The short version of Heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-03. Anything still debated is marked as such rather than presented as settled.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
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.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
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.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
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.
== Desmale Ossifikation == Bei der desmalen Ossifikation entsteht das Knochengewebe direkt aus dem embryonalen Bindegewebe (Mesenchym), weshalb man auch von direkter Ossifikation spricht. So gebildete Knochen nennt man Bindegewebs-, Geflecht-, Deck- oder Belegknochen. Auf diese Art und Weise entstehen die Knochen des Schädeldachs und des Gesichtsschädels sowie das Schlüsselbein. Mesenchymzellen verdichten sich inselartig zu Vorläuferzellen. Diese differenzieren sich zu Osteoblasten und bauen die Knochengrundsubstanz (Osteoid) auf, die anschließend mineralisiert. Dabei mauern sie sich durch die Anlagerung weiterer Osteoidschichten allmählich selbst ein und werden zu Osteozyten (ruhenden Zellen). Es entstehen so einzelne Verknöcherungspunkte, die sich zu Knochenspangen vereinigen und so den fertigen Knochen bilden. Kommt es zu einem Knochenbruch, so wird immer zuerst einmal neues Knochengewebe gebildet, welches später zu Lamellenknochen umgewandelt wird (→ Knochenheilung).
Bei dieser Form entstehen aus dem Mesenchym zunächst durch die Differenzierung von Mesenchymzellen zu Chondroblasten knorpelige Skelettelemente, das hyaline Primordialskelett, weshalb sie auch als indirekte Ossifikation bezeichnet wird. Man nennt die aus Primordialknochen gebildeten Skelettteile auch Ersatzknochen. Es gibt die Verknöcherung von innen her (enchondrale Ossifikation), dabei wachsen in das Knorpelgewebe Blutgefäße ein, in deren Begleitung sich Mesenchymzellen befinden. Diese differenzieren sich zu Chondroklasten (Knorpelabbau) und Osteoblasten (für den Knochenaufbau). Im Bereich der Epiphysenfugen kommt es durch den ständigen Auf- und Abbau zu einem Längenwachstum (interstitielles Wachstum). Bei der Verknöcherung von außen (perichondrale Ossifikation) sondern sich von der Knorpelhaut (Perichondrium) Osteoblasten ab. Diese lagern sich ringförmig um das Knorpelmodell und es entsteht so eine Knochenmanschette. Die perichondrale Ossifikation findet am Mittelschaft (Diaphyse) der langen Röhrenknochen statt. Die perichondrale Ossifikation dient somit dem Dickenwachstum (appositionelles Wachstum). Auch entsteht im Inneren des Knochens ein Innenraum (primäres Mark), welches durch pluripotente Mesenchymzellen ersetzt wird und somit das eigentliche Knochenmark darstellt. Bei beiden Formen der chondralen Ossifikation sondern die Osteoblasten eine Grundsubstanz, das Osteoid, ab. Durch den Einfluss der Osteoblastenfermente werden Kalksalze abgelagert. Die Osteoblasten differenzieren sich daraufhin zu Osteozyten.
Die Punkte, von denen die Verknöcherung ausgeht, nennt man Knochenkerne, Verknöcherungs- oder Ossifikationszentren. Die Ossifikationszentren entstehen bei Nestflüchtern vor, bei den Nesthockern zumeist erst nach der Geburt.
== Knochenumbildung == Sowohl durch desmale als auch durch chondrale Ossifikation und auch bei der Heilung von Knochenbrüchen entsteht zunächst Geflecht- oder Faserknochen. Hier sind die Kollagenfibrillen der Knochengrundsubstanz noch ungeordnet. Die Faserknochen haben eine große Wachstumspotenz, jedoch eine geringe mechanische Festigkeit. Durch mechanische Beanspruchung (formative Reize) kommt es in den ersten Lebensjahren zum Umbau in den stabileren und strenger organisierten Lamellenknochen.
Sources: de.wikipedia.org
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
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.