mass spectrometry 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.
Last reviewed on 2026-07-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Analog of the tetrapeptide tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Reported consistently across pharmacopoeial descriptions |
| Appearance | White to off-white lyophilized powder | Typical form of research-grade material |
| Solubility | Freely soluble in water | Aqueous buffers; poor in nonpolar solvents |
| Typical storage temperature | -20 degrees Celsius | Lyophilized powder; protect from moisture |
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.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
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.
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.
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.
=== Reduced NMDA‐receptor function === Reduced NMDA receptor function has been linked to reduced social interactions, locomotor hyperactivity, self-injury, prepulse inhibition (PPI) deficits, and sensory hypersensitivity, among others. Results suggest that NMDA dysregulation could contribute to core ASD symptoms.
TabA (P31851), an enzyme related to lysA (diaminopimelate decarboxylase) TabB (P31852), an enzyme related to dapD (THDPA succinyl-CoA succinyltransferase, THDPA-ST) TblA (P31850), an enzyme with no close paralogs (identified as a member of SAMe-dependent methyltransferase superfamily by InterPro) This pathway produces TBL; the enzyme TblF finalize the synthesis by linking TBL to Thr to form tabtoxin.
== Further reading == Brooks, Maurice (1965). The Appalachians: The Naturalist's America; illustrated by Lois Darling and Lo Brooks. Boston; Houghton Mifflin Company. Caudill, Harry M. (1963). Night Comes to the Cumberlands. ISBN 0-316-13212-8. Constantz, George (2004). Hollows, Peepers, and Highlanders: an Appalachian Mountain Ecology (2nd edition). West Virginia University Press; Morgantown. 359 p. Olson, Ted (1998). Blue Ridge Folklife. University Press of Mississippi, 211 pages, ISBN 1-57806-023-0. Rehder, John (2013). "Appalachian Folkways", Koxville: University of Tennessee Press. Semple, E. C. (1903). Chapters III, IV, and V. American History and Its Geographic Conditions. Boston. Weidensaul, Scott (2000). Mountains of the Heart: A Natural History of the Appalachians. Fulcrum Publishing, 288 pages, ISBN 1-55591-139-0. Bailey Willis, The Northern Appalachians, and C. W. Hayes, The Southern Appalachians, both in The Physiography of the United States. Appalachian flora and fauna-related journals Banisteria, a journal devoted to the natural history of Virginia. Castanea, the journal of the Southern Appalachian Botanical Society. The Journal of the Torrey Botanical Society.
== Prosperity == The Legatum Institute's yearly Legatum Prosperity Index for 2015 ranks Thailand 48 of 142 (1=best, 142=worst) nations. The ranking is based on a variety of factors including wealth, economic growth, education, health, freedom, personal well-being, and quality of life. Other ASEAN nations ranked were Singapore, 17; Malaysia, 44; Vietnam, 55; Indonesia, 69; Philippines, 74; Laos, 95; Cambodia, 112.
Sources: en.wikipedia.org
=== Enzymatic method for RNA oligonucleotide synthesis === One approach under investigation for overcoming length limitations in oligonucleotide synthesis involves the use of engineered enzymes to construct RNA sequences, rather than relying solely on traditional chemical methods. A key enzyme studied in this context is CID1 poly(U) polymerase (PUP), which naturally catalyzes the addition of nucleotides to the 3′ end of an RNA strand. In its native form, PUP functions as a template-independent polymerase, typically adding repeated sequence nucleotide tails to RNA molecules. To enable controlled sequence synthesis, enzymatic RNA synthesis has been adapted into a cyclic two-step process consisting of nucleotide extension and deblocking. During the extension step, a single nucleotide is enzymatically added, while the deblocking step removes a protecting group to allow subsequent incorporation. One investigated method involves the use of nucleoside triphosphates modified with a 3′-O-allyl blocking group. These modified nucleotides are synthesized and purified using techniques such as ion-exchange chromatography and preparative high-performance liquid chromatography (HPLC). Upon incorporation by PUP, the 3′-O-allyl group prevents further extension, thereby enabling single-nucleotide addition per cycle. Chemical removal of the blocking group then permits the next round of extension. Studies have shown that wild-type PUP exhibits limited efficiency when incorporating modified nucleotides.
The history of sertraline dates to the early 1970s when Pfizer chemist Reinhard Sarges invented a novel series of psychoactive compounds, including lometraline, based on the structures of the neuroleptics thiothixene and pinoxepin. Further work on these compounds led to tametraline, a norepinephrine and weaker dopamine reuptake inhibitor. Development of tametraline was soon stopped because of undesired stimulant effects observed in animals. A few years later, in 1977, pharmacologist Kenneth Koe, after comparing the structural features of a variety of reuptake inhibitors, became interested in the tametraline series. He asked another Pfizer chemist, Willard Welch, to synthesize some previously unexplored tametraline derivatives. Welch generated several potent norepinephrine and triple reuptake inhibitors, but to the surprise of the scientists, one representative of the generally inactive cis-analogs was a serotonin reuptake inhibitor. Welch then prepared stereoisomers of this compound, which were tested in vivo by animal behavioral scientist Albert Weissman. The most potent and selective (+)-isomer was taken into further development and eventually named sertraline. Weissman and Koe recalled that the group did not set up to produce an antidepressant of the SSRI type—in that sense their inquiry was not "very goal driven", and the invention of the sertraline molecule was serendipitous. According to Welch, they worked outside the mainstream at Pfizer, and even "did not have a formal project team".
The official language of Brazil is Portuguese (Article 13 of the Constitution of the Federal Republic of Brazil), which almost all of the population speaks and is virtually the only language used in newspapers, radio, television, and for business and administrative purposes. Brazil is the only Portuguese-speaking nation in the Americas, making the language an important part of Brazilian national identity and giving it a national culture distinct from those of its Spanish-speaking neighbors. Brazilian Portuguese has had its own development, mostly similar to 16th-century Central and Southern dialects of European Portuguese (despite a very substantial number of Portuguese colonial settlers, and more recent immigrants, coming from Northern regions, and in minor degree Portuguese Macaronesia), with a few influences from the Amerindian and African languages, especially West African and Bantu restricted to the vocabulary only. As a result, the language is somewhat different, mostly in phonology, from the language of Portugal and other Portuguese-speaking countries (the dialects of the other countries, partly because of the more recent end of Portuguese colonialism in these regions, have a closer connection to contemporary European Portuguese). These differences are comparable to those between American and British English.
Sources: en.wikipedia.org
The king cobra (Ophiophagus hannah) is the longest venomous snake in the world, and it can inject very high volumes of venom in a single bite. The venom LD50 is 1.80 mg/kg SC according to Broad et al. (1979). The mean value of subcutaneous LD50 of five wild-caught king cobras in Southeast Asia was determined to be 1.93 mg/kg. Between 350 and 500 mg (dry weight) of venom can be injected at once (Minton, 1974). In another study by Broad et al. (1979), the average venom quantity was 421 mg (dry weight of milked venom). The maximum venom yield is approximately 1000 mg (dry weight). The king cobra has a fearsome reputation. When annoyed, it spreads a narrow hood and growls loudly, but some scientists claim that their aggressiveness is grossly exaggerated. In most of the local encounters with live, wild king cobras, the snakes appear to be of rather placid disposition, and they usually end up being killed or subdued with hardly any histrionics. These support the view that wild king cobras generally have a mild temperament, and despite their frequent occurrence in disturbed and built-up areas, are adept at avoiding humans. Naturalist Michael Wilmer Forbes Tweedie felt that "this notion is based on the general tendency to dramatise all attributes of snakes with little regard for the truth about them. A moment's reflection shows that this must be so, for the species is not uncommon, even in populated areas, and consciously or unconsciously, people must encounter king cobras quite frequently.
On the night of 24/25 July 1261, Strategopoulos and his men approached the city walls and hid at a monastery near the Gate of the Spring. Strategopoulos sent a detachment of his men, led by some of the thelematarioi, to make their way to the city through a secret passage. This afforded them the opportunity to attack the walls from the inside, which surprised the guards and opened the gate, giving the Nicaean forces an entry into the city. The Latins were taken completely unaware, and after a short struggle, the Nicaeans gained control of the Theodosian land walls. As news of this spread across the city, the Latin inhabitants, from Emperor Baldwin II downwards, hurriedly rushed to the harbours of the Golden Horn, hoping to escape by ship. At the same time, Strategopoulos' men set fire to the Venetian buildings and warehouses along the coast to prevent them from landing there. Due to the timely arrival of the returning Venetian fleet, many of the Latins managed to evacuate to the still Latin-held parts of Greece, marking the end of the Latin occupation with the city's restoration to the Byzantines.
=== Mixing solutions === Often mixing hydroponic solutions using individual salts is impractical for hobbyists or small-scale commercial growers because commercial products are available at reasonable prices. However, even when buying commercial products, multi-component fertilizers are popular. Often these products are bought as three part formulas which emphasize certain nutritional roles. For example, solutions for vegetative growth (i.e. high in nitrogen), flowering (i.e. high in potassium and phosphorus), and micronutrient solutions (i.e. with trace minerals) are popular. The timing and application of these multi-part fertilizers should coincide with a plant's growth stage. For example, at the end of an annual plant's life cycle, a plant should be restricted from high nitrogen fertilizers. In most plants, nitrogen restriction inhibits vegetative growth and helps induce flowering.
Sources: en.wikipedia.org
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.
The first four residues of Selank reproduce the tuftsin sequence Thr-Lys-Pro-Arg. A Pro-Gly-Pro extension at the C-terminus was added to slow enzymatic breakdown and extend residence time.
It holds marketing authorization in Russia, where nasal drop formulations are sold. No equivalent approval exists in the European Union, the United States, or most other countries.
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.