freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Modeled on tuftsin |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues |
| Approximate molecular mass | Around 750 Da | Depends on counter-ion and hydration |
| Common forms | Lyophilized powder | Also described as aqueous solution |
| Primary origin of research | Russian laboratories | Mid-1990s onward |
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
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.
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.
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.
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.
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.
Further development yielded β-lactamase-resistant penicillins, including flucloxacillin, dicloxacillin, and methicillin. These were significant for their activity against β-lactamase-producing bacterial species, but were ineffective against the MRSA strains. Another development of the line of penicillins was the antipseudomonal penicillins, such as carbenicillin, ticarcillin, and piperacillin, useful for their activity against Gram-negative bacteria. The usefulness of the β-lactam ring was such that related antibiotics, including the mecillinams, the carbapenems and, most important, the cephalosporins, still retain it at the centre of their structures.
=== ColdFusion MX 7 === With the release of ColdFusion 7.0 on February 7, 2005, the naming convention was amended, rendering the product name "Macromedia ColdFusion MX 7" (the codename for CFMX7 was "Blackstone"). CFMX 7 added Flash-based and XForms-based web forms, and a report builder that output in Adobe PDF as well as FlashPaper, RTF and Excel. The Adobe PDF output is also available as a wrapper to any HTML page, converting that page to a quality printable document. The enterprise edition also added Gateways. These provide interaction with non-HTTP request services such as IM Services, SMS, Directory Watchers, and an asynchronous execution. XML support was boosted in this version to include native schema checking. ColdFusion MX 7.0.1 (codename "Merrimack") added support for Mac OS X, improvements to Flash forms, RTF support for CFReport, the new CFCPRoxy feature for Java/CFC integration, and more. ColdFusion MX 7.0.2 (codenamed "Mystic") included advanced features for working with Adobe Flex 2 as well as more improvements for the CF Report Builder.
== SJ == SJ (s) Svalbard and Jan Mayen (ISO 3166 digram) (i) Societas Iesu (Latin: The Society of Jesus, the Jesuit order) (i) Statens Järnvägar (Swedish State Railways) SJA – (i) Staff Judge Advocate (military law) SJC – (i) Supreme Judicial Court of Massachusetts (note: the highest court in the state of Maine is also called the Supreme Judicial Court) SJM – (s) Svalbard and Jan Mayen (ISO 3166 trigram) SJW – (i) Social Justice Warrior
Sources: en.wikipedia.org
A germline mutation in the reproductive cells of an individual gives rise to a constitutional mutation in the offspring, that is, a mutation that is present in every cell. A constitutional mutation can also occur very soon after fertilization, or continue from a previous constitutional mutation in a parent. A germline mutation can be passed down through subsequent generations of organisms. The distinction between germline and somatic mutations is important in animals that have a dedicated germline to produce reproductive cells. However, it is of little value in understanding the effects of mutations in plants, which lack a dedicated germline. The distinction is also blurred in those animals that reproduce asexually through mechanisms such as budding, because the cells that give rise to the daughter organisms also give rise to that organism's germline. A new germline mutation not inherited from either parent is called a de novo mutation.
Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that uses an inductively coupled plasma to ionize the sample. It atomizes the sample and creates atomic and small polyatomic ions, which are then detected. It is known and used for its ability to detect metals and several non-metals in liquid samples at very low concentrations. It can detect different isotopes of the same element, which makes it a versatile tool in isotopic labeling. Compared to atomic absorption spectroscopy, ICP-MS has greater speed, precision, and sensitivity. However, compared with other types of mass spectrometry, such as thermal ionization mass spectrometry (TIMS) and glow discharge mass spectrometry (GD-MS), ICP-MS introduces many interfering species: argon from the plasma, component gases of air that leak through the cone orifices, and contamination from glassware and the cones.
Watson was selected at pick 40 under the father–son rule in the 2002 national draft. He was initially coached as a key forward by Kevin Sheedy, who also coached his father Tim. His poor kicking by AFL standards drew criticism, and it was determined that he would be more suited to the midfield at Essendon. At the time, his weight was criticised by the media, as he was overweight for an AFL player. Over the next two seasons, he began to develop his craft in the Essendon midfield and became one of the competition's elite midfielders. Watson had a consistent season in 2009, polling ten Brownlow Medal votes and winning the Essendon best-and-fairest award, the Crichton Medal. Watson polled 335 votes in 15 of the 21 games he played in the 2009 season, with only one game missed due to an ankle injury. Watson was 46 votes ahead of runner-up Dustin Fletcher, who polled 289 votes. By the end of the 2009 season, Watson had gathered a reputation as Essendon's most important midfielder (coming first in the club's overall clearances) and improved his once-criticised kicking ability to above the standard of an AFL player. Watson was announced as Essendon captain on 21 December 2009, taking over from retired goalkicker Matthew Lloyd. Despite Essendon suffering a disappointing 2010 season, winning only seven games and finishing 14th on the AFL ladder, Watson enjoyed a successful first year as captain.
Dakin's solution is a dilute solution of sodium hypochlorite (0.4% to 0.5%) and other stabilizing ingredients, traditionally used as an antiseptic, e.g. to cleanse wounds in order to prevent infection. The preparation was for a time called also Carrel–Dakin solution or Carrel–Dakin fluid.
Sources: en.wikipedia.org
The Romanian revolution (Romanian: Revoluția română) was a period of violent civil unrest in the Socialist Republic of Romania during December 1989 as a part of the revolutions of 1989 that occurred in several countries around the world, primarily within the Eastern Bloc. The Romanian revolution started in the city of Timișoara and soon spread throughout the country, ultimately culminating in the drumhead trial and execution of longtime Romanian Communist Party (PCR) General Secretary Nicolae Ceaușescu and his wife Elena, and the end of 42 years of Communist rule in Romania. It was also the last removal of a Marxist–Leninist government in a Warsaw Pact country during the events of 1989, and the only one that violently overthrew a country's leadership and executed its leader; according to estimates, over one thousand people died and thousands more were injured. Following World War II, Romania found itself inside the Soviet sphere of influence, with Communist rule officially declared in 1947. In April 1964, when Romania published a general policy paper worked out under Gheorghe Gheorghiu-Dej's instructions, the country was well on its way of carefully breaking away from Soviet control. Nicolae Ceaușescu became the country's leader the following year. Under his rule, Romania experienced a brief waning of internal repression that led to a positive image both at home and in the West. However, repression again intensified by the 1970s, and Ceaușescu's regime eventually became one of the most repressive in the world and one of the most repressive of modern times.
==== April 2008 norovirus ==== In 2008, Chipotle was implicated in a norovirus outbreak in Kent, Ohio, where over 400 people became ill after eating at a Chipotle restaurant. Officials at the Ohio Department of Health said that the outbreak was caused by Norovirus Genotype G2. Many of the victims were students at Kent State University. The initial source of the outbreak was never found.
== Affimer proteins == Affimer proteins are small robust affinity reagents, with a molecular weight of 12–14kDa. They are engineered to bind to their target proteins with high affinity and specificity and as such are a member of the synthetic antibody family. The Affimer protein scaffold is derived from the cysteine protease inhibitor family of cystatins. Within the protein scaffold there exist two variable peptide loops and a variable N-terminal sequence that provide a high affinity binding surface for the specific target protein. Affimer binders have been produced to a large number of targets including ubiquitin chains, immunoglobulins and C-reactive protein for use in a number of molecular recognition applications. Affimer technology has been commercialised and developed by Avacta Life Sciences, who are developing Affimer binders as reagents for research, diagnostic and therapeutic applications.
Sources: en.wikipedia.org
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.
It originates from research in Russia, associated with the Institute of Molecular Genetics of the Russian Academy of Sciences. The first descriptions date to the mid-1990s. Most published studies come from Russian laboratories.
No, Selank itself does not occur naturally. Its backbone is based on tuftsin, which is produced in the body, but the seven-residue version is a synthetic construct. It is supplied as a manufactured peptide.
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.