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 2025-09-05. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
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.
| 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 |
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
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.
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.
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.
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.
Betaine transporter (SLC6A12) InterPro: IPR002983 Creatine transporter (SLC6A8) InterPro: IPR002984 Dopamine neurotransmitter transporter (SLC6A3) InterPro: IPR002436 Inebriated neurotransmitter transporter InterPro: IPR002944 GABA neurotransmitter transporter GAT-1 (SLC6A1) InterPro: IPR002980 GABA neurotransmitter transporter GAT-2 (SLC6A13) InterPro: IPR002981 GABA neurotransmitter transporter GAT-3 (SLC6A11) InterPro: IPR002982 Glycine neurotransmitter transporter, type 1 (SLC6A9) InterPro: IPR003028 Noradrenaline neurotransmitter transporter (SLC6A2) InterPro: IPR002435 Orphan neurotransmitter transporter (SLC6A15) InterPro: IPR002438 Serotonin (5-HT) neurotransmitter transporter, N-terminal (SLC6A4) InterPro: IPR013086 Taurine transporter (SLC6A6) InterPro: IPR002434
=== Bitcoin's theoretical roots and ideology === According to the European Central Bank, the decentralization of money offered by bitcoin has its theoretical roots in the Austrian school of economics, especially with Friedrich Hayek's The Denationalisation of Money, in which he advocates a complete free market in the production, distribution and management of money to end the monopoly of central banks. Sociologist Nigel Dodd argues that the essence of the bitcoin ideology is to remove money from social, as well as governmental, control. The Economist describes bitcoin as "a techno-anarchist project to create an online version of cash, a way for people to transact without the possibility of interference from malicious governments or banks". These philosophical ideas initially attracted libertarians and anarchists.
More zeroes may be added in a process called zero filling to improve the appearance of the final spectrum although there is no improvement in resolution. Alternatively, interpolation after the Fourier transform gives a similar result.
Sources: en.wikipedia.org
However, in the event of a radioiodine release too massive and widespread to be controlled by the limited stock of iodide and iodate prophylaxis drugs, then the addition of perchlorate ions to the water supply, or distribution of perchlorate tablets would serve as a cheap, efficacious, second line of defense against carcinogenic radioiodine bioaccumulation. The ingestion of goitrogen drugs is, much like potassium iodide also not without its dangers, such as hypothyroidism. In all these cases however, despite the risks, the prophylaxis benefits of intervention with iodide, iodate, or perchlorate outweigh the serious cancer risk from radioiodine bioaccumulation in regions where radioiodine has sufficiently contaminated the environment.
Phenylalkylpyrrolidines like PEP, MPEP, prolintane, α-PPP, α-PVP, pyrovalerone, and MDPV Phenylalkylpiperidines like AC927 (phenethylpiperidine), diphenidine, fentanyl, and ifenprodil Tetrahydroisoquinolines (THIQs) like anhalinine, pellotine, lophophorine, DOM-CR, nomifensine, tetrabenazine, and zelandopam Isoquinolines like perafensine, quinisocaine, and tilisolol Dihydroindoles and aminochromes like adrenochrome and adrenolutin 2-Aminoindanes (2-AIs) like 2-aminoindane, MDAI, MMAI, DOM-AI, and Pyr-AI 2-Aminotetralins (2-ATs) like 2-aminotetralin, MDAT, DOM-AT, 8-OH-DPAT, rotigotine, and UH-232 1-Aminomethylindanes (1-AMIs) like 2CB-Ind, AMMI, jimscaline, and bromojimscaline 3-Benzazepines like fenoldopam and lorcaserin Benzocyclobutenes (BCBs) like 2CBCB-NBOMe, S33005, TCB-2, tomscaline, and bromotomscaline 3-Aminochromans like CT-5126, 5-MeO-DPAC, robalzotan, and ebalzotan Benzoxepins like TFMBOX Phenylmethylpyrrolidines (benzylpyrrolidines) like APA-01 (PharmAla-1) 2-Benzylpiperidines and phenidates like 2-benzylpiperidine, methylphenidate, rimiterol, and DMBMPP Phenylcyclopropylamines like tranylcypromine, TMT, and DMCPA 3-Phenylpiperidines (3PIPs) like 3-phenylpiperidine, 3-PPP, OSU-6162 (PNU-96391), LPH-5, LPH-48, 2C-B-3PIP, 2C-B-3PIP-NBOMe, 2C-B-3PIP-POMe, and Z3517967757 (Z7757) 2-Phenylmorpholines like 2-phenylmorpholine, phenmetrazine, manifaxine, radafaxine, flumexadol, oxaflozane, and PF-219,061 Phenyloxazolamines or aminorex analogues like aminorex and pemoline Tricyclic compounds like benzoctamine and dizocilpine Ergolines and lysergamides like ergine (LSA) and LSD Partial ergolines and lysergamides like NDTDI, RU-27849, UCD0179, and UCD0120 Pyridopyrroloquinoxalines like lumateperone, IHCH-7113, IHCH-7086, and ITI-1549 Anthracenes like AMDA and SpAMDA Phenanthrenes like atherosperminine Aporphines like aporphine, apomorphine, glaucine, and nuciferine Others like 6-AB, 2-ADN, 2C-B-PYR, 2C-B-5-hemiFLY-α6 (BNAP), 2CB7 (2C-B-5-hemiFLY-β7), 2CBecca, 2CJP, 2CLisaB, 2CLisaH, 2-naphthylamine, AMMI, GYKI-52895, ivabradine, milnacipran, Org 6582, and ZC-B Some additional cyclized phenethylamines have also been described. Other related families that are not phenethylamines themselves include phenylpiperazines, benzylpiperazines, and 4-phenylpiperidines.
== See also == Houses of Parliament, Cape Town List of acts of the Parliament of South Africa Politics of South Africa List of legislatures by country List of committees of the Parliament of South Africa Provincial legislatures of South Africa
Sources: en.wikipedia.org
Most of these cells develop into separate bone, cartilage, and joint cells, and they are then articulated with one another. Specialized skeletal tissues are unique to vertebrates. Cartilage grows more quickly than bone, causing it to be more prominent earlier in an animal's life before it is overtaken by bone. Cartilage is also used in vertebrates to resist stress at points of articulation in the skeleton. Cartilage in vertebrates is usually encased in perichondrium tissue. Ligaments are elastic tissues that connect bones to other bones, and tendons are elastic tissues that connect muscles to bones.
==== Parkinson's disease ==== Creatine's impact on mitochondrial function has led to research on its efficacy and safety for slowing Parkinson's disease. As of 2014, the evidence did not provide a reliable foundation for treatment decisions, due to risk of bias, small sample sizes, and the short duration of trials.
3 September 1917: "With reference to a suggestion that the matter might be postponed, [Balfour] pointed out that this was a question on which the Foreign Office had been very strongly pressed for a long time past. There was a very strong and enthusiastic organisation, more particularly in the United States, who were zealous in this matter, and his belief was that it would be of most substantial assistance to the Allies to have the earnestness and enthusiasm of these people enlisted on our side. To do nothing was to risk a direct breach with them, and it was necessary to face this situation." 4 October 1917: "... [Balfour] stated that the German Government were making great efforts to capture the sympathy of the Zionist Movement. This Movement, though opposed by a number of wealthy Jews in this country, had behind it the support of a majority of Jews, at all events in Russia and America, and possibly in other countries ... Mr. Balfour then read a very sympathetic declaration by the French Government which had been conveyed to the Zionists, and he stated that he knew that President Wilson was extremely favourable to the Movement." 25 October 1917: "...
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.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.