reversed-phase HPLC comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-05-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Principal proposed target | GABA-A receptor complex | Hypothesis derived mainly from animal pharmacology |
| Common behavioral assay | Elevated plus maze | Rodent test for anxiety-like behavior |
| Reported molecular marker | Hippocampal BDNF expression | Measured by immunoassay or mRNA quantification |
| Typical dosing route | Intranasal | Chosen to reduce first-pass metabolism |
| Reported plasma half-life | Minutes | Based on limited peptide stability data |
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.
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.
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.
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.
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.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
=== Criticism of expert witnesses === Several medical experts have questioned the reliability of the prosecution's expert witness, Dewi Evans. Svilena Dimitrova, an NHS consultant neonatologist, and Roger Norwich, a medico-legal expert, submitted formal complaints to the General Medical Council regarding Evans's evidence. Dimitrova told The Guardian that she believed "the theories proposed in court were not plausible and the prosecution was full of medical inaccuracies", adding that while she could not assert Letby's innocence, she saw "no proof of guilt". Evans rejected suggestions of bias and noted that the defence could have called its own expert witnesses at trial but did not do so. Other prosecution experts broadly supported Evans' conclusions. The New Yorker reported that in an unrelated earlier case, a Court of Appeal judge had described one of Evans's expert reports as "worthless", containing opinions that were "tendentious and partisan" and outside his professional competence. Another paediatrician who testified as an expert for the prosecution has since resigned from her position as a consultant following multiple complaints about her practice. The prosecution's endocrinologist, Peter Hindmarsh, was under investigation by the General Medical Council (GMC) when he gave evidence during the trial. The investigation was prompted by "multiple and wide-ranging concerns" about his practice from both of the hospitals he was affiliated with. A medical tribunal placed restrictions on his ability to practise, arguing that he "may pose a real risk to members of the public".
Ethanol (alcohol) reduces the calcium-dependent secretion of AVP by blocking voltage-gated calcium channels in neurohypophyseal nerve terminals in rats. Angiotensin II stimulates AVP secretion, in keeping with its general pressor and pro-volumic effects on the body. Atrial natriuretic peptide inhibits AVP secretion, in part by inhibiting Angiotensin II-induced stimulation of AVP secretion. Cortisol inhibits secretion of antidiuretic hormone.
=== Some roles in development === Since G protein–coupled receptors are known to activate Signal transduction in cells, it should not be surprising to find MC1R involved in development. As one example at the cellular level, preventing signalling by MC1R stopped erythropoiesis from proceeding from the polychromatic cell stage (poly-E in the figure) to the orthochromatic cell stage (ortho-E in the diagram). The same report showed that neutralizing antibodies to MC1R prevented phosphorylation of STAT5 by erythropoietin, and that MC2R and MC5R were also involved, as shown in their model.
== Discovery and Research == The partial purification of 17 alpha- and 17 beta-estradiol dehydrogenase activities from chicken liver was reported by Renwick AG and Engel LL in 1967, shedding light on the enzyme's properties and functions. Subsequent research has further elucidated its physiological significance, with ongoing studies aiming to understand its regulation and potential therapeutic applications.
Sources: en.wikipedia.org
=== Chemical constituents === About 140 chemical compounds are in the subterranean portions of R. rosea. Rhodiola roots contain phenols, rosavin, rosin, rosarin, organic acids, terpenoids, phenolic acids and their derivatives, flavonoids, anthraquinones, alkaloids, tyrosol, and salidroside. The chemical composition of the essential oil from R. rosea root growing in different countries varies. For example, rosavin, rosarin, and rosin at their highest concentration according to many tests can be found only in R. rosea of Russian origin; the main components of the essential oil from Rhodiola growing in Bulgaria are geraniol and myrtenol; in China the main components are geraniol and 1-octanol; and in India the main component is phenethyl alcohol. Cinnamyl alcohol was discovered only in the sample from Bulgaria. Rosavin, rosarin, rosin, and salidroside (and sometimes p-tyrosol, rhodioniside, rhodiolin, and rosiridin) are mostly polyphenols, and have no evidence of a physiological effect in humans. Although these phytochemicals are typically mentioned as specific to Rhodiola rosea extracts, rosea and other Rhodiola species contain many other constituent polyphenols, including proanthocyanidins, quercetin, gallic acid, chlorogenic acid, and kaempferol.
While transdermal progesterone is not approved for use in menopausal hormone therapy or as a systemic medication, it is registered in some countries under the brand name Progestogel as a 1% gel (10 mg/g) for direct local application to the breasts to treat premenstrual breast pain. The medication has been found in clinical studies to inhibit estrogen-induced proliferation of breast epithelial cells, to be highly effective in the treatment of benign breast disease, to significantly decrease breast nodularity, and to almost completely alleviate breast pain and tenderness in women with the condition. Conversely, transdermal progesterone has been found to be almost completely ineffective in fibrocystic breast disease, breast cysts, and breast fibroadenomas, whereas oral progestins were found to be significantly effective. The effectiveness of progesterone and other progestogens in the treatment of breast disorders may be due to their functional antiestrogenic effects in the breasts.
=== 10 June === The SAF accused the LNA of carrying out a joint attack with the RSF in the Libya-Egypt-Sudan border triangle. Eight people were killed in an SAF drone attack on a school sheltering IDPs in Abu Zabad, West Kordofan.
== Regulatory involvement == RQA has links with DEFRA, in particular with a joint code of practice for veterinary activities. Members of RQA committees regulatory attend and contribute to stakeholder meetings run by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK and the European Medicines Agency (EMA) in Europe. RQA attends the annual Research and Development Forum run by the NHS.
An exceptional case appears with the benzylideneprotecting group, which also admits reductive cleavage. This proceeds either through catalytic hydrogenation or with the hydride donor diisobutyl aluminum hydride (DIBAL). The cleavage with DIBAL deprotects one alcohol group, for the benzyl moiety stays as a benzyl ether on the second, sterically hindered hydroxy group.
Sources: en.wikipedia.org
Diazepam, sold under the brand name Valium among others, is a medication of the benzodiazepine family that acts as an anxiolytic. It is used to treat a range of conditions, including anxiety, seizures, alcohol withdrawal syndrome, muscle spasms, insomnia, and restless legs syndrome. It may also be used to cause memory loss during certain medical procedures. It can be taken orally (by mouth), as a suppository (inserted into the rectum), intramuscularly (injected into muscle), intravenously (injection into a vein) or used as a nasal spray. When injected intravenously, effects begin in one to five minutes and last up to an hour. When taken by mouth, effects begin after 15 to 60 minutes. Common side effects include sleepiness and trouble with coordination. Serious side effects are rare. They include increased risk of suicide, decreased breathing, and a paradoxical increased risk of seizures if used too frequently in those with epilepsy. Occasionally, excitement or agitation may occur. Long-term use can result in tolerance, dependence, and withdrawal symptoms on dose reduction. Abrupt stopping after long-term use can be potentially dangerous. After stopping, cognitive problems may persist for six months or longer. It is not recommended during pregnancy or breastfeeding. Its mechanism of action works by increasing the effect of the neurotransmitter gamma-aminobutyric acid (GABA). Diazepam was patented in 1959 by Hoffmann-La Roche. It has been one of the most frequently prescribed medications in the world since its launch in 1963.
BCG vaccine should be given intradermally. If given subcutaneously, it may induce local infection and spread to the regional lymph nodes, causing either suppurative (production of pus) or nonsuppurative lymphadenitis. Conservative management is usually adequate for nonsuppurative lymphadenitis. If suppuration occurs, it may need needle aspiration. For unresolved suppuration, surgical excision may be required. Evidence for the treatment of these complications is scarce. Uncommonly, breast and gluteal abscesses can occur due to haematogenous (carried by the blood) and lymphangiomatous spread. Regional bone infection (BCG osteomyelitis or osteitis) and disseminated BCG infection are rare complications of BCG vaccination, but potentially life-threatening. Systemic antituberculous therapy may be helpful in severe complications. When BCG is used for bladder cancer, around 2.9% of treated patients discontinue immunotherapy due to a genitourinary or systemic BCG-related infection, however while symptomatic bladder BCG infection is frequent, the involvement of other organs is very uncommon. When systemic involvement occurs, liver and lungs are the first organs to be affected (1 week [median] after the last BCG instillation). If BCG is accidentally given to an immunocompromised patient (e.g., an infant with severe combined immune deficiency), it can cause disseminated or life-threatening infection. The documented incidence of this happening is less than one per million immunizations given.
The solute carrier (SLC) group of membrane transport proteins include over 400 members organized into 66 families. Most members of the SLC group are located in the cell membrane. The SLC gene nomenclature system was originally proposed by the HUGO Gene Nomenclature Committee (HGNC) and is the basis for the official HGNC names of the genes that encode these transporters. A more general transmembrane transporter classification can be found in TCDB database. Solutes that are transported by the various SLC group members are extremely diverse and include both charged and uncharged organic molecules as well as inorganic ions and the gas ammonia. As is typical of integral membrane proteins, SLCs contain a number of hydrophobic transmembrane alpha helices connected to each other by hydrophilic intra- and extra-cellular loops. Depending on the SLC, these transporters are functional as either monomers or obligate homo- or hetero-oligomers. Many SLC families are members of the major facilitator superfamily.
Tellurium readily alloys with iron, as ferrotellurium (50–58% tellurium), and with copper, in the form of tellurium copper (40–50% tellurium). Ferrotellurium is used as a stabilizer for carbon in steel casting. Of the non-metallic elements less often recognised as metalloids, selenium – in the form of ferroselenium (50–58% selenium) – is used to improve the machinability of stainless steels.
Sources: en.wikipedia.org
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.
Behavioral endpoints include time spent in open arms of the elevated plus maze and avoidance latencies. Biochemical endpoints include BDNF concentration, cytokine levels, and monoamine metabolite ratios in brain tissue.
Most published studies are small, originate from a limited number of laboratories, and lack independent replication. Dose-response relationships, measured brain exposure, and long-term outcomes are not well characterized.
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.