lyophilization 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 2025-10-09 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
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.
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.
Recommendations are to include multiple types of exercise in exercise programs, and to prescribe exercise as early as possible in addition to medication, to gain the benefits of regular, long-term activity. Aerobic and resistance training exercise guidelines for Parkinson disease recommend 3–5 days per week of aerobic training (doing 20–60 minutes at moderate intensity) and 2–3 days per week of resistance training (doing 1-3 sets, of 8-12 repetitions, at between 40%-50% of the maximum for 1 repetition). Exercise is generally considered safe, with studies in PD reporting no serious adverse events and a very low risk of other events such as soreness, joint inflammation, fatigue, dizziness, or falls. Drop-out rates were comparable for exercising and non-exercising controls, with a generally high rate of exercise adherence.
=== Classification === The notion that atrophic gastritis could be classified depending on the level of progress as "closed type" or "open type" was suggested in early studies, but no universally accepted classification exists as of 2017.
=== Hurdles === Given the uneven distribution of vaccines across jurisdictions, granting privileges based on vaccination status certification means that those with easier vaccine access have unfair access to those privileges. If vaccination status is only verifiable using digital technology, those without that technology may also lose access even if they are vaccinated. Such privileging mechanisms may exacerbate inequality, increase risks of deliberate infections or transmission, Public health justifications for restricting behavior based on vaccine status have become less frequent over the course of the pandemic as vaccines do not stop transmission.
The hexagonal lattice structure of isolated, single-layer graphene can be directly seen with transmission electron microscopy (TEM) of sheets of graphene suspended between bars of a metallic grid. Some of these images showed a "rippling" of the flat sheet, with an amplitude of about one nanometer. These ripples may be intrinsic to the material as a result of the instability of two-dimensional crystals, or may originate from the ubiquitous dirt seen in all TEM images of graphene. Photoresist residue, which must be removed to obtain atomic-resolution images, may be the "adsorbates" observed in TEM images, and may explain the observed rippling. The hexagonal structure is also seen in scanning tunneling microscope (STM) images of graphene supported on silicon dioxide substrates The rippling seen in these images is caused by the conformation of graphene to the substrates' lattice and is not intrinsic.
== Inherited thrombocytopenia with normal MPV == ATRUS Syndrome Thrombocytopenia 2 (THC2) Congenital amegakaryocytic thrombocytopenia TAR syndrome Familial platelet disorder with predisposition to AML
Sources: en.wikipedia.org
=== Post-Cold War === The first seizures of nuclear or otherwise radioactive material were reported in Switzerland and Italy in 1991. Later, reports of incidents of nuclear material occurred in Germany, the Czech Republic, Hungary and other central European countries. Nuclear forensics became a new branch of scientific research with the intent of not only determining the nature of the material, but also the intended use of the seized material as well as its origin and about the potential trafficking routes. Nuclear forensics relies on making these determinations through measurable parameters including, but not limited to chemical impurities, isotopic composition, microscopic appearance, and microstructure. By measuring these parameters, conclusions can be drawn as to the origin of the material. Identification of these parameters is an ongoing area of research, however, data interpretation also relies on the availability of reference information and on knowledge of the fuel cell operations. The first seizures of nuclear materials from trafficking in the early 1990s allowed the nuclear forensic methodology to be adopted by a wider scientific community. When scientific laboratories outside the weapons and intelligence community took an interest in this methodology was when the term "Nuclear Forensics" was coined. Unlike standard forensics, nuclear forensics focuses mainly on the nuclear or radioactive material and aims to provide knowledge of the intended use of the materials.
== Metabolism == The exact metabolic pathways of dimethocaine have not been researched, but the different metabolites have been examined in Wistar rats. After administration of dimethocaine, different metabolites have been found and identified in their urine. Due to these metabolites, different metabolic pathways could have been postulated. The main phase I reactions are ester hydrolysis, deethylation, hydroxylation of the aromatic system, or a combination of these three. The main phase II reactions are N-acetylation, glucuronidation and a combination of both. Different cytochrome P450 isozymes are involved in the initial steps of human metabolism. The N-acetylation is catalyzed by the NAT2 isozyme.
27 May A new compact CRISPR gene editing tool better suited for therapeutic (temporary) RNA editing than Cas13 is reported, Cas7-11, – of which an early version was used for in vitro editing in 2021. Science and the 2022 Russian invasion of Ukraine:According to a news report academics in Russia are compiling or circulating a list of researchers who have supported Russia's invasion to prevent them from being elected to the Russian Academy of Sciences. An editorial published in a journal notes that remote surgery and types of videoconferencing for sharing expertise (e.g. ad hoc assistance) have been and could be used to support doctors in Ukraine (3 May). A forum contribution analyzes Russian users' reactions to the Bucha massacre on social media – on nationalist Telegram channels (9 May). The FAO estimates that "at least 20 percent of Ukraine's winter crops" "may not be harvested or planted" (13 May). A preprint estimates potential impacts of the EU embargoing fossil fuels from Russia, suggesting implementing such via a partial embargo with tariffs may be beneficial (25 May). 28 May – A new direct air capture system using isophorone diamine is demonstrated, able to remove carbon dioxide with 99% efficiency and more than twice as fast as existing systems. 30 May – Frontier is announced by Oak Ridge National Laboratory as the world's first exascale supercomputer. 31 May – Success of record-long (3 days rather than usually <12 hours) of human transplant organ preservation with machine perfusion of a liver is reported.
History of environmental chemistry – history of the scientific study of the chemical and biochemical phenomena that occur in natural places. History of immunochemistry – history of the branch of chemistry that involves the study of the reactions and components of the immune system. History of medicinal chemistry – history of the discipline at the intersection of chemistry, especially synthetic organic chemistry, and pharmacology and various other biological specialties, where they are involved with design, chemical synthesis and development for market of pharmaceutical agents (drugs). History of natural product chemistry – history of the scientific study of chemical compounds or substances produced by living organisms—history of chemical compounds found in nature that usually have a pharmacological or biological activity for use in pharmaceutical drug discovery and drug design. History of neurochemistry – history of the specific study of neurochemicals, which include neurotransmitters and other molecules such as neuro-active drugs that influence neuron function. History of computational chemistry – history of the branch of chemistry that uses principles of computer science to assist in solving chemical problems. History of chemo-informatics – history of the use of computer and informational techniques, applied to a range of problems in the field of chemistry. History of molecular mechanics – history of the uses of Newtonian mechanics to model molecular systems. History of flavor chemistry – history of the use of chemistry to engineer artificial and natural flavors.
Sources: en.wikipedia.org
=== Phase III - further modification and excretion === After phase II reactions, the xenobiotic conjugates may be further metabolised. A common example is the processing of glutathione conjugates to acetylcysteine (mercapturic acid) conjugates. Here, the γ-glutamate and glycine residues in the glutathione molecule are removed by Gamma-glutamyl transpeptidase and dipeptidases. In the final step, the cystine residue in the conjugate is acetylated. Conjugates and their metabolites can be excreted from cells in phase III of their metabolism, with the anionic groups acting as affinity tags for a variety of membrane transporters of the multidrug resistance protein (MRP) family. These proteins are members of the family of ATP-binding cassette transporters and can catalyse the ATP-dependent transport of a huge variety of hydrophobic anions, and thus act to remove phase II products to the extracellular medium, where they may be further metabolised or excreted.
The 23S rRNA is a 2,904 nucleotide long (in E. coli) component of the large subunit (50S) of the bacterial/archean ribosome and makes up the peptidyl transferase center (PTC). The 23S rRNA is divided into six secondary structural domains titled I-VI, with the corresponding 5S rRNA being considered domain VII. The ribosomal peptidyl transferase activity resides in domain V of this rRNA, which is also the most common binding site for antibiotics that inhibit translation, making it a target for ribosomal engineering. A well-known member of this antibiotic class, chloramphenicol, acts by inhibiting peptide bond formation, with recent 3D-structural studies showing two different binding sites depending on the species of ribosome. Numerous mutations in domains of the 23S rRNA with Peptidyl transferase activity have resulted in antibiotic resistance. 23S rRNA genes typically have higher sequence variations, including insertions and/or deletions, compared to other rRNAs. The eukaryotic homolog of the 23S LSU rRNA is the 28S ribosomal RNA, with a region filled by the 5.8S ribosomal RNA.
Because it has similar antiseptic qualities to chlorine, bromine can be used in the same manner as chlorine as a disinfectant or antimicrobial in applications such as swimming pools. Bromine came into this use in the United States during World War II due to a predicted shortage of chlorine. However, bromine is usually not used outside for these applications due to it being relatively more expensive than chlorine and the absence of a stabiliser to protect it from the sun. For indoor pools, it can be a good option as it is effective at a wider pH range. It is also more stable in a heated pool or hot tub.
=== Mechanism of action === Miconazole inhibits the fungal enzyme 14α-sterol demethylase, resulting in a reduced production of ergosterol. In addition to its antifungal actions, miconazole, similarly to ketoconazole, is known to act as an antagonist of the glucocorticoid receptor. Miconazole is also known to bind to tubulin and inhibit its polymerization. Miconazole inhibits CYP2J2.
Cupuaçu butter is a triglyceride composed of saturated and unsaturated fatty acids, giving the butter a low melting point (approximately 30 °C) and texture of a soft solid, lending its use as a confectionery resembling white chocolate. The main fatty acid components of cupuaçu butter are stearic acid (38%), oleic acid (38%), palmitic acid (11%), and arachidic acid (7%).
Sources: en.wikipedia.org
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.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.