The short version of intranasal delivery fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-02. Anything still debated is marked as such rather than presented as settled.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
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.
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.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
| 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 |
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
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.
=== Widespread application === Since the 1950s, electrophoresis methods have diversified considerably, and new methods and applications are still being developed as affinity electrophoresis, capillary electrophoresis, electroblotting, electrophoretic mobility shift assay, free-flow electrophoresis, isotachophoresis, preparative native PAGE, and pulsed-field gel electrophoresis.
When total translated protein was run on an SDS-polyacrylamide gel electrophoresis and sucrose gradient, peaks corresponding to insulin and proinsulin were isolated. However, to the surprise of Weber a third peak was isolated corresponding to a molecule larger than proinsulin. After reproducing the experiment several times, he consistently noted this large peak prior to proinsulin that he determined must be a larger precursor molecule upstream of proinsulin. In May 1975, at the American Diabetes Association meeting in New York, Weber gave an oral presentation of his work where he was the first to name this precursor molecule "preproinsulin". Following this oral presentation, Weber was invited to dinner to discuss his paper and findings by Donald Steiner, a researcher who contributed to the characterization of proinsulin. A year later in April 1976, this molecule was further characterized and sequenced by Steiner, referencing the work and discovery of Hans Weber. Preproinsulin became an important molecule to study the process of transcription and translation. The first genetically engineered (recombinant), synthetic human insulin was produced using E. coli in 1978 by Arthur Riggs and Keiichi Itakura at the Beckman Research Institute of the City of Hope in collaboration with Herbert Boyer at Genentech. Genentech, founded by Swanson, Boyer and Eli Lilly and Company, went on in 1982 to sell the first commercially available biosynthetic human insulin under the brand name Humulin.
== Mechanism == The in vivo mechanism of action is not entirely clear, but an inhibition of the enzyme phosphodiesterase causing elevation of cyclic AMP and cyclic GMP levels is significant. It may also alter mitochondrial respiration. Papaverine has also been demonstrated to be a selective phosphodiesterase inhibitor for the PDE10A subtype found mainly in the striatum of the brain. When administered chronically to mice, it produced motor and cognitive deficits and increased anxiety, but conversely may produce an antipsychotic effect, although not all studies support this view.
=== 1960 === January 10: British prime minister Harold Macmillan delivers his first 'Wind of Change' speech in Accra. His speech hints at a move towards decolonisation of British possessions in Africa. January 19: The United States and Japan sign the Treaty of Mutual Cooperation and Security, a defence treaty allowing the US to maintain military bases in Japan. February 11: Skirmishes on the Chinese-Indian border cause the deaths of 12 Indian soldiers. February 16: France successfully tests its first atomic bomb, Gerboise Bleue, in the middle of the Algerian Sahara Desert. April: Jupiter IRBM deployment to Italy begins, placing nuclear missiles within striking range of Moscow (as with the Thor IRBMs deployed in the UK). April 25: The April Revolution ousts South Korean President Syngman Rhee from office and installs Yun Posun as president. May 1: American pilot Francis Gary Powers is shot down in his U-2 spy plane while flying at high altitude over the Soviet Union, resulting in the U-2 Incident, an embarrassment for President Eisenhower. June: Sino-Soviet split: the Chinese leadership, angered at being treated as the "junior partner" to the Soviet Union, declares its version of Communism superior and begin to compete with the Soviets for influence, thus adding a third dimension to the Cold War. June 15: Following the April Revolution the Second Republic of Korea is created. July 1: A Soviet fighter jet shoots down an RB-47 reconnaissance plane over the Barents Sea, resulting in the 1960 RB-47 shootdown incident. July 5: The Congo Crisis begins.
Sources: en.wikipedia.org
Sperm count, or sperm concentration to avoid confusion with total sperm count, measures the concentration of sperm in ejaculate, distinguished from total sperm count, which is the sperm count multiplied with volume. Over 16 million sperm per milliliter is considered normal, according to the WHO in 2021. Older definitions state 20 million. A lower sperm count is considered oligozoospermia. A vasectomy is considered successful if the sample is azoospermic (zero sperm of any kind found). Cryptozoospermia is when a sample contains less than 100,000 spermatozoa per milliliter. Some define success as when rare/occasional non-motile sperm are observed (fewer than 100,000 per millilitre). Others advocate obtaining a second semen analysis to verify the counts are not increasing (as can happen with re-canalization) and others still may perform a repeat vasectomy for this situation. Chips for home use are emerging that can give an accurate estimation of sperm count after three samples taken on different days. Such a chip may measure the concentration of sperm in a semen sample against a control liquid filled with polystyrene beads.
For the above reasons, the demand for in-situ analysis is increasing. In-situ means analyzing monazite grains in their original host rocks without separation (refer to in situ) such that the texture and zonation pattern are kept intact in order to reveal a more comprehensive geological history of the host rock. Direct sampling techniques, high spatial resolution and precision are required for in-situ analysis. With technological advancement, more and more measurement tools such as laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and laser microprobe mass spectrometer (LMMS) are capable of such analysis.
== Veterinary use == The veterinary use of chlorpromazine has generally been superseded by the use of acepromazine. Chlorpromazine may be used as an antiemetic in dogs and cats, or, less often, as a sedative before anesthesia. In horses, it often causes ataxia and lethargy and is therefore seldom used. It is commonly used to decrease nausea in animals that are too young for other common antiemetics. It is sometimes used as a preanesthetic and muscle relaxant in cattle, swine, sheep, and goats. The use of chlorpromazine in food-producing animals is not permitted in the European Union, as a maximum residue limit could not be determined following assessment by the European Medicines Agency.
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.