freeze-thaw raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-06-04. Anything still debated is marked as such rather than presented as settled.
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.
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.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
| Property | Value | Notes |
|---|---|---|
| Common route | Intranasal | Also injected in some animal work |
| Solubility class | Freely soluble in water | Solid form is hygroscopic |
| Typical storage | About -20 degrees Celsius | Keep desiccated and dark |
| Purity method | Reverse-phase HPLC | Reported as area percent |
| Confirmatory method | Mass spectrometry | Verifies expected molecular mass |
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
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.
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 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.
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.
=== Vegetable === Many plants have coagulating properties. Homer suggests in the Iliad that the Greeks used an extract of fig juice to coagulate milk. Other examples include several species of Galium, dried caper leaves, nettles, thistles, mallow, Withania coagulans (also known as Paneer Booti, Ashwagandh and the Indian Cheesemaker), and ground ivy. Some traditional cheese production in the Mediterranean uses enzymes from thistle or Cynara (artichokes and cardoons). Phytic acid, derived from unfermented soybeans, or fermentation-produced chymosin (FPC) may also be used. Vegetable rennet might be used in the production of kosher and halal cheeses, but nearly all kosher cheeses are produced with either microbial rennet or FPC. Commercial so-called vegetable rennets usually contain an extract from the mold Rhizomucor miehei described below.
Xylazine is a structural analog of clonidine and an α2-adrenergic receptor agonist, sold under many trade names worldwide, most notably the Bayer brand name Rompun, as well as Anased, Sedazine and Chanazine. Xylazine is a common veterinary drug used for sedation, anesthesia, muscle relaxation, and analgesia in animals such as horses, cattle, and other mammals. In veterinary anesthesia, it is often used in combination with ketamine. Veterinarians also use xylazine as an emetic, especially in cats. Drug interactions vary with different animals. Xylazine was first investigated for human use in the 1960s in West Germany for antihypertensive effects before being discontinued and marketed as a veterinary sedative. Xylazine's mechanism of action was discovered in 1981, which led to the creation of other α2-adrenergic receptor agonists such as medetomidine and dexmedetomidine. Xylazine has become a commonly abused street drug in the United States where it is known by the street name "tranq", particularly in the territory of Puerto Rico. The drug is used as a cutting agent for heroin and fentanyl.
For services to School Governance and to Children and Young People with Special Educational Needs. Nigel Gavin Begg. Founder, Aspire Technology Solutions. For services to Digital and Technology Industry Growth in North East England. Lynda Janet Suzanne Bennett. For services to Hockey in Wales. Trudy Helen Berlet. Lately Lead Midwife for Bereavement Care, Worcestershire Acute Hospitals NHS Trust. For services to Midwifery. Professor Miriam Bernard. Professor Emerita, Social Gerontology, Keele University. For services to Ageing Research and to Older People. Jane Alison Betsworth. Headteacher, Millfields Community School, London Borough of Hackney. For services to Education. Dr. Sanjay Bhandari. Chair, Kick It Out. For services to Sport. Dr. Manav Bhavsar. Lately Clinical Lead, Critical Care. For services to Healthcare, particularly during Covid-19. Helen Binns. Manager, Families First Team, Leeds City Council. For services to Vulnerable People. Amanda Jayne Bird. Senior Supply Chain Coordinator, Leidos Europe Limited. For services to Defence Logistics. Zachary Birks. Team Leader, Ministry of Defence. For services to Defence. Professor Anthony John Bjourson. Emeritus Professor of Genomics and lately Director, Northern Ireland Centre for Stratified Medicine, Ulster University. For services to Higher Education and to Research. Anthony Grant Bloom. Chairman, Brighton and Hove Albion Football Club. For services to Association Football and to the community in Brighton. Anthony John Bloxham.
=== Laboratory automation === In research fields such as synthetic biology, where highly iterative experimentation is common, considerable efforts have been made to automate workflows. Digital microfluidics is often touted as a laboratory automation solution, with a number of advantages over alternative solutions such as pipetting robots and droplet microfluidics. These stated advantages often include a reduction in the required volume of experimental reagents, a reduction in the likelihood of contamination and cross-contamination, potential improvements in reproducibility, increased throughput, individual droplet addressability, and the ability to integrate with sensor and detector modules to perform end-to-end or even closed loop workflow automation.
Sources: en.wikipedia.org
=== Preparation === Wheatgrass juice is cold-pressed from 7–9-day-old shoots, harvested before jointing, when chlorophyll, antioxidant enzymes, vitamin C, and phenolics peak. The grass should be washed with potable water, cold-pressed not blended or heated, and consumed within 10–15 minutes to avoid oxidation and enzyme loss. Heat, boiling, spray-drying, and high-speed blending are consistently discouraged due to chlorophyll degradation. When fresh juice is impractical, frozen fresh juice or low-temperature (<40 °C) dehydrated powder is acceptable with partial nutrient retention. Studies stress hygienic cultivation, pesticide-free medium, microbial and heavy-metal testing for safety. Wheatgrass juice is often available at juice bars, and some people grow and juice their own in their homes. It is available fresh as produce, in tablets, frozen juice, and powder. Wheatgrass is also sold commercially as a spray, cream, gel, massage lotion, and liquid herbal supplement.
Materials and samples from the original experiments remained in 2017 under the care of Miller's former student, Jeffrey Bada, a professor at the UCSD, Scripps Institution of Oceanography who also conducts origin of life research. As of 2013, the apparatus used to conduct the experiment was on display at the Denver Museum of Nature and Science.
In the wild they inhabit very soft, acidic waters (pH 4.0 to 4.8) Ideal pH for aquarium is 7.0, but a range of 6.0 to 8.0 is tolerable. They can have a lifespan of as long as ten years, but normally just two to three years in an aquarium. Neon tetras are considered easy to keep in an aquarium of at least 10 US gallons (38 L; 8.3 imp gal) with a temperature range of between 72–76 °F (22–24 °C), a water pH of between 6.0 and 7.0, GH of below 10 dGH and KH of 1–2 dKH, and under 20 ppm of nitrate. They are shoaling fish and must be kept in groups of at least six, but will be more active in groups of eight to 12 or more. Neon tetras are best kept in a densely planted tank to resemble their native Amazon environments.
Sources: en.wikipedia.org
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.
Reported human trials are few, brief and originate mainly from one country. They describe effects on anxiety-related measures, but sample sizes are small and reporting is limited. The results are widely regarded as preliminary rather than confirmed.
Reverse-phase liquid chromatography is used to assess purity and separation of related impurities. Mass spectrometry confirms that the observed molecular mass matches the expected peptide. A certificate of analysis from the supplier is the usual document of record.
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.