The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-08-11 and is reviewed periodically as new material appears.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
| Property | Value | Notes |
|---|---|---|
| Primary route studied | Intranasal | Also examined parenterally in animal work |
| Reported plasma half-life | Minutes to tens of minutes | Values vary widely between reports |
| Main model systems | Rodent behavioural and cell assays | Human trials are few and small |
| Principal proposed targets | GABA-A receptor, GABA transaminase | Monoamine and neurotrophic pathways also reported |
| Evidence grade | Preliminary | Limited independent replication |
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
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 complete blood count is interpreted by comparing the output to reference ranges, which represent the results found in 95% of apparently healthy people. Based on a statistical normal distribution, the tested samples' ranges vary with sex and age. On average, adult females have lower hemoglobin, hematocrit, and red blood cell count values than males; the difference lessens, but is still present, after menopause. CBC results for children and newborn babies differ from those of adults. Newborns' hemoglobin, hematocrit, and red blood cell count are extremely high to compensate for low oxygen levels in the womb and the high proportion of fetal hemoglobin, which is less effective at delivering oxygen to tissues than mature forms of hemoglobin, inside their red blood cells. The MCV is also increased, and the white blood cell count is elevated with a preponderance of neutrophils. The red blood cell count and related values begin to decline shortly after birth, reaching their lowest point at about two months of age and increasing thereafter. The red blood cells of older infants and children are smaller, with a lower MCH, than those of adults. In the paediatric white blood cell differential, lymphocytes often outnumber neutrophils, while in adults neutrophils predominate. Other differences between populations may affect the reference ranges: for example, people living at higher altitudes have higher hemoglobin, hematocrit, and RBC results, and people of African heritage have lower white blood cell counts on average.
=== Early life, start of career and Basel === Photaki was born in Corinth in 1921 and finished her secondary education at the 2nd Girls' Gymnasium of Athens in 1938. In the same year she enrolled at the Department of Chemistry in the University of Athens, where she specialised in Organic chemistry under the mentorship of Leonidas Zervas. Her studies were interrupted during the Axis occupation of Greece when the Laboratory of Organic Chemistry was destroyed and Zervas was imprisoned as a member of the Greek Resistance. Photaki was finally awarded her degree summa cum laude in 1946 and subsequently continued her postgraduate studies under Zervas, earning her PhD in 1950 with a dissertation regarding glucosamine. Concurrently, she held a paid laboratory assistant position at the university already from 1943, carrying on as a research assistant until 1953. In 1953, Photaki was awarded a scholarship to conduct research in Basel after examinations by the Greek State Scholarships Foundation. At the University of Basel she worked in the Laboratory of Organic Chemistry, at the time headed by Nobel laureate Tadeusz Reichstein. For the first two years of her stay (1953–1955) she was part of the Max Brenner research group, later moving as an independent scientific associate of Hans Erlenmeyer. Upon returning to Greece, she initially worked at the biochemical lab of the Evangelismos Hospital before being invited by Zervas to the nascent National Hellenic Research Foundation (NHRF) which he had helped found.
Diazepam undergoes oxidative metabolism by demethylation (CYP2C9, 2C19, 2B6, 3A4, and 3A5), hydroxylation (CYP3A4 and 2C19) and glucuronidation in the liver as part of the cytochrome P450 enzyme system. It has several pharmacologically active metabolites. The main active metabolite of diazepam is desmethyldiazepam (also known as nordazepam or nordiazepam). Its other active metabolites include the minor active metabolites temazepam and oxazepam. These metabolites are conjugated with glucuronide and are excreted primarily in the urine. Because of these active metabolites, the serum values of diazepam alone are not useful in predicting the effects of the drug. Diazepam has a biphasic half-life of about one to three days and two to seven days for the active metabolite desmethyldiazepam. Most of the drug is metabolized; little diazepam is excreted unchanged. The elimination half-life of diazepam and also the active metabolite desmethyldiazepam increases significantly in the elderly, which may result in prolonged action, as well as accumulation of the drug during repeated administration.
Sources: en.wikipedia.org
The Weimaraner is a German breed of hunting dog of medium to large size, with history going back at least to the nineteenth century. It originated in the area of the city of Weimar (then in Saxe-Weimar-Eisenach, now in the state of Thuringia), for which it is named. It was recognised as a breed in 1891. It is an all-purpose gun dog, characterised by its speed and stamina, its good nose and eye, and its courage and intelligence; in Germany it is not considered suitable for keeping as a companion dog.
Til the Casket Drops (2009) was the final Clipse album before the duo split to make solo material. The breakup was initiated by Malice, who had multiple conversations with Pusha T about quitting the duo; the first time was after a studio session with Rick Rubin. Toward the end of the duo's partnership, their then-manager and various people in their personal lives were arrested on drug charges. One day, when both brothers were to board a plane, Pusha T was unusually late, and Malice worried that he had been arrested; although Pusha T eventually boarded, it was the final straw for Malice, who angrily declared to his brother in front of the other passengers that he was done with the duo. Although the breakup wasn't made public at the time, rumors that the duo was over began when Malice (then named Malicious) changed his stage name to No Malice, converted to Christianity, and started making Christian rap, as opposed to the "coke rap" of Clipse. In 2014, he firmly denied the possibility of a reunion. His attitude had softened by 2016: "I'ma tell you that I learned to never say never, and I don't shut the door on anything. I really don't. In fact, I would like to see Clipse do it. But I just do things differently." The duo appeared together (credited as Clipse) on "Use This Gospel" by Kanye West, from his Christian hip-hop and gospel album Jesus Is King (2019), having also worked on a demo version of "Follow God". Speaking on the reunion, Pusha T said: "I'm the younger brother, man.
=== 90Sr === Strontium-90 has been used by the Soviet Union in terrestrial RTGs. 90Sr decays by β− decay into 90Y, which quickly β-decays again. It has a lower decay energy than 238Pu, but its shorter half-life of 28.8 years and lower atomic weight yield a power density for pure metal of 0.95 watts per gram. As 90Sr is a very reactive alkaline earth metal and a bone seeker that accumulates in bone-tissue due to its chemical similarity to calcium (once in the bones it can significantly damage the bone marrow, a rapidly dividing tissue), it is usually not used in pure form in RTGs. The most common form is the perovskite strontium titanate (SrTiO3) which is chemically nigh-inert and has a high melting point. While its Mohs hardness of 5.5 has made it ill-suited as a diamond simulant, it is of sufficient hardness to withstand some forms of accidental release from its shielding without too fine dispersal of dust. The downside to using SrTiO3 instead of the native metal is it reduces power density, as the TiO3 part of the material does not produce any decay heat. 90Sr has a high fission product yield in the fission of both 235U and 239Pu and is thus available in large quantities at a relatively low price if extracted from spent nuclear fuel. Starting from the oxide or the native metal, one pathway to obtaining SrTiO3 is to let it transform to strontium hydroxide in aqueous solution, which absorbs carbon dioxide from air to become less soluble strontium carbonate.
Sources: en.wikipedia.org
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.
The peptide enters plasma rapidly and is broken down by ordinary proteases into amino acids and shorter fragments. Reported half-lives are short. Whether meaningful amounts of the intact molecule reach the brain is an open question.
Most clinical reports are small, published in Russian and not independently replicated. English-language reviews highlight the absence of large randomised trials. Conclusions about efficacy should be treated as provisional.
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.