A practical reference on reverse-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-08-13. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical purity specification | 95 percent or higher by RP-HPLC | Area percentage of the main peak |
| Identity confirmation | Electrospray ionization mass spectrometry | Observed mass compared with the theoretical value near 751.9 Da |
| Recommended dry storage | -20 °C, desiccated | -80 °C for multi-year archival material |
| Solution handling | Prepare fresh; avoid long storage | Sterile filtration reduces microbial load |
| Common synonyms | TKPRPGP; TP-7 | Sequence code and laboratory designation used interchangeably |
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
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.
=== Depression === Levodopa has been reported to be inconsistently effective as an antidepressant in the treatment of depressive disorders. However, it was found to enhance psychomotor activation in people with depression.
== Other hormone-producing structures == Many body organs not normally considered endocrine organs contain isolated cell clusters that secrete hormones. Examples include the heart (atrial natriuretic peptide); gastrointestinal tract organs (gastrin, secretin, and others); the placenta (hormones of pregnancy—estrogen, progesterone, and others); the kidneys (erythropoietin and renin); the thymus; skin (cholecalciferol); and adipose tissue (leptin and resistin).
In April 2015, Hardee's announced the opening of its 300th restaurant in the Middle East with longtime franchisee, The Americana Group. In 2015, Nation's Restaurant News ranked Hardee's as the No. 28 foodservice chain by sales in the United States through 2011. Carl's Jr. was ranked at No. 37. Combined sales would rank the two at No. 15. In 2013, QSR listed Hardee's at No. 20 and Carl's Jr. at No. 24; if combined they would have been listed at No. 14. In July 2015, Hardee's announced that it would be offering The All-Natural Burger, which launched at sister-chain Carl's Jr. restaurants in December 2014. As of March 2016, CKE has a total of 3,664 franchised or company-operated restaurants in 44 states and 37 foreign countries and U.S. territories. The Hardee's in Millvale, Pennsylvania closed suddenly on August 25, 2025, after 52 years, marking the withdrawal of Hardee's from Greater Pittsburgh. Hardee's, which had entered Pennsylvania with the Sandy's purchase a year before the Millvale location opened, retains one location in Western Pennsylvania in Waynesburg (near the West Virginia border) while the rest in Pennsylvania are in South Central Pennsylvania. In 2026, Hardee's franchise operator Boddie-Noell announced that a location in Virginia Beach would close and be converted to a concept called Biscuits & Bird that focused on breakfast biscuits and chicken tenders, with the restaurant opening under the new branding in July 2026. On July 9, 2026, Superior Star LLC, a Phoenix-based Hardee's franchisee operating in the Midwest, filed for Chapter 11 bankruptcy protection.
Sources: en.wikipedia.org
=== 5 June === Ukrainian forces were reported to be advancing towards Bakhmut, with the Wagner Group's Yevgeny Prigozhin confirming that Ukrainian soldiers had retaken part of the settlement of Berkhivka, north of the city. Hanna Malyar, Ukrainian Deputy Defence Minister said that 'offensive actions' were underway in "some areas" in eastern Ukraine, adding that Ukrainian troops gained from 200 to 1,600 meters (660 to 5,250 ft) in Orikhovo-Vasulivka and Paraskoviivka, while in Ivanivske and Klishchiivka they advanced between 100 and 700 meters (330 and 2,300 ft). The Russian defense ministry said it was holding back attacks by Ukrainian forces near the settlements of Novodonetske and Oktyabrske. The Ukrainian government accused Russia of violating the terms of the Black Sea Grain Initiative by registering two vessels that declared their participation in the deal the same day, adding it went against accepted vessel inspection rules that required priority inspection and registration of longer-standing ships. The Wagner Group said it had detained a regular Russian military officer who opened fire on one of their vehicles near Bakhmut. The officer was said to have disliked the group and attacked the vehicle while intoxicated. The officer was later identified as Lt. Col. Roman Venevitin, who was later released and subsequently accused the group of stoking "anarchy" on Russia's frontlines by stealing arms, forcing mobilized soldiers to sign contracts with the group and attempting to extort weapons from the defence ministry.
== Other functions == Blood specimen test tubes, vacutainers, and capillary tubes that use the lithium salt of heparin (lithium heparin) as an anticoagulant are usually marked with green stickers and green tops. Heparin has the advantage over EDTA of not affecting levels of most ions. However, the concentration of ionized calcium may be decreased if the concentration of heparin in the blood specimen is too high. Heparin can interfere with some immunoassays, however. As lithium heparin is usually used, a person's lithium levels cannot be obtained from these tubes; for this purpose, royal-blue-topped (and dark green-topped) vacutainers containing sodium heparin are used. Heparin-coated blood oxygenators are available for use in heart-lung machines. Among other things, these specialized oxygenators are thought to improve overall biocompatibility and host homeostasis by providing characteristics similar to those of native endothelium. The DNA binding sites on RNA polymerase can be occupied by heparin, preventing the polymerase from binding to promoter DNA. This property is exploited in a range of molecular biological assays. Common diagnostic procedures require PCR amplification of a patient's DNA, which is easily extracted from white blood cells treated with heparin. This poses a potential problem, since heparin may be extracted along with the DNA, and it has been found to interfere with the PCR reaction at levels as low as 0.002 U in a 50 μL reaction mixture. Heparin has been used as a chromatography resin, acting as both an affinity ligand and an ion exchanger.
However, while LSD and salvinorin A may have comparative potencies, in the sense that both can produce their effects at low dosages, they are otherwise quite different. The two substances are not chemically similar or related, as salvinorin A is found naturally in a single plant while LSD is chemically semisynthesized from lysergamides like ergotamine. They are ingested in different ways and produce different effects, which manifest themselves over different timescales. For example, the effects of salvia when smoked typically last for only a few minutes as compared to LSD, whose effects can persist for 8 to 12 hours.
Certain drugs that have been introduced for uses other than analgesics are also used in pain management. Both first-generation (such as amitriptyline) and newer antidepressants (such as duloxetine) are used alongside NSAIDs and opioids for pain involving nerve damage and similar problems. Other agents directly potentiate the effects of analgesics, such as using hydroxyzine, promethazine, carisoprodol, or tripelennamine to increase the pain-killing ability of a given dose of opioid analgesic. Adjuvant analgesics, also called atypical analgesics, include orphenadrine, mexiletine, pregabalin, gabapentin, cyclobenzaprine, hyoscine (scopolamine), and other drugs possessing anticonvulsant, anticholinergic, and/or antispasmodic properties, as well as many other drugs with CNS actions. These drugs are used along with analgesics to modulate and/or modify the action of opioids when used against pain, especially of neuropathic origin. Dextromethorphan has been noted to slow the development of and reverse tolerance to opioids, as well as to exert additional analgesia by acting upon NMDA receptors, as does ketamine. Some analgesics such as methadone and ketobemidone and perhaps piritramide have intrinsic NMDA action. The anticonvulsant carbamazepine is used to treat neuropathic pain. Similarly, the gabapentinoids gabapentin and pregabalin are prescribed for neuropathic pain, and phenibut is available without prescription. Gabapentinoids work as α2δ-subunit blockers of voltage-gated calcium channels, and tend to have other mechanisms of action as well.
Sources: en.wikipedia.org
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.
A reported purity value reflects the share of the main peak in one chromatographic run and says nothing about identity. Confirming that the expected sequence is present requires a separate measurement such as mass spectrometry. Purity and identity are distinct questions.
A mass spectrum reports the molecular masses present in a sample and shows whether they match the value expected for selank, near 751.9 Da. It also flags common artifacts such as truncation or adduct formation. It does not establish correct stereochemistry or complete sequence order on its own.
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.