Reversed-phase HPLC 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.
Updated 2026-01-14. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
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.
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.
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.
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.
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.
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.
A common way to increase vitamin B intake is by using dietary supplements. B vitamins are commonly added to energy drinks, many of which have been marketed with large amounts of B vitamins. Because they are soluble in water, excess B vitamins are generally readily excreted, although individual absorption, use and metabolism may vary. The elderly and athletes may need to supplement their intake of B12 and other B vitamins due to problems in absorption and increased needs for energy production. In cases of severe deficiency, B vitamins, especially B12, may also be delivered by injection to reverse deficiencies. Both type 1 and type 2 diabetics may also be advised to supplement thiamine based on high prevalence of low plasma thiamine concentration and increased thiamine clearance associated with diabetes. Also, folate deficiency in early embryo development has been linked to neural tube defects. Thus, women planning to become pregnant are usually encouraged to increase daily dietary folate intake or take a supplement.
=== Tourism === Located between the North Sea and the Baltic Sea, Schleswig-Holstein is also a popular tourist destination in Germany. Its islands, beaches, and cities attract millions of tourists every year. It has the second highest tourism intensity per local among the German states, after Mecklenburg-Vorpommern, but in absolute value it is rank 6th and only 1/3 of top destination Bavaria. According to a ruling by the Federal Administrative Court, everyone has the right to free access to the beach. Nevertheless, most of the seaside resorts kept cashing in (2-€3 /day/person).
== Environmental effects == Considering the volume of polyacrylamide produced, these materials have been heavily scrutinized with regards to environmental and health impacts. Polyacrylamide is of low toxicity but its precursor acrylamide is a neurotoxin and carcinogen. Thus, concerns naturally center on the possibility that polyacrylamide is contaminated with acrylamide. Considerable effort is made to scavenge traces of acrylamide from the polymer intended for use near food. Additionally, there are concerns that polyacrylamide may de-polymerise to form acrylamide. Under conditions typical for cooking, polyacrylamide does not de-polymerise significantly. The single claim that polyacrylamide reverts to acrylamide has been widely challenged. Polyacrylamide is most commonly partially biodegraded by the action of amidases, producing ammonia and polyacrylates. Polyacrylates are hard to biodegrade, but some soil microbe cultures have been shown to do so in aerobic conditions.
== Biochemistry == Tetrodotoxin binds to what is known as site 1 of the fast voltage-gated sodium channel. Site 1 is located at the extracellular pore opening of the ion channel. Any molecule bound to this site will block sodium ions from going into the nerve cell through this channel (which is ultimately necessary for nerve conduction). Saxitoxin, neosaxitoxin, and several of the conotoxins also bind the same site. The use of this toxin as a biochemical probe has elucidated two distinct types of voltage-gated sodium channels (VGSCs) present in mammals: tetrodotoxin-sensitive voltage-gated sodium channels (TTX-s Na+ channels) and tetrodotoxin-resistant voltage-gated sodium channels (TTX-r Na+ channels). Tetrodotoxin inhibits TTX-s Na+ channels at concentrations of around 1–10 nM, whereas micromolar concentrations of tetrodotoxin are required to inhibit TTX-r Na+ channels. Nerve cells containing TTX-r Na+ channels are located primarily in cardiac tissue, while nerve cells containing TTX-s Na+ channels dominate the rest of the body. TTX and its analogs have historically been important agents for use as chemical tool compounds, for use in channel characterization and in fundamental studies of channel function. The prevalence of TTX-s Na+ channels in the central nervous system makes tetrodotoxin a valuable agent for the silencing of neural activity within a cell culture.
Sources: en.wikipedia.org
== References == Hall of Fame: Michael Laposata." Association for Diagnostics & Laboratory Medicine (ADLM). Retrieved 30 September 2026. "Association for Molecular Pathology Honors Michael Laposata with Champion for Innovation Award" (Press release). Association for Molecular Pathology. 2025. Retrieved 30 September 2026. Carried over from the current article: PBS Frontline, "If It's Not Abuse"; NBC News (13 December 2019); ProPublica (21 February 2012); NPR (28 June 2011). Federal District Court Vacates FDA's Laboratory Developed Tests Final Rule." FDA Law Blog. Hyman, Phelps & McNamara. April 2025. Retrieved 30 September 2026. Committee on Diagnostic Error in Health Care (2015). Balogh, Erin P.; Miller, Bryan T.; Ball, John R. (eds.). Improving Diagnosis in Health Care. Washington, DC: National Academies Press. doi:10.17226/21794. https://www.houstonchronicle.com/news/houston-texas/houston/article/Experts-say-the-state-should-add-safeguards-to-14902941.php https://www.thepathologist.com/issues/2025/articles/december/michael-laposata-receives-champion-for-innovation-award/ https://www.thepathologist.com/issues/2025/articles/november/peertopeer-ivan-damjanov-interviews-michael-laposata/ https://www.thepathologist.com/issues/2016/articles/jun/it-s-our-turn/ https://www.thepathologist.com/issues/2016/articles/jun/we-need-to-talk-pathologists-patients-and-diagnostic-errors-part-i/ https://www.thepathologist.com/issues/2016/articles/aug/it-s-our-turn-to-talk-pathologists-patients-and-diagnostic-errors-part-ii/ Laposata, M.; Connor, A. M.; Hicks, D. G.; Phillips, D. K. (1989).
Cyanobactins are diverse metabolites from cyanobacteria with N-to-C macrocylization of a 6–20 amino acid chain. Cyanobactins are natural products isolated from cyanobacteria, and close to 30% of all cyanobacterial strains are thought to contain cyanobacterial gene clusters. However, while thus far all cyanobactins are credited to cyanobacteria, there exists the possibility that other organisms could produce similar natural products. The precursor peptide of the cyanobactin family is traditionally designated the "E" gene, whereas precursor peptides are designated gene "A" in most RiPP gene clusters. "A" is a serine protease involved in cleavage of the leader peptide and subsequent macrocyclization of the peptide natural product, in combination with an additional serine protease homologue, the encoded by gene "G". Members of the cyanobactin family may bear thiazolines/oxazolines, thiazoles/oxazoles, and methylations depending on additional modification enzymes. For example, perhaps the most famous cyanobactin is patellamide A, which contains two thiazoles, a methyloxazoline, and an oxazoline in its final state, a macrocycle derived from 8 amino acids.
=== Optical sensors === Polymer optical fibers have generated increasing interest in recent years. Because of low cost, ease of handling, long wavelength transparency, great flexibility, and biocompatibility, polymer optical fibers show great potential for short-distance networking, optical sensing and power delivery. Electrospun nanofibers are particularly well-suitable for optical sensors because sensor sensitivity increases with increasing surface area per unit mass. Optical sensing works by detecting ions and molecules of interest via fluorescence quenching mechanism. Wang et al. successfully developed nanofibrous thin film optical sensors for metal ion (Fe3+ and Hg2+) and 2,4-dinitrotoluene (DNT) detection using the electrospinning technique. Quantum dots show useful optical and electrical properties, including high optical gain and photochemical stability. A variety of quantum dots have been successfully incorporated into polymer nanofibers. Meng et al. showed that quantum dot-doped polymer nanofiber sensor for humidity detection shows fast response, high sensitivity, and long-term stability while requiring low power consumption. Kelly et al. developed a sensor that warns first responders when the carbon filters in their respirators have become saturated with toxic fume particles. The respirators typically contain activated charcoal that traps airborne toxins. As the filters become saturated, chemicals begin to pass through and render the respirators useless.
== Function == This gene encodes the subunit of a collagen-like molecule associated with acetylcholinesterase in skeletal muscle. Each molecule is composed of three identical subunits. Each subunit contains a proline-rich attachment domain (PRAD) that binds an acetylcholinesterase tetramer to anchor the catalytic subunit of the enzyme to the basal lamina. Multiple transcript variants encoding different isoforms have been found for this gene.
== History == In 1834, Théophile-Jules Pelouze distilled tartaric acid and isolated glutaric acid and another unknown organic acid. Jöns Jacob Berzelius characterized this other acid the following year and named pyruvic acid because it was distilled using heat. The correct molecular structure was deduced by the 1870s.
Sources: en.wikipedia.org
A historian with a very strong work ethic, Peukert believed that history "belonged to everybody", not just the historians, and was very energetic in attempting to break down barriers to interest the public in history by settling up exhibitions about Alltagsgeschichte in the Third Reich. In 1980, Peukert planned the historical exhibition at the Old Synagogue of Essen on the subject "Resistance and Persecution in Essen 1933-1945". In 1984, Peukert won the Heinz Maier-Leibnitz Prize for his habilitation on youth policy in Germany in late 19th and early 20th centuries. Moving beyond the subject of resistance (Widerstand), Peukert became interested in "oppositionality" (Widerständigkeit) in everyday life in Nazi Germany. Peukert was especially interested in the Edelweiss Pirates, a group of working class teenagers in Cologne and the other cities of the Rhineland who formed a distinctive anti-Nazi subculture, and who often fought the Hitler Youth. Another related area of interest for Peukert was resistance, opposition and dissent in the Third Reich. Peukert developed a pyramid model starting with "nonconformity" (behavior in private that featured partial rejection of the Nazi regime) running to "refusal of co-operation" (Verweigerung) to "protest", and finally to Widerstand (resistance), which involved total rejection of the Nazi regime. In particular, Peukert looked at how in "everyday life" in Nazi Germany, aspects of both "normality" and "criminality" co-existed with another.
== Structure == OcDH is a monomer with a molecular weight of 38kD made of two functionally distinct subunits. The first, Domain I, is composed of 199 amino acids and contains a Rossmann fold. Domain II is composed of 204 amino acids and is connected to the Rossmann fold of Domain I via its N-terminus.
The subject is required to touch his or her nose with eyes closed; people with normal proprioception may make an error of no more than 20 mm (0.79 in), while people with impaired proprioception (a symptom of moderate to severe alcohol intoxication) fail this test due to difficulty locating their limbs in space relative to their noses.
=== Nitrides, azides, and nitrido complexes === Nitrogen bonds to almost all the elements in the periodic table except the first two noble gases, helium and neon, and some of the very short-lived elements after bismuth, creating an immense variety of binary compounds with varying properties and applications. Many binary compounds are known: with the exception of the nitrogen hydrides, oxides, and fluorides, these are typically called nitrides. Many stoichiometric phases are usually present for most elements (e.g. MnN, Mn6N5, Mn3N2, Mn2N, Mn4N, and MnxN for 9.2 < x < 25.3). They may be classified as "salt-like" (mostly ionic), covalent, "diamond-like", and metallic (or interstitial), although this classification has limitations generally stemming from the continuity of bonding types instead of the discrete and separate types that it implies. They are normally prepared by directly reacting a metal with nitrogen or ammonia (sometimes after heating), or by thermal decomposition of metal amides:
Brindisi Limonta insisted that his disbarment was illegal, because Valdés García should have recused himself from the case to begin with. Many Cuban Freemasons considered this as an act of retribution by Urquía Carreño, and questioned the legality of the Supreme Court's decision, because Urquía Carreño was in violation of his own expulsion at the time of the sentencing. They alleged that Urquía Carreño was either complicit in the theft or was attempting to cause a distraction so that people would stop asking about the stolen Llansó money. They also noted that the outcome document's lack of signatures or seals indicated that the expulsion was not legally binding. On March 19, 2024, Pompilio Portuondo, a Cuban Freemason on an exchange program with the Grand Lodge of Colombia, wrote on Facebook that he believed a grand conspiracy was taking place in Cuba to cover up the theft. He wrote that certain members of the Grand Lodge were either complicit in the coverup or directly responsible for the theft; Grand Secretary Misiel Hernandez Peraza was alleged to be an active agent in Military Intelligence, Grand Treasurer Airam Cervera Reigosa was allegedly an accomplice in the robbery, Supreme Court of Masonic Justice President Ernesto Valdés García, Yamil Valiente, accountant Rolando Mena, Calos Lorenzo Perez, and Magistrate of the Supreme Court of Masonic Justice Inti Paneca were also all allegedly involved in the plot. He requested that any Lodge in Florida or anywhere else in the United States deny these men asylum or membership in their Lodges.
Sources: en.wikipedia.org
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.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.