RP-HPLC purity 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 2026-01-07. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
| Property | Value | Notes |
|---|---|---|
| Common route | Intranasal | Also injected in some animal work |
| Solubility class | Freely soluble in water | Solid form is hygroscopic |
| Typical storage | About -20 degrees Celsius | Keep desiccated and dark |
| Purity method | Reverse-phase HPLC | Reported as area percent |
| Confirmatory method | Mass spectrometry | Verifies expected molecular mass |
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.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
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.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
=== Signal transduction === The effects of insulin are initiated by its binding to a receptor, the insulin receptor (IR), present in the cell membrane. The receptor molecule contains an α- and β subunits. Two molecules are joined to form what is known as a homodimer. Insulin binds to the α-subunits of the homodimer, which faces the extracellular side of the cells. The β subunits have tyrosine kinase enzyme activity which is triggered by the insulin binding. This activity provokes the autophosphorylation of the β subunits and subsequently the phosphorylation of proteins inside the cell known as insulin receptor substrates (IRS). The phosphorylation of the IRS activates a signal transduction cascade that leads to the activation of other kinases as well as transcription factors that mediate the intracellular effects of insulin. The cascade that leads to the insertion of GLUT4 glucose transporters into the cell membranes of muscle and fat cells, and to the synthesis of glycogen in liver and muscle tissue, as well as the conversion of glucose into triglycerides in liver, adipose, and lactating mammary gland tissue, operates via the activation, by IRS-1, of phosphoinositol 3 kinase (PI3K). This enzyme converts a phospholipid in the cell membrane by the name of phosphatidylinositol 4,5-bisphosphate (PIP2), into phosphatidylinositol 3,4,5-triphosphate (PIP3), which, in turn, activates protein kinase B (PKB). Activated PKB facilitates the fusion of GLUT4 containing endosomes with the cell membrane, resulting in an increase in GLUT4 transporters in the plasma membrane.
Some Australian cities (such as Sydney) have instituted legal diamorphine supervised injecting centers, in line with other wider harm minimization programs. Since January 2009, Denmark has prescribed diamorphine to a few addicts who have tried methadone and buprenorphine without success. Beginning in February 2010, addicts in Copenhagen and Odense became eligible to receive free diamorphine. Later in 2010, other cities including Århus and Esbjerg joined the scheme. It was estimated that around 230 addicts would be able to receive free diamorphine. However, Danish addicts would only be able to inject heroin according to the policy set by Danish National Board of Health. Of the estimated 1500 drug users who did not benefit from the then-current oral substitution treatment, approximately 900 would not be in the target group for treatment with injectable diamorphine, either because of "massive multiple drug abuse of non-opioids" or "not wanting treatment with injectable diamorphine". In July 2009, the German Bundestag passed a law allowing diamorphine prescription as a standard treatment for addicts; a large-scale trial of diamorphine prescription had been authorized in the country in 2002. On 26 August 2016, Health Canada issued regulations amending prior regulations it had issued under the Controlled Drugs and Substances Act; the "New Classes of Practitioners Regulations", the "Narcotic Control Regulations", and the "Food and Drug Regulations", to allow doctors to prescribe diamorphine to people who have a severe opioid addiction who have not responded to other treatments.
== Pathogenicity == Rhizopus oryzae is one of the most common causes of a disease known as mucormycosis, characterized by growing hyphae within and surrounding blood vessels. The causal agents of mucormycosis may also produce toxins like agroclavine which is toxic to humans, sheep and cattle. This infection usually occurs in immunocompromised individuals but is rare. Common risk factors associated with primary cutaneous mucormycosis is ketoacidosis, neutropenia, acute lymphobloastic leukemia, lymphomas, systemic steroids, chemotherapy, and dialysis. Treatment includes amphotericin B, posaconazole, itraconazole, and fluconazole. The majority of the cases of infection are rhinocerebral infections. At the same time, it has been found in literature that R. oryzae can produce antibiotic activity on some bacteria. The pathogenicity towards plants is attributed to the presence of large number of carbohydrate digesting enzymes.
Many proteinogenic and non-proteinogenic amino acids have biological functions beyond being precursors to proteins and peptides. In humans, amino acids also have important roles in diverse biosynthetic pathways. Defenses against herbivores in plants sometimes employ amino acids. Examples:
Enthesitis, wherein there is inflammation of the entheses, the sites where tendons or ligaments insert into the bone. It is associated with HLA B27 arthropathies such as ankylosing spondylitis, psoriatic arthritis, and reactive arthritis. Apophysitis, inflammation of the bony attachment, generally associated with overuse among growing children.
Sources: en.wikipedia.org
=== Indium(I) compounds === Indium(I) compounds are not common. The chloride, bromide, and iodide are deeply colored, unlike the parent trihalides from which they are prepared. The fluoride is known only as an unstable gas. Indium(I) oxide black powder is produced when indium(III) oxide decomposes upon heating to 700 °C.
=== Sexuality === Applications of AI in this domain include AI-enabled menstruation and fertility trackers that analyse user data to offer predictions, AI-integrated sex toys (e.g., teledildonics), AI-generated sexual education content, and AI agents that simulate sexual and romantic partners (e.g., Replika). AI is also used for the production of non-consensual deepfake pornography, raising significant ethical and legal concerns. AI technologies have also been used to attempt to identify online gender-based violence and online sexual grooming of minors.
On 5 May, a national uprising began spontaneously in Prague, and the newly formed Czech National Council (cs) almost immediately assumed leadership of the revolt. Over 1,600 barricades were erected throughout the city, and some 30,000 Czech men and women battled for three days against 40,000 German troops backed by tanks, aircraft and artillery. On 8 May, the German Wehrmacht capitulated; Soviet troops arrived on 9 May.
Smaller quantities can be synthesized from the same starting materials, but in air and using tetrabutylammonium bromide as a catalyst. The corresponding yield is below 82%. The major problem, both in the industrial synthesis and in the extraction from plants, is separation of diallyl disulfide from higher sulfides (diallyl trisulfide (DATS), etc.). They have very similar physical properties and therefore, a typical commercial product contains only 80% of diallyl disulfide. The conversion of allicin to diallyl disulfide and trisulfide takes place particularly rapidly above 37 °C.
That same day, Peru and the OAS signed a joint declaration in favor of democracy and human rights. The OAS leader Luis Almagro said that "We have seen that president Castillo has much determination to fight corruption, especially corruption that may appear in his government. Let his management be as clean as possible. This requires important efforts in investigation. Let there be a permanent monitoring of transparency, of justice, so that there isn't any element of shadow over official members." On 5 December, Cuarto Poder finally released the audio clip. The audio showed the owner of the Breña house offering "scoops and headlines" to a journalist in exchange for the journalist shelving an unfavorable news story. The host of ATV news, Juliana Oxenford, claimed that it is "much more revealing to know the high content of trans fats in Cheese Tris than the audio of Cuarto Poder." Meanwhile, the journalist Juan Carlos Tafur said that the Cuarto Poder audio "qualifies as a journalistic scam." Following the release of the Cuarto Poder clips, the impeachment motion rapidly fell apart as less hardline members of the opposition rescinded their support for the impeachment motion. On 7 December 2021, with 46 in favor, 76 against, and 4 abstentions, Congress refused to admit the impeachment motion. Following the defeat of the impeachment motion, President Castillo said: "I am grateful that the congressional voted to put Peru first before other interests."
Sources: en.wikipedia.org
== Honors == Nier was a member of the National Academy of Sciences, the American Philosophical Society, the American Academy of Arts and Sciences, and a foreign scientific member of the Max Planck Society. The Martian crater Nier and the mineral nierite (tiny silicon nitride inclusions in meteorites) were named after him. The Nier Prize is awarded annually by the Meteoritical Society and recognizes outstanding research in meteoritics and closely allied fields by young scientists.
Dihydroergotamine (DHE), sold under the brand names D.H.E. 45 and Migranal among others, is an ergot alkaloid used to treat migraines. It is a derivative of ergotamine. It is administered as a nasal spray or injection and has an efficacy similar to that of sumatriptan. Nausea is a common side effect. It has similar actions to the triptans, acting as an agonist to the serotonin receptors and causing vasoconstriction of the intracranial blood vessels, but also interacts centrally with dopamine and adrenergic receptors. It can be used to treat acute intractable headache or withdrawal from analgesics.
=== July === 1 July – First Minister Humza Yousaf announces that the SNP has changed the way it records donations after the issue was highlighted by its auditors. Having previously only kept online records of donations under £250, the party will now keep documented records of the donations. 2 July – During an appearance on BBC Radio Scotland's The Sunday Show, Conservative MSP Jamie Greene alleges that he lost his post in the Shadow Cabinet of Douglas Ross for supporting the Scottish Government's controversial Gender Recognition Reform Bill. 3 July ScotRail train fares are increased by 4.8%. Members of Orkney Islands Council, a Council area of Scotland, vote 15–6 in favour of investigating alternative methods of government that includes the potential to become a crown dependency of the UK or a self-governing territory of Norway. 5 July King Charles III is presented with the Honours of Scotland during a ceremony held at Edinburgh's St Giles Cathedral. SNP MP Angus McNeil is suspended from the party for a week following an argument with the party's chief whip, Brendan O'Hara, after he allegedly threatened O'Hara. 6 July The Scottish and UK governments confirm plans to collaborate on new legislation to prevent landlords excluding parents and people on benefits from renting properties. The 2023 Tiree Music Festival is cancelled a day before events are due to begin due to "extreme weather". 7 July The Scottish Government urges Westminster to decriminalise the personal possession of all illegal drugs, and puts forward a number of proposals for the managed use of drugs.
=== Genetic labeling === Fluorescence in situ hybridization (FISH), is an example of a genetic labeling technique that utilizes probes that are specific for chromosomal sites along the length of a chromosome, also known as chromosome painting. Multiple fluorescent dyes that each have a distinct excitation and emission wavelength are bound to a probe which is then hybridized to chromosomes. A fluorescence microscope can detect the dyes present and send it to a computer that can reveal the karyotype of a cell. This technique allows abnormalities such as deletions and duplications to be revealed.
=== Governmental districts (Regierungsbezirke) === The large states of Baden-Württemberg, Bavaria, Hesse, and North Rhine-Westphalia are divided into governmental districts, or Regierungsbezirke. In Rhineland-Palatinate, these districts were abolished or re-organized on 1 January 2000, in Saxony-Anhalt on 1 January 2004, and in Lower Saxony on 1 January 2005. From 1990 until 2012, Saxony was divided into three districts (called Direktionsbezirke since 2008). In 2012, these districts' authorities were merged into one central authority, the Landesdirektion Sachsen.
Sources: en.wikipedia.org
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.
Reported human trials are few, brief and originate mainly from one country. They describe effects on anxiety-related measures, but sample sizes are small and reporting is limited. The results are widely regarded as preliminary rather than confirmed.
Reverse-phase liquid chromatography is used to assess purity and separation of related impurities. Mass spectrometry confirms that the observed molecular mass matches the expected peptide. A certificate of analysis from the supplier is the usual document of record.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.