freeze-thaw comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
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.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
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.
=== Acute === According to the EPS, chlorothalonil is a toxicity category I eye irritant, producing severe eye irritation. It is in toxicity category II, "moderately toxic", if inhaled (inhaled LD50 0.094 mg/L in rats.) For skin contact and ingestion, chlorothalonil is rated toxicity category IV, "practically nontoxic", meaning the oral and dermal LD50 is greater than 10,000 mg/kg.
The enzyme characterised from Saccharopolyspora erythraea converts erythromycin D into erythromycin C by introduction of a hydroxy group at the C-12 position of the macrocycle. It uses reduced nicotinamide adenine dinucleotide phosphate (NADPH) and oxygen as cofactors. Erythromycin C is subsequently converted to the antibiotic, erythromycin A, by the enzyme erythromycin 3''-O-methyltransferase.
== Training and testing == Researchers have attempted to build world models and reinforcement learning environments to train or evaluate AI agents. For example, video games such as Minecraft and No Man's Sky as well as replicas of company websites, have also been used for training such agents.
An enzyme inhibitor is characterised by its dissociation constant Ki, the concentration at which the inhibitor half occupies the enzyme. In non-competitive inhibition the inhibitor can also bind to the enzyme-substrate complex, and the presence of bound substrate can change the affinity of the inhibitor for the enzyme, resulting in a second dissociation constant Ki'. Hence Ki and Ki' are the dissociation constants of the inhibitor for the enzyme and to the enzyme-substrate complex, respectively. The enzyme-inhibitor constant Ki can be measured directly by various methods; one especially accurate method is isothermal titration calorimetry, in which the inhibitor is titrated into a solution of enzyme and the heat released or absorbed is measured. However, the other dissociation constant Ki' is difficult to measure directly, since the enzyme-substrate complex is short-lived and undergoing a chemical reaction to form the product. Hence, Ki' is usually measured indirectly, by observing the enzyme activity under various substrate and inhibitor concentrations, and fitting the data via nonlinear regression to a modified Michaelis–Menten equation.
=== France === France was obligated to join Russia due to their 1893 military alliance. French bankers did have financial interests in Russia, especially in railroads. However, France had no territorial ambitions in Manchuria, as its sphere of influence was in southern China (see Sino-French War). The French actually had cordial relations with the Japanese: French military advisors had been sent to train the Imperial Japanese Army since the expedition in 1867 and a number of Japanese ships were built in French shipyards. However, France did not wish to be diplomatically isolated, as she had been previously during Bismarck’s diplomatic quarantine of revanchist France after the Franco-Prussian War, especially given the growing power of Germany.
Sources: en.wikipedia.org
She had formerly had the same symptoms of arsenical poison herself, and it was some time before she discovered it to be the mesmeric work of an enemy. Soon after her marriage her husband began to manifest the same symptoms and had since shown them from time to time; but was, with her help, always able to overcome them. A few weeks ago she observed that he did not look well, and when questioned he said that he was unable to get the idea of this arsenical poison out of his mind. He had been steadily growing worse ever since, but still had hoped to overcome the trouble until the last. After the death the body had turned black. A doctor performed an autopsy and showed Eddy her husband's diseased heart, but she responded by giving more interviews about mesmerism. Fraser wrote that the articles made Eddy a household name, a real-life version of the charismatic and beautiful Verena Tarrant in Henry James's The Bostonians (1885–1886), with her interest in spiritualism, women's rights and the mind cure. Shortly after the death, Eddy moved next door to 571 Columbus Avenue with several students. The following year, 1883, she founded the Journal of Christian Science (later called the Christian Science Journal), which spread news of her ideas across the United States.
==== Dystrophic calcinosis cutis ==== Dystrophic calcinosis cutis is the most prevalent kind of calcification on the skin. The ectopic calcified mass usually consists of amorphous calcium phosphate and hydroxyapatite. Dystrophic calcification is linked to a number of illnesses, such as infections, hereditary diseases, cutaneous neoplasms, and connective tissue diseases. The clinical manifestation can be as minor as an accidental radiography imaging finding or as severe as subcutaneous nodules or plaques.
Anaerobic exercise is a type of exercise that breaks down glucose in the body without using oxygen; anaerobic means "without oxygen". This type of exercise leads to a buildup of lactic acid. In practical terms, this means that anaerobic exercise is more intense, but shorter in duration than aerobic exercise.
The only feature that differentiates one brand from another is the product name in a standard color, position, font size, and style. In response to these regulations, Philip Morris International, Japan Tobacco Inc., British American Tobacco Plc., and Imperial Tobacco attempted to sue the Australian government. On August 15, 2012, the High Court of Australia dismissed the suit and made Australia the first country to introduce brand-free plain cigarette packaging with health warnings covering 90% of the back and 70% of the front packaging. This took effect on December 1, 2012. Similar policies have since been introduced in the United Kingdom, where standardised packaging of tobacco products regulations (SPOT) were introduced in 2015. These regulations were also challenged by cigarette manufacturers.
Sources: en.wikipedia.org
Calcitonin gene-related peptide (CGRP) receptor antagonists, commonly known as gepants, are a class of drugs that act as antagonists of the calcitonin gene-related peptide receptor (CGRPR). The CGRP family of small proteins are present in the sensory nerves of the head and neck and are involved in transmission of pain. Nerve activation can trigger the release of CGRP and other neuropeptides, leading to inflammation, pain, and swelling in the case of migraine. Several monoclonal antibodies that bind to the CGRP receptor or peptide have been approved for prevention of migraine. As of March 11, 2024, the American Headache Society issued a statement that "CGRP targeting therapies are a first-line option for migraine prevention" in the United States. The prior use of non-specific migraine preventive medication approaches is therefore no longer required before CGRP treatments can be prescribed. Small molecule CGRPR antagonists have also been approved in the U.S. as antimigraine agents.
The ambitious hydro-electric project was intended to carry electricity across the South China Sea to satisfy electricity demand in peninsular Malaysia. Work on the dam was eventually suspended due to the Asian financial crisis. In 1995, Mahathir visited the Massachusetts Institute of Technology (MIT) and facilitated the establishment of a university modelled after MIT, leading to the founding of the Malaysia University of Science & Technology (MUST). The 1997 Southeast Asian haze, the worst haze event in history caused by Indonesian forest fires, was a major air pollution crisis for the country; Mahathir launched a cross-border firefighting operation in response.
Now perhaps it's a pretty well kept secret that one of the most uninspiring acts of the University of Cambridge over this past century was to turn down Francis Crick when he applied to be the Professor of Genetics, in 1958. Now there may have been a series of arguments, which led them to reject Francis. It was really saying, don't push us to the frontier. The apparently "pretty well kept secret" had already been recorded in Soraya De Chadarevian's Designs For Life: Molecular Biology After World War II, published by Cambridge University Press in 2002. His major contribution to molecular biology in Cambridge is well documented in The History of the University of Cambridge: Volume 4 (1870 to 1990), which was published by CUP in 1992. According to the University of Cambridge's genetics department official website, the electors of the professorship could not reach consensus, prompting the intervention of then University Vice-Chancellor Lord Adrian. Lord Adrian first offered the professorship to a compromise candidate, Guido Pontecorvo, who refused, and is said to have offered it then to Crick, who also refused. In 1976, Crick took a sabbatical year at the Salk Institute for Biological Studies in La Jolla, California. Crick had been a nonresident fellow of the Institute since 1960. Crick wrote, "I felt at home in Southern California." After the sabbatical, Crick left Cambridge to continue working at the Salk Institute. He was also an adjunct professor at the University of California, San Diego. He taught himself neuroanatomy and studied many other areas of neuroscience research.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
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.