freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2026-03-10 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
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.
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.
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
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.
== Medicine == An exudate is any fluid that filters from the circulatory system into lesions or areas of inflammation. It can be a pus-like or clear fluid. When an injury occurs, leaving skin exposed, it leaks out of the blood vessels and into nearby tissues. The fluid is composed of serum, fibrin, and leukocytes. Exudate may ooze from cuts or from areas of infection or inflammation. Although blood itself is not an exudate, some types of exudates contain blood cells.
=== Religion, heritage, and values === As Sanders described his upbringing as an American Jew in a 2016 speech: his father generally attended synagogue only on Yom Kippur; he attended public schools while his mother "chafed" at his yeshiva Sunday schooling at a Hebrew school; and their religious observances were mostly limited to Passover seders with their neighbors. Larry Sanders said of their parents, "They were very pleased to be Jews, but didn't have a strong belief in God." Bernie had a bar mitzvah at the historic Kingsway Jewish Center in Midwood, Brooklyn, where he grew up. In 1963, in cooperation with the Labor Zionist youth movement Hashomer Hatzair, Sanders and his first wife volunteered at Sha'ar HaAmakim, a kibbutz in northern Israel. His motivation for the trip was as much socialistic as it was Zionistic. As mayor of Burlington, Sanders allowed a Chabad public menorah to be placed at city hall, an action the ACLU contested. He publicly inaugurated the Hanukkah menorah and performed the Jewish religious ritual of blessing Hanukkah candles. His early and strong support played a significant role in the now widespread public menorah celebrations around the globe. When asked about his Jewish heritage, Sanders has said that he is "proud to be Jewish." Sanders rarely speaks about religion. He describes himself as "not particularly religious" and "not actively involved" with organized religion. A press package issued by his office states his religion as Jewish.
Polymer-protein hybrids are a class of nanostructure composed of protein-polymer conjugates (i.e. complexes composed of one protein attached to one or more polymer chains). The protein component generally gives the advantages of biocompatibility and biodegradability, as many proteins are produced naturally by the body and are therefore well tolerated and metabolized. Although proteins are used as targeted therapy drugs, the main limitations—the lack of stability and insufficient circulation times still remain. Therefore, protein-polymer conjugates have been investigated to further enhance pharmacologic behavior and stability. By adjusting the chemical structure of the protein-polymer conjugates, polymer-protein particles with unique structures and functions, such as stimulus responsiveness, enrichment in specific tissue types, and enzyme activity, can be synthesized. Polymer-protein particles have been the focus of much research recently because they possess potential uses including bioseparations, imaging, biosensing, gene and drug delivery.
==== Laboratory methods ==== In the laboratory, formic acid can be obtained by heating oxalic acid in glycerol followed by steam distillation. Glycerol acts as a catalyst, as the reaction proceeds through a glyceryl oxalate intermediate. If the reaction mixture is heated to higher temperatures, allyl alcohol results. The net reaction is thus:
Sources: en.wikipedia.org
David Andrew Sinclair (born June 26, 1969) is an Australian-American biologist and academic known for his research on aging and epigenetics. Sinclair is a professor of genetics at Harvard Medical School and the founding director of the Paul F. Glenn Laboratories for the Biological Mechanisms of Aging at Harvard. He is the co-author of Lifespan: Why We Age – and Why We Don't Have To.
transcytosis The transport of molecules across the interior of a cell, i.e. through the cytoplasm, especially a polarized cell such as an epithelial cell with contrasting apical and basal surfaces, thereby providing a spatially oriented transport system. Molecules undergoing transcytosis are usually contained within vesicles.
Glucose is an osmotic molecule, and can have profound effects on osmotic pressure in high concentrations possibly leading to cell damage or death if stored in the cell without being modified. Glycogen is a non-osmotic molecule, so it can be used as a solution to storing glucose in the cell without disrupting osmotic pressure.
== Animal welfare == The welfare of animals used in Burger King products has been a subject of company activity, as well as a source of controversy. In 2001, Burger King entered into an agreement with People for the Ethical Treatment of Animals (PETA) following a corporate campaign regarding the treatment of poultry by its suppliers. The agreement established a framework for implementing animal welfare standards, including third-party compliance monitoring. In 2006, PETA, acting as a shareholder in Burger King's parent company, brought a resolution before the board advocating for the adoption of controlled atmosphere killing (CAK) as a more humane and cost-effective slaughter method. In response, Burger King announced new supplier policies in 2007, prioritizing CAK and committing to incremental use of cage-free eggs and crate-free pork. These changes were recognized by advocacy groups as establishing a higher industry standard for animal welfare compliance.
== Prognosis == Symptoms of fibromyalgia are regarded as persistent in nearly all patients. The German Federal Ministry of Health guidance on FM refers to a longitudinal study (n = 1555) in which 10% of patients had substantial improvement in pain, 15% had moderate improvement, and 39% worsened. FM severity worsened in 36%. No average meaningful change in symptoms was found, and high levels of self-reported symptoms and distress continued for most patients. Fibromyalgia can cause substantial disability, with impacts on the ability to work, engage in recreational activities, and do household duties. Amongst people with fibromyalgia, the proportion that are able to maintain their jobs has been estimated at between 34% and 77%, and some research suggest the typical reduction in work hours is between 50-70%. There is variation in the level of impact, with 71.4% of those who are mild remaining in employment, compared to 61.2% of those who are moderate and 28.5% of those who are severe. Levels of pain can vary significantly over time, from severe pain to almost symptom-free phases. A 2023 meta-analysis found that FM people were at a standardized mortality ratio (i.e., observed mortality rates in the study population, compared to expected levels based on a standard population) of 3.37 (95% CI 1.52 to 7.50) for mortality due to suicide.
Sources: en.wikipedia.org
== External links == Countercurrent multiplier animation from Colorado University. Research about elephant seals using countercurrent heat exchange to keep heat from leaving their body while breathing out, during hibernation. Patent for a snow mask with a removable countercurrent exchange module which keeps the warmth from leaving the mask when breathing out.
== Scientists and inventors == Samuel Bard* (1763), personal physician to George Washington; founder of the Columbia University College of Physicians and Surgeons John Stevens (King's 1768), builder of the first oceangoing steamboat in the U.S. Nicholas Romayne* (1774), physician, president of the Columbia University College of Physicians and Surgeons David Hosack (1790), physician, botanist, educator John Eatton Le Conte (1800), naturalist Samuel Akerly (1804), physician, co-founder of the New York Institute for the Education of the Blind Valentine Mott (1806), surgeon pioneer James Renwick (1807), English-American scientist and engineer, professor of Natural philosophy at Columbia University; father of architect James Renwick Jr. John Brodhead Beck (1813), New York physician Daniel Levy Maduro Peixotto (1816), Dutch-born Jewish American physician, former president of the Willoughby Medical College Henry James Anderson (1818), scientist and educator who participated in the U.S. Dead Sea exploration expedition Alfred Charles Post (1822), surgeon, professor at New York University School of MedicineS Horatio Allen (1823), imported the Stourbridge Lion, first successful steam locomotive to run in the U.S. John Clarkson Jay (1827), physician and notable conchologist, grandson of John Jay Alfred W. Craven (1829), chief engineering of Croton Aqueduct; founding member of the American Society of Civil Engineers Edward S.
== Treatment == Due to the deterministic nature of moist desquamation, once symptoms occur the condition itself can not be reversed and a patient must wait for the condition to subside. Management of these partial-thickness wounds has been influenced by the Winter principle of moist wound healing, which suggests that wounds heal more rapidly in a moist environment. Hydrocolloid dressings applied directly to these wounds prevent the evaporation of moisture from the exposed dermis and create a moist environment at the wound site that promotes cell migration. As additional radiation exposure may either exacerbate or cause the re-occurrence of moist dequamation, patients are advised to use sunscreen over the irradiated area after completion of treatment.
== External links == Clinical trial number NCT03669588 for "An Efficacy and Safety Study of ARGX-113 in Patients With Myasthenia Gravis Who Have Generalized Muscle Weakness (ADAPT)" at ClinicalTrials.gov
== Further reading == Author I'm Not the Only One (2004) Mr Galloway Goes to Washington (2005) Fidel Castro Handbook (2006), MQ Publications. ISBN 1-84072-688-1 Respect: Documents of the Crisis (2008) with Salma Yaqoob and Alan Thornett Open Season: The Neil Lennon Story (2011) Miranda Media
Sources: en.wikipedia.org
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.