Heptapeptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-10-22. Anything still debated is marked as such rather than presented as settled.
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.
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.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
| 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 |
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.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
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.
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.
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.
Although the agreement was rejected in the subsequent October plebiscite, the same month, then-president of Colombia Juan Manuel Santos was awarded the Nobel Peace Prize for his efforts to bring the country's more than 50-year-long civil war to an end. A revised peace deal was signed the following month and submitted to Congress for approval. The House of Representatives unanimously approved the plan on November 30, a day after the Senate gave its backing.
== Honors and awards == Independent Scientist Research (K02) Award, National Institute of Mental Health, 2002–2007. Fellow, Association for Psychological Science, 2003. Fellow, Society for Personality and Social Psychology, 2005. Fellow, American Psychological Association, 2005. Career Trajectory Award, Society of Experimental Social Psychology, 2006. Cattell Fund Fellowship, 2007–2008. NIH Director's Pioneer Award, 2007–2012, to study how the brain creates emotion. Kavli Fellow, National Academy of Sciences, 2008. Elected Fellow, American Association for the Advancement of Science, 2008. Arts in Academics award, University of Waterloo, 2010. Excellence in Research and Creative Activity Award, Northeastern University, 2012. Elected Fellow, Royal Society of Canada, 2012. Award for Distinguished Service in Psychological Science, American Psychological Association, 2013. Elected Fellow, Society of Experimental Psychologists, 2013. Diener Award in Social Psychology, Society for Personality and Social Psychology, 2014. Heritage Wall of Fame, Foundation for Personality and Social Psychology, 2016. Mentor Award for Lifetime Achievement, Association for Psychological Science, 2018. Elected Fellow, American Academy of Arts and Sciences, 2018. President, Association for Psychological Science, 2019–2020. Guggenheim Fellowship in neuroscience, 2019. John P. McGovern Award in the Behavioral Sciences, American Association for the Advancement of Science, 2020. APA Award for Distinguished Scientific Contributions, American Psychological Association, 2021.
In practice, the solid support is used in excess (often tenfold) to be sure that all expected components are formed. The above limitation is completely removed if the solid support is omitted and the synthesis is carried out in solution. In this case, there is no upper limit concerning the number of components of the library. Both the number of components and the quantity of the library can be freely decided based only on practical considerations. An important modification was introduced in the synthesis of DNA encoded combinatorial libraries by Harbury and Halpin. The solid support in their case is replaced by the encoding DNA oligomers. This makes it possible to synthesize libraries containing even trillions of components and screen them using affinity binding methods. A different way of carrying out solution-phase S&P synthesis is applying scavenger resins to remove the byproducts. Scavenger resins are polymers having functional groups that make it possible to react with and bind components of the excess of reagents then filtered them out from the reaction mixture Two examples: a resin containing primary amino groups can remove the excess of acyl chlorides from reaction mixtures while an acyl chloride resin removes amines. A fluorous technology was described by Curran The fluorous synthesis employs functionalized perfluoroalkyl (Rf) groups like 4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononyl {CF3(CF2)4CF2CH2CH2-} group attached to substrates or reagents. The Rf groups make it possible to remove either the product or the reagents from the reaction mixture.
Sources: en.wikipedia.org
=== Skin === The weak connective tissue causes abnormal skin. This may present as stretchy or, in other types, simply be velvet soft. In all types, some increased fragility occurs, but the degree varies depending on the underlying subtype. The skin may tear and bruise easily, and may heal with abnormal atrophic scars; atrophic scars that resemble cigarette paper are a sign seen in those whose skin might appear otherwise normal. In some subtypes, though not the hypermobile subtype, redundant skin folds occur, especially on the eyelids. Redundant skin folds are areas of excess skin lying in folds. Other skin symptoms include molluscoid pseudotumors, especially on pressure points, petechiae, subcutaneous spheroids, livedo reticularis; piezogenic papules are less common. In vascular EDS, skin can also be thin and translucent. In dermatosparaxis EDS, the skin is extremely fragile and saggy.
=== Ullrich congenital muscular dystrophy === Ullrich congenital muscular dystrophy (UCMD) is a condition that primarily affects the function of skeletal muscles. UCMD has been associated with mutations in the COL6A1, COL6A2, and COL6A3 gene. The most common pattern of inheritance for UCMD is autosomal recessive, although an autosomal dominant pattern of inheritance is observed in rare cases.
Different isotopes of thorium are chemically identical, but have slightly differing physical properties: for example, the densities of pure 228Th, 229Th, 230Th, and 232Th are respectively expected to be 11.5, 11.6, 11.6, and 11.7 g/cm3. The isotope 229Th is fissionable and the bare critical mass of estimated at 2839 kg, although with steel reflectors this value would drop to 994 kg. 232Th is not fissionable, but it is fertile as it can be converted to fissile 233U by neutron capture and subsequent beta decay.
Sources: en.wikipedia.org
6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2 Biological energy is frequently stored and released using redox reactions. Photosynthesis involves the reduction of carbon dioxide into sugars and the oxidation of water into molecular oxygen. The reverse reaction, respiration, oxidizes sugars to produce carbon dioxide and water. As intermediate steps, the reduced carbon compounds are used to reduce nicotinamide adenine dinucleotide (NAD+) to NADH, which then contributes to the creation of a proton gradient, which drives the synthesis of adenosine triphosphate (ATP) and is maintained by the reduction of oxygen. In animal cells, mitochondria perform similar functions.
Maúrtua further added that Castillo met Maduro during the VI Summit of CELAC, where many Latin American leaders were present. The Foreign Minister stated that in such multilateral events, spontaneous meetings are natural. Subsequently, the Free Peru caucus accused Maúrtua of trying to impose his political agenda on the President, and called for Maúrtua's resignation: "The foreign minister remained silent... in the face of the audacity of his Vice Foreign Minister Luis Enrique Chávez to contradict the president in his decision to maintain friendly relations and cooperation with Venezuela and the Maduro government. Therefore, having transgressed the provisions of Article 118, paragraph 11 of the Political Constitution, our caucus demands the resignation of both the minister and the vice minister." On 15 October 2021, following the appointment of the Vásquez cabinet, Richard Rojas Garcia was appointed as Peru's ambassador to Venezuela. This in effect established official diplomatic relations with Venezuela. Some media outlets have claimed that Rojas is the right-hand man of Vladimir Cerrón. However, soon afterward a judge ruled that Rojas could not leave the country for 6 months, due to his alleged link with members of "Los Dinámicos del Centro." Afterward, Foreign Minister Óscar Maúrtua claimed that Rojas' appointment as ambassador to Venezuela never took place, "since the corresponding process was not concluded. In this sense, Peru is proceeding to inform the Government of Venezuela that the proposed appointment of Mr.
Lariocidin (abbreviated as LAR) is a naturally occurring lasso peptide antibiotic. It is the first lasso peptide reported to inhibit protein synthesis in bacteria through interactions with the ribosome. LAR kills a broad spectrum of bacteria, including multiple human pathogens that are classified as priority pathogens by the World Health Organization such as Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, and Escherichia coli.
However, the organism makes antibodies against this viral protein, and those antibodies also kill the human ACTH hormone, which leads to the suppression of adrenal gland function. Such adrenal suppression is a way for a virus to evade immune detection and elimination. This viral strategy can have severe consequences for the host (human that is infected by the virus), as cortisol is essential for regulating various physiological processes, such as metabolism, blood pressure, inflammation, and immune response. A lack of cortisol can result in a condition called adrenal insufficiency, which can cause symptoms such as fatigue, weight loss, low blood pressure, nausea, vomiting, and abdominal pain. Adrenal insufficiency can also impair the ability of the host to cope with stress and infections, as cortisol helps to mobilize energy sources, increase heart rate, and downregulate non-essential metabolic processes during stress. Therefore, by suppressing cortisol production, some viruses can escape the immune system and weaken the host's overall health and resilience.
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.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.