with significantly increased analgesic activity of over x50 codeine.
=== Characteristics === Unintentional weight loss may result from loss of body fats, loss of body fluids, muscle atrophy, or a combination of these. It is generally regarded as a medical problem when at least 10% of a person's body weight has been lost in six months or 5% in the last month. Another criterion used for assessing weight that is too low is the body mass index (BMI). However, even lesser amounts of weight loss can be a cause for serious concern in a frail elderly person. Unintentional weight loss can occur because of an inadequately nutritious diet relative to a person's energy needs (generally called malnutrition). Disease processes, changes in metabolism, hormonal changes, medications or other treatments, disease- or treatment-related dietary changes, or reduced appetite associated with a disease or treatment can also cause unintentional weight loss. Poor nutrient utilization can lead to weight loss, and can be caused by fistulae in the gastrointestinal tract, diarrhea, drug-nutrient interaction, enzyme depletion and muscle atrophy. Continuing weight loss may deteriorate into wasting, a vaguely defined condition called cachexia. Cachexia differs from starvation in part because it involves a systemic inflammatory response. It is associated with poorer outcomes. In the advanced stages of progressive disease, metabolism can change so that they lose weight even when they are getting what is normally regarded as adequate nutrition and the body cannot compensate.
==== Elimination ==== The elimination of trazodone is biphasic: the first phase's half-life (distribution) is 3 to 6 hours, and the following phase's half-life (elimination) is 4.1 to 14.6 hours. The elimination half-life of extended-release trazodone is 9.1 to 13.2 hours. The elimination half-life of mCPP is 2.6 to 16.0 hours and is longer than that of trazodone. Metabolites are conjugated to gluconic acid or glutathione and around 70 to 75% of 14C-labelled trazodone was found to be excreted in the urine within 72 hours. The remaining drug and its metabolites are excreted in the faeces via biliary elimination. Less than 1% of the drug is excreted in its unchanged form. After an oral dose of trazodone, it was found to be excreted 20% in the urine as TPA and conjugates, 9% as the dihydrodiol metabolite, and less than 1% as unconjugated mCPP. mCPP is glucuronidated and sulfated similarly to other trazodone metabolites.
The first strategy, referred to as "prolonged resistance" on state television, would involve several small military units carrying out sabotage and other guerrilla-style tactics, according to sources. The second strategy that was not officially mentioned, "anarchization", aims to "make Venezuela ungovernable for foreign forces" by creating disorder in the capital, Caracas. The approach, labeled an acknowledgement of Venezuela's "debilitated" military, would be unlikely to succeed, as noted by sources. After USS Gravely arrived in Trinidad and Tobago on 26 October, Venezuela condemned that country's joint drills with the US, referring to them as a "military provocation", and withdrew from an energy agreement it had established with the island nation in 2015. Vice President Delcy Rodríguez claimed without evidence that Venezuela had captured a group of mercenaries "with direct information of the American intelligence agency" whose goal was to carry out a false flag attack in the region. Minister of the Interior Diosdado Cabello said on 27 October the captured cell was four members "financed by the CIA" who had plans to blame Venezuela for an attack on the Gravely.
Sources: en.wikipedia.org
LECO Corporation, founded in 1936 by Carl Schultz and George Krasl, operates its analytical instrumentation research and development, and manufacturing from its headquarters located in St. Joseph, Michigan.
The significance of these additional actions for Auvelity's antidepressant effects remains unclear. The combined pharmacological actions of DXM and bupropion make Auvelity function similarly to an SNDRI (serotonin-norepinephrine-dopamine reuptake inhibitor), simultaneously enhancing all three monoamine neurotransmitter systems. This characteristic may contribute to its relatively rapid antidepressant onset. The role of NMDA antagonism in Auvelity appears to be relatively limited. Ketamine and related compounds do indeed owe their rapid antidepressant effects to NMDA receptor antagonism. However, subsequent studies of numerous NMDA antagonists have found that most do not exhibit antidepressant efficacy. The reason appears to be that antidepressant activity requires exceptionally stringent molecular properties for NMDA receptor antagonism, particularly highly specific receptor-binding kinetics. In practice, neither DXM nor dextrorphan fulfills these requirements. This likely explains why Auvelity requires approximately 8 days to produce antidepressant effects, whereas esketamine can begin working within only a few hours. Therefore, although Auvelity substantially shortens the onset of action compared with conventional oral antidepressants, its mechanism underlying the accelerated antidepressant response appears to have only a limited relationship to the rapid antidepressant mechanism of ketamine.
== Interactions == CYP3A4 inhibitors can increase exposure to suvorexant while CYP3A4 inducers can decrease exposure to suvorexant. Combination of suvorexant with the strong CYP3A4 inhibitor ketoconazole increased suvorexant overall exposure by 2.79-fold and peak levels by about 1.25-fold, combination with the moderate CYP3A4 inhibitor diltiazem increased suvorexant overall exposure by 2.05-fold and peak levels by about 1.25-fold, and combination with the strong CYP3A4 inducer rifampin decreased suvorexant overall exposure by 88% and peak levels by about 65%. The elimination half-life of suvorexant (about 12 hours for suvorexant alone) was increased to 19.4 hours with ketoconazole and to 16.1 hours with diltiazem while it was decreased to 7.7 hours with rifampin. Concomitant use of suvorexant with strong CYP3A4 inhibitors is not recommended, while lower doses of suvorexant are recommended with moderate CYP3A4 inhibitors (5 mg starting dose and 10 mg maximum dose generally). The substantial decrease in suvorexant exposure with strong CYP3A4 inducers may result in loss of effectiveness. Suvorexant does not appear to have been assessed in combination with moderate CYP3A4 inducers (e.g., modafinil).
An aglycone (aglycon or genin) is the chemical compound remaining after the glycosyl group on a glycoside is replaced by a hydrogen atom. For example, the aglycone of a cardiac glycoside would be a steroid molecule.
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 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.