This is a working overview of freeze-thaw, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Modeled on tuftsin |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues |
| Approximate molecular mass | Around 750 Da | Depends on counter-ion and hydration |
| Common forms | Lyophilized powder | Also described as aqueous solution |
| Primary origin of research | Russian laboratories | Mid-1990s onward |
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
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.
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.
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.
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.
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.
Untreated transgender people experience high rates of depression, anxiety, addiction, and suicide compared to the general population. In systematic reviews, hormone therapy and gender-affirming surgery were associated with improved mental health outcomes. In follow-up studies, most trans people experience improved psychological, social, and sexual functioning, improved global functioning, and significantly reduced suicidal ideation. Less than 1% of post-operative trans patients regret surgery. Gender-affirming surgery alone may not eliminate dysphoria or suicidality, and some trans people may need further mental health care in addition to surgery. Some researchers have expressed a need for further high-quality research on mental health outcomes following gender-affirming treatments. Certain statistically robust study designs, such as randomized controlled trials, are not applicable in studying some aspects of transgender health care due to ethical concerns (for example, it would be severely unethical to test the long-term efficacy of hormone therapy by treating some prospective patients with a placebo) as well as methodological hurdles (largely because affirmative treatments have evident effects on physiology, thus compromising blinding).
Morgan's athletic teams are known as the Bears, and they compete in the Mid-Eastern Athletic Conference (MEAC). Between 1926 and 1928, a young Charles Drew served as Athletic Director. During this time he made great improvements in the school's teams' records. From the 1930s through 1960s, led by coach and then athletic director Edward P. Hurt, Morgan's athletic teams were legendary. More than thirty of its football players were drafted by and played in the NFL and many of its track athletes competed internationally and received world-class status. By the late 1960s most white colleges and universities ended their segregation against black high school students and many top black high school students and athletes started matriculating to schools from which they had previously been barred. While achieving a national goal of desegregation, integration depleted the athletic strength of schools like Morgan State and Grambling State University. For example, the annual contest between Morgan State and Grambling played in New York City in the late 1960s drew more than 60,000 fans. Morgan State's rivals are the Howard University Bison (the matchup is often called the Battle of the Beltway) and the Coppin State Eagles.
==== Chemically reactive agents ==== Agents such as hydrogen peroxide, elemental chlorine, hypochlorous acid (chlorine water), bromine, bromine water, iodine, nitric and oxidising acids, and ozone react with sensitive moieties such as sulfide/thiol, activated aromatic rings (phenylalanine) in effect damage the protein and render it useless.
Short proteins can be synthesized chemically by a family of peptide synthesis methods. These rely on organic synthesis techniques such as chemical ligation to produce peptides in high yield. Chemical synthesis allows for the introduction of non-natural amino acids into polypeptide chains, such as attachment of fluorescent probes to amino acid side chains, (this can also be achieved via genetic engineering when producing recombinant proteins). These methods are useful in laboratory biochemistry and cell biology, though generally not for commercial applications. Chemical synthesis is inefficient for polypeptides longer than about 300 amino acids, and the synthesized proteins may not readily assume their native tertiary structure. Most chemical synthesis methods proceed from C-terminus to N-terminus, opposite the biological reaction.
Sources: en.wikipedia.org
In early November 2020, Israel Hadassah Medical Center director-general Zeev Rotstein stated that Hadassah's branch in Moscow's Skolkovo Innovation Center was collaborating on a phase III clinical trial. The ongoing phase III study is a randomised, double-blind, placebo-controlled, multi-centre clinical trial involving 40,000 volunteers in Moscow, and is scheduled to run until May 2021. In 2020–2021, phase III clinical studies were also being conducted in Belarus, UAE, India, Kazakhstan and Venezuela. On 13 April 2021, India's health ministry said its drug regulator had found that safety and immunogenicity data from a local trial of Sputnik V coronavirus vaccine was comparable to that of a late-stage trial done in Russia.
A monomer ( MON-ə-mər; mono-, "one" + -mer, "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or two- or three-dimensional network in a process called polymerization.
However, the results of the 2012 presidential elections gave the PS wins in both districts with a smaller margin in the 7th (Hollande: 51.71% / Sarkozy: 48.29%) than in the 8th (Hollande 64.21% / Sarkozy: 35.79%).
An advantage of the bacterial one-hybrid system over the yeast one-hybrid system (Y1H) lies in the higher transformation efficiency of plasmids into bacteria which allows for more complex “prey” libraries to be examined.
== Occupational exposure == Occupational exposure to PFAS occurs in numerous industries due to the widespread use of the chemicals in products and as an element of industrial process streams. People who are exposed to PFAS through their jobs typically have higher blood concentrations of PFAS than the general population due to their elevated risk for accidental ingestion, inhalation exposure, and skin contact of PFAS. Occupational exposure can occur both during production of PFAS at fluorochemical facilities and in other industries that utilize these chemicals in their processes and products.
Sources: en.wikipedia.org
=== 2 May === Russia claimed to have taken Berdychi, near Avdiivka. It also claimed to have shot down a drone over Crimea. Two people were killed in separate Russian attacks in Donetsk and Kharkiv Oblasts.
Therefore, the Royal College of Pathologists and Royal College of Physicians have developed combined infection training, that medical trainees gain a much more patient focused experience, and undertake physician examinations in addition to pathology training. The result of this is that several regional medical deaneries no longer permit medical doctors to train in microbiology or virology as single disciplines, and instead advocate dual-specialisation as infectious disease/microbiology or infectious disease/virology. Simultaneously, the expansion of higher specialist scientist trainees in microbiology means that many of the laboratory and scientific responsibilities of medical doctors may be taken on by clinical scientists, and medical doctors will instead be expected to perform a much more patient facing role. The exception in microbiology is the sub-discipline of virology, which is well suited to the expertise of clinical scientists due to reliance on cutting-edge scientific methods, increasing use of specialised genetic technologies, and a technical understanding of virus biology, with a reduced emphasis on patient management compared with microbiology as a whole.
Custom peptide synthesis is the commercial production of peptides for use in biochemistry, biology, biotechnology, pharmacology and molecular medicine. Custom peptide synthesis provides synthetic peptides as valuable tools to biomedical laboratories. Synthetic oligopeptides are used extensively in research for structure-function analysis (for example to study protein-protein interfaces), for the development of binding assays, the study of receptor agonist/antagonists or as immunogens for the production of specific antibodies. Generally, peptides are synthesized by coupling the carboxyl group or C-terminus of one amino acid to the amino group or N-terminus of another using automated solid phase peptide synthesis chemistries. However, liquid phase synthesis may also be used for specific needs.
In the United Kingdom, it is a criminal offence to sell, supply, or import any medicinal product containing kava for human consumption. It is legal to possess kava for personal use or to import it for purposes other than human consumption (e.g., for animals). Until August 2018, Poland was the only EU country with an "outright ban on kava" and where the mere possession of kava was prohibited and may have resulted in a prison sentence. Under the new legislation, kava is no longer listed among prohibited substances and it is therefore legal to possess, import, and consume the plant, but it remains illegal to sell it within Poland for the purpose of human consumption. In the Netherlands the ban was never lifted, and it is still prohibited to prepare, manufacture, or trade kava or goods containing kava. Due to safety concerns, including reports of hepatotoxicity and limitations in clinical evidence, the Committee on Herbal Medicinal Products (HMPC) concluded in 2017 that the benefit-risk balance for the oral use of kava in the treatment of anxiety disorders is unfavorable, and therefore a European Union herbal monograph could not be established.
Sources: en.wikipedia.org
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.
It originates from research in Russia, associated with the Institute of Molecular Genetics of the Russian Academy of Sciences. The first descriptions date to the mid-1990s. Most published studies come from Russian laboratories.
No, Selank itself does not occur naturally. Its backbone is based on tuftsin, which is produced in the body, but the seven-residue version is a synthetic construct. It is supplied as a manufactured peptide.
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.