The short version of heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-08. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
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.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
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.
== History == Loperamide hydrochloride was first synthesized in 1969 by Paul Janssen from Janssen Pharmaceuticals in Beerse, Belgium, following previous discoveries of diphenoxylate hydrochloride (1956) and fentanyl citrate (1960). The first clinical reports on loperamide were published in 1973 with the inventor being one of the authors. The trial name for it was "R-18553". Loperamide oxide has a different research code: R-58425. The trial against placebo was conducted from December 1972 to February 1974, its results being published in 1977. In 1973, Janssen started to promote loperamide under the brand name Imodium. In December 1976, Imodium got US FDA approval. During the 1980s, Imodium became the best-selling prescription antidiarrheal in the United States. In March 1988, McNeil Pharmaceutical began selling loperamide as an over-the-counter drug under the brand name Imodium A-D. In the 1980s, loperamide also existed in the form of drops (Imodium Drops) and syrup. Initially, it was intended for children's usage, but Johnson & Johnson voluntarily withdrew it from the market in 1990 after 18 cases of paralytic ileus (resulting in six deaths) were registered in Pakistan and reported by the World Health Organization (WHO). In the following years (1990-1991), products containing loperamide have been restricted for children's use in several countries (ranging from two to five years of age). In the 1980s, before the US patent expired on 30 January 1990, McNeil started to develop Imodium Advanced containing loperamide and simethicone for treating both diarrhea and gas.
Long after the Cisplatine War that resulted in the independence of Uruguay, Brazil won three international wars during the 58-year reign of Pedro II: the Platine War, the Uruguayan War and the devastating Paraguayan War, the largest war effort in Brazilian history. Although there was no desire among the majority of Brazilians to change the country's form of government, on 15 November 1889, in disagreement with the majority of the Imperial Army officers, as well as with rural and financial elites, the monarchy was overthrown by a military coup. A few days later, the national flag was replaced with a new design that included the national motto "Ordem e Progresso", influenced by positivism. 15 November is now Republic Day, a national holiday.
Official website Tracy Morgan at IMDb Tracy Morgan at Emmys.com Interview with Tracy Morgan National Transportation Safety Board report on Morgan's 2014 accident "Tracy Morgan: Film Actor, Actor, Television Actor, Comedian (1968–)". Biography.com. Archived from the original on April 10, 2019.
Sources: en.wikipedia.org
The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering Organizations working for the advancement of the chemical sciences, especially by developing nomenclature and terminology. It is a member of the International Science Council (ISC). IUPAC is registered in Zürich, Switzerland, and its administrative office, known as the "IUPAC Secretariat", is in Research Triangle Park, North Carolina, United States. IUPAC was established in 1919 as the successor of the International Congress of Applied Chemistry for the advancement of chemistry. Its members, the National Adhering Organizations, can be national chemistry societies, national academies of sciences, or just other bodies representing chemists. There are a total of fifty-four National Adhering Organizations and three Associate National Adhering Organizations. IUPAC's Inter-divisional Committee on Nomenclature and Symbols (IUPAC nomenclature) is the recognized world authority in developing standards for naming chemical elements and compounds. Since its creation, IUPAC has been run by many different committees with different responsibilities. These committees run different projects; of those which include standardizing nomenclature, finding ways to bring chemistry to the world, and publishing works. IUPAC is best known for its works standardizing nomenclature in chemistry, but they have publications in many science fields including chemistry, biology, and physics.
== Medical uses == Diazoxide is used as a vasodilator in the treatment of acute hypertension or malignant hypertension. Diazoxide also inhibits the secretion of insulin by opening ATP-sensitive potassium channel of beta cells of the pancreas; thus, it is used to counter hypoglycemia in disease states such as insulinoma (a tumor producing insulin) or congenital hyperinsulinism.
=== Valve Corporation v. Zaiger, LLC === In 2023, Valve sued a law firm, Zaiger, alleging that it attempted to extort settlements from Valve by threatening to bring numerous antitrust arbitration cases on behalf of Steam customers, a tactic referred to as "mass arbitration". Valve also brought suit against a litigation financier for Zaiger over the funding of a social media campaign to recruit Steam users as clients. Valve alleged that it improperly interfered with its contracts with Steam customers and abused the arbitration process by signing up clients with the intent of obtaining settlements slightly lower than the cost of arbitration filing fees, rather than arbitrating their claims. Valve said that it was targeted due to the terms of the Steam Subscriber Agreement, in which Valve would be responsible for the fees and costs associated with arbitration. The lawsuit was dismissed without prejudice by the US District Court for the Western District of Washington in 2024 due to personal jurisdiction issues. In September 2024, Valve changed its Steam Subscriber Agreement to require disputes to proceed in court, specifically in King County, Washington, with no option of arbitration.
A study compared different particle sizes of oral micronized estradiol. A preparation with the smallest particles (mainly <0.6 μm) was found to have the most rapid absorption and the highest bioavailability. However, a sharp peak in estradiol levels, without an accompanying rise in estrone levels, was observed during the first 2 hours with this particle size. It was suggested that the smallest estradiol particles may have been absorbed by the lymphatic system, partially bypassing first-pass metabolism and resulting in very high initial estradiol levels. The preparations with the larger particle sizes (mainly <3.5 μm and <20 μm) were found to be absorbed more slowly, without a pronounced initial peak in estradiol levels. Levels of estradiol were more even and similar to physiological levels with these particle sizes. Differences in area-under-the-curve estradiol levels with the different particle sizes were relatively small. As such, micronization may improve absorption but does not necessarily improve therapeutic effect. Micronized estradiol is rapidly and completely absorbed with oral administration. This is true for oral doses of 2 mg and 4 mg, but absorption was found to be incomplete for an oral dose of 8 mg. This dose showed 76% of the expected bioavailability based on dose proportionality and area-under-the-curve levels, indicating a small deviation from linearity. The absolute bioavailability of oral micronized estradiol is approximately 5%, with a possible range of 0.1% to 12%. As such, the bioavailability of oral estradiol is very low even with micronization.
Sources: en.wikipedia.org
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.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.