Enkephalinase raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-10-08 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
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.
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.
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.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
In enzymology, cholestenone 5alpha-reductase (EC 1.3.1.22) is an enzyme that catalyzes several chemical reactions of steroids in which a cholest-4-en-3-one is converted to the corresponding 5α-dihydrocholestan-3-one. For example, 5α-dihydroprogesterone is the product of the reduction of progesterone:
Nuclear export of SENP2 additionally downregulates endothelial nitric oxide synthase, eNOS while it upregulates inflammatory adhesion molecules. As eNOS is required for healthy vascular physiology, pathological oxidative stress ensues in vascular endothelial cells. With the oxidative stress comes subsequent accumulation of cellular lipids; this results in the inflammatory foamy cell state that is typified by atherosclerosis as well as the similarly inflammatory myelin-laden macrophages known to produce chronic inflammation in SCI. In cardiovascular disease, many proteins are subject to SUMOylation. To say SUMOylation itself is bad or good regarding this or any other class of disease is to overlook the role of the multiple proteins in question. One common denominator among many conditions is fibrosis; in myocardial fibrosis, PPARγ1 is understood to have a role in regulating expression of some key genes, and its transcriptional activity is generally inhibited by SUMOylation. Therefore, one possible therapeutic intervention in the case of cardiac hypertrophy may be countering the SUMOylation of PPARγ1. In neurodegenerative disease, we often observe pathological accumulation of proteins. Inclusion bodies form when for example, the Huntington's disease protein, aptly named Huntingtin, accumulates and folds into a form which is impervious to the proteasome.
The GPUGRID.net Project (GPUGRID.net) The Blue Gene Project (IBM) JawBreakers.org Materials modelling and computer simulation codes A few tips on molecular dynamics Movie of MD simulation of water (YouTube)
Sources: en.wikipedia.org
== Life and work == Bergmann was born in Fürth, Bavaria, Germany on February 12, 1886, the seventh child of coal wholesalers Salomon and Rosalie Bergmann. Bergmann started studying biology at the Ludwig-Maximilians-Universität München, but lectures by Adolf von Baeyer captured his interest and eventually persuaded him to switch to Organic Chemistry. He continued his chemical studies at the Friedrich Wilhelm University of Berlin, where he was taught by Emil Fischer. After receiving his PhD under the supervision of Ignaz Bloch [de] in 1911 for his thesis on acyl(polysulfides), he became the assistant to Fischer at the University of Berlin, where he stayed until Fischer's death in 1919. He received his habilitation in 1921. In 1922 Bergmann was made the first director of the Kaiser Wilhelm Institute for Leather Research in Dresden, which was created in 1921 and from which the Max Planck Institute of Biochemistry descends. It was there that he worked with his former doctoral student, Leonidas Zervas, who eventually rose to vice-director of the institute and briefly succeeded Bergmann as director. In the early 1930s, the two scientists developed the Bergmann-Zervas carbobenzoxy method for the synthesis of polypeptides, which started the field of controlled peptide chemical synthesis and remained the dominant method in it for the next 20 years. Bergmann and Zervas gained international academic fame as a result. Bergmann was nonetheless forced to abandon his institute due to his Jewish origin after the passage of the Civil Service Law and emigrated from Nazi Germany in 1933.
== Thermal conductivity == The thermal conductivity is a measure of the capacity of a material to conduct heat. In a nanofluid this conductivity is influenced by the nanoparticles suspended in the solution. A simple model only considered the thermal conductivity of the liquid and the suspended solids. This is called the Maxwell–Garnett model (1891) and is defined as:
== Metabolism and survival == The metabolism of endolithic microorganisms is versatile; genes involved in sulphur metabolism, iron metabolism and carbon fixation have been found in many endolithic communities. Whether they metabolize directly from the surrounding rock, or excrete an acid to dissolve it first is yet undetermined. According to Meslier & DiRuggiero there are genes found in the endolithic community involved in nitrogen fixation. The Ocean Drilling Program found microscopic trails in basalt from the Atlantic, Indian, and Pacific oceans that contain DNA. Photosynthetic endoliths have also been discovered. As water and nutrients are sparse in the endolith's surrounding environment, water limitation is a key factor in the capacity of survival of many endolithic microorganisms. Many of those microorganisms have adaptations to survive in low concentrations of water. Additionally, pigments such as beta carotenes and chlorophyll, especially in cyanobacteria and some algae, help to protect against dangerous radiation and act as a way to obtain energy. Another characteristic is the presence of a very slow reproduction cycle. Early data suggest some only engage in cell division once every hundred years. In August 2013, researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old and reproducing only once every 10,000 years. Most of their energy is spent repairing cell damage caused by cosmic rays or racemization, and very little is available for reproduction or growth.
== Mutations == Mitochondrial acetoacetyl-CoA thiolase, also known as thiolase II, the enzyme responsible for catalyzing the synthesis of acetoacetyl-CoA within ketogenesis as mentioned, is also involved within acetoacetyl-CoA cleavage in ketolysis. It is observed to play a role within cleavage of acetyl-CoA from acetoacetyl-CoA and 2-methylacetoacetyl-CoA. The enzyme is involved in an autosomal recessive disorders that impacts the catabolism of ketone bodies and isoleucine: beta-ketothiolase deficiency, leading to their deficiency within mitochondria. The mutation takes place within the acetoacetyl-CoA thiolase (ACAT) gene mapped on chromosome 11q22.3-23.1. Mutations in mitochondrial 3-hydroxy-3-methylglutaryl-CoA synthase (HMG-CoA synthase) is another inherited autosomal recessive disorder affecting the catabolism of ketone bodies and can lead to the build-up of acetoacetyl-CoA.
Sources: en.wikipedia.org
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.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
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.