TKPRPGP is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-02-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
| 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 |
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
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.
==== Gel spinning ==== Gel spinning produces fibers with exceptional strength or other unique qualities. During extrusion, the polymer is not in a pure liquid condition. The polymer chains are linked at different locations in liquid crystal form, partially apart as they would be in a real solution. The resultant filaments have substantial inter-chain forces, which can significantly raise the fiber's tensile strength additionally, the shear forces the liquid crystals to be arranged along the fiber axis during extrusion. Strength is further enhanced by the filaments' exceptionally high degree of alignment as they emerge from one another. Due to the filaments' first air-to-cool cooling phase, the method is known as dry-wet spinning.
== Maximum parsimony and maximum likelihood == There are many approaches to reconstructing phylogenetic trees, each with advantages and disadvantages, and there is no straightforward answer to "what is the best method?". Maximum parsimony (MP) and maximum likelihood (ML) are traditional methods widely used for the estimation of phylogenies and both use character information directly, as Bayesian methods do. Maximum Parsimony recovers one or more optimal trees based on a matrix of discrete characters for a certain group of taxa and it does not require a model of evolutionary change. MP gives the most simple explanation for a given set of data, reconstructing a phylogenetic tree that includes as few changes across the sequences as possible. The support of the tree branches is represented by bootstrap percentage. For the same reason that it has been widely used, its simplicity, MP has also received criticism and has been pushed into the background by ML and Bayesian methods. MP presents several problems and limitations. As shown by Felsenstein (1978), MP might be statistically inconsistent, meaning that as more and more data (e.g. sequence length) is accumulated, results can converge on an incorrect tree and lead to long branch attraction, a phylogenetic phenomenon where taxa with long branches (numerous character state changes) tend to appear more closely related in the phylogeny than they really are.
== Presence == In cephalochordates (lancelets), the notochord persists throughout life as the main structural support of the body. In tunicates, the notochord is present only in the larval stage, becoming completely absent in the adult animal, and the notochord is not vacuolated. In all vertebrates other than the hagfish, the notochord is present only during early embryonic development and is later replaced by the bony and/or cartilaginous vertebral column, with its original structure being integrated into the intervertebral discs as the nucleus pulposus.
Iran, meanwhile, has embarked on a nuclear program which, while officially for civilian purposes, has come under close scrutiny by the United Nations and many individual states. Recent studies undertaken by the CIA cite the enduring India-Pakistan conflict as the one "flash point" most likely to escalate into a nuclear war. During the Kargil War in 1999, Pakistan came close to using its nuclear weapons in case the conventional military situation underwent further deterioration. Pakistan's foreign minister had even warned that it would "use any weapon in our arsenal", hinting at a nuclear strike against India. The statement was condemned by the international community, with Pakistan denying it later on. This conflict remains the only war (of any sort) between two declared nuclear powers. The 2001-2002 India-Pakistan standoff again stoked fears of nuclear war between the two countries. Despite these very serious and relatively recent threats, relations between India and Pakistan have been improving somewhat over the last few years. However, with the November 26, 2008 Mumbai terror attacks, tensions again worsened.
=== October === 7 October – A study published in Current Biology reports a 63% decline in occupied chinstrap penguin nests on Zavodovski Island between 2011 and 2025, causing the island to lose its status as home to the world's largest penguin colony. Researchers link the decline to climate-driven changes in the availability of Antarctic krill, while the island's macaroni penguin population has increased.
Sources: en.wikipedia.org
The 4n+1 chain of neptunium-237 is commonly called the "neptunium series" or "neptunium cascade". In this series, only two of the isotopes involved are found naturally in significant quantities, namely the final two: bismuth-209 and thallium-205. Some of the other isotopes have been detected in nature, originating from trace quantities of 237Np produced by the (n,2n) knockout reaction in primordial 238U. This series terminates with the stable isotope thallium-205, 8 alpha decays and 4 beta decays from neptunium. The neptunium series is fairly unique among the 4, for several reasons:
, which may allow to redefine the distributions as simple functions of the age only. If the flow is steady (but a generalization to non-steady flow is possible) and is conservative, then the exit age distribution and the internal age distribution can be related one to the other:
oxidative phosphorylation during aerobic respiration in the mitochondrion from adenosine diphosphate (ADP). substrate-level phosphorylation during glycolysis and the Krebs cycle. By photophosphorylation in the chloroplasts of plant cells.
=== Oral bacteria === Erythritol is tooth-friendly; since it cannot be metabolized by oral bacteria, it does not contribute to tooth decay. In addition, erythritol, like xylitol, has antibacterial effects against streptococci bacteria, reduces dental plaque, and may be protective against tooth decay.
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 heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.