This is a working overview of mass spectrometry, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-09-19. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 |
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.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Naturally occurring erbium is composed of 6 stable isotopes, 162Er, 164Er, 166Er, 167Er, 168Er, and 170Er, with 166Er being the most abundant (33.503% natural abundance). Of the artificial radioisotopes characterized, the most stable are 169Er with a half-life of 9.39 d, 172Er with a half-life of 49.3 h, and 160Er with a half-life of 28.58 h. All of the remaining radioactive isotopes have half-lives that are less than 11 h, and the majority of these have half-lives that are less than 4 minutes. This element also has 26 meta states, with the most stable being 149m1Er with a half-life of 8.9 s. The known isotopes of erbium range from 143Er to 180Er. The primary decay mode before the most abundant stable isotope, 166Er, is electron capture, and the primary mode after is beta decay. The primary decay products before 166Er are element 67 (holmium) isotopes, and the primary products after are element 69 (thulium) isotopes. 165Er has been identified as useful for use in Auger therapy, as it decays via electron capture and emits no gamma radiation. It can also be used as a radioactive tracer to label antibodies and peptides, though it cannot be detected by any kind of imaging for the study of its biological distribution. The isotope can be produced via the bombardment of 165Ho with beams of protons or deuterium, a reaction which is especially convenient because 165Ho is a monoisotopic element and relatively inexpensive.
Sacrificial bonds are non-covalent interactions such as hydrogen bonds, ionic interactions, and hydrophobic interactions, that can break and reform under mechanical stress. The reforming of these bonds takes time, especially when there are more of them, which leads to an increase in hysteresis. However, there is currently research focused on the development of highly entangled hydrogels, which instead rely on the long chain length of the polymers and their entanglement to limit the deformation of the hydrogel, thereby increasing the toughness without increasing hysteresis as there is no need for the reformation of the bonds.
From the example above, if the descendant with genes A1 and B underwent another speciation event where gene A1 duplicated, the new species would have genes B, A1a, and A1b. In this example, genes A1a and A1b are symparalogs.
== Spiking studies == In many cases, the concentration of viruses in a given sample is extremely low. In other extraction processes, low levels of impurity may be negligible, but because viruses are infective impurities, even one viral particle may be enough to ruin an entire process chain. It is for this reason that special measures must be taken to determine the appropriate removal or inactivation method for whatever type of virus is being extracted from whatever type of solution. Spiking studies were created specifically for this purpose. A spiking study is a study done in order to determine the possible methods of viral removal or inactivation. The results of these studies are numerical and, based on these numbers, researchers can determine whether or not the process on which the study was conducted will be suitable for the viruses they are trying to extract and the solution from which they are trying to extract them.
Sources: en.wikipedia.org
Alsos Digital Library – Radioactive Waste (annotated bibliography) Euridice European Interest Group in charge of Hades URL operation (link) Ondraf/Niras, the waste management authority in Belgium (link) Critical Hour: Three Mile Island, The Nuclear Legacy, And National Security (PDF) Environmental Protection Agency – Yucca Mountain[link removed] (documents) Grist.org – How to tell future generations about nuclear waste (article) International Atomic Energy Agency – Internet Directory of Nuclear Resources (links) Nuclear Files.org – Yucca Mountain (documents) Nuclear Regulatory Commission – Radioactive Waste (documents) Nuclear Regulatory Commission – Spent Fuel Heat Generation Calculation (guide) Radwaste Solutions (magazine) UNEP Earthwatch – Radioactive Waste Archived 2008-12-23 at the Wayback Machine (documents and links) World Nuclear Association – Radioactive Waste Archived 2010-06-11 at the Wayback Machine (briefing papers) Worries can't be buried as nuclear waste piles up, Los Angeles Times, January 21, 2008
=== Inhalable insulin === Inhalable insulin, also known as technosphere insulin, is a powdered form of insulin, delivered with an inhaler into the lungs where it is absorbed. In general, inhaled insulins have been more rapidly absorbed than subcutaneous injected insulin, with faster peak concentration in serum and more rapid metabolism. Exubera, developed by Inhale Therapeutics (later named Nektar Therapeutics), became the first inhaled insulin product to be marketed, in 2006 by Pfizer, but poor sales led Pfizer to withdraw it in 2007. Afrezza, a monomeric inhaled, ultra rapid-acting insulin developed by Mannkind, was approved by the FDA in 2014 and is the only inhaled insulin commercialized as of 2025.
Dayhoff died of a heart attack at the age of 57 on February 5, 1983. A fund was established after her death in 1984 to endow the Margaret O. Dayhoff Award, one of the top national honors in biophysics. The award is presented to a woman who "holds very high promise or has achieved prominence while developing the early stages of a career in biophysical research within the purview and interest of the Biophysical Society." It is presented at the annual meeting of the Biophysical Society and includes an honorarium of $2,000. She was survived by her husband, Edward S. Dayhoff of Silver Spring; two daughters, Ruth E. Dayhoff Brannigan of College Park, and Judith E. Dayhoff of Silver Spring, and her father, Kenneth W. Oakley of Silver Spring.
== Further reading == Bryant, Alfred T. (1964). A History of the Zulu and Neighbouring Tribes. Cape Town: C. Struik. p. 157. Cana, Frank Richardson (1911). "Zululand" . Encyclopædia Britannica. Vol. 28 (11th ed.). pp. 1050–1055. Morris, Donald R. (1965). The Washing of the Spears: the Rise of the Zulu Nation. New York: Simon and Schuster. p. 655. Deflem, Mathieu. (1999). Warfare, Political Leadership, and State Formation: The Case of the Zulu Kingdom, 1808–1879. Ethnology 38(4):371–391. Knight, Ian. (2010). Zulu Rising: The Epic Story of Isandlwana and Rorke's Drift, London: Macmillan. ISBN 978-1-405-09185-5
== Screening == Initial screening for CIP/CIM may be performed using an objective scoring system for muscle strength. The Medical Research Council (MRC) score is one such tool, and sometimes used to help identify CIP/CIM patients in research studies. The MRC score involves assessing strength in 3 muscle groups in the right and left sides of both the upper and lower extremities. Each muscle tested is given a score of 0–5, giving a total possible score of 60. An MRC score less than 48 is suggestive of CIP/CIM. However, the tool requires that patients be awake and cooperative, which is often not the case. Also, the screening tool is non-specific, because it does not identify the cause a person's muscle weakness. Once weakness is detected, the evaluation of muscle strength should be repeated several times. If the weakness persists, then a muscle biopsy, a nerve conduction study (electrophysiological studies), or both should be performed.
Sources: en.wikipedia.org
Chuvash erythrocytosis or Chuvash polycythemia is an autosomal recessive form of erythrocytosis endemic in patients from the Chuvash Republic in Russia. Chuvash erythrocytosis is associated with homozygosity for a C598T mutation in the von Hippel–Lindau gene (VHL), which is needed for the destruction of hypoxia-inducible factors in the presence of oxygen. Clusters of patients with Chuvash erythrocytosis have been found in other populations, such as on the Italian island of Ischia, located in the Bay of Naples. Patients with Chuvash erythrocytosis experience a significantly elevated risk of events. PHD2 erythrocytosis: Heterozygosity for loss-of-function mutations of the PHD2 gene are associated with autosomal dominant erythrocytosis and increased hypoxia-inducible factors activity. HIF2α erythrocytosis: Gain-of-function mutations in HIF2α are associated with autosomal dominant erythrocytosis and pulmonary hypertension.
=== Elderly === An increasing trend of anorexia among the elderly, termed "Anorexia of Aging", is observed, characterized by behaviors similar to those seen in typical anorexia nervosa but often accompanied by excessive laxative use. Most geriatric anorexia patients limit their food intake to dairy or grains, whereas an adolescent anorexic has a more general limitation. This eating disorder that affects older adults has two types – early onset and late onset. Early onset refers to a recurrence of anorexia in late life in an individual who experienced the disease during their youth. Late onset describes instances where the eating disorder begins for the first time late in life. The stimulus for anorexia in elderly patients is typically a loss of control over their lives, which can be brought on by many events, including moving into an assisted living facility. This is also a time when most older individuals experience a rise in conflict with family members, such as limitations on driving or limitations on personal freedom, which increases the likelihood of an issue with anorexia. There can be physical issues in the elderly that leads to anorexia of aging, including a decline in chewing ability, a decline in taste and smell, and a decrease in appetite. Psychological reasons for the elderly to develop anorexia can include depression and bereavement, and even an indirect attempt at suicide.
The new 17th district is anchored in Waco and its surrounding metropolitan area, with a small sliver of the district extending into the east side of Temple and a southern sliver of Williamson County, with the Austin suburb of Cedar Park connected to the rest of the district via a small sliver of Round Rock. The incumbent is Republican Pete Sessions, who was re-elected with 66.4% of the vote in 2024. The new district gave 60% of the vote to Donald Trump and 57.5% to Ted Cruz in 2024.
The integumentary system consists of the covering of the body (the skin), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands. The skin provides containment, structure, and protection for other organs, and serves as a major sensory interface with the outside world.
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.
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.