intranasal delivery raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-04-01 and is reviewed periodically as new material appears.
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
== Z == Zeaxanthin 7,8-dioxygenase - Zfp14 zinc finger protein - Zfp28 zinc finger protein - zinc finger - Zinc finger and scan domain containing 30 - Zinc finger containing ubiquitin peptidase 1 - Zinc finger nfx1-type containing 1 - Zinc finger protein 93 - Zinc finger protein 101 - Zinc finger protein 175 - Zinc finger protein 222 - Zinc finger protein 230 - Zinc finger protein 280b - Zinc finger protein 296 - Zinc finger protein 414 - Zinc finger protein 433 - Zinc finger protein 490 - Zinc finger protein 530 - Zinc finger protein 556 - Zinc finger protein 562 - Zinc finger protein 574 - Zinc finger protein 577 - Zinc finger protein 585b - Zinc finger protein 586 - Zinc finger protein 730 - Zinc finger protein 770 - Zinc finger protein 773 - Zinc finger protein 780a - Zinc finger protein 780b - Zinc finger protein 791 - Zinc finger protein 836 - Zinc finger protein 846
=== Academic career === William H. Stein began his higher education as a chemistry major at Harvard University in 1929. He spent one year as a graduate student at Harvard University before transferring to the Department of Biological Chemistry at the College of Physicians and Surgeons, Columbia University, in 1934 to focus on biochemistry. Hans Thatcher Clarke, the chairman of the department at the time, was collecting many talented graduate students who would become the distinguished biochemists of the early twentieth century. In 1937, Stein completed his thesis on the amino acid composition of elastin, earning his Ph.D. Stein was introduced to potassium trioxalatochromate and ammonium rhodanilate by Max Bergmann, a Jewish-German biochemist who fled to the United States in 1934 under threat of Nazi occupation and worked in a laboratory at the Rockefeller Institute. He used these two precipitating agents to isolate the amino acids glycine and proline, respectively, for his research on elastin. With the conclusion of his academic career, Stein went on to work under Bergmann.
=== Amélie of Leuchtenberg === Amélie of Leuchtenberg (1812–1873) was Empress of Brazil as the wife of Emperor Pedro I (also King Pedro IV of Portugal). Between February and September 2012, researchers from the University of São Paulo exhumed her remains, along with those of Pedro I and his first wife, Maria Leopoldina. The investigation revealed that Amélie's body had been mummified, with her skin, hair, and internal organs preserved. Forensic examinations at the Hospital das Clínicas identified an incision in the jugular vein, used to inject aromatic substances such as camphor and myrrh during the original embalming. According to forensic archaeologist Valdirene Ambiel, the preservation was aided by the casket's hermetic seal, which prevented the growth of microorganisms. Before reinterment, the body was re-embalmed using methods similar to the original 19th-century process. The remains of Amélie, Pedro I, and Maria Leopoldina are interred within the crypt of the Monument to the Independence of Brazil in São Paulo.
Sources: en.wikipedia.org
=== Insects and fish === It is attractive to males of various species of orchid bees, which apparently gather the chemical to synthesize pheromones; it is commonly used as bait to attract and collect these bees for study. It also attracts female cucumber beetles. Eugenol and isoeugenol, which both are floral volatile scent compounds, are catalyzed by a single type of enzyme in the genus Gymnadenia and the gene encoding for this enzyme is the first functionally characterized gene in these species. Eugenol is an ingredient in some insecticides. Clove oil is common as an anesthetic for use on aquarium fish as well as on wild fish when sampled for research and management purposes. Where readily available, it presents a humane method to euthanize sick and diseased fish either by direct overdose or to induce sleep before an overdose of eugenol.
[PtCl4]2- + 2 H2NCH(R)CO2− → [Pt(H2NCH(R)CO2)2] + 4 Cl− Relevant to bioinorganic chemistry, amino acid complexes can be generated by the hydrolysis of amino acid esters and amides (en = ethylenediamine):
They tend to be reactive towards metals, except for the noble gases, which are inert towards most substances. They are brittle when solid as their atoms are held tightly in place. They are less dense and conduct electricity poorly, because there are no mobile electrons. Near the borderline, band gaps are small and thus many elements in that region are semiconductors, such as silicon, germanium, and tellurium. Selenium has both a semiconducting grey allotrope and an insulating red allotrope; arsenic has a metallic grey allotrope, a semiconducting black allotrope, and an insulating yellow allotrope (though the last is unstable at ambient conditions). Again there are exceptions; for example, diamond has the highest thermal conductivity of all known materials, greater than any metal. It is common to designate a class of metalloids straddling the boundary between metals and nonmetals, as elements in that region are intermediate in both physical and chemical properties. However, no consensus exists in the literature for precisely which elements should be so designated. When such a category is used, silicon, germanium, arsenic, and tellurium are almost always included, and boron and antimony usually are; but most sources include other elements as well, without agreement on which extra elements should be added, and some others subtract from this list instead. For example, unlike all the other elements generally considered metalloids or nonmetals, antimony's only stable form has metallic conductivity.
The bacteria might induce systemic resistance in the host plant, so it can better resist attack by a true pathogen. The bacteria might outcompete other (pathogenic) soil microbes, e.g., by siderophores, giving a competitive advantage at scavenging for iron. The bacteria might produce compounds antagonistic to other soil microbes, such as phenazine-type antibiotics or hydrogen cyanide. To be specific, certain P. fluorescens isolates produce the secondary metabolite 2,4-diacetylphloroglucinol (2,4-DAPG), the compound found to be responsible for antiphytopathogenic and biocontrol properties in these strains. The phl gene cluster encodes factors for 2,4-DAPG biosynthesis, regulation, export, and degradation. Eight genes, phlHGFACBDE, are annotated in this cluster and conserved organizationally in 2,4-DAPG-producing strains of P. fluorescens. Of these genes, phlD encodes a type III polyketide synthase, representing the key biosynthetic factor for 2,4-DAPG production. PhlD shows similarity to plant chalcone synthases and has been theorized to originate from horizontal gene transfer. Phylogenetic and genomic analysis, though, has revealed that the entire phl gene cluster is ancestral to P. fluorescens, many strains have lost the capacity, and it exists on different genomic regions among strains. Some experimental evidence supports all of these theories, in certain conditions; a good review of the topic is written by Haas and Defago. Several strains of P. fluorescens, such as Pf-5 and JL3985, have developed a natural resistance to ampicillin and streptomycin.
Sources: en.wikipedia.org
This is an important consideration because cholesterol—the precursor to all steroid hormones—does not leave the membrane once it has embedded itself inside. The difference between cholesterol and these hormones is that cholesterol is in a much larger negative Gibb's free energy well once inside the membrane, as compared to these hormones. This is because the aliphatic tail on cholesterol has a very favorable interaction with the interior of lipid bilayers.
=== Initial development === A predecessor compound of minoxidil was developed in the late 1950s by the Upjohn Company (later became part of Pfizer) to treat ulcers. In trials using dogs, the compound did not cure ulcers but proved to be a powerful vasodilator. Upjohn synthesized over 200 variations of the compound, including the one it developed in 1963 and named minoxidil. These studies resulted in the U.S. Food and Drug Administration (FDA) approving minoxidil (with the brand name Loniten) in the form of oral tablets to treat high blood pressure in 1979.
This is seen as the beginning of the second phase of the 1948 Palestine war. June 12: Mátyás Rákosi becomes General Secretary of the Hungarian Working People's Party and, therefore, the de facto leader of the Second Hungarian Republic. June 18: A communist insurgency in Malaya begins against British and Commonwealth forces. June 21: In Germany, the British zone and the French zone launch a common currency, the Deutsche Mark. June 24: Stalin orders the Berlin Blockade, closing all land routes from West Germany to Berlin, in an attempt to starve out the French, British, and American forces from the city. In response, the three Western powers launch the Berlin Airlift to supply the citizens of Berlin by air. June 28: The Soviet Union expels Yugoslavia from the Communist Information Bureau (COMINFORM) for the latter's position on the Greek Civil War. June 28: Stalin attempts to starve West Berlin with a blockade. The Berlin Airlift begins. August 1: French zone of occupation created in Germany and Berlin. August 15: The United States declares the Republic of Korea to be the legitimate government of the Korean Peninsula, with Syngman Rhee installed as the leader. September 9: The Soviet Union declares the Democratic People's Republic of Korea to be the legitimate government of all of the Korean Peninsula, with Kim Il Sung installed as the leader. September 11: Muhammad Ali Jinnah dies. September 13: India annexes Hyderabad under the code name, Operation Polo.
Sources: en.wikipedia.org
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.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.