This is a working overview of electrospray ionization, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-12-04. Anything still debated is marked as such rather than presented as settled.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
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.
The importation of mephedrone into the UK was banned on 29 March 2010. The next day, the ACMD in the UK published a report on the cathinones, including mephedrone, and recommended they be classified as Class B drugs. On 7 April 2010, the Misuse of Drugs Act 1971 (Amendment) Order 2010 was passed by parliament, making mephedrone and other substituted cathinones, Class B drugs from 16 April 2010. Prior to the ban taking effect, mephedrone was not covered by the Misuse of Drugs Act 1971. It was, though, an offence under the Medicines Act to sell it for human consumption, so it was often sold as "plant food" or "bath salts", although it has no use as these products; this, too, was possibly illegal under the Trade Descriptions Act 1968. In the US, similar descriptions have been used to describe mephedrone, as well as methylenedioxypyrovalerone (MDPV). In May 2010, the Republic of Ireland made mephedrone illegal, followed by Belgium, Italy, Lithuania, France and Norway in June and Russia in July. In August 2010, Austria and Poland made it illegal and China announced it would be illegal as of 1 September 2010. Mephedrone had been reported to be used in Singapore in February 2010, but it was made illegal in November 2010. In December 2010, following the advice of the EMCDDA, mephedrone was made illegal throughout the EU, a move Switzerland also made shortly afterwards. Countries which have not already banned it, such as the Netherlands, Greece and Portugal, will need to change legislation to comply with the EU ruling.
=== Nuclear fission === The longest-lived and most abundant isotope, 231Pa, can fission from fast neutrons exceeding ~1 MeV. 233Pa, the other isotope of protactinium produced in nuclear reactors, also has a fission threshold of 1 MeV.
Modafinil is an eugeroic medication, which means that it promotes wakefulness and alertness. Modafinil is sold under the brand name Provigil among others. Modafinil is used to treat excessive daytime sleepiness due to narcolepsy, shift work sleep disorder, or obstructive sleep apnea. While it has seen off-label use as a purported cognitive enhancer, the research on its effectiveness for this use is not conclusive. Despite being a CNS stimulant, the addiction and dependence liabilities of modafinil are considered very low. Although modafinil shares biochemical mechanisms with stimulant drugs, it is less likely to have mood-elevating properties. The similarities in effects with caffeine are not clearly established. Unlike other stimulants, modafinil does not induce a subjective feeling of pleasure or reward, which is commonly associated with euphoria, an intense feeling of well-being. Euphoria is a potential indicator of drug abuse, which is the compulsive and excessive use of a substance despite adverse consequences. In clinical trials, modafinil has shown no evidence of abuse potential, that is why modafinil is considered to have a low risk of addiction and dependence, however, caution is advised.
Sources: en.wikipedia.org
== External links == Cold War International History Project: The End of the Cold War Cold War Files: The End of the Cold War Jeffrey W. Knopf "Did Reagan Win the Cold War?" Cold War Air Museum: Aircraft from this period of the Cold War
==== 2025 CDC leadership dispute ==== On May 14, 2025, Robert F. Kennedy Jr. stated that lawyer Matthew Buzzelli is acting CDC director, though the CDC web site did not list that name. Susan Monarez was confirmed as CDC head on July 31, 2025, but on August 27, she was fired. Monarez disputed the legality of the firing, as it had not been carried out by the president, and it had been falsely reported that she had resigned. The president later officially carried out the firing. The firing was due to her refusing to rubber stamp what were expected to be unscientific recommendations from the senior staff vaccine experts, as well as refusing to fire them. The dispute began over demands from Kennedy and his top staff for changing the recommendation for COVID vaccine to persons with higher-risk conditions and senior citizens only. The official recommendation also affects insurance coverage and whether vaccines are available in pharmacies. Senator Bill Cassidy called for the next meeting of the Advisory Committee on Immunization Practices to be postponed. He said, "Serious allegations have been made about the meeting agenda, membership, and lack of scientific process being followed for the now announced September ACIP meeting. These decisions directly impact children's health and the meeting should not occur until significant oversight has been conducted." The next day, the Trump administration announced the selection of Deputy Secretary of Health and Human Services Jim O'Neill as a replacement.
The surgeon measures the dimensions (length, width, depth) of the nasal wound, and then delineates them upon the nasal septum, and, if possible, incorporates an additional margin of 3–5 mm of width to the wound measurements; furthermore, the base of the mucosal tissue flap should be at least 1.5-cm wide. The surgeon then makes two parallel incisions along the floor and the roof of the nasal septum; the incisions converge anteriorly, towards the front of the nasal spine. Using an elevator, the flap is dissected in a sub-mucoperichondrial plane. The (far) distal edge of the flap is cut with a right-angle Beaver blade, and then is transposed into the wound. The exposed cartilages will reepithelialise (regenerate the epithelium), provided the opposite (contralateral) side of the septal mucosa is undisturbed. A technical variant of the septal mucosal flap technique is the trap-door flap, which is used to reconstruct one side of the upper half of the nasal lining. It is emplaced in the contralateral nasal cavity, as a superiorly based septal mucosal flap of rectangular shape, like that of a "trap-door". This septomucosal flap variant is a random flap with its pedicle based at the junction of the septum and the lateral nasal skeleton. The surgeon elevates the flap of septal mucosa to the roof of the nasal septum, and then traverses it into the contralateral (opposite) nasal cavity through a slit made by removing a small, narrow portion of the dorsal roof of the septum. Afterwards, the septomucosal flap is stretched across the wound in the mucosal lining of the lateral nose.
=== Primary or secondary === The distinction between primary and secondary immunodeficiencies is based on whether the cause originates in the immune system itself or insufficiency of a supporting component or an external factor.
Sources: en.wikipedia.org
== Chemistry == Mycosporine–like amino acids are rather small molecules (<400 Da). The structures of over 30 MAAs have been resolved and all contain a central cyclohexenone or cyclohexenimine ring and a wide variety of substitutions. The ring structure is thought to absorb UV light and accommodate free radicals. All MAAs absorb ultraviolet wavelengths, typically between 310 and 362 nm. They are considered to be amongst the strongest natural absorbers of UV radiation. It is this light absorbing property that allows MAAs to protect cells from the harmful UV-B and UV-A components of sunlight. Biosynthetic pathways of MAAs depend on the specific MAA molecule and the organism that is producing it. These biosynthetic pathways often share common enzymes and metabolic intermediates with pathways of the primary metabolism. An example is the shikimate pathway that is classically used to produce the aromatic amino acids (phenylalanine, tyrosine and tryptophan); with many intermediates and enzymes from this pathway utilized in MAA biosynthesis.
OHPH, also known as hydroxyprogesterone enanthate (OHPE), as well as 17α-hydroxyprogesterone heptanoate or 17α-hydroxypregn-4-ene-3,20-dione 17α-heptanoate, is a synthetic pregnane steroid and a derivative of progesterone and 17α-hydroxyprogesterone. It is a progestogen ester; specifically, it is the C17α heptanoate (enanthate) ester of 17α-hydroxyprogesterone. Analogues of OHPH include the more well-known medications hydroxyprogesterone acetate and hydroxyprogesterone caproate (hydroxyprogesterone hexanoate). The C3 benzilic acid hydrazone of OHPH, hydroxyprogesterone heptanoate benzilic acid hydrazone (OHPHBH), is known and has been studied in animals. In terms of chemical structure, OHPH is very similar to hydroxyprogesterone caproate, differing from it only in having one additional carbon in its fatty acid ester chain.
87Rb, 187Re, 176Lu, 232Th, and 238U have half-lives long enough that their decay is limited over geological time scales; 40K and 235U have shorter half-lives and are hence severely depleted, but are still long-lived enough to remain present in significant amount on Earth. The longest-lived isotope not proven to be primordial is 146Sm, which has a half-life of 9.20×107 years, followed by 244Pu (8.13×107 years) and 92Nb (3.47×107 years). 244Pu was reported to exist in nature as a primordial nuclide in 1971, but this detection could not be confirmed by further studies in 2012 and 2022. Taking into account that all these nuclides must exist for at least 4.58×109 years, 146Sm must survive 50 half-lives (and hence be reduced by 250 ≈ 1×1015), 244Pu must survive 57 (and be reduced by a factor of 257 ≈ 1×1017), and 92Nb must survive 130 (and be reduced by 2130 ≈ 1×1039). Mathematically, considering the likely initial abundances of these nuclides, primordial 146Sm and 244Pu should persist somewhere within the Earth today, even if they are not identifiable in the relatively minor portion of the Earth's crust available to human assays, while 92Nb and all shorter-lived nuclides should not. Nuclides such as 92Nb that were present in the primordial solar nebula but have long since decayed away completely are termed extinct radionuclides if they have no other means of being regenerated. As for 244Pu, calculations suggest that as of 2022, sensitivity limits were about one order of magnitude away from detecting it as a primordial nuclide.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.