Peptidase stability 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 2025-12-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Route studied | Intranasal | Predominant route in published reports |
| Circulation stability | Short, minutes scale | Peptidases cleave it; the tail slows the process |
| Analytical method | RP-HPLC with mass spectrometry | Used for identity and purity assessment |
| Reported outcome domains | Anxiety and cognitive measures | Derived from small, mostly regional trials |
| Regulatory status | Marketed in Russia | Availability outside that market is limited |
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
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.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
Muscimol is said to have similar effects on sleep in rodents as the related experimental pharmaceutical drug gaboxadol (THIP). In humans, gaboxadol decreases sleep onset latency, increases sleep duration, increases slow wave sleep (SWS) and slow wave activity (SWA), and does not suppress REM sleep. The effects of muscimol and gaboxadol on sleep differ from those of widely used GABAA receptor positive allosteric modulators like benzodiazepines and Z-drugs, which can instead disrupt SWS and SWA despite improving sleep onset and duration. Although muscimol and gaboxadol have similar effects on sleep, muscimol has additionally been found to increase REM sleep unlike gaboxadol. Ibotenic acid, a prodrug of muscimol, is active at doses of approximately 20 to 100 mg orally in humans. About 10 to 20% of ibotenic acid is said to be converted into muscimol following decarboxylation. Substantial amounts of ibotenic acid are also rapidly excreted unchanged.
Many different foods can be prepared by dehydration. Meat has held a historically significant role. For centuries, much of the European diet depended on dried cod—known as salt cod, bacalhau (with salt), or stockfish (without). It formed the main protein source for the slaves on the West Indian plantations, and was a major economic force within the triangular trade. Dried fish most commonly cod or haddock, known as Harðfiskur, is a delicacy in Iceland, while dried reindeer meat is a traditional Sámi food. Dried meats include prosciutto (Parma ham), bresaola, biltong and beef jerky. Dried fruits have been consumed historically due to their high sugar content and sweet taste, and a longer shelf-life from drying. Fruits may be used and named differently when dried. The plum becomes a prune, the grape a raisin. Figs and dates may be transformed into different products that can either be eaten as they are, used in recipes, or rehydrated. Freeze-dried vegetables are often found in food for backpackers, hunters, and the military. Garlic and onion are often dried and stored with their stalks braided. Edible mushrooms are sometimes dried for preservation or to be used as seasonings.
Secondary algae are eukaryotes with "secondary chloroplasts", i.e. those evolved from phagocytosis and subsequent endosymbiosis of primary algae (mainly green or red algae) or other secondary algae, thus "stealing" the endosymbionts' photosynthetic capability. As a result, these algae have chloroplasts surrounded by three or more membranes, and appeared independently in various distantly related protist lineages. Two lineages of secondary algae, chlorarachniophytes and euglenophytes have "green" chloroplasts containing chlorophylls a and b. Their chloroplasts are surrounded by four and three membranes, respectively, and were probably retained from ingested green algae.
==== HCG Pubergen, Pregnyl warnings ==== In the case of female patients who want to be treated with HCG Pubergen, Pregnyl: a) Since infertile female patients who undergo medically assisted reproduction (especially those who need in vitro fertilization), are known to often be suffering from tubal abnormalities, after a treatment with this drug they might experience many more ectopic pregnancies. This is why early ultrasound confirmation at the beginning of a pregnancy (to see whether the pregnancy is intrauterine or not) is crucial. Pregnancies that have occurred after a treatment with this drug have a higher risk of multiple pregnancy. Female patients who have thrombosis, severe obesity, or thrombophilia should not be prescribed this medicine as they have a higher risk of arterial or venous thromboembolic events after or during a treatment with HCG Pubergen, Pregnyl. b)Female patients who have been treated with this medicine are usually more prone to pregnancy losses. In the case of male patients: A prolonged treatment with HCG Pubergen, Pregnyl is known to regularly lead to increased production of androgen. Therefore: Patients who have overt or latent cardiac failure, hypertension, renal dysfunction, migraines, or epilepsy might not be allowed to start using this medicine or may require a lower dose of HCG Pubergen, Pregnyl. This drug should be used with extreme caution in the treatment of prepubescent teenagers in order to reduce the risk of precocious sexual development or premature epiphyseal closure.
Sources: en.wikipedia.org
== History == One of the challenges in studying abiogenesis is that the system of reproduction and metabolism utilized by all extant life involves three distinct types of interdependent macromolecules (DNA, RNA, and proteins), none of which can function and reproduce without the others, the classic chicken-and-egg paradox. This suggests that life could not have arisen in its current form, which has led researchers to hypothesize mechanisms whereby the current system might have arisen from a simpler precursor system. American molecular biologist Alexander Rich was the first to posit a coherent hypothesis on the origin of nucleotides as precursors of life. In a 1962 article he explained that the primitive Earth's environment could have produced RNA molecules (polynucleotide monomers) that eventually acquired enzymatic and self-replicating functions. Other mentions of RNA as a primordial molecule can be found in papers by Francis Crick and Leslie Orgel, as well as in Carl Woese's 1967 book The Genetic Code. Hans Kuhn in 1972 laid out a possible process by which the modern genetic system might have arisen from a nucleotide-based precursor, and this led Harold White in 1976 to observe that many of the cofactors essential for enzymatic function are either nucleotides or could have been derived from nucleotides.
== Matrix-assisted laser desorption/ionization == MALDI is an ionization technique where laser energy is absorbed by a matrix to create ions from large molecules without fragmentation. The matrix, typically in excess, is mixed with the analyte molecule and deposited on a target. A table of matrix compounds, their structures, laser wavelengths typically used, and typical application is shown below.
=== Form factor === The physical design of refrigerators also plays a large part in its energy efficiency. The most efficient is the chest-style freezer, as its top-opening design minimizes convection when opening the doors, reducing the amount of warm moist air entering the freezer. On the other hand, in-door ice dispensers cause more heat leakage, contributing to an increase in energy consumption.
Plastination is a technique or process used in anatomy to preserve bodies or body parts, first developed by Gunther von Hagens in 1977. The water and fat are replaced by certain plastics, yielding specimens that can be touched, do not smell or decay, and even retain most properties of the original sample.
=== Infertility === It can be difficult to become pregnant with PMOS due to irregular ovulation. The first management step is to improve the general health of the mother, such as through lifestyle interventions. GLP-1 agonist for weight loss can be used, but should be stopped at least 2 months before conception. As of 2025, there is not enough data to know if they are safe in pregnancy. Pregnancy in PMOS is more risky than normal, and treatment is focused on getting a single pregnancy, rather than, for instance, twins (multiple pregnancy). With treatment, the eventual family size of women with PMOS does not seem different to those without. The first-line medical treatment for infertility in women with PMOS is letrozole (Femara) to induce ovulation. This is, in general, more effective than clomiphene citrate to improve both pregnancy rates and live births. Other medications that can be used to treat infertility, listed from most to least effective, are metformin + clomiphene citrate, clomiphene citrate alone, and metformin alone. Women may be more likely to experience gastrointestinal side effects with metformin. Gonadotrophin therapy may be effective too, but requires monitoring and increases the risks of multiple pregnancies. When medication and lifestyle interventions are ineffective, infertility can be treated with a laparoscopic procedure called "ovarian drilling", which involves puncture of 4–10 small follicles with electrocautery, laser, or biopsy needles.
Sources: en.wikipedia.org
== Further reading == WHO traditional medicine strategy: 2014-2023. World Health Organization. 2013. hdl:10665/92455. ISBN 978-92-4-150609-0. Retrieved 1 April 2023. Baran GR, Kiana MF, Samuel SP (2014). "Chapter 2: Science, Pseudoscience, and Not Science: How Do They Differ?". Healthcare and Biomedical Technology in the 21st Century. Springer. pp. 19–57. doi:10.1007/978-1-4614-8541-4_2. ISBN 978-1-4614-8540-7. Barnes, Linda L. (2005). Needles, Herbs, Gods, and Ghosts: China, Healing, and the West to 1848. Cambridge, Mass: Harvard University Press. ISBN 0-674-01872-9. Shows early use of Chinese medicine not always perceived as "Chinese." Baum, Emily (2020). "Medicine and Public Health in Twentieth-Century China: Histories of Modernization and Change". History Compass. 18 (7) e12616. doi:10.1111/hic3.12616. S2CID 225622823. Liu, Lihong (2019). Classical Chinese Medicine. Translated by Weiss, Gabriel; Henry Buchtel; Sabine Wilms. Shatin, NT Hong Kong: Chinese University of Hong Kong Press; distributed by Columbia University Press. ISBN 978-988-237-057-9. Lloyd, G. E. R.; Sivin, Nathan (2002). The Way and the Word: Science and Medicine in Early China and Greece. New Haven: Yale University Press. ISBN 0-300-09297-0. Lo, Vivienne; Stanley-Baker, Michael, eds. (2022), Routledge Handbook of Chinese Medicine, New York: Routledge, ISBN 978-0-415-83064-5 The Open Access version of this book, available at Online Open Access Archived 4 March 2024 at the Wayback Machine, has been made available under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license.
Gynecomastia (also spelled gynaecomastia) is the non-cancerous enlargement of one or both breasts in men due to the growth of breast tissue as a result of a hormone imbalance between estrogens and androgens. Physically speaking, gynecomastia is completely benign, but it is associated with significant psychological distress, social stigma, and dysphoria. Gynecomastia can be normal in newborn male babies due to exposure to estrogen from the mother, in adolescent boys going through puberty, in older men over the age of 50, and in obese men. Most occurrences of gynecomastia do not require diagnostic tests. Abnormal hormone changes that cause gynecomastia may be caused by any condition that leads to an increase in the ratio of estrogens/androgens such as liver disease, kidney failure, thyroid disease and some non-breast tumors. Alcohol and some drugs can also cause breast enlargement. Other causes may include Klinefelter syndrome, metabolic dysfunction, or a natural decline in testosterone production. This may occur even if the levels of estrogens and androgens are both appropriate, but the ratio is altered. Gynecomastia is the most common benign disorder of the male breast tissue and affects 35% of men, being most prevalent between the ages of 50 and 69. It is normal for up to 70% of adolescent boys to develop gynecomastia to some degree. Of these, 75% resolve within two years of onset without treatment. If the condition does not resolve within 2 years, or if it causes embarrassment, pain or tenderness, treatment is warranted.
=== Sensory === PDL is heavily innervated; it involves mechanoreception, nociception and reflexes. Periodontal mechanoreceptors are present in PDL. They will transmit information about the stimulated tooth, direction and amplitude of forces.
where ci and zi stand for the concentration and ionic charge of ion type i, and the sum is taken over all the N types of charged species in solution. When the concentration of dissolved salt is much higher than the analytical concentrations of the reagents, the ions originating from the dissolved salt determine the ionic strength, and the ionic strength is effectively constant. Since activity coefficients depend on ionic strength, the activity coefficients of the species are effectively independent of concentration. Thus, the assumption that Γ is constant is justified. The concentration quotient is a simple multiple of the equilibrium constant.
== See also == Maintenance respiration: maintenance as a functional component of cellular respiration Microphysiometry Pasteur point Respirometry: research tool to explore cellular respiration Tetrazolium chloride: cellular respiration indicator Complex 1: NADH:ubiquinone oxidoreductes
Sources: en.wikipedia.org
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.
Intranasal delivery is the route described in most published work. It is used because the peptide is degraded quickly once it reaches circulation. Direct evidence of brain penetration in humans is lacking.
Most trials are small, regionally concentrated, and often lack rigorous blinding or placebo control. Independent replication is limited. Reviews in English generally rate the evidence as preliminary.
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.