If you have been reading about Semax and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-09-12. Where a claim depends on a specific study, the study is described rather than over-claimed.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
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.
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.
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.
Captodiame (INN), also known as captodiamine, is an antihistamine sold under the trade names Covatine, Covatix, and Suvren which is used as a sedative and anxiolytic. The structure is related to diphenhydramine. A 2004 study suggested captodiame may be helpful in preventing benzodiazepine withdrawal syndrome in people discontinuing benzodiazepine treatment. In addition to its actions as an antihistamine, captodiamine has been found to act as a 5-HT2C receptor antagonist and σ1 receptor and D3 receptor agonist. It produces antidepressant-like effects in rats. However, captodiamine is unique among antidepressant-like drugs in that it increases brain-derived neurotrophic factor (BDNF) levels in the hypothalamus but not in the frontal cortex or hippocampus. This unique action may be related to its ability to attenuate stress-induced anhedonia and corticotropin-releasing factor (CRF) signaling in the hypothalamus.
. Stress intensity replaced strain energy release rate and a term called fracture toughness replaced surface weakness energy. Both of these terms are simply related to the energy terms that Griffith used:
== History == The ridge was named in 1907 by Mary Schäffer, the same year that Jasper National Park was established. In her book, "A Hunter of Peace," Mary wrote: "A short distance beyond the rock-slide and on the river's right, begins a low, rocky ridge, which for length and unadulterated ugliness cannot be beaten. We trailed it for a day and a half and then named it The Endless Chain, well named too, for on reaching the Athabasca shores, we found that it still stretched on in an unbroken line for miles down the river." The toponym was officially adopted in 1947 by the Geographical Names Board of Canada.
== Use in specific populations == Hydrocodone can cause neonatal opioid withdrawal syndrome when taken during pregnancy. Reproductive and developmental studies of acetaminophen in rats and mice have shown fetotoxicity, necrosis of the liver and kidney in the pregnant rat and the fetus, retarded growth and decreased reproductive capacity of the offspring. Hydrocodone and acetaminophen are present in breast milk. Chronic opioid use can cause infertility. Safety and efficacy has not been established in patients under the age of 18. Patients over the age of 65 may have heightened sensitivity to hydrocodone. Benzhydrocodone/APAP is mainly excreted through the kidneys; therefore, geriatric patients with impaired renal function may experience more adverse reactions. The effect of renal impairment on the pharmacokinetics of benzhydrocodone/APAP has not been determined. The effect of hepatic impairment on the pharmacokinetics of benzhydrocodone/APAP has not been determined.
Sources: en.wikipedia.org
== Variation in other animals == Stanniocalcin was also detected in mammals. In mammals there are two variant forms, STC1, which is fundamentally similar to fish stanniocalcin, and STC2, which is more different in structure and function. In invertebrates, freshwater leeches are found to contain the hormone. In leeches it is produced in the fat cells (adipocytes).
=== Energy expenditure === The Na+/K+-ATPase is an active enzyme. It uses energy from ATP to move ions against their concentration gradient. In fact, all cells expend a large fraction of the ATP they produce (typically 30% and up to 70% in nerve cells) to maintain their required cytosolic Na and K concentrations. For neurons, the Na+/K+-ATPase can be responsible for up to three-fourths of the cell's energy expenditure. In many types of tissue, ATP consumption by the Na+/K+-ATPases have been related to glycolysis. This was first discovered in red blood cells (Schrier, 1966), but has later been evidenced in renal cells, smooth muscles surrounding the blood vessels, and cardiac cells which compose Purkinje fibers. Recently, glycolysis has also been shown to be of particular importance for Na+/K+-ATPase in skeletal muscles, where inhibition of glycogen breakdown (a substrate for glycolysis) leads to reduced Na+/K+-ATPase activity and lower force production.
=== United Kingdom === Beak trimming is legal but regulated in the UK; it is expected that the practice will be prohibited in the near future. In 2011, the British government set up the Beak Trimming Action Group (BTAG) to review the matter with representatives from different stakeholders, including the industry, the government, animal welfare groups and veterinarians. A late 2015 BTAG report endorsed by Farming Minister George Eustice concluded that banning it in January 2016 would be too early as the sector needed more time to change its management techniques in order to avoid feather pecking, but that beak trimming should be phased out in the future. Laying Hen Welfare Forum chairman Andrew Joret stated in March 2020: 'A ban is coming. In my opinion, we have five years at most to prepare for this. We need to work out ways of keeping birds well-feathered, and if we can, eventually do that without beak trimming.'
Sources: en.wikipedia.org
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.