mass spectrometry 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 2025-09-04 and is reviewed periodically as new material appears.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
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.
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 |
|---|---|---|
| Common route | Intranasal | Also injected in some animal work |
| Solubility class | Freely soluble in water | Solid form is hygroscopic |
| Typical storage | About -20 degrees Celsius | Keep desiccated and dark |
| Purity method | Reverse-phase HPLC | Reported as area percent |
| Confirmatory method | Mass spectrometry | Verifies expected molecular mass |
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.
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.
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.
It was the country's only NGO specializing in media issues, Internet access, and media monitoring during election campaigns. It had operated without government approval, and had monitored violations of journalists' rights and had taken up the cause of the ban on the dissemination of many newspapers and magazines. Ba'athist Syrian security forces arrested and beat up protestors on 15 June 2020. The protest started on 7 June 2020, in front of the governorate center against government's failure of handling economic downfall, deteriorating living conditions and corruption. HRW appealed the Syrian authority to release the peacefully protesting detainees. Pro-regime journalists who were allowed to report within the country were arrested by security forces over social media posts or ambiguous charges like being "out of line".
== History == Up until the late 1970s, the management of laboratory samples and the associated analysis and reporting were time-consuming manual processes often riddled with transcription errors. This gave some organizations impetus to streamline the collection of data and how it was reported. Custom in-house solutions were developed by a few individual laboratories, while some enterprising entities sought to develop commercial reporting solutions in the form of special instrument-based systems. In 1982 the first generation of LIMS was introduced in the form of a centralized minicomputer, which offered automated reporting tools. As the interest in these early LIMS grew, industry leaders like Gerst Gibbon of the Federal Energy Technology Center in Pittsburgh began planting the seeds through LIMS-related conferences. By 1988 the second-generation commercial offerings were tapping into relational databases to expand LIMS into more application-specific territory, and International LIMS Conferences were in full swing. As personal computers became more powerful and prominent, a third generation of LIMS emerged in the early 1990s. These new LIMS took advantage of client/server architecture, allowing laboratories to implement better data processing and exchanges. By 1995 the client/server tools allowed the processing of data anywhere on the network. Web-enabled LIMS were introduced the following year, enabling researchers to extend operations outside the laboratory.
== General biochemistry concepts == Major categories of bio-compounds: Carbohydrates : sugar – disaccharide – polysaccharide – starch – glycogen Lipids : fatty acid – fats – essential oils – oils – waxes – cholesterol Nucleic acids : DNA – RNA – mRNA – tRNA – rRNA – codon – adenosine – cytosine – guanine – thymine – uracil Proteins : amino acid – glycine – arginine – lysine peptide – primary structure – secondary structure – tertiary structure – conformation – protein folding Chemical properties: molecular bond – covalent bond – ionic bond – hydrogen bond – ester – ethyl molecular charge – hydrophilic – hydrophobic – polar pH – acid – alkaline – base oxidation – reduction – hydrolysis Structural compounds: In cells: flagellin – peptidoglycan – myelin – actin – myosin In animals: chitin – keratin – collagen – silk In plants: cellulose – lignin – cell wall Enzymes and enzyme activity: enzyme kinetics – enzyme inhibition proteolysis – ubiquitin – proteasome kinase – dehydrogenase Membranes : fluid mosaic model – diffusion – osmosis phospholipids – glycolipid – glycocalyx – antigen – isoprene ion channel – proton pump – electron transport – ion gradient – antiporter – symporter – quinone – riboflavin Biomolecule (list) Biomolecular engineering Biomolecular structure Multi-state modeling of biomolecules Energy pathways : pigments : chlorophyll – carotenoids – xanthophyll – cytochrome – phycobilin – bacteriorhodopsin – hemoglobin – myoglobin – absorption spectrum – action spectrum – fluorescence Photosynthesis : light reaction – dark reaction Fermentation : Acetyl-CoA – lactic acid Cellular respiration : Adenosine triphosphate (ATP) – NADH – pyruvate – oxalate – citrate Chemosynthesis Regulation hormones : auxin signal transduction – growth factor – transcription factor – protein kinase – SH3 domain Malfunctions : tumor – oncogene – tumor suppressor gene Receptors : Integrin – transmembrane receptor – ion channel Techniques : electrophoresis – chromatography – mass spectrometry – x-ray diffraction – Southern blot – fractionation – Gram stain – Surface Plasmon Resonance – Microscale Thermophoresis
==== Intranasal ==== The intranasal route for naloxone was studied as early as 2001 by Paramedics in Denver, Colorado to test the route's feasibility as an alternative to IV administration. In a small sample size over the course of one month, 91% of patients who responded to naloxone by any route responded to IN naloxone without additional IV naloxone being administered. Narcan nasal spray was approved in the US in 2015 and is the first FDA-approved nasal spray for emergency treatment of suspected overdose. It was developed in a partnership between LightLake Therapeutics and the National Institute on Drug Abuse. The approval process was fast-tracked. A generic version of the nasal spray was approved in the United States in 2019, though did not come to market until 2021. In 2021, the FDA approved Kloxxado, an 8 mg dose of intranasal naloxone developed by Hikma Pharmaceuticals. Citing the frequent need for multiple 4 mg doses of Narcan to successfully reverse overdose, packs of Kloxxado Nasal Spray contain two pre-packaged nasal spray devices, each containing 8 mg of naloxone. However, a wedge device (nasal atomizer) can also be attached to a syringe that may also be used to create a mist to deliver the drug to the nasal mucosa. This is useful near facilities where many overdoses occur that already stock injectors.
Sources: en.wikipedia.org
Chronic intermittent hypoxia impairs endothelial function, reducing nitric oxide production, which leads to vasoconstriction and reduced blood flow to the optic nerve head. Additionally, fluctuations in pressure within the thoracic cavity during apnea episodes can alter intraocular pressure, affecting the blood supply to the optic nerve head. Sleep apnea often causes dips in blood pressure during sleep, particularly in the early morning hours, reducing blood supply to the optic nerve head and increasing the risk of ischemia.
For example, a green solution of trivalent chromium sulfate or chloride refuses to crystallize without slowly changing into the violet form, even if boiled until it concentrates into a tarry mass. When suspended in the waterglass solution, that tar forms downward twig-like growths. This is because all the fluid inside the membrane is too dense to float and thereby exerts a downward force. The concentration of sodium silicate becomes important in growth rate. After the growth has ceased, the sodium silicate solution can be removed by a continuous addition of water at a very slow rate. This prolongs the life of the garden. In one specific experimental variation, researchers produced the chemical garden with a single growth "tube". In many modern chemical garden growth experiments, the solid reactant seed is replaced by the continuous injection of the corresponding reactant solution at a controlled flow rate, or more recently, under controlled osmotic pressure.
Research published by the RAC indicates that the target set by the UK government for installing rapid or ultra-rapid chargers near motorways was missed during 2023. Provisional data released by the Met Office indicates 2023 was the second warmest year on record in the UK behind 2022, with Wales and Northern Ireland experiencing their warmest year on record during 2023. 16-year-old Luke Littler beats Rob Cross to reach the World Darts Championship final, making him the youngest person to reach the final; overtaking Kirk Shepherd who was 21 years and 88 days old when he reached the 2008 final. 3 January Luke Littler becomes the youngest finalist of the PDC World Darts Championship as he faces Luke Humphries in the 2024 final at the age of 16 years and 348 days. Humphries wins the final. Halifax, the UK's largest moneylender, cuts its mortgage rates by almost 1%, with other banks and lenders following. 4 January Prime Minister Rishi Sunak says his "working assumption" is that the general election will take place in the second half of this year. Sainsbury's announces that they will offer pay rises from March as supermarkets continue their battle to retain workers. The increase means that all their workers will be paid the voluntary Real Living Wage, which is higher than the compulsory National Living Wage. A man is arrested after firing shots at a cinema, newsagent, and a house in Croxteth, Liverpool.
Stratum corneum Stratum lucidum (only in palms and soles) Stratum granulosum Stratum spinosum Stratum basale (also called the stratum germinativum) Keratinocytes in the stratum basale proliferate through mitosis and the daughter cells move up the strata changing shape and composition as they undergo multiple stages of cell differentiation to eventually become anucleated. During that process, keratinocytes will become highly organized, forming cellular junctions (desmosomes) between each other and secreting keratin proteins and lipids which contribute to the formation of an extracellular matrix and provide mechanical strength to the skin. Keratinocytes from the stratum corneum are eventually shed from the surface (desquamation). The epidermis contains no blood vessels, and cells in the deepest layers are nourished by diffusion from blood capillaries extending to the upper layers of the dermis.
== Flow types == Microfluidic flows need only be constrained by geometrical length scale – the modalities and methods used to achieve such a geometrical constraint are highly dependent on the targeted application. Traditionally, microfluidic flows have been generated inside closed channels with the channel cross section being in the order of 10 μm x 10 μm. Each of these methods has its own associated techniques to maintain robust fluid flow which have matured over several years.
Sources: en.wikipedia.org
In September 2013, the Supreme People's Court authorized a three-year prison term for bloggers who shared more than 500 times any content considered "defamatory". In 2014, the Chinese government launched the Cleaning the Web campaign, aiming to crack down on pornographic, vulgar, and politically questionable content. It also launched Operation Qinglang campaigns since 2016 to "clean up" the Chinese internet. China under Xi has taken a strong stand to control internet usage inside China, including Google, Facebook and Wikipedia, advocating Internet censorship under the concept of internet sovereignty. Likewise, the situation for users of Weibo has been described as a change from fearing one's account would be deleted, to fear of arrest. The Provisions on the Governance of the Online Information Content Ecosystem, which came into effect in 2020, defined the scope of legal expression for service platforms and content creators. Under Xi's administration, China started enforcing an Internet real-name system for online platforms, requiring them to collect users' real names, ID numbers, and other information when providing services.
The Annals of Clinical & Laboratory Science is a quarterly academic journal. It is the official journal of, and is published by, the Association of Clinical Scientists. It was established in 1971 as Annals of Clinical Laboratory Science by F. William Sunderman and obtained its current title in 1973. As of 2022, the editor-in-chief is Nina Tatevian.
The procedure is illustrated by the synthesis of a dipeptide library using the same three amino acids as building blocks in both cycles. Each component of this library contains two amino acids arranged in different orders. The amino acids used in couplings are represented by yellow, blue and red circles in the figure. Divergent arrows show the division of solid support resin (green circles) into equal portions, vertical arrows mean coupling, and convergent arrows represent the mixing and homogenizing of the portions of the support. The figure shows that, in the two synthetic cycles, 9 dipeptides are formed. In the third and fourth cycles, 27 tripeptides and 81 tetrapeptides would form respectively. The "split-mix synthesis" has several outstanding features:
==== Metabolites ==== Desmetramadol is metabolized in the liver into the active metabolite N,O-didesmethyltramadol via CYP3A4 and CYP2B6. The inactive tramadol metabolite N-desmethyltramadol is metabolized into the active metabolite N,O-didesmethyltramadol by CYP2D6.
=== Cancer === Bleomycin is mostly used to treat testicular cancer, ovarian cancer, and Hodgkin's disease, and less commonly non-Hodgkin's disease. It can be given intravenously, by intramuscular injection, or under the skin.
Sources: en.wikipedia.org
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.
Reported human trials are few, brief and originate mainly from one country. They describe effects on anxiety-related measures, but sample sizes are small and reporting is limited. The results are widely regarded as preliminary rather than confirmed.
Reverse-phase liquid chromatography is used to assess purity and separation of related impurities. Mass spectrometry confirms that the observed molecular mass matches the expected peptide. A certificate of analysis from the supplier is the usual document of record.
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.