This is a working overview of lyophilization, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-09 and is reviewed periodically as new material appears.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
| Property | Value | Notes |
|---|---|---|
| Typical purity report | 95% or higher by HPLC | Area percentage at 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray or MALDI |
| Powder storage | -20 C, desiccated | Protect from light |
| Solution storage | 2-8 C short term | Freeze aliquots for longer |
| Quality document | Certificate of analysis | States method and value |
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.
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.
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.
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.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
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.
== Mechanism of activation == CRF1 is activated through the binding of CRF or a CRF-agonist. The ligand binding and subsequent receptor conformational change depends on three different sites in the second and third extracellular domains of CRF1. In the majority of tissues, CRF1 is coupled to a stimulatory G-protein that activates the adenylyl cyclase signaling pathway, and ligand-binding triggers an increase in cAMP levels. However, the signal can be transmitted along multiple signal transduction cascades, according to the structure of the receptor and the region of its expression. Alternate signaling pathways activated by CRF1 include PKC and MAPK. This wide variety of cascades suggests that CRF1 mediates tissue-specific responses to CRF and CRF-agonists.
In the famous Monty Python "Spam" sketch Bromley was stated to be the location of the fictional Green Midget Café, where every item on the menu was composed of spam in varying degrees. In another Monty Python sketch, it was stated that all seven continents are visible from the top of the Kentish Times building in Bromley. The Bromley Contingent was the name given to the entourage that followed the Sex Pistols and helped popularise the punk movement. It was so called because many of its members were from Bromley, some of whom later became famous as musicians in their own right, like Siouxsie Sioux and Billy Idol. The 2018 comedy film, The Bromley Boys is set in Bromley and surroundings in the late 1960s and early 1970s. Based on a real-life memoir by Dave Roberts about following Bromley F.C., it includes many scenes filmed locally, although Crockenhill F.C. was used as a substitute for the Hayes Lane stadium. Guitarist Billy Jenkins, born in Bromley, released an album titled "Sounds like Bromley" in 1982 and another in 1997 titled "Still Sounds Like Bromley". In a BBC Radio 3 interview he said that "if Kent is the Garden of England then Bromley is one of the compost heaps". He then moved to Lewisham.
== Overview == Ascorbate-dependent peroxidase activity was first reported in 1979, more than 150 years after the first observation of peroxidase activity in horseradish plants and almost 40 years after the discovery of the closely related cytochrome c peroxidase enzyme. Peroxidases have been classified into three types (class I, class II and class III): ascorbate peroxidases is a class I peroxidase enzyme. APXs catalyze the H2O2-dependent oxidation of ascorbate in plants, algae and certain cyanobacteria. APX has high sequence identity to cytochrome c peroxidase, which is also a class I peroxidase enzyme. Under physiological conditions, the immediate product of the reaction, the monodehydroascorbate radical, is reduced back to ascorbate by a monodehydroascorbate reductase (monodehydroascorbate reductase (NADH)) enzyme. In the absence of a reductase, two monodehydroascorbate radicals disproportionate rapidly to dehydroascorbic acid and ascorbate. APX is an integral component of the glutathione-ascorbate cycle.
Sources: en.wikipedia.org
==== Season 1 ==== The following table represents viewership data for each episode's airing on The CW, as DC Universe did not release viewership information. The pilot episode was tied for the second-best series debut on The CW for the 2019–20 television season with Nancy Drew after Batwoman, and was the best summer series premiere on the network since Whose Line Is It Anyway? season nine in 2013. Through the first seven episodes of the season, Stargirl was averaging a 0.2 rating for adults 18–49 and close to 1 million initial viewers per episode, which was "on par" with The CW's Arrowverse series.
=== Essential oil === The leaves are steam distilled to extract eucalyptus oil. E. globulus is the primary source of global eucalyptus oil production, with China being the largest commercial producer. Oil yield ranges from 1.0 to 2.4% (fresh weight), with cineole being the major isolate. E. globulus oil has established itself internationally because it is virtually phellandrene free, a necessary characteristic for internal pharmaceutical use. In 1870, Cloez identified and ascribed the name "eucalyptol" — now more often called cineole — to the dominant portion of E. globulus oil. E. globulus essential oil is described as herbal, (characteristically) eucalyptus, camphoreous, and medicinal. The European Medicines Agency Committee on Herbal Medicinal Products concluded that traditional medicines based on eucalyptus oil can be used for treating cough associated with the common cold, and to relieve symptoms of localized muscle pain. Eucalyptus products appear safe and somewhat effective in reducing cough symptoms from respiratory infections, but the clinical significance is unclear and more high-quality studies are needed.
Historically, the Wernicke-Kleist-Leonhard school considered periodic catatonia a distinct form of "non-system schizophrenia", characterized by recurrent acute phases with hyperkinetic and akinetic features and often psychotic symptoms. There is also a residual state between these phases, characterized by low-level catatonic features and abulia of varying severity.
UNICEF spokesperson Toby Fricker stated, "There is no safe place for children anywhere across the strip right now." On 19 December, the United Nations stated Gaza was "by far the most dangerous place in the world to be a child". James Elder, a UNICEF spokesperson, called the conflict in Gaza a "war on children." On 6 January 2024, Tanya Haj-Hassan, a doctor with Doctors Without Borders, stated children in Gaza were "dying in every way possible." On 18 January 2024, the deputy executive director of UNICEF stated the suffering of children in Gaza were the "most horrific conditions I have ever seen." On 2 February 2024, the UNICEF chair stated, "The situation for children in Gaza grows bleaker every day. The world cannot abandon them." On 5 March, UNICEF called the war on Gaza "a test of human conscience" and stated that the lack of humanitarian aid in the north was worsening children's health situation. Adele Khodr, UNICEF's Middle East regional director, stated on 19 March: "The world’s inaction is shocking as more children succumb to a slow death."
Sources: en.wikipedia.org
Purity is usually reported as an HPLC area percentage, most often measured at 214 nm. Identity is confirmed separately by mass spectrometry. A certificate of analysis should state both the method and the observed value.
Dry powder is kept frozen, desiccated, and shielded from light. Dissolved material is aliquoted and frozen to limit freeze-thaw cycles. Short-term refrigerated storage is common for working solutions.
Russia registers it as a prescription nasal product. Most other markets classify it as a research chemical with no approved medical use. Oversight of purity and labeling is consequently minimal in those markets.
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.