The short version of reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-11-14 and is reviewed periodically as new material appears.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
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.
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.
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.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
The messages revealed that his friendship with Epstein lasted for nine years, including well after Epstein was initially charged with soliciting sex from a minor. Ariely also suggested that Epstein use learnings from his research to help rehabilitate his public image, stating via email, "If you want to talk about where to take this research or other questions...[l]et me know." Ariely said in response: "At the time of our meetings, I was deep into research on dishonesty and crime, and I spoke with many individuals who had broken the law..." and "our relationship wasn't a friendship, and he didn't financially support any of my projects."
== In animals == In some regions (e.g. much of the northeastern and northwestern US and adjacent Canada, and the southeastern US), selenium deficiency in some animal species is common unless supplementation is carried out. Selenium deficiency is responsible (either alone or together with vitamin E deficiency) for many of the cases of WMD ("white muscle disease"), evidenced at slaughter or during necropsy by the whitish appearance of striated muscle tissue due to bleaching by peroxides and hydroperoxides. Although this degenerative disease can occur in foals, pigs, and other animal species, ruminants are particularly susceptible. In general, absorption of dietary selenium is lower in ruminants than in non-ruminants and lower from forages than from grain. Sheep are more susceptible than cattle to WMD, and goats are more susceptible than sheep. Because of selenium's role in certain peroxidases (converting hydroperoxides to alcohols) and because of the antioxidant role of vitamin E (preventing hydroperoxide formation), a low level of Se can be somewhat (but not wholly) compensated by a high level of vitamin E. (In the animal, localization of peroxidases and vitamin E differs, partly because of the fat-solubility of vitamin E.) Some studies have indicated that about 0.12 or 0.23 mg Se per kg of dry matter intake may be sufficient for avoiding Se deficiency in sheep. However, a somewhat higher Se intake may be required to avoid WMD where certain legumes are consumed.
=== Anion-exchange resins === Formula: R-OH basic Anion resins may be either strongly or weakly basic. Strongly basic anion resins maintain their negative charge across a wide pH range, whereas weakly basic anion resins are neutralized at higher pH levels. Weakly basic resins do not maintain their charge at a high pH because they undergo deprotonation. They do, however, offer excellent mechanical and chemical stability. This, combined with a high rate of ion exchange, make weakly base anion resins well suited for the organic salts. For anion resins, regeneration typically involves treatment of the resin with a strongly basic solution, e.g. aqueous sodium hydroxide. Regenerant strength (1–4 % NaOH) and contact time must be optimized to avoid excessive osmotic stress on the polymer matrix. These anion resins can be regenerated by flushing them with a caustic solution (typically 1–4 % NaOH as mentioned before). During regeneration process, the regenerant chemical is passed through the resin, and trapped negative ions are flushed out, renewing the resin exchange capacity.
Sources: en.wikipedia.org
=== China === Journalist Joshua Kurlantzick writes that China has been engaging in a "charm offensive" in the 21st century to improve relations with many other countries, especially in the developing world. Kurlantzick contends that the Chinese government has leveraged the construction of large works of architecture abroad to better its standing with these countries. He also criticizes many of these projects, such as large-sized buildings and government ministries, as white-elephant projects. Kurlantzick cites examples of Chinese-led construction in Mozambique and East Timor as examples.
One aptamer, in particular, proved effective as a recognition element in an electrochemical sensor, enabling the detection of sGP and GP1.2 in solution, as well as GP1.2 within a membrane context. The results of this research point to the intriguing possibility that certain regions on protein surfaces may possess aptatropic qualities. Identifying the key features of such sites, in conjunction with improved 3-D structural predictions for aptamers, holds the potential to enhance the accuracy of predicting aptamer interaction sites on proteins. This, in turn, may help identify aptamers with a heightened likelihood of binding proteins with high affinity, as well as shed light on protein mutations that could significantly impact aptamer binding. This comprehensive understanding of the structure-based interactions between aptamers and proteins is vital for refining the computational predictability of aptamer-protein binding. Moreover, it has the potential to eventually eliminate the need for the experimental SELEX protocol.
=== Liquid-liquid equilibrium calculations === In order to calculate the phase equilibrium, it is necessary to use a thermodynamic model such as NRTL, UNIQUAC, etc. The corresponding parameters of these models can be obtained from literature (e.g. Dechema Chemistry Data Series, Dortmund Data Bank, etc.) or by a correlation process of experimental data.
=== 1989 === 9 July Moving Pictures, with Sir Jonathan Miller, the documentary explains how the brain sees images, with relation to television; Gotthold Ephraim Lessing and his work Laocoön; animator Sergio Simonetti; the National Science and Media Museum in Bradford; the Asteroid theme of Pearl & Dean; cognitive scientist Jerome Lettvin; John Grover and the 1989 film Licence to Kill; with the documentary editor Simon Rose. Produced by Patrick Uden, directed by Michael Proudfoot, made by Uden Associates 23 July The Bicycle: The Green Machine, Columbus of Italy that made cycle steel tubing from 130 kg steel billets; Cinelli of Milan; sports scientist Adrienne Hardman of Loughborough University; cycle chains were mostly made in Japan; 2m would be sold in UK - 700k by Raleigh. Narrated by the Radio 4 newsreader John Hedges, produced by Jeremy Llewellyn-Jones, made by Chrysalis Television 30 July Earth Calling Basingstoke, about Guy Hurst, who collates sightings for The Astronomer (BAA); Dave Graham from Brompton-on-Swale; John Wall, known for his Crayford focuser; the documentary was filmed around April 1989, and the astronomers in County Durham saw the effects of the March 1989 geomagnetic storm.
Sources: en.wikipedia.org
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.