All articles starting with S
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Selenium-stabilized carbanions, ylides and radicals
Selenium-stabilized carbanions, ylides and radicals are three families of reactive organoselenium intermediates, stabilized by the selenium atom and used in synthesis for carbon–carbon bond formation, epoxidation, and cyclopropanation.
Selennyakh
Selennyakh (Селеннях; Yakut Силээннээх), a 796 km left tributary of the Indigirka in Yakutia, Russia, draining 30,800 km² from the Chersky Range through the Moma-Selennyakh Depression and Aby Lowland; mean discharge about 180-220 m³/s, freezes October to May.
Selenocarbonyl and tellurocarbonyl compounds
Selenocarbonyl and tellurocarbonyl compounds are the selenium and tellurium analogs of carbonyl compounds, containing C=Se or C=Te double bonds; they are far less stable than oxygen and sulfur counterparts and often must be trapped as cycloadducts.
Selenocysteine
Selenocysteine (Sec, U), the 21st amino acid, is cysteine with selenium replacing sulfur. Encoded by UGA with SECIS elements, it has pKa 5.2, high nucleophilicity, and forms the catalytic center of 25 human selenoproteins.
Selenocysteine tRNA and selenocysteine decoding
Selenocysteine decoding is the process by which tRNA charged with selenocysteine reads selected UGA stop codons, directed by an mRNA structure called the SECIS element.
Selenoethers and telluroethers
Selenoethers and telluroethers, formally called selenides and tellurides, are organochalcogen compounds in which a divalent selenium or tellurium atom bonds two organic groups, valued as ligands and synthesis intermediates.
Selenol
Selenol, also called selenomercaptan or selenothiol, is an organoselenium compound of structure RSeH, the selenium analog of a thiol, found biologically as selenocysteine and methylselenol.
Selenolate and tellurolate anions
Selenolate (RSe−) and tellurolate (RTe−) anions are anionic selenium and tellurium species that act as soft nucleophiles in carbon–chalcogen bond formation, typically generated by reductive cleavage of diselenides and ditellurides.
Selenomethionine
Selenomethionine (SeMet) is the selenium analog of the amino acid methionine, occurring in cereal grains, soybeans, and enriched yeast and widely used as a dietary supplement.
Selenomonas
Selenomonas, also called moon monad, is a genus of anaerobic, Gram-stain-negative rods in Selenomonadaceae; ruminal and oral species, with 2026 reclassification moving S. ruminantium to Pseudoselenomonas.
Selenophosphate synthetase
Selenophosphate synthetase (SelD; SPS2/SEPHS2, EC 2.7.9.3) synthesizes selenophosphate from selenide and ATP, the selenium donor for selenocysteine and 2-selenouridine; its inactive metazoan paralog SPS1 regulates redox homeostasis.
Selenoprotein
Selenoproteins are proteins containing selenocysteine, the 21st genetically encoded amino acid, inserted at UGA codons via SECIS-dependent recoding. Humans have 25 selenoprotein genes, mostly antioxidant oxidoreductases such as glutathione peroxidases and thioredoxin reductases.
Selenoprotein P
Selenoprotein P (SELENOP, SEPP1), liver-made plasma glycoprotein with 10 selenocysteine residues; transports selenium to brain and testis via ApoER2, acts as antioxidant, and serves as biomarker of selenium status.
Selenopyrylium
Selenopyrylium is a six-membered heteroaromatic cation in which selenium replaces the oxygen of pyrylium; its salts are handled as isolable ionic compounds used as photosensitizers, laser dyes, and synthesis intermediates.
Selenourea
Selenourea is the selenium analog of urea, an organoselenium compound with formula CH4N2Se, used as a synthetic building block, ligand, and phasing reagent in protein crystallography.
Selenoxide elimination
Selenoxide elimination is a mild, concerted syn elimination in which an alkyl selenoxide loses a β-hydrogen and the selenium group to form an alkene and a selenenic acid, often at room temperature.
Selenoxides and selenones
Selenoxides and selenones are organoselenium compounds, R2Se=O and R2SeO2, prepared by oxidation of selenides; selenoxides bearing a beta-hydrogen eliminate to alkenes at or below room temperature, underpinning a widely used route to α,β-unsaturated carbonyl compounds.
Seletracetam
Seletracetam (ucb 44212) is an investigational second-generation racetam antiseizure drug, a levetiracetam derivative binding SV2A with tenfold higher affinity; reached phase IIa for epilepsy, discontinued in favor of brivaracetam, now redeveloped intranasally by PrevEp for acute seizure rescue.
Seleucia/Claudioseleucia/Seleucia Sidera
Seleucia Sidera (Claudioseleucia), a Seleucid colony in northern Pisidia near Bayat, Isparta, Türkiye, founded by Seleucus I or Antiochus I to guard a military road; known for iron metallurgy and a fifth-century AD blacksmith workshop.
Seleucid Empire
The Seleucid Empire (312–64 BCE), founded by Seleucus I Nicator, was the largest Hellenistic successor state to Alexander's empire, ruled from Antioch and Seleucia, fought the Ptolemies and Parthians, and fell to Rome in 64 BCE.
Seleucid era
The Seleucid era, also called the era of the Greeks, is a system of continuous year numbering beginning in 312/11 BCE, used across the Middle East into the twentieth century.
Seleucid–Mauryan War
The Seleucid–Mauryan War (सेल्यूकस–मौर्य युद्ध) was the 305–303 BC conflict between Seleucus I Nicator and Chandragupta Maurya, ending with Seleucus ceding three satrapies for 500 war elephants.
Seleucid–Parthian War of Arsaces I
The Seleucid–Parthian War of Arsaces I (جنگ سلوکی–اشکانی) was a mid-3rd-century BC conflict in which Arsaces I invaded Parthia around 238 BC, killed the satrap Andragoras, and defeated Seleucus II.
Seleucus (son of Bithys)
Seleucus, son of Bithys, was a Ptolemaic official of probable Rhodian origin who governed Cyprus as general, admiral, and high priest under Ptolemy VIII, known from four honorific inscriptions dated 142–131 BC.
Seleucus I Nicator
Seleucus I Nicator (c. 358–354–281 BC), Macedonian officer of Alexander and founder of the Seleucid Empire; won Babylonia in 312, traded eastern lands to Chandragupta for 500 elephants, won Ipsus (301) and Corupedium (281), founded Antioch and Seleucia, assassinated by Ptolemy Keraunos.
SELEX
SELEX (Systematic Evolution of Ligands by EXponential enrichment) is an in vitro selection method, reported in 1990, that isolates aptamers binding a chosen target molecule.
Selexipag
Selexipag (Uptravi, ACT-293987, NS-304) is an oral, non-prostanoid prostacyclin IP receptor agonist prodrug for pulmonary arterial hypertension, hydrolyzed to ACT-333679; approved 2015 after the GRIPHON trial.
Self
In philosophy, the self is the subject of a person's own experience and identity, sometimes meaning an unchanging, immaterial subject of consciousness rather than the person.
Self (film)
Self (2024) is a six-minute Pixar SparkShorts stop-motion/CGI short directed by Searit Huluf, released on Disney+ February 2, 2024, about a wooden doll's ill-fated wish to fit in, exploring self-sabotage and Ethiopian immigrant identity.
Self Administration
Self Administration: a person administering a drug or biomedical intervention to themselves, under physician direction (MeSH D012646, 1977) or per WHO self-care definitions; distinct from self-medication, spanning hospital SAM schemes, OPAT, contraception, and addiction research.