A practical reference on RP-HPLC purity: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-07-15 and is reviewed periodically as new material appears.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
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.
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.
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.
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.
== Medical uses == The vaccine can be formulated in two ways: as a ready-to-use solution in water that is frozen at the common home-freezer storage temperature of −18 °C or 0 °F or lower, and as a freeze-dried (lyophilized) powder, "Gam-COVID-Vac-Lyo", which can be stored at 2–8 °C or 36–46 °F. The freeze-dried powder must be reconstituted with sterile water before use. The lyophilized formulation of Gam-COVID-Vac is similar to the smallpox vaccine, circumventing the need for continuous "colder chain" or cold-chain storage – as required for the Pfizer–BioNTech and Moderna vaccines – and allowing transportation to remote locations with reduced risk of vaccine spoilage. The first dose (based on Ad26) is administered on the first day, and the second dose (based on Ad5) is administered on the 21st day to boost immune response. Both doses are administered into the deltoid muscle. Sputnik Light is a registered single-dose vaccine consisting of only the first dose of Sputnik V. It is intended for areas with acute outbreaks and it will be used as a third (booster) dose for those who have received Sputnik V at least 6 months earlier. It can be stored at a normal refrigerator temperature of 2–8 °C (36–46 °F). The institute says this version would be ideally suited for areas with acute outbreaks, allowing more people to be vaccinated quickly. Although Sputnik Light was not authorized by Ukraine or international organizations, tens of thousands of doses were shipped by Russia for use in non-government controlled parts of the eastern Donbas region from January 2021.
== History == Waterlogged wood is a wooden object that has been submerged or partially submerged in water and has affected the original intended purpose or look of the object. Waterlogged wood objects can also include wood found within moist soil from archaeological sites, underwater archaeology, maritime debris, or damaged wood objects. Conservation of waterlogged wood has changed throughout time. Due to the delicate structure of this organic material, conservators and museum professionals alike have struggled with finding a textbook method. An example of the conservation of wood and how it has changed over time can be illustrated by the conservation treatments of a Kefermarkt altar. The earliest attempt at wood conservation is recorded as late as 1852–1855, A. Stifter treated the Kefermarkt altar in Austria with table salt in an attempt to protect the wood against pests. In around 1916-1918 Councillor Bolle attempted to protect the wood altar from pests included brushing the wood with petroleum and hexachloroethane. Finally, in 1929 the use of hydrogen cyanide relieved the pest problem and preserve the woods longevity. From a conservation standpoint, waterlogged or not, wood has been difficult to preserve because it is an organic material.
The mainstay of type 1 diabetes treatment is the regular injection of insulin to manage hyperglycemia. Subcutaneous injection using either a syringe multiple times a day, or with a continuous infusion insulin pump are necessary, adjusting dosages to account for food intake, blood glucose levels, and physical activity. The goal of treatment is to maintain blood sugar in a normal range—80–130 mg/dL (4.4–7.2 mmol/L) before a meal; <180 mg/dL (10.0 mmol/L) after—as often as possible. To achieve this, people with type 1 diabetes monitor their blood glucose levels at home. Around 83% of type 1 diabetics monitor their blood glucose by capillary blood testing: pricking the finger to draw a drop of blood, and determining blood glucose with a glucose meter. The American Diabetes Association recommends testing blood glucose around 6–10 times per day: before each meal, before exercise, at bedtime, occasionally after a meal, and any time someone feels the symptoms of hypoglycemia. 82% of people under 18 years old and 53% of those over 18 with type 1 diabetes use a continuous glucose monitor, a device with a filament under the skin that constantly measures glucose levels and communicates those levels to an external device as of 2025. Continuous glucose monitoring is associated with better blood sugar control than finger stick capillary blood testing alone; however, continuous glucose monitoring is much more expensive. Healthcare providers can also monitor someone's hemoglobin A1C levels, which reflect the average blood sugar over the last three months.
Sweating allows the body to regulate its temperature. Sweating is controlled from a center in the preoptic and anterior regions of the brain's hypothalamus, where thermosensitive neurons are located. The heat-regulatory function of the hypothalamus is also affected by inputs from temperature receptors in the skin. High skin temperature reduces the hypothalamic set point for sweating and increases the gain of the hypothalamic feedback system in response to variations in core temperature. Overall, however, the sweating response to a rise in hypothalamic ('core') temperature is much larger than the response to the same increase in average skin temperature. Sweating causes a decrease in core temperature through evaporative cooling at the skin surface. As high energy molecules evaporate from the skin, releasing energy absorbed from the body, the skin and superficial vessels decrease in temperature. Cooled venous blood then returns to the body's core and counteracts rising core temperatures. There are two situations in which the nerves will stimulate the sweat glands, causing perspiration: during physical heat and during emotional stress. In general, emotionally induced sweating is restricted to palms, soles, armpits, and sometimes the forehead, while physical heat-induced sweating occurs throughout the body. Human sweat is not pure water; though it contains no protein, it always contains a small amount (0.2–1%) of solute. When a person moves from a cold climate to a hot climate, adaptive changes occur in the sweating mechanisms of the person.
=== IGF-1 === In December 2012, topical application of IGF-1 in a liposomal vehicle led to thicker and more rapid hair growth in transgenic mice with androgenic alopecia. The study did not show measurable systemic levels or hematopoietic side effects, suggesting potential for use in humans. Low energy radiofrequency irradiation induces IGF-1 in cultured human dermal papilla cells. Adenosine stimulates dermal papillae in vitro to induce IGF-1, along with fibroblast growth factors FGF7, FGF-2 and VEGF. β-catenin transcription increased, which promotes dermal papillae as well. Dietary isoflavones increase IGF production in scalp dermal papillae in transgenic mice. Topical capsaicin also stimulates IGF at hair follicles via release of vanilloid receptor-1, which in turn leads to more CGRP. Ascorbic acid has led to increased IGF expression in vitro.
Sources: en.wikipedia.org
=== Bibliography === Woodward, A.S. (1900): On some remains of Grypotherium (Neomylodon) listai and associated mammals from a cavern near Consuelo Cove, Last Hope Inlet. Proceedings of the Zoological Society of London, 1900(5): 64–79.
== Awards and recognition == Pfizer has received various awards and recognitions related to its workplace policies and corporate practices. In the United States, Pfizer earned a 100% score from the Human Rights Campaign (2025) on the Corporate Equality Index for LGBTQ workplace equality and ranked highly in the Hispanic Association on Corporate Responsibility (2024) Corporate Inclusion Index. Pfizer was named a "Best Place to Work for Disability Inclusion" in the Disability Equality Index (2024) and received awards such as Top Diverse Employer, Top Hispanic Employer, and Top Disability-Friendly Company by DiversityComm, Inc. (2024). Other recognitions include being named one of "America's Greatest Workplaces" by Newsweek (2023), Clinical Trials Arena Excellence Awards 2023, inclusion in the top 10 of the "World's Most Admired Companies" by Fortune (2023), and being listed as a Top Employer for Diversity and Best Employer for Women by Forbes (2022). Pfizer was also recognized as a "Best Place to Work" by Glassdoor (2021) and a Top Employer by Science (2021) for its practices during the pandemic.
=== History of research === It was not until relatively recently that medicine recognised the worldwide prevalence of lactose intolerance and its genetic causes. Its symptoms were described as early as Hippocrates (460–370 BC), but until the 1960s, the prevailing assumption in Western medicine was that tolerance was the norm. Intolerance was explained as the result of a milk allergy, intestinal pathogens, or as being psychosomatic – it being recognised that some cultures did not practice dairying, and people from those cultures often reacted badly to consuming milk. Two reasons have been given for this misconception. One was that early research was conducted solely on European-descended populations, which have an unusually low incidence of lactose intolerance and an extensive cultural history of dairying. As a result, researchers wrongly concluded that tolerance was the global norm. Another reason is that lactose intolerance tends to be under-reported: most lactose-intolerant individuals can tolerate at least some lactose before they show symptoms, and their symptoms differ in severity. The large majority of people are able to digest a small quantity of milk (e.g., the amount used in a cup of tea or coffee) without developing any adverse effects. Fermented dairy products, such as cheese, also contain significantly less lactose than plain milk. Therefore, in societies where tolerance is the norm, many lactose intolerant people who consume only small amounts of dairy, or have only mild symptoms, may be unaware that they cannot digest lactose.
=== Woodhouse Grammar School === Cyril Fletcher, comedian famous for his "odd odes" Giles Hart, engineer and trade union activist Ian Bedford, cricketer John Somerville, sculptor Oliver Postgate, animator and creator of Bagpuss Paul Davies, astrophysicist Robert G. W. Anderson, director of the British Museum Jagdip Jagpal, director of India Art Fair
Sources: en.wikipedia.org
The Court of Justice held that the Directive could be relied on by her because equality was also a general principle of EU law. Fourth, if the defendant is an emanation of the state, even if not central government, it can still be bound by Directives. In Foster v British Gas plc the Court of Justice held that Mrs Foster was entitled to bring a sex discrimination claim against her employer, British Gas plc, which made women retire at age 60 and men at 65, if (1) pursuant to a state measure, (2) it provided a public service, and (3) had special powers. This could also be true if the enterprise is privatised, as it was held with a water company that was responsible for basic water provision. Fifth, national courts have a duty to interpret domestic law "as far as possible in the light of the wording and purpose of the directive". Textbooks (though not the Court itself) often called this "indirect effect". In Marleasing SA v La Comercial SA the Court of Justice held that a Spanish Court had to interpret its general Civil Code provisions, on contracts lacking cause or defrauding creditors, to conform with the First Company Law Directive article 11, that required incorporations would only be nullified for a fixed list of reasons. The Court of Justice quickly acknowledged that the duty of interpretation cannot contradict plain words in a national statute. But, if a member state has failed to implement a Directive, a citizen may not be able to bring claims against other non-state parties. It must instead sue the member state itself for failure to implement the law.
== Family == Eastlack lived in Philadelphia, Pennsylvania, with his sister and his parents. Eastlack was of Anglo-Scottish, Irish, and German descent, and his father was a World War I military veteran and a firefighter. Harry's elder sister Helene Davridge (née Eastlack) was born on (1932-08-20)20 August 1932 in Philadelphia, Pennsylvania, and became a music teacher later as an adult. She died in September 1998, at the age of 66, in Sharon Hill, Pennsylvania, leaving behind her husband and daughter, Kristen.
Plasma was already well known when described by William Harvey in de Motu Cordis in 1628, but knowledge of it probably dates as far back as Vesalius (1514–1564). The discovery of fibrinogen by William Henson, c. 1770, made it easier to study plasma, as ordinarily, upon coming in contact with a foreign surface – something other than the vascular endothelium – clotting factors become activated and clotting proceeds rapidly, trapping RBCs etc. in the plasma and preventing separation of plasma from the blood. Adding citrate and other anticoagulants is a relatively recent advance. Upon the formation of a clot, the remaining clear fluid (if any) is blood serum, which is essentially plasma without the clotting factors The use of blood plasma as a substitute for whole blood and for transfusion purposes was proposed in March 1918, in the correspondence columns of the British Medical Journal, by Gordon R. Ward. "Dried plasmas" in powder or strips of material format were developed and first used in World War II. Prior to the United States' involvement in the war, liquid plasma and whole blood were used.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.