lyophilised powder raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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 a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
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.
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.
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.
| 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 |
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.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
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.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
=== Migraine prophylaxis === Candesartan may be helpful in migraine prevention as it has better tolerability and fewer side effects compared to other first line medications. It has been recommended by multiple guidelines for migraine prophylaxis in adults with different levels of recommendations, however further studies on larger populations are needed.
== Prognosis == Mortality in affected felid litters varies between 20 and 100%. Mortality of FPLV is 25–90% in domestic cats with the acute form of the disease and up to 100% in cats with peracute disease. In 2010, a retrospective study of 244 infected cats showed that "leukocyte and thrombocyte counts as well as serum albumin and potassium concentrations at presentation are prognostic indicators in cats with panleukopenia, whereas vaccination status, age, clinical signs, and housing conditions are not." A survival rate of about 50% has been reported with supportive therapies. Cats with FPLV that survive the first five days of treatment usually recover; however, the decrease in the cat's white blood cells compromises its immune system, leaving it vulnerable to secondary infection. Lifelong immunity is thought to follow recovery from disease, and a carrier state of the disease has never been identified.
Hypospermia is a condition in which a man has an unusually low ejaculate (or semen) volume, less than 1.5 mL. It is the opposite of hyperspermia, which is a semen volume of more than 5.5 mL. It should not be confused with oligospermia, which means low sperm count. Normal ejaculate when a man is not drained from prior sex and is suitably aroused is around 1.5–6 mL, although this varies greatly with mood, physical condition, and sexual activity. Of this, around 1% by volume is sperm cells. The U.S.-based National Institutes of Health defines hypospermia as a semen volume lower than 2 mL on at least two semen analyses. The presence of high levels of fructose (a sugar) is normal in the semen and originates almost entirely from the seminal vesicles. The seminal vesicles, which are major contributors to ejaculate volume, render semen viscous with a pH of 7.2–7.8. An acidic seminal pH (pH < 7.2) suggests damage to the seminal vesicles and an alkaline seminal pH (pH > 8) suggests prostatic involvement. In addition, low fructose may indicate problems in the prostate, while low semen pH may indicate problems related to the [seminal vesicles]. Obstruction of the seminal vesicles results in low semen volumes since they normally produce 70% of the seminal plasma.
=== ICD-11 === The ICD-11 defines catatonia as a syndrome of psychomotor disturbances, characterized by the co-occurrence of several symptoms such as stupor, catalepsy, waxy flexibility, mutism, negativism, posturing, mannerisms, stereotypies, psychomotor agitation, grimacing, echolalia, and echopraxia. Catatonia may occur in the context of specific mental disorders, including mood disorders, schizophrenia or other primary psychotic disorders, and neurodevelopmental disorders. It may also be induced by psychoactive substances, including medications, or caused by a medical condition not classified under mental, behavioral, or neurodevelopmental disorders.
Sources: en.wikipedia.org
=== Stereocilia === The stereocilia of the epididymis are long cytoplasmic projections that have an actin filament backbone. These filaments have been visualized at high resolution using fluorescent phalloidin that binds to actin filaments. The stereocilia in the epididymis are non-motile. These membrane extensions increase the surface area of the cell, allowing for greater absorption and secretion. It has been shown that the epithelial sodium channel ENaC that allows the flow of Na+ ions into the cell is localized on stereocilia. Because sperm are initially non-motile as they leave the seminiferous tubules, large volumes of fluid are secreted to propel them to the epididymis. The core function of the stereocilia is to resorb 90% of this fluid as the spermatozoa start to become motile. This absorption creates a fluid current that moves the immobile sperm from the seminiferous tubules to the epididymis. Spermatozoa only reach full motility when inside a vagina, where the alkaline pH is neutralized by acidic vaginal fluids.
== History == The compound may have been synthesised by either Jābir ibn Hayyān in the 8th century or Ramon Llull in 1275. It was synthesised in 1540 by Valerius Cordus, who called it "sweet oil of vitriol" (oleum dulce vitrioli) – the name reflects the fact that it is obtained by distilling a mixture of ethanol and sulfuric acid (then known as oil of vitriol) – and noted some of its medicinal properties. At about the same time, Paracelsus discovered the analgesic properties of the molecule in dogs. The name ether was given to the substance in 1729 by August Sigmund Frobenius. It was considered to be a sulfur compound until the idea was disproved in about 1800. The synthesis of diethyl ether by a reaction between ethanol and sulfuric acid has been known since the 13th century.
Immunohistochemical staining of cyclin D1 antibodies is used to diagnose mantle cell lymphoma. Cyclin D1 has been found to be overexpressed in breast carcinoma. Its potential use as a biomarker was suggested.
Sources: en.wikipedia.org
=== Other organs === Diffuse scleroderma can cause musculoskeletal, pulmonary, gastrointestinal, renal, and other complications. Patients with greater cutaneous involvement are more likely to have involvement of the internal tissues and organs. Most patients (over 80%) have vascular symptoms and Raynaud's phenomenon, which leads to attacks of discoloration of the hands and feet in response to cold. Raynaud's normally affects the fingers and toes. Systemic scleroderma and Raynaud's can cause painful ulcers on the fingers or toes, which are known as digital ulcers. Calcinosis (deposition of calcium in lumps under the skin) is also common in systemic scleroderma, and is often seen near the elbows, knees, or other joints.
Although the term was coined in the late 1980s one of the first retroactively recognized examples of a killer application is the VisiCalc spreadsheet, released in 1979 for the Apple II. Because it was not released for other computers for 12 months, people spent US$100 (equivalent to $400 in 2025) for the software first, then $2,000 to $10,000 (equivalent to $9,000 to $44,000) on the requisite Apple II. Byte wrote in 1980, "VisiCalc is the first program available on a microcomputer that has been responsible for sales of entire systems", and Creative Computing's VisiCalc review is subtitled "reason enough for owning a computer". Others also chose to develop software, such as EasyWriter, for the Apple II first because of its higher sales, helping Apple defeat rivals Commodore International and Tandy Corporation. The co-creator of WordStar, Seymour Rubinstein, argued that the honor of the first killer app should go to that popular word processor, given that it came out a year before VisiCalc and that it gave a reason for people to buy a computer. However, whereas WordStar could be considered an incremental improvement (albeit a large one) over smart typewriters like the IBM Electronic Selectric Composer, VisiCalc, with its ability to instantly recalculate rows and columns, introduced an entirely new paradigm and capability unavailable on larger computers. Lotus 1-2-3 similarly benefited sales of the IBM PC. Noting that computer purchasers did not want PC compatibility as much as compatibility with certain PC software, InfoWorld suggested "let's tell it like it is.
=== Re-hydration === If a dried product cannot be easily or fully re-hydrated, it is considered to be of lower quality. If the final freeze dried product is porous, complete re-hydration can occur in the food. This signifies greater quality of the product and makes it ideal for ready-to-eat instant meals.
This supposedly caused Liu Wenhui to break down, tearily accepting a retreat to the Min River line from Guanxian to Leshan. On 8 July 1933, Liu Wenhui offered his resignation as governor of Sichuan, although the central government did not accept this until December 1934 when he was officially reappointed.
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.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.