The short version of freeze-thaw fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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.
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.
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.
| 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 |
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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, 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.
MRI, or Magnetic Resonance Imaging, is considered the imaging study of choice in identifying Tarlov cysts. MRI provides better resolution of tissue density, absence of bone interference, multiplanar capabilities, and is noninvasive. Plain films may show bony erosion of the spinal canal or of the sacral foramina. On MRI pictures, the signal is the same as the CSF one. If MRI made with a contrast medium:
Pyruvate, the product of glycolysis under aerobic conditions, is a metabolic branch point. As a preliminary to following the central path of aerobic metabolism from glycolysis to the citric acid cycle, we put pyruvate in perspective by considering its various possible fates. We also consider the broader context of common carboxylation and decarboxylation reactions in biochemistry.
=== Impact upon pensions === Soon after sentencing, the Illinois Teachers' Retirement System announced that Hastert would forfeit future teachers' pension benefits, effective immediately. Hastert challenged this decision on the grounds that the specific federal crime to which he pleaded guilty was not directly related to his time as a teacher. Hastert's pension for his service in the Illinois General Assembly—about $28,000 a year—was originally unaffected. However, in October 2016, the General Assembly Retirement System board of trustees unanimously voted to suspend Hastert's pension and in April 2017 the board voted, 5–2, to terminate the pension. As of 2015, Hastert continued to receive his congressional pension, which amounted to approximately $73,000 a year.
Eculizumab (Soliris) appears to be useful for atypical hemolytic uremic syndrome (aHUS). In September 2011 the U.S. Food and Drug Administration (FDA) approved it as an orphan drug to treat people with aHUS. This approval was based on two small prospective trials of 17 people and 20 people. In the UK, NICE issued guidance on the use of Eculizumab for treating aHUS, based on five evidence sources, including those used by the FDA No randomised controlled trials were identified. All prospective studies were phase 2, open‑label, non‑randomised, single‑arm studies that included patients with different clinical baseline characteristics. The prospective studies lasted 26 weeks; however, patients were allowed to continue treatment with eculizumab in a long‑term extension study. Ravulizumab-cwvz (Ultomiris) is a second generation monoclonal antibody for aHUS made by Alexion pharmaceuticals, Inc. The target of ravulizumab-cwvz is the same eculizumab (Soliris) with changes to the structure of the antibody resulting in a longer serum half life and therefore reduced dosing regimen.
Sources: en.wikipedia.org
For comparison, other antidepressants, including fluoxetine, paroxetine, duloxetine, vilazodone, adjunctive aripiprazole, olanzapine/fluoxetine, and extended-release quetiapine, have NNTs ranging from 6 to 8 in terms of depression response and 7 to 14 in terms of depression remission. On the basis of these results, it was concluded that transdermal selegiline has similar effectiveness to other antidepressants. NNTs are measures of effect size and indicate how many individuals would need to be treated in order to encounter one additional outcome of interest. Lower NNTs are better, and NNTs corresponding to Cohen's d effect sizes have been defined as 2.3 for a large effect (d = 0.8), 3.6 for a medium effect (d = 0.5), and 8.9 for a small effect (d = 0.2). The effectiveness of transdermal selegiline for depression relative to side effects and discontinuation was considered to be favorable. While several large regulatory clinical trials of transdermal selegiline versus placebo for depression have been conducted, there is a lack of trials comparing selegiline to other antidepressants. Although multiple doses of transdermal selegiline were assessed, a dose–response relationship for depression was never established. Transdermal selegiline has shown similar clinical effectiveness in the treatment of atypical depression relative to typical depression and in the treatment of anxious depression relative to non-anxious depression.
17 February – A global review of harms from personal car automobility finds cars have killed 60–80 million people since their invention, with automobility causing roughly every 34th death, and summarises interventions that are ready for implementation to reduce the, largely crash-linked or pollution-mediated, deaths from automobility-centrism and dependency. 19 February Astronomers announce the most luminous object ever discovered, quasar QSO J0529-4351, located 12 billion light-years away in the constellation Pictor. Researchers with the University of Tennessee and University of Missouri publish an academic study about how survivors from the 2011 Joplin tornado recover from "Tornado Brain", a new term for the PTSD of tornado survivors. 20 February – The northern green anaconda (Eunectes akayima), a new species of the giant snake, is described for the first time. 21 February Researchers use artificial intelligence to forecast plasma instabilities in fusion reactors up to 300 milliseconds in advance. The first neuroimaging study that shows flow state-related brain activity during a creative production task, jazz improvisation, is published. Its results support a theory that creative flow represents optimized specialized processing enabled by extensive experience, relaxing conscious control.
AIDA is a freeware computer program that permits the interactive simulation of plasma insulin and blood glucose profiles for demonstration, teaching, self-learning, and research purposes. Originally developed in 1991, it has been updated and enhanced since, and made available without charge from 1996 on the World Wide Web. The program, which is still being updated, has gone through a number of revisions and developments in the 16+ years since its original internet launch. Further copies of the simulator have been made available, in the past, on diskette by the system developers and from the British Diabetic Association (BDA) — now called 'Diabetes UK' — London, England, following the BDA's own independent evaluation of the software. More than 1,075,000 diabetes simulations have been run via a web-based version of the AIDA diabetes simulator. The AIDA software is intended to serve as an educational support tool and can be used by anyone — person with diabetes, relative of a patient, health care professional (doctor, nurse, clinical diabetes educator, dietician, pharmacist, etc.), or student — even if they may have minimal knowledge of the pathophysiology of diabetes mellitus.
Sources: en.wikipedia.org
== Potential Health benefits == PRP-rich preparations from bovine colostrum have shown possible efficacy against various illnesses including neurodegenerative diseases (such as Alzheimer's), viral infections, and ailments characterized by an overactive immune system, such as allergies, asthma and autoimmune diseases. Some recent research has also indicated possible efficacy in combating obesity.
Qualitatively the shape of the atomic orbitals of multi-electron atoms resemble the states of the hydrogen atom. The Pauli principle requires the distribution of these electrons within the atomic orbitals such that no more than two electrons are assigned to any one orbital; this requirement profoundly affects the atomic properties and ultimately the bonding of atoms into molecules.
== Safety and regulation == The European Food Safety Authority (EFSA) and the United States Food and Drug Administration (FDA) have evaluated TBHQ and determined that it is safe to consume at the concentration allowed in foods. The FDA and European Union both set an upper limit of 0.02% (200 mg/kg) of the oil or fat content in foods. It has not been approved in Japan, hence import of food containing TBHQ for selling is not allowed in Japan as of 2007. At very high doses, it has some negative health effects on lab animals, such as producing precursors to stomach tumors and damage to DNA. A number of studies have shown that prolonged exposure to very high doses of TBHQ may be carcinogenic, especially for stomach tumors. Other studies, however, have shown opposite effects, including inhibition against HCA-induced carcinogenesis (by depression of metabolic activation) for TBHQ and other phenolic antioxidants (TBHQ was one of several, and not the most potent) and reduction of nitrosamine-induced carcinogenesis (likely due to phase-II enzyme induction via Nrf2). The EFSA considers TBHQ to be noncarcinogenic. A 1986 review of scientific literature concerning the toxicity of TBHQ determined that a wide margin of safety exists between the levels of intake by humans and the doses that produce adverse effects in animal studies. In addition, TBHQ has been identified by high-throughput screening as having potential immunotoxic effects in 2021. It was previously reported in 2014 that TBHQ enhances allergy response in mice by promoting Th2 cells through Nrf2.
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.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.