If you have been reading about mass spectrometry and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-07-03. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
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.
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.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
== Function == So far, ArMs can catalyze planty of chemical reactions, such as: allylic alkylation, allylic amination, aldol reaction, alcohol oxidation, C-H activation, click reaction, catechol oxidation, CO2 reduction, cyclopropanation, Diels-Alder reaction, epoxidation, epoxide ring opening, Friedel-Crafts alkylation, hydrogenation, hydroformylation, Heck reaction, Metathesis, Michael addition, nitrite reduction, NO reduction, Suzuki reaction, Si-H insertion, polymerization (atom transfer radical polymerization), atom transfer radical cyclization (ATRC), radical fluorination and proton reduction.
Griffith's work was largely ignored by the engineering community until the early 1950s. The reasons for this appear to be (a) in the actual structural materials the level of energy needed to cause fracture is orders of magnitude higher than the corresponding surface energy, and (b) in structural materials there are always some inelastic deformations around the crack front that would make the assumption of linear elastic medium with infinite stresses at the crack tip highly unrealistic.
The hydrocarbon-generating potential and thermal maturity of petroleum source rocks are commonly evaluated using Rock-Eval pyrolysis and vitrinite reflectance measurements, which provide quantitative indicators of organic matter type, maturation level, and the likelihood of oil or gas generation. Catagenesis was pyrolytic despite the fact that it happened at relatively low temperatures (when compared to commercial pyrolysis plants) of 60 to several hundred °C. Pyrolysis was possible because of the long reaction times involved. Heat for catagenesis came from the decomposition of radioactive materials of the crust, especially 40K, 232Th, 235U and 238U. The heat varied with geothermal gradient and was typically 10–30 °C per km of depth from the Earth's surface. Unusual magma intrusions, however, could have created greater localized heating.
==== Omega-6:omega-3 ratio ==== A 2024 review stated that dietary recommendations should not be made based on the omega-6:omega-3 ratio, but rather on their absolute dietary intake levels. The omega-6:omega-3 ratio is calculated by accounting for all of the omega-6 fatty acids in the diet or blood divided by the sum of all omega-3 fatty acids. Concern about a high omega-6:omega-3 ratio was based on the competition between linoleic acid and alpha-linolenic acid for desaturation enzymes, and because metabolites of omega-6 fatty acids were considered to be pro-inflammatory. However, there is insufficient evidence in humans that omega-6 fats are pro-inflammatory and that omega-3 fats are anti-inflammatory. In contrast, higher omega-6 levels are associated with lower inflammatory status, indicating that intake of omega-6 fats is not a dietary concern, and that relatively low intake of dietary omega-3 fats may lead to inflammation. Accordingly, use of the omega-6:omega-3 ratio has been rejected as an inflammation biomarker by health agencies worldwide. Numerous health and scientific organizations recommend intake of omega-6 seed oils as part of a healthy diet to replace sources of saturated fats, such as in palm and coconut oils, butter, tallow, and lard.
=== Soviet use of RTGs === Many Beta-M RTGs produced by the Soviet Union to power lighthouses and beacons have become orphaned sources of radiation. Its design allowed for the use of normal industrial bolts instead of intrinsically safe or safety interlocked bolts (most likely to reduce cost), and did not require the use of intrinsically safe opening mechanisms or made any use of tamper resistant shielding systems. Several of these units have also been illegally dismantled for scrap metal, or been exposed to storm conditions, freezing and water penetration, common issues in those abandoned in the harsh Russian arctic. Some have even fallen into the ocean, or have defective shielding due to poor design or physical damage. The US Department of Defense cooperative threat reduction program has expressed concern that material from the Beta-M RTGs can be used by terrorists to construct a dirty bomb. However, the strontium titanate perovskite used is resistant to all likely forms of environmental degradation and cannot melt or dissolve in water. Bioaccumulation is unlikely as SrTiO3 passes through the digestive tract of humans or other animals unchanged, but the animal or human who ingested it would still receive a significant radiation dose to the sensitive intestinal lining during passage. Mechanical degradation of "pebbles" or larger objects into fine dust is more likely and could disperse the material over a wider area, however this would also reduce the risk of any single exposure event resulting in a high dose.
Sources: en.wikipedia.org
== Chemical properties == Ethylene oxide readily reacts with diverse compounds with opening of the ring. Its typical reactions are with nucleophiles which proceed via the SN2 mechanism both in acidic (weak nucleophiles: water, alcohols) and alkaline media (strong nucleophiles: OH−, RO−, NH3, RNH2, RR'NH, etc.). The general reaction scheme is
Frank Furedi (born 1947) is a Hungarian Jewish British Canadian academic known for work on sociology of fear, education, therapy culture, paranoid parenting and sociology of knowledge; in 1970s, was member of International Socialists (IS); later formed the Revolutionary Communist Group, and then broke from that to form Revolutionary Communist Tendency, refounded as the Revolutionary Communist Party in 1978; RCP was distinguished by its contrarianism; among its positions were support for IRA and Saddam Hussein Furedi is now associated with the RCP's successor, the web site Spiked Online. Neil Gaiman fantasy writer Uri Geller (Hebrew: אורי גלר; born 20 December 1946 in British Mandate of Palestine Mandatory Palestine (now Israel), of Hungarian Jewish ancestry, is an Israeli-British illusionist, magician, television personality, self-proclaimed psychic and author of over ten books, both fiction and non-fiction. Ernest Gellner social anthropologist, scholar of nationalism and identity, of Austrian Jewish and Czech Jewish origin. Adele Geras, (née Weston; born 15 March 1944) FRSL is an English writer for young children, teens and adults. She has written more than 95 books for children, young adults, and adults.
company was sold to Cardinal Health and the Canadian company was sold to an investor group. Today the technology of the U.S. company is controlled by Abbott Laboratories (2007) and the Canadian company was acquired by Cerner Corp. (2013)
Soon after the Big Bang, roughly 14 Gya (14 billion years ago), the only chemical elements present in the universe were hydrogen, helium, and lithium, the three lightest atoms in the periodic table. These elements gradually condensed into vast clouds of gas, which collapsed under gravity into rotating protostellar disks. Gravitational accretion of material at the hot and dense centers of these disks formed the first stars by the fusion of hydrogen. Early stars were massive and short-lived, producing all the heavier elements by stellar nucleosynthesis. Such element formation proceeds to its most stable element Iron-56. Heavier elements were formed during supernovas at the end of a star's lifecycle. Carbon, currently the fourth most abundant element in the universe, was formed mainly in white dwarf stars. As these stars reached the end of their lifecycles, they ejected heavier elements, including carbon and oxygen, throughout the universe. These allowed for the formation of rocky planets. According to the nebular hypothesis, the Solar System began to form 4.6 Gya with the gravitational collapse of part of a giant molecular cloud. Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets formed.
Sources: en.wikipedia.org
=== New Zealand === On 12 March, the New Zealand Government released six days' worth of petroleum following a global directive by the International Energy Agency to release 400 million barrels of petrol in response to supply disruptions caused by the 2026 Iran war. On 24 March, the New Zealand Government announced that about 143,000 working families with children would receive a $50 tax credit to help with rising fuel costs from 7 April. Another 14,000 families were also expected to be eligible for a lower tax credit. On 27 March, the New Zealand Government released its four-level fuel alert level system in response to fuel shortages caused by the Iran conflict. That day the country was placed on the first phase, watchful, with the public advised to use fuel cautiously.
=== Physical === Childhood obesity, however, can also lead to life-threatening conditions including diabetes, high blood pressure, heart disease, sleep problems, cancer, and other disorders. Some of the other disorders would include liver disease, early puberty or menarche, eating disorders such as anorexia and bulimia, skin infections, and asthma and other respiratory problems. The early physical effects of obesity in adolescence include almost all of the child's organs being affected, gallstones, hepatitis, sleep apnoea and increased intracranial pressure. Overweight children are also more likely to grow up to be overweight adults. Obesity during adolescence has been found to increase mortality rates during adulthood. A 2008 study has found that children who are obese have carotid arteries which have prematurely aged by as much as thirty years as well as abnormal levels of cholesterol.
== Asymptomology == There are documented asymptomatic males who present no ALD symptoms well into their 60s and 70s. It's not understood how they can have an ABCD1 gene variant and possess elevated VLCFAs and not exhibit either Cerebral ALD, Adrenal Insufficiency, or Adrenomyeloneuropathy symptoms. Daughters of asymptomatic males become obligate carriers, who may themselves be asymptomatic and who can pass the variant onto their children, which then silently perpetuates ALD. Sons of asymptomatic males only receive their father's Y chromosome and therefore can't inherit ALD.
== Uses == Blasticidin S is widely used in cell culture for selecting and maintaining genetically manipulated cells. Cells of interest express the blasticidin S resistance genes BSD or bsr, and can then survive blasticidin S being added to the culture media. Blasticidin S is typically used at 2–300 micrograms per milliliter of media, depending on the type of cell being grown.
== Weak and strong ion exchangers == A "strong" ion exchanger will not lose the charge on its matrix once the column is equilibrated and so a wide range of pH buffers can be used. "Weak" ion exchangers have a range of pH values in which they will maintain their charge. If the pH of the buffer used for a weak ion exchange column goes out of the capacity range of the matrix, the column will lose its charge distribution and the molecule of interest may be lost. Despite the smaller pH range of weak ion exchangers, they are often used over strong ion exchangers due to their having greater specificity. In some experiments, the retention times of weak ion exchangers are just long enough to obtain desired data at a high specificity. Resins (often termed 'beads') of ion exchange columns may include functional groups such as weak/strong acids and weak/strong bases. There are also special columns that have resins with amphoteric functional groups that can exchange both cations and anions. Some examples of functional groups of strong ion exchange resins are quaternary ammonium cation (Q), which is an anion exchanger, and sulfonic acid (S, -SO2OH), which is a cation exchanger. These types of exchangers can maintain their charge density over a pH range of 0–14. Examples of functional groups of Weak ion exchange resins include diethylaminoethyl (DEAE, -C2H4N(C2H5)2), which is an anion exchanger, and carboxymethyl (CM, -CH2-COOH), which is a cation exchanger. These two types of exchangers can maintain the charge density of their columns over a pH range of 5–9.
Sources: en.wikipedia.org
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.