HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
| 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 |
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
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.
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.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
=== Mechanism of action === Posaconazole works by disrupting the functions of certain fungal and protozoal membrane-bound enzyme systems. It does this by blocking the synthesis and turnover of the eukaryotic cell membrane component ergosterol via the inhibition of an enzyme known as CYP51. Posaconazole is significantly more potent at binding to CYP51 than itraconazole.
Neanderthal pigmentation genes in modern non-African people are associated with both lighter and darker skin tones, as well as lighter and darker hair colors, suggesting Neanderthals themselves may have had variable pigmentation. Variants associated with red hair have been found in some Neanderthals, but they do not appear to have been common. Neanderthal skin and hair pigmentation variants are under positive selection in non-Africans, unlike most other Neanderthal genes, suggesting that the adaptive value of lighter features was beneficial for modern humans in Eurasia, where there is significantly less sunlight as compared to Africa.
== Detection == Alan Fryday (1991) outlined a technique for the detection of confluentic acid in lichen samples. This method involves placing a section of the lichen's thallus or apothecium (fruiting body) on a microscope slide, which is then saturated with a 10% potassium hydroxide (KOH) solution. When examined under a compound microscope at 40x magnification, a distinctive 'halo' of small oil droplets or bubbles emanating from the tissue section indicates the presence of confluentic acid. The oil droplets generated during this detection process consist of 4-O-methylolivetonide, a compound that is insoluble in potassium hydroxide solution. This substance forms as a result of confluentic acid undergoing hydrolysis in the presence of potassium hydroxide. This test is useful in distinguishing between morphologically similar yet chemically distinct species within the genus Porpidia.
An FA disciplinary commission found Wenger guilty; he received a 12-match touchline ban and a fine of four weeks' salary. He successfully appealed the ban, but was reprimanded and fined £10,000 for his actions. Following the 2007 Football League Cup Final, he called a linesman a liar, for stating Emmanuel Adebayor aimed a punch at Chelsea's Frank Lampard. This led to an investigation by the FA, a fine of £2,500 and a warning. In March 2011, Wenger was charged with improper conduct by UEFA, over comments made to referee Massimo Busacca, after his team's defeat to Barcelona. He was fined €10,000 and suspended for one UEFA club competition match; however, the ban was later extended to a further two games, after Wenger was found guilty of communicating with Arsenal's bench while serving a touchline ban against Udinese. A year later, Wenger was charged for post-match comments made about referee Damir Skomina, in Arsenal's defeat to Milan in the Champions League. He was fined £33,000 and handed a three-match touchline ban in the competition.
In 1928, it became a separate province. Between 1914 and 1928, the Ma clique ruled the provinces of Qinghai, Ningxia and Gansu; General Ma Hongkui was the military governor of Ningxia and had absolute authority in the province. The Muslim conflict in Gansu, which lasted from 1927 to 1930, spilt over into Ningxia. In 1934, warlord and National Revolutionary Army general Sun Dianying attempted to conquer the province, but was defeated by an alliance led by the Ma clique. From 1950 to 1958, a Kuomintang Islamic insurgency resulted in fighting throughout Northwest China, including Ningxia. In 1954, the Chinese government merged Ningxia with Gansu, but in 1958 Ningxia formally became an autonomous region of China. In 1969, Ningxia received a part of the Inner Mongolian Autonomous Region, but this area was returned in 1979. A number of Chinese artifacts dating from the Tang dynasty and Song dynasty, some of which had been owned by Emperor Zhenzong, were excavated and then came into the hands of Ma Hongkui, who refused to publicize the findings. Among the artifacts were a white marble tablet from the Tang dynasty, gold nails, and bands made out of metal. It was not until after Ma Hongkui died that his wife went to Taiwan in 1971 from America to bring the artifacts to Chiang Kai-shek, who turned them over to the Taipei National Palace Museum.
Sources: en.wikipedia.org
== External links == Rudra MN, Chowdhury LM (30 September 1950). "Methionine Content of Cereals and Legumes". Nature. 166 (568): 568. Bibcode:1950Natur.166..568R. doi:10.1038/166568a0. PMID 14780151. S2CID 3026278.
The Cochrane reviews on the treatment of ADHD in children, adolescents, and adults with pharmaceutical amphetamines stated that short-term studies have demonstrated that these drugs decrease the severity of symptoms, but they have higher discontinuation rates than non-stimulant medications due to their adverse side effects. However, a 2025 meta-analytic systematic review of 113 randomized controlled trials found that stimulant medications were the only intervention with robust short-term efficacy, and were associated with lower all-cause treatment discontinuation rates than non-stimulant medications (e.g., atomoxetine). A Cochrane review on the treatment of ADHD in children with tic disorders such as Tourette syndrome indicated that stimulants in general do not make tics worse, but high doses of dextroamphetamine could exacerbate tics in some individuals.
== Structure == There is little information related to the p3 peptides composition and structure, and moreover most of it has to do with characteristics that concern to its role in Alzheimer's disease. p3 can be found as a 24 or 26 residues peptide, depending on which is gamma secretase's cleavage. The peptide which has 26 residues, presents the following sequence:
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive drug globally. It is mainly used for its eugeroic (wakefulness promoting), ergogenic (physical performance-enhancing), or nootropic (cognitive-enhancing) properties (particularly in workplace settings); it is also used recreationally, often in social settings. Caffeine acts by blocking the binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonizes GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption. Caffeine is a bitter, white crystalline purine, a methylxanthine alkaloid, and is chemically related to the adenine and guanine bases of deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). It is found in the seeds, fruits, nuts, or leaves of a number of plants native to Africa, East Asia, and South America and helps to protect them against herbivores and from competition by preventing the germination of nearby seeds, as well as encouraging consumption by select animals such as honey bees.
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.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.