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 2025-08-31. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
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.
"Precautionary measures in radiation protection use the generally accepted model that the risk of lung cancer increases uniformly (linearly) with radon concentration. This means that an increased risk of lung cancer does not only occur above a certain value, but that a guideline or limit value only adjusts the magnitude of the risk in a meaningful way to other existing risks. Achieving a guideline or limit therefore means taking a risk that is still (socially) acceptable. It therefore makes perfect sense to take simple measures to reduce radon levels, even if they are below the guideline values." In Austria, the Radon Protection Ordinance in its version of September 10, 2021 is currently in force, which also defines the radon protection areas and radon precautionary areas.
Vicuña wool is considered the rarest and most expensive legal wool in the world; in 2010, raw wool traded for about 7-15 dollars per ounce. The sorted and spun yarn trades at about $300 per ounce. It is usually processed in its natural color, as the structure of vicuña hair suffers from bleaching or dyeing. Northern populations of vicuñas display a more cinnamon-like coat color on the back, southern ones a beige hue; the hair on the belly represents a smaller portion that is much lighter in color. White wool is traded at higher prices. In addition to knitted sweaters and socks, vicuña wool is also used to weave fabrics that are made into exclusive tailored clothing. A sport coat can cost up to $21,000, a made-to-measure suit starts at $32,000.
== Legal status == Ketazolam is a List 3 drug under the Betäubungsmittelgesetz, like almost all benzodiazepines in Germany. Ketazolam is a List II drugs of the Opium Law in the Netherlands. Ketazolam is a Schedule IV drug under the Controlled Substances Act in the US.
The team consisted of officials from the Department of Foreign Affairs and members of the Defence Forces, including Army Ranger Wing personnel. 24 April – Fifty Irish citizens were evacuated on French and Spanish aircraft from Khartoum in Sudan to safety in Djibouti. It was announced that Ireland had purchased two Airbus C295 maritime patrol aircraft capable of future airlift missions, while Airbus will supply an additional military transport aircraft to Ireland in 2025. 25 April Seventy-two Irish citizens and their families were rescued with the help of France and Spain from violence in Sudan to safety in Djibouti and Jordan. An Irish metal and polymer lunar soil experiment produced by the Dublin City University School of Chemical Sciences was lost when the Japanese Hakuto-R Mission 1 Moon landing spacecraft carrying the Rashid Lunar Rover built by the United Arab Emirates stopped communicating during the final moments of an automated Moon landing attempt in the Atlas Crater. 26 April – Sixteen more Irish citizens and their family members were rescued since the day before via Djibouti, Jordan, and Cyprus, from the fighting which broke out on 15 April in Sudan. More than 100 Irish people remained in the country. 30 April – After evacuating 209 Irish people and their families in the past week, the Emergency Civil Assistance Team was withdrawn from Sudan.
== H == Habituation A form of non-associative learning in which an organism decreases or ceases its responses to a repetitive, harmless stimulus over time. Hallucination A perception in the absence of external stimulus, such as hearing voices or seeing things that are not present. Common in conditions like schizophrenia or sensory deprivation. Hemispheres of the brain The two symmetrical halves of the brain—left and right—that control opposite sides of the body. Each hemisphere has specialized functions but works in coordination with the other. Hemispatial neglect A neuropsychological condition in which a person fails to attend to one side of space, usually the left, following damage to the right parietal lobe. Hering’s law of equal innervation A principle in ocular motor control stating that yoked eye muscles receive equal neural signals to maintain coordinated binocular eye movements. Hertz (Hz) A unit of frequency equal to one cycle per second. Used in neuroscience to describe brain wave activity, neural firing rates, and oscillations. Hindbrain The posterior part of the brain, including the medulla oblongata, pons, and cerebellum. It regulates vital autonomic functions and coordinates movement. Hippocampus A brain structure located in the medial temporal lobe, critical for memory formation, spatial navigation, and learning. Damage is associated with anterograde amnesia. Histamine A neurotransmitter involved in arousal, wakefulness, and inflammatory responses. Histaminergic neurons are primarily located in the hypothalamus.
Sources: en.wikipedia.org
The Moon race is often analyzed as a microcosm of the Space Race's broader dynamics. Historians such as Jennifer Frost argue that if the Space Race is measured in terms of overall spaceflight capability, the Soviet Union "won it hands down." Asif A. Siddiqi, a noted space historian, provides a more nuanced view, emphasizing the Soviet Union's dominance in smaller aspects of the race to the moon, yet critical, benchmarks such as the first lunar impact, first photos of the Moon's far side, first soft lunar landing, and first lunar orbit. These accomplishments laid the groundwork for lunar exploration, though they are often overshadowed by the Apollo 11 mission. After the period of détente, the Soviet Union managed to send 18 crafts to Venus. However, this did not generate wide speculation from the western world.Before that landing [Apollo 11], there was an enormous amount of investment in the robotic exploration of the Moon, both by the Soviets and the US, in terms of all sorts of smaller benchmarks like the first lunar impact, the first pictures of the far side of the Moon, the first soft lunar landing, and the first lunar orbit. We forget, but in those little races, the Soviet Union dominated almost every benchmark, but it is forgotten as the United States won the big one.
Ménière's disease "Biologic disease-modifying antirheumatic drugs" This may not happen in the absence of infection. Atlanto-axial joint instability can cause symptoms including vertigo and sudden death. Atypical Cogan's syndrome may be associated with rheumoatoid arthritis.
Titration curves can be computed within a continuum electrostatics approach with formally exact but more elaborate analytical or Monte Carlo (MC) methods, or inexact but fast approximate methods. MC methods that have been used to compute titration curves are Metropolis MC or Wang–Landau MC. Approximate methods that use a mean-field approach for computing titration curves are the Tanford–Roxby method and hybrids of this method that combine an exact statistical mechanics treatment within clusters of strongly interacting sites with a mean-field treatment of intercluster interactions.
V. A. Shiva Ayyadurai (born Vellayappa Ayyadurai Shiva on December 2, 1963) is an American engineer, entrepreneur, and anti-vaccine activist. He has become known for promoting conspiracy theories, pseudoscience, and unfounded medical claims. Ayyadurai holds four degrees from the Massachusetts Institute of Technology (MIT), including a PhD in biological engineering, and is a Fulbright grant recipient. In a 2011 article published by Time, Ayyadurai claimed to have invented email as a teenager; in August 1982, he registered the copyright on an email application he had written, asserting in his copyright filing, "I, personally, feel EMAIL is as sophisticated as any electronic mail system on the market today." Historians strongly dispute this account because email was already in use in the early 1970s. Ayyadurai sued Gawker Media and Techdirt for defamation for disputing his account of inventing email; both lawsuits were settled out of court. Ayyadurai and Techdirt agreed to Techdirt's articles remaining online with a link to Ayyadurai's rebuttal on his own website. Ayyadurai also attracted attention for two reports: the first questioning the working conditions of India's largest scientific agency; the second questioning the safety of genetically modified food, such as soybeans. During the COVID-19 pandemic, Ayyadurai became known for a social media COVID-19 disinformation campaign, spreading conspiracy theories about the cause of COVID-19, promoting unfounded COVID-19 treatments, and campaigning to fire Anthony Fauci for allegedly being a deep state actor.
The aroma chemicals acetamide and cumarine have been found in the e-cigarette vapor. Acrylonitrile and ethylbenzene have been found in the e-cigarette vapor. Benzene and 1,3-Butadiene have been found in the e-cigarette vapor at many-fold lower than in cigarette smoke. Some e-cigarettes contain diacetyl and acetaldehyde in the e-cigarette vapor. Diacetyl and acetylpropionyl have been found at greater levels in the e-cigarette vapor than is accepted by the National Institute for Occupational Safety and Health, although diacetyl and acetylpropionyl are normally found at lower levels in e-cigarettes than with traditional cigarettes. A 2018 PHE report stated that diacetyl was identified at hundreds of times in lesser amounts than found in cigarette smoke. A 2016 WHO report found that acetaldehyde from second-hand vapor was between two and eight times greater compared to background air levels.
Sources: en.wikipedia.org
=== Type 1 PSSM === Type 1 PSSM is caused by an autosomal dominant genetic mutation known as GSY1. This mutation causes an up-regulation of glycogen synthase, and high levels of glycogen synthase relative to glycogen branching enzyme (GBE). This altered ratio of glycogen synthase to GBE results in glycogen molecules with long chains and few branches, making these molecules somewhat resistant to amylase breakdown on amylase-PAS (periodic acid-Schiff) stained biopsies. The GSY1 mutation is associated with altered glucose metabolism (but normal glycogen metabolism), as well as accumulation of high levels of glycogen and abnormal polysaccharide in the muscles of the horse. Additionally, some horses have been shown to have insulin sensitivity, which improves glucose uptake by muscle cells and contributes to excessive glycogen storage that is already elevated secondary to the GSY1 mutation.
1993/1887) Occupational Pension Schemes (Public Service Pension Schemes) (Amendment) Regulations 1993 (S.I. 1993/1888) Magistrates' Courts Fees (Amendment) Order 1993 (S.I. 1993/1889) Medicines (Products Other Than Veterinary Dmgs) (Prescription Only) Amendment Order 1993 (S.I. 1993/1890) Colleges of Further Education (Changes of Names) (Scotland) Order 1993 (S.I. 1993/1891) Education (Access Funds) (Scotland) Amendment Regulations 1993 (S.I. 1993/1892) Offshore Installations (Safety Zones)(No. 3) Order 1993 (S.I. 1993/1893) Assisted Areas (Amendment) Order 1993 (S.I. 1993/1894) Legal Aid in Criminal and Care Proceedings (General) (Amendment) (No. 2) Regulations 1993 (S.I. 1993/1895) Neath—Abergavenny Trunk Road (A465) (Improvement from Aberdulais to Glynneath, Aberdulais Slip Roads) Order 1993 (S.I. 1993/1896) Management and Administration of Safety and Health at Mines Regulations 1993 (S.I. 1993/1897) Poultry Breeding Flocks and Hatcheries Order 1993 (S.I. 1993/1898) Meat and Livestock Commission Levy (Variation) Scheme (Confirmation) Order 1993 (S.I. 1993/1899)
== Research career == After obtaining his Ph.D., his first job was in research for Parke, Davis and Company, and his first task was to isolate the hormone associated with the thyroid gland. He continued this research at St. Luke's Hospital in New York until 1914. He was appointed Head of the Biochemistry Section in the Graduate School of the Mayo Foundation, and the following year he was appointed as the Director of the Division of Biochemistry. Kendall made several significant contributions to biochemistry and medicine. His most important discovery was the isolation of thyroxine, although it was not the work for which he received the most accolades. Along with associates, Kendall was involved with the isolation of glutathione and determining its structure. He also isolated several steroids from the adrenal gland cortex, one of which was initially called Compound E. Working with Mayo Clinic physician Philip Showalter Hench, Compound E was used to treat rheumatoid arthritis. The compound was eventually named cortisone. In 1950, Kendall and Hench, along with Swiss chemist Tadeus Reichstein were awarded the 1950 Nobel Prize in Physiology or Medicine for "their discoveries relating to the hormones of the adrenal cortex, their structure and biological effects." His Nobel lecture focused on the basic research that led to his award, and was titled "The Development of Cortisone As a Therapeutic Agent." As of the 2010 awards, Kendall and Hench were the only Nobel Laureates to be affiliated with Mayo Clinic.
==== Psychosis ==== Cocaine has a similar potential to induce temporary psychosis with more than half of cocaine abusers reporting at least some psychotic symptoms at some point. Typical symptoms include paranoid delusions that they are being followed and that their drug use is being watched, accompanied by hallucinations that support the delusional beliefs. Delusional parasitosis with formication ('cocaine bugs') is also a fairly common symptom. Cocaine-induced psychosis shows sensitization toward the psychotic effects of the drug. This means that psychosis becomes more severe with repeated intermittent use.
Sources: en.wikipedia.org
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.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.