The short version of freeze-thaw fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Principal proposed target | GABA-A receptor complex | Hypothesis derived mainly from animal pharmacology |
| Common behavioral assay | Elevated plus maze | Rodent test for anxiety-like behavior |
| Reported molecular marker | Hippocampal BDNF expression | Measured by immunoassay or mRNA quantification |
| Typical dosing route | Intranasal | Chosen to reduce first-pass metabolism |
| Reported plasma half-life | Minutes | Based on limited peptide stability data |
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.
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.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
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.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
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.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
Bernoulli's principle states that within a flow of constant energy, when fluid flows through a region of lower pressure it speeds up and when it flows through a region of higher pressure it slows down. Thus, Bernoulli's principle quantifies changes in speed and changes in pressure within a flow field. Bernoulli's equation is derived by considering the forces or energy along a streamline, but it can also be applied to a flow field where all the streamlines come from a region of uniform velocity and pressure. It cannot be used to compare different flow fields, for example comparing a plume or jet of air with the surrounding stationary air. (See this example below). Fluid particles are subject only to pressure and their own weight. If a fluid is flowing horizontally, when its speed increases it can only be because the fluid on that section has moved from a region of higher pressure to a region of lower pressure; and if its speed decreases, it can only be because it has moved from a region of lower pressure to a region of higher pressure. Consequently, within a fluid flowing horizontally, the highest speed occurs where the pressure is lowest, and the lowest speed occurs where the pressure is highest. Bernoulli's principle is only applicable for isentropic flows: when the effects of irreversible processes (like turbulence) and non-adiabatic processes (e.g. thermal radiation) are small and can be neglected. The simple form of Bernoulli's equation is valid for incompressible flows (e.g. most liquid flows and gases moving at low Mach number).
Sodium compounds have been known since ancient times; salt (sodium chloride) has been an important commodity in human activities. While potash has been used since ancient times, it was not understood for most of its history to be a fundamentally different substance from sodium mineral salts. Georg Ernst Stahl obtained experimental evidence which led him to suggest the fundamental difference of sodium and potassium salts in 1702, and Henri-Louis Duhamel du Monceau was able to prove this difference in 1736. The exact chemical composition of potassium and sodium compounds, and the status as chemical element of potassium and sodium, was not known then, and thus Antoine Lavoisier did not include either alkali in his list of chemical elements in 1789. Pure potassium was first isolated in 1807 in England by Humphry Davy, who derived it from caustic potash (KOH, potassium hydroxide) by the use of electrolysis of the molten salt with the newly invented voltaic pile. Previous attempts at electrolysis of the aqueous salt were unsuccessful due to potassium's extreme reactivity. Potassium was the first metal that was isolated by electrolysis. Later that same year, Davy reported extraction of sodium from the similar substance caustic soda (NaOH, lye) by a similar technique, demonstrating the elements, and thus the salts, to be different.
== Other species == All mammals have an extremely closely related blood coagulation process, using a combined cellular and serine protease process. It is possible for any mammalian coagulation factor to "cleave" its equivalent target in any other mammal. The only non-mammalian animal known to use serine proteases for blood coagulation is the horseshoe crab. Exemplifying the close links between coagulation and inflammation, the horseshoe crab has a primitive response to injury, carried out by cells known as amoebocytes (or hemocytes) which serve both hemostatic and immune functions.
There's no way it (KFC) could have grown as it did without the Collectramatic. Stores were doing about $200,000 a year in sales on average with the pots...but they could never have done the $900,000 a year it became without Win's fryer. He (Shelton) helped set the stage for that with true engineering thinking. Although a number of franchisees bought the Collectramatic, which had the support of Colonel Sanders from 1970 onwards, John Y. Brown Jr. had given tacit approval to franchisees to exclusively use the older L S Hartzog fryer, saying "Though those old pots were damn dangerous, at least we knew they worked! I was mostly afraid these new fryers would break down in the middle of business." Brown warned franchisees that they were in violation of their contract if they used the Collectramatic. Brown held his ground on the issue until he learned that his father, John Y. Brown Sr., who owned multiple KFC franchises, was successfully using the Collectramatic in every franchise he owned. The issue was eventually resolved after Heublein purchased KFC, acquired Hartzog and nullified the contract. The Collectramatic has been an approved pressure fryer for KFC from 1972 onwards. From 2013 onwards, KFC has been transitioning from using Collectramatic cookers to pressure fryers produced by Henny Penny, which supplies KFC with various equipment. The 'Velocity' series of pressure fryers includes increased load capacity, automatic oil filtration and increased oil longevity.
(company) with violating the whistleblower protection Rule 21F-17 by having employees sign confidentiality agreements that threatened repercussions for discussing internal matters with outside parties. President Donald Trump announced plans to dismantle Dodd-Frank in 2016. In addition to the Dodd-Frank programs and the False Claims Act, other U.S. agencies have their own whistleblower reward programs, including the Internal Revenue Service, the Financial Crimes Enforcement Network, the Department of Transportation, and two programs administered by the Department of Justice, one focused on corporate crime and the other on antitrust violations. The US Department of Labor's Whistleblower Protection Program can handle many types of retaliation claims based on legal actions an employee took or was perceived to take in the course of their employment. Moreover, in the United States, if the retaliation occurred due to the perception of who the employee is as a person, the Equal Employment Opportunity Commission may be able to accept a complaint of retaliation. The importance of whistleblowers has risen within the technology industry in particular as it has expanded in recent years. Prominent tech whistleblowers such as Frances Haugen, Mark MacGann, and Peiter "Mudge" Zatko have all come forward publicly to draw attention to particular problems at their companies. With technology companies increasingly acting as federal contractors, the importance of whistleblower laws to the industry continues to expand.
Sources: en.wikipedia.org
Förster resonance energy transfer is named after the German scientist Theodor Förster. When both chromophores are fluorescent, the term "fluorescence resonance energy transfer" is often used instead, although the energy is not actually transferred by fluorescence. In order to avoid an erroneous interpretation of the phenomenon that is always a nonradiative transfer of energy (even when occurring between two fluorescent chromophores), the name "Förster resonance energy transfer" is preferred to "fluorescence resonance energy transfer"; however, the latter enjoys common usage in scientific literature. FRET is not restricted to fluorescence and occurs in connection with phosphorescence as well. The energy transfer donor can also be an excited electronic state of a chemical product of a bioluminescent enzyme, in which Förster resonance energy transfer is often referred to as bioluminescence resonance energy transfer (BRET). However, the energy transfer also occurs before bioluminescence emission, and thus the term BRET is also mechanistically incorrect, although it also is commonly used to specify the type of donor.
246Cm(12C,xn)258−xNo (4,5) This reaction was studied in 1958 by scientists at the LBNL using a 5% 246Cm curium target. They were able to measure 7.43 MeV decays from250Fm, associated with a 3 s 254No parent activity, resulting from the 4n channel. The 3 s activity was later reassigned to 252No, resulting from reaction with the predominant 244Cm component in the target. It could however not be proved that it was not due to the contaminant250mFm, unknown at the time. Later work in 1959 produced 8.3 MeV alpha particles with a half-life of 3 s and a 30% SF branch. This was initially assigned to 254No and later reassigned to 252No, resulting from reaction with the 244Cm component in the target. The reaction was restudied in 1967 and activities assigned to 254No and 253No were detected.
Rivastigmine, sold under the brand name Exelon among others, is an acetylcholinesterase inhibitor used for the treatment of dementia associated with Alzheimer's disease and with Parkinson's disease. Rivastigmine can be administered orally or via a transdermal patch; the latter form reduces the prevalence of side effects, which typically include nausea and vomiting. Rivastigmine is eliminated through the urine, and appears to have relatively few drug-drug interactions. It was patented in 1985 and came into medical use in 1997.
=== Names === Etilefrine is the generic name of the drug and its INNTooltip International Nonproprietary Name and BANTooltip British Approved Name, while étiléfrine is its DCFTooltip Dénomination Commune Française and etilefrina is its DCITTooltip Denominazione Comune Italiana. In the case of the hydrochloride salt, its generic name is etilefrine hydrochloride and this is its BANMTooltip British Approved Name and JANTooltip Japanese Accepted Name. Synonyms of etilefrine include ethylnorphenylephrine, ethylphenephrine, etiladrianol, aethyladrianol, and M-I-36. Brand names of the drug include Effortil, Circupon, Apocretin, Palsamin, Kertasin, Pressoton, Effoless, and Sanlephrin.
Sources: en.wikipedia.org
Intranasal administration predominates in both animal and human research because it avoids hepatic first-pass metabolism. Injectable and intraperitoneal routes appear in animal work mainly for comparison.
Behavioral endpoints include time spent in open arms of the elevated plus maze and avoidance latencies. Biochemical endpoints include BDNF concentration, cytokine levels, and monoamine metabolite ratios in brain tissue.
Most published studies are small, originate from a limited number of laboratories, and lack independent replication. Dose-response relationships, measured brain exposure, and long-term outcomes are not well characterized.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.