Everything below concerns mass spectrometry. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-12-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
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.
| Property | Value | Notes |
|---|---|---|
| Typical purity report | 95% or higher by HPLC | Area percentage at 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray or MALDI |
| Powder storage | -20 C, desiccated | Protect from light |
| Solution storage | 2-8 C short term | Freeze aliquots for longer |
| Quality document | Certificate of analysis | States method and value |
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.
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.
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.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
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.
Growth of spermatogenic tissue in testicles, male fertility, penis or clitoris enlargement, increased libido and frequency of erection or clitoral engorgement occurs. Growth of jaw, brow, chin, and nose and remodeling of facial bone contours, in conjunction with human growth hormone occurs. Completion of bone maturation and termination of growth. This occurs indirectly via estradiol metabolites and hence more gradually in men than women. Increased muscle strength and mass, shoulders become broader and rib cage expands, deepening of voice, growth of the Adam's apple. Enlargement of sebaceous glands. This enlargement might cause acne, subcutaneous fat in face decreases. Pubic hair extends to thighs and up toward umbilicus, development of facial hair (sideburns, beard, moustache), loss of scalp hair (androgenetic alopecia), increase in chest hair, periareolar hair, perianal hair, leg hair, armpit hair.
=== Smoking cessation === Prescribed as an aid for smoking cessation, bupropion reduces the severity of craving for nicotine and withdrawal symptoms such as depressed mood, irritability, difficulty concentrating, and increased appetite. Initially, bupropion slows the weight gain that often occurs in the first weeks after quitting smoking. With time, however, this effect becomes negligible. The bupropion treatment course lasts for seven to twelve weeks, with the patient halting the use of tobacco about ten days into the course. After the course, the effectiveness of bupropion for maintaining abstinence from smoking declines over time, from 37% of tobacco abstinence at three months to 20% at one year. It is unclear whether extending bupropion treatment helps to prevent relapse of smoking. Overall, six months after the therapy, bupropion increases the likelihood of quitting smoking approximately 1.6-fold as compared to placebo. In this respect, bupropion is as effective as nicotine replacement therapy but inferior to varenicline. Combining bupropion and nicotine replacement therapy does not improve the quitting rate. In children and adolescents, the use of bupropion for smoking cessation does not appear to offer any significant benefits. The evidence for its use to aid smoking cessation in pregnant women is insufficient.
Glyceraldehyde-3-phosphate can double up to form larger sugar molecules like glucose and fructose. These molecules are processed, and from them, the still larger sucrose, a disaccharide commonly known as table sugar, is made, though this process takes place outside of the chloroplast, in the cytoplasm. Alternatively, glucose monomers in the chloroplast can be linked together to make starch, which accumulates into the starch grains found in the chloroplast. Under conditions such as high atmospheric CO2 concentrations, these starch grains may grow very large, distorting the grana and thylakoids. The starch granules displace the thylakoids, but leave them intact. Waterlogged roots can also cause starch buildup in the chloroplasts, possibly due to less sucrose being exported out of the chloroplast (or more accurately, the plant cell). This depletes a plant's free phosphate supply, which indirectly stimulates chloroplast starch synthesis. While linked to low photosynthesis rates, the starch grains themselves may not necessarily interfere significantly with the efficiency of photosynthesis, and might simply be a side effect of another photosynthesis-depressing factor.
The history of smallpox extends into pre-history. Genetic evidence suggests that the smallpox virus emerged 3,000 to 4,000 years ago. Prior to that, similar ancestral viruses circulated, but possibly only in other mammals, and possibly with different symptoms. Only a few written reports dating from about 500–1000 CE are considered reliable historical descriptions of smallpox, so understanding of the disease prior to that has relied on genetics and archaeology. However, during the second millennium, especially starting in the 16th century, reliable written reports become more common. The earliest physical evidence of smallpox is found in the Egyptian mummies of people who died some 3,000 years ago. Smallpox has had a major impact on world history, not least because indigenous populations of regions where smallpox was non-native, such as the Americas and Australia, were rapidly and greatly reduced by smallpox (along with other introduced diseases) during periods of initial foreign contact, which helped pave the way for conquest and colonization. During the 18th century, the disease killed an estimated 400,000 Europeans each year, including five reigning monarchs, and was responsible for a third of all blindness. Between 20 and 60% of all those infected—and over 80% of infected children—died from the disease. During the 20th century, it is estimated that smallpox was responsible for 250–500 million deaths. In the early 1950s, an estimated 50 million cases of smallpox occurred in the world each year.
Sources: en.wikipedia.org
=== Antibody Epitope Mapping === Antibody epitope mapping is used to find the specificity of an antibody. The epitope (antibody binding site of antigens) is expressed on the bacterial cell surface by expressing a region of the gene encoding the antigen. Flow cytometry with fluorescently-labelled antibodies is used to detect the amount of antibody binding to epitope.
==== Direct sequencing ==== The first reported method of methylation analysis using bisulfite-treated DNA utilized PCR and standard dideoxynucleotide DNA sequencing to directly determine the nucleotides resistant to bisulfite conversion. Primers are designed to be strand-specific as well as bisulfite-specific (i.e., primers containing non-CpG cytosines such that they are not complementary to non-bisulfite-treated DNA), flanking (but not involving) the methylation site of interest. Therefore, it will amplify both methylated and unmethylated sequences, in contrast to methylation-specific PCR. All sites of unmethylated cytosines are displayed as thymines in the resulting amplified sequence of the sense strand, and as adenines in the amplified antisense strand. By incorporating high throughput sequencing adaptors into the PCR primers, PCR products can be sequenced with massively parallel sequencing. Alternatively, and labour-intensively, PCR product can be cloned and sequenced. Nested PCR methods can be used to enhance the product for sequencing. All subsequent DNA methylation analysis techniques using bisulfite-treated DNA is based on this report by Frommer et al. (Figure 2). Although most other modalities are not true sequencing-based techniques, the term "bisulfite sequencing" is often used to describe bisulfite-conversion DNA methylation analysis techniques in general.
=== Dyes === Primary aromatic amines are used as a starting material for the manufacture of azo dyes. It reacts with nitrous acid to form diazonium salt, which can undergo coupling reaction to form an azo compound. As azo-compounds are highly coloured, they are widely used in dyeing industries, such as:
If Gaddafi's Free Officers had not preempted the Shelhis, they would have almost certainly been defeated by the combined forces of Abdul Aziz Shelhi, the deputy commander of Libya's army, and the prominent families in Cyrenaica that supported the Shelhi family. On 1 September, Gaddafi's Free Officers occupied airports, police depots, radio stations, and government offices in Tripoli and Benghazi. Gaddafi took control of the Berka barracks in Benghazi, while Umar Muhayshi occupied Tripoli barracks and Jalloud seized the city's anti-aircraft batteries. Khweldi Hameidi took over the Tripoli radio station and arrested crown prince Sayyid Hasan ar-Rida al-Mahdi as-Sanussi, forcing him to relinquish his claim to the throne. They met no serious resistance and wielded little violence against the monarchists. Once Gaddafi removed the government, he announced the foundation of the Libyan Arab Republic. Addressing the populace by radio, he proclaimed an end to the "reactionary and corrupt" regime, "the stench of which has sickened and horrified us all". Due to the coup's bloodless nature, it was initially labelled the "White Revolution", although was later renamed the "One September Revolution" after its date. Gaddafi insisted that the Free Officers' coup represented a revolution, marking the start of widespread change in the socio-economic and political nature of Libya. He proclaimed that the revolution meant "freedom, socialism, and unity", and soon implemented measures to achieve this.
=== La–Lem === Marc Lacroix (b. 1963). Belgian biochemist at the Institut Jules Bordet (Brussels), who specializes in breast cancer biology, metastasis and therapy. Keith Laidler (1916–2003). British-Canadian chemist and biochemist at the University of Ottawa. Expert on chemical and enzyme kinetics. Fellow of the Royal Society of Canada. Henry Lardy (1917–2010). American biochemist at the University of Wisconsin, noted for work on metabolism. Member Natl. Acad. Sci. USA. Michel Lazdunski (b. 1938). French biochemist and neuroscientist at Sophia Antipolis. Known especially for work on ion channels. Full Member of the French Academy of Sciences. Jack Legge (1917–1996). Australian biochemist known for his work on blood pigment metabolism and participation in mustard gas trials on Australian Defence Force volunteers during WW2. Albert L. Lehninger (1917–1986). American biochemist at the University of Wisconsin. He discovered, with Eugene P. Kennedy, that mitochondria are the site of oxidative phosphorylation in eukaryotes. Author of several influential texts, including The Mitochondrion, Bioenergetics and Biochemistry. Member Natl. Acad. Sci. USA. Luis Federico Leloir FRS (foreign associate) (1906–1987). Argentinian biochemist at the Fundación Instituto Campomar (Buenos Aires) who worked on sugar nucleotides, carbohydrate metabolism, and renal hypertension. Nobel Prize for Chemistry (1970). Rudi Lemberg FRS (1896–1975). German-Australian biochemist, director of the Kolling Institute of Medical Research from 1935 to 1972. Known for porphyrin research.
Sources: en.wikipedia.org
The Furman is a unit of angular measure equal to 1⁄65,536 of a circle, or just under 20 arcseconds. It is named for Alan T. Furman, the American mathematician who adapted the CORDIC algorithm for 16-bit fixed-point arithmetic sometime around 1980. 16 bits give a resolution of 216 = 65,536 distinct angles. A related unit of angular measure equal to 1⁄256 of a circle, represented by 8 bits, has found some use in machinery control where fine precision is not required, most notably crankshaft and camshaft position in internal combustion engine controllers, and in video game programming. There is no consensus as to its name, but it has been called the 8-Bit Furman. These units are convenient because binary integer overflow resembles angular arithmetic: the value of an 8-bit integer overflows from 255 to 0 when a full circle has been traversed. This means binary addition and subtraction work as expected for angular arithmetic. Measures are often made using a Gray code, which is trivially converted into more conventional notation. Its value is equivalent to about 0.0245 radians or 1.41°.
Broadly referred to as arrayed primer extension (APEX), this technology has several benefits over methods based on differential hybridization of probes. Comparatively, APEX methods have greater discriminating power than methods using this differential hybridization, as it is often impossible to obtain the optimal hybridization conditions for the thousands of probes on DNA microarrays (usually this is addressed by having highly redundant probes). However, the same density of probes cannot be achieved in APEX methods, which translates into lower output per run. Illumina Incorporated's Infinium assay is an example of a whole-genome genotyping pipeline that is based on primer extension method. In the Infinium assay, over 100,000 SNPs can be genotyped. The assay uses hapten-labelled nucleotides in a primer extension reaction. The hapten label is recognized by anti-bodies, which in turn are coupled to a detectable signal. APEX-2 is an arrayed primer extension genotyping method which is able to identify hundreds of SNPs or mutations in parallel using efficient homogeneous multiplex PCR (up to 640-plex) and four-color single-base extension on a microarray. The multiplex PCR requires two oligonucleotides per SNP/mutation generating amplicons that contain the tested base pair. The same oligonucleotides are used in the following step as immobilized single-base extension primers on a microarray (Krjutskov et al. 2008).
RCH(NH2)CO2H ⇌ RCH(N+H3)CO−2 The ratio of the concentrations of the two species in solution is independent of pH. The zwitterionic form in the solid state is stabilized by hydrogen bonds. Zwitterions may also be present in the gas phase for some cases different from the simple carboxylic acid-to-amine transfer.
However, benzodiazepines have been used clinically to manage the adverse psychological effects of psychedelics, for instance in clinical studies and in the emergency department. A clinical trial of psilocybin and midazolam coadministration found that midazolam clouded the effects of psilocybin and impaired memory of the experience. Benzodiazepines might interfere with the therapeutic effects of psychedelics, such as sustained antidepressant effects. Some serotonergic psychedelics, for instance dimethyltryptamine (DMT) and 5-MeO-DMT, are highly susceptible substrates for monoamine oxidase (MAO), specifically MAO-A, and hence can be greatly potentiated by monoamine oxidase inhibitors (MAOIs). An example of this is ayahuasca, in which plants containing both DMT and harmala alkaloids acting as MAOIs such as harmine and harmaline are combined. This allows DMT to become orally active and to have a much longer duration of action than usual. The 2C psychedelics, such as 2C-B, 2C-I, and 2C-E, are also substrates of both MAO-A and MAO-B, and may likewise be greatly potentiated by MAOIs. Examples of MAOIs that may potentiate psychedelics behaving as MAO-A and/or MAO-B substrates include phenelzine, tranylcypromine, isocarboxazid, moclobemide, and selegiline. Combination of MAO-substrate psychedelics with MAOIs can result in overdose and serious toxicity, including death. Other psychedelics, such as LSD, are not substrates of MAO and are not potentiated by MAOIs.
Sources: en.wikipedia.org
Purity is usually reported as an HPLC area percentage, most often measured at 214 nm. Identity is confirmed separately by mass spectrometry. A certificate of analysis should state both the method and the observed value.
Dry powder is kept frozen, desiccated, and shielded from light. Dissolved material is aliquoted and frozen to limit freeze-thaw cycles. Short-term refrigerated storage is common for working solutions.
Russia registers it as a prescription nasal product. Most other markets classify it as a research chemical with no approved medical use. Oversight of purity and labeling is consequently minimal in those markets.
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.