Semax is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-07-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
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.
The mechanism by which toxicity results is complex, but is believed to involve reaction between unconjugated NAPQI and critical proteins as well as increased susceptibility to oxidative stress caused by the depletion of glutathione.
According to scholar Shirley Anne Tate, skin whiteners in the United States were initially predominantly used by white women. European immigrants introduced recipes for cosmetic skin lighteners into the American colonies, where they eventually evolved to incorporate indigenous and West African herbal traditions. Skin whitening grew in popularity in the 1800s, as white women in the United States began to emulate the skin-whitening practices performed by those in Europe. As such, American women similarly used ceruse, arsenic wafers, and products that contained toxic dosages of lead and mercury. Mormon denominations, like the Church of Jesus Christ of Latter-day Saints (LDS church), taught into the 1970s that God would whiten the skin color of Native American adherents, and that skin color was correlated with premortal obedience to God. In the 2015 book, Skin bleaching in Black Atlantic zones: shade shifters, author Shirley Anne Tate writes that skin lightening was often not well-received in Black culture. Women in Black cultures who used skin whiteners were described as artificial, while Black men who used skin whiteners were described as overly effeminate. Despite this reception, skin whitening remained a popular practice. Historians note that advertisements for skin whiteners in the 20th century often associated pale skin with gentility. According to historian Kathy Peiss, skin whitening among black American women had been documented starting in the mid-nineteenth century.
=== Aortic regurgitation === Patients with aortic regurgitation may experience heart failure symptoms, such as dyspnea on exertion, orthopnea and paroxysmal nocturnal dyspnea, palpitations, and angina pectoris. In acute cases patients may experience cyanosis and circulatory shock. Medical signs of aortic regurgitation include increased pulse pressure by increased systolic and decreased diastolic blood pressure, but these findings may not be significant if acute. The patient may have a diastolic decrescendo murmur best heard at left sternal border, water hammer pulse, Austin Flint murmur, and a displaced apex beat down and to the left. A third heart sound may be present
Sources: en.wikipedia.org
6 May 1986 – USS Ray, USS Archerfish and USS Hawkbill meet and surface together at the Geographic North Pole. First three-submarine surfacing at the Pole. 19 May 1987 – HMS Superb joined USS Billfish and USS Sea Devil at the North Pole. March 2007 – USS Alexandria participated in the Joint US Navy/Royal Navy Ice Exercise 2007 (ICEX-2007) in the Arctic Ocean with the Trafalgar-class submarine HMS Tireless. March 2009 – USS Annapolis took part in Ice Exercise 2009 to test submarine operability and war-fighting capability in Arctic conditions.
People with Aarskog–Scott syndrome often have distinctive facial features, such as widely spaced eyes (hypertelorism), a small nose, a long area between the nose and mouth (philtrum), and a widow's peak hairline. They frequently have mild to moderate short stature during childhood, but their growth usually catches up with that of their peers during puberty. Hand abnormalities are common in this syndrome and include short fingers (brachydactyly), curved pinky fingers (fifth finger clinodactyly), webbing of the skin between some fingers (cutaneous syndactyly), and a single crease across the palm. Other abnormalities in people with Aarskog–Scott syndrome include heart defects and a split in the upper lip (cleft lip) with or without an opening in the roof of the mouth (cleft palate). Most males with Aarskog–Scott syndrome have a shawl scrotum, in which the scrotum surrounds the penis instead of hanging below. Less often, they have undescended testes (cryptorchidism) or a soft out-pouching around the belly-button (umbilical hernia) or in the lower abdomen (inguinal hernia). The intellectual development of people with Aarskog–Scott syndrome varies widely. Some may have mild learning and behavior problems, while others have normal intelligence. In rare cases, severe intellectual disability has been reported.
Droplet countercurrent chromatography (DCCC) was introduced in 1970 by Tanimura, Pisano, Ito, and Bowman. DCCC uses only gravity to move the mobile phase through the stationary phase which is held in long vertical tubes connected in series. In the descending mode, droplets of the denser mobile phase and sample are allowed to fall through the columns of the lighter stationary phase using only gravity. If a less-dense mobile phase is used it will rise through the stationary phase; this is called ascending mode. The eluent from one column is transferred to another; the more columns that are used, the more theoretical plates can be achieved. DCCC enjoyed some success with natural product separations but was largely eclipsed by the rapid development of high-speed countercurrent chromatography. The main limitation of DCCC is that flow rates are low, and poor mixing is achieved for most binary solvent systems.
Sources: en.wikipedia.org
Despite this shift, bismuth therapies persisted in several regions, such as France, where they remained in use for specific stages of the disease until at least the late 1970s. "Milk of bismuth" (an aqueous suspension of bismuth hydroxide and bismuth subcarbonate) was marketed as an alimentary cure-all in the early 20th century, and has been used to treat gastrointestinal disorders. Bismuth subnitrate (Bi5O(OH)9(NO3)4) and bismuth subcarbonate (Bi2O2(CO3)) are also used in medicine.
== Adverse effects == Side effects from taking glimepiride include gastrointestinal tract (GI) disturbances, occasional allergic reactions, and rarely blood production disorders including thrombocytopenia, leukopenia, and hemolytic anemia. In the initial weeks of treatment, the risk of hypoglycemia may be increased. Alcohol consumption and exposure to sunlight should be restricted because they can worsen side effects.
Brain levels of endogenous trace amines are several hundred-fold below those for the classical neurotransmitters noradrenaline, dopamine, and serotonin, but their rates of synthesis are equivalent to those of noradrenaline and dopamine and they have a very rapid turnover rate. Endogenous extracellular tissue levels of trace amines measured in the brain are in the low nanomolar range. These low concentrations arise because of their very short half-life. Because of the pharmacological relationship between phenethylamine and amphetamine, the original paper and both reviews suggest that phenethylamine plays a prominent role in mediating the mood-enhancing euphoric effects of a runner's high, as both phenethylamine and amphetamine are potent euphoriants. Skydiving has also been shown to induce a marked increase in urinary phenethylamine concentrations.
The Digico Micro 16V had a standard memory of 4k words with 950 nano second cycle time, expandable to 64k words, and able to support up to 64 external interfaces. It had an optional microprogrammed floating-point unit. The Micro 16V was supported by a simple and flexibly sized executive that could optionally support multiprogramming, disc files and teletypes. The Micro 16V used semiconductor memory, rather than magnetic-core memory as in the previous models. The instruction set architecture is single accumulator based with instructions generally having a consistent 12-bit address field. A direct address thus limits memory size to 4k (4096) words in the current selected memory region, named a "stack". Three instructions (load, store, add) permit indirect addressing where the direct address contains the 16-bit address of the operand. A carry register supports multi-word arithmetic; there is no integer multiply or divide instruction. One instruction uses the address field to specify a variety of non-addressing sub-instructions such as shift, carry manipulation and input-output. Floating-point arithmetic is handled by software or an optional floating-point unit with its own registers that can work in 32, 48 or 80-bit modes. The Micro 16 sold primarily into the data logging market until 1969, when it expanded into areas like process control, stock control and front-end processors for the ICL 1900 mainframe. In 1978 the Digico Micro 16E stackable minicomputer, which was well suited to an office environment, won a Design Council Award for Engineering Products.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.