If you have been reading about mass spectrometry and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-07-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
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.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
The NO can then contribute to two suggested pathways. Under typical conditions, nitric oxide (NO) interacts non-covalently with the heme and copper (Cu) subunits of CCO, competing with oxygen molecules and inhibiting cellular respiration, leading to reduced production of adenosine triphosphate (ATP). Low energy light can revise the mitochondrial inhibition of cellular respiration by photodissociating of NO from CCO, and thereby increasing ATP synthesis. The second pathway proposes that released nitric oxide (NO) will boost Cytochrome c Oxidase (CCO) activity, as an enzyme nitrite reductase. This mechanism includes the transfer of electrons to oxygen molecules, resulting in the production of water and reactive oxygen species (ROS). The ROS then activates enzymes necessary for producing vital cellular components like nucleic acids and proteins. LED therapy may also increase ROS, which may activate transcription factors that manage genes important for cell growth, cytokine production, and making growth factors for cell repair and proliferation.
== Northern Hemisphere == In the Northern Hemisphere, there are two towns in Sakha, Russia that compete for the title of "Pole of Cold". These are Verkhoyansk (located at 67°33′N 133°23′E, altitude 127 metres (417 ft)) and Oymyakon (located at 63°15′N 143°9′E, altitude 745 metres (2,444 ft)). However, the World Meteorological Organization has recognized in 2020 a temperature of −69.6 °C (−93.3 °F), measured near the topographic summit of the Greenland Ice Sheet on 22 December 1991, as the lowest in the Northern Hemisphere. The record was measured at an automatic weather station and was uncovered after nearly 30 years. In December 1868 and then in February 1869 Ivan Khudyakov made the discovery of the Northern Pole of Cold by measuring a record temperature of −63.2 °C (−81.8 °F) in Verkhoyansk. Later, on January 15, 1885, a temperature of −67.8 °C (−90.0 °F) was registered there by Sergey Kovalik. This measurement was published in the Annals of the General Physical Observatory in 1892; by mistake it was written as −69.8 °C (−93.6 °F), which was later corrected. One can still find this incorrect value in some literature. The coldest reliably measured temperature in Verkhoyansk was −67.8 °C (−90.0 °F) on February 5 and 7 of 1892. On February 6, 1933, a temperature of −67.7 °C (−89.9 °F) was recorded at Oymyakon's weather station. At the time, this was the coldest reliably measured temperature for the Northern Hemisphere. The weather station is in a valley between Oymyakon and Tomtor.
R−S−S−R' + 2 GSH → R−SH + R'−SH + GSSG where R and R' are parts of the micro-nanogel structure, and GSSG is oxidized glutathione (glutathione disulfide). The breaking of disulfide bonds causes the nanogel to degrade into smaller fragments. This degradation process leads to the release of encapsulated drugs. The released drug molecules can then exert their therapeutic effects, such as inducing apoptosis in cancer cells.
== Pregnancy == About 50% of women experience low back pain during pregnancy. Some studies have suggested that women who have experienced back pain before pregnancy are at a higher risk of experiencing back pain during pregnancy. It may be severe enough to cause significant pain and disability in as many as one third of pregnant women. Back pain typically begins at approximately 18 weeks of gestation and peaks between 24 and 36 weeks. Approximately 16% of women who experience back pain during pregnancy report continued back pain years after pregnancy, indicating that those with significant back pain are at greater risk of back pain following pregnancy. Biomechanical factors of pregnancy shown to be associated with back pain include increased curvature of the lower back, or lumbar lordosis, to support the added weight on the abdomen. Also, the hormone relaxin is released during pregnancy, which softens the structural tissues in the pelvis and lower back to prepare for vaginal delivery. This softening and increased flexibility of the ligaments and joints in the lower back can result in pain. Back pain in pregnancy is often accompanied by radicular symptoms, suggested to be caused by the baby pressing on the sacral plexus and lumbar plexus in the pelvis. Typical factors aggravating the back pain of pregnancy include standing, sitting, forward bending, lifting and walking.
Here, phenyllithium 1 attacks the carbonyl group of DMF 2, giving tetrahedral intermediate 3. Because the dimethylamide anion is a poor leaving group, the intermediate does not collapse and another nucleophilic addition does not occur. Upon acidic workup, the alkoxide is protonated to give 4, then the amine is protonated to give 5. Elimination of a neutral molecule of dimethylamine and loss of a proton give benzaldehyde, 6. A new class of amide reactions was discovered in 2015 by the research teams of Neil Garg and Ken Houk, showing that amides can be converted to esters using nickel catalysis. The nickel catalyst breaks the ordinarily strong amide C-N bond through oxidative addition. Many other amide cross-couplings were subsequently developed using nickel or palladium catalysis, including Suzuki-Miyaura couplings, allowing for amides to be readily converted to numerous other functional groups.
Sources: en.wikipedia.org
=== Nontoxicity for animals and humans === In different animal models, tuftsin showed no toxicity when administered intravenously or intraperitoneally. In a phase I study, tuftsin was shown to be nontoxic in adult human patients with advanced cancer when it was injected once intravenously (0.96 mg/kg body weight). Extensive augmentation of white blood counts and enhanced cytotoxicity of lymphocytes was notable. No detectable tuftsin-related toxicity was noticed in human patients during a phase II study, where the peptide was injected intravenously twice a week at total doses of 5 mg per injection.
== Adverse events == Rare but serious adverse events reported following Proquad vaccination include allergic reactions, including swelling of the lips, tongue, or face; difficulty breathing or closing of the throat; hives; paleness; weakness; dizziness; a fast heartbeat; deafness; long-term seizures, coma, or lowered consciousness; seizures (jerking or staring) caused by fever; or temporary low platelet count. For children aged two and younger, the MMRV vaccine is associated with significantly more adverse events compared to separate administration of MMR and varicella vaccinations on the same day. There are 4.3 additional febrile seizures per 10,000 vaccinated children (95% CI 2.6–5.6), 7.5 additional mostly mild fever episodes per 100 vaccinated children (95% CI, 5.4–9.4) and 1.1 additional measles-like rash per 100 children (95% CI, 0.2–1.8). Febrile seizures caused by the MMRV vaccine occur 7 to 10 days after vaccination. In children age 4–6, there is no evidence for an increased risk in febrile seizures after the administration of Proquad compared to the separate administration of MMR and Varicella vaccines.
Microbes may naturally develop resistance through genetic mutations that occur during cell division, and although random mutations are rare, many microbes reproduce frequently and rapidly, increasing the chances of members of the population acquiring a mutation that increases resistance. In contrast to that, recent research suggests that, contrary to the traditional model of rapid genetic mutation, mycobacteria maintain high genomic stability under antibiotic pressure, relying instead on phenotypic tolerance and DNA-repair mechanisms for survival. Many individuals stop taking antibiotics when they begin to feel better. When this occurs, it is possible that the microbes that are less susceptible to treatment still remain in the body. If these microbes are able to continue to reproduce, this can lead to an infection by bacteria that are less susceptible or even resistant to an antibiotic. Microbes may also get genes from each other, which makes them drug-resistant. Bacteria that have drug-resistant DNA often transfer a copy of these genes to the other bacteria. They can then multiply and thrive. This process, known as horizontal gene transfer, allows resistance genes to spread rapidly between different bacterial species through mechanisms such as conjugation, transformation, and transduction. Bacteria become resistant to antibiotics by changing themselves or acquiring resistance genes from other bacteria.
In the early stages after the procedure, the use of interdental brushes is strongly advised against due to the potential damage to interdental tissues in the operated area, toothpicks are recommended as an alternative. The patient is asked to visit every two weeks for monitoring of their plaque levels. The time between visits will gradually increase if the patients’ plaque control is up to standard.
=== Types === Plasma retinol-binding protein, the retinol transport vehicle in serum. CRBP I/II, cellular-binding proteins involved in transport of retinol and metabolites into retinyl esters for storage or into retinoic acid. CRABPs, cellular retinoic acid–binding proteins capable of binding retinol and retinoic acid with high affinity. It has also been characterized that CRABPs are involved in many aspects of the retinoic acid signaling pathway such as the regulation and availability of retinoic acid to nuclear receptors.
Sources: en.wikipedia.org
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.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.