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 2026-03-11. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
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.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
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.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
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.
== Animal studies == Research in mice suggests that gelsolin, like other actin-severing proteins, is not expressed to a significant degree until after the early embryonic stage—approximately 2 weeks in murine embryos. In adult specimens, however, gelsolin is particularly important in motile cells, such as blood platelets. Mice with null gelsolin-coding genes undergo normal embryonic development, but the deformation of their blood platelets reduced their motility, resulting in a slower response to wound healing. An insufficiency of gelsolin in mice has also been shown to cause increased permeability of the vascular pulmonary barrier, suggesting that gelsolin is important in the response to lung injury.
== Veterinary use == Fentanyl is commonly used for analgesia and as a component of balanced sedation and general anesthesia in small animal patients. The short-acting nature, wide safety profile, lower rate of adverse effect compared to other opioids, and high potency make fentanyl one of the most effective and common analgesics in veterinary medicine; the ability to reduce the minimum alveolar concentration leads to fentanyl being commonly used in dogs that are elderly or have cardiovascular issues. Due to its short duration and quick onset, fentanyl is commonly used as a constant rate infusion or as a transdermal patch, with the latter being able to last 3 to 4 days. Fentanyl can provide sedation for dogs. Fentanyl is less common and has more adverse effects in livestock and equine compared to cats and dogs. In horses at analgesic doses tachycardia, restlessness, and excitement occur. Subcutaneous administration often causes pain, but a bicarbonate solution exists which does not cause pain when given subcutaneously. Fentanyl is highly lipophilic, about 1000 times more than morphine. In dogs it has low protein binding of 15.6% and a half-life of 2–6 hours. In cats the half-life is 2.5 hours. Fentanyl has poor oral bio-availability due to it being metabolized by the liver. Transdermal and transmucosal formulations are common for out-patients, although the latter's efficacy is not well supported by evidence.
The chemists used an "atomic mass unit" (amu) scale such that the natural mixture of oxygen isotopes had an atomic mass 16, while the physicists assigned the same number 16 to only the atomic mass of the most common oxygen isotope (16O, containing eight protons and eight neutrons). However, because oxygen-17 and oxygen-18 are also present in natural oxygen this led to two different tables of atomic mass. The unified scale based on carbon-12, 12C, met the physicists' need to base the scale on a pure isotope, while being numerically close to the chemists' scale. This was adopted as the 'unified atomic mass unit'. The current International System of Units (SI) primary recommendation for the name of this unit is the dalton and symbol 'Da'. The name 'unified atomic mass unit' and symbol 'u' are recognized names and symbols for the same unit. The term atomic weight is being phased out slowly and being replaced by relative atomic mass, in most current usage. This shift in nomenclature reaches back to the 1960s and has been the source of much debate in the scientific community, which was triggered by the adoption of the unified atomic mass unit and the realization that weight was in some ways an inappropriate term.
=== Names === Nemonapride is the generic name of the drug and its INNTooltip International Nonproprietary Name and JANTooltip Japanese Accepted Name. It was also previously known as emonapride and by its former developmental code name YM 09151-2. In addition, nemonapride is known by its brand name Emilace (JPTooltip Japanese language: エミレース) in Japan and China.
== History == Students Michael Schrader, Livio Valenti, Kathryn Kosuda, and Patrick Ho started Vaxess in December 2011, based on a technology created by David Kaplan and Fiorenzo Omenetto. Schrader graduated with an MBA from Harvard Business School in 2012. Valenti attended the John F. Kennedy School of Government. Kosuda had been a Harvard postdoctoral fellow in chemistry, and Patrick Ho had earned a J.D in 2012. In 2012, Vaxess was awarded $25,000 from Harvard Business School for Harvard's Business Plan Contest in the Business Ventures Track. Vaxess Technologies was a semi-finalist for MIT's $100K Entrepreneurship Competition in the Life Sciences section. In 2012, it won the Harvard President's Challenge in the Global Health section and was awarded $70,000. The company was selected as a finalist for two 2013 MassTLC Awards, Start-Up to Watch and Innovative Technology of the Year: Healthcare/Life Sciences. In May 2013, Vaxess received $3.75M in funding from Norwich Ventures and an undisclosed amount of money from angel investor Jeffrey Walker. In August 2013, the company announced that it would be moving out of Harvard's Innovation Lab to a new location at LabCentral in Cambridge. In December 2013, the Massachusetts Life Sciences Center awarded $1.5M to local startups. Vaxess received $1M of that amount which is the most that the MLSC's Accelerator Loan Program will lend to one organization.
Sources: en.wikipedia.org
CPC offers direct scale-up from analytical apparatuses (few milliliters) to industrial apparatuses (several liters) for fast batch-production. CPC seems particularly suited to accommodate aqueous two-phase solvent systems. Generally, CPC instruments can retain solvent systems that are not well-retained in a hydrodynamic instrument due to small differences in density between the phases. It has been very helpful for the development of CPC instrumentation to visualize the flow patterns which give rise to the mixing and settling in the CPC chamber with an asynchronous camera and a stroboscope triggered by the CPC rotor.
Each species of pathogen has a characteristic spectrum of interactions with its human hosts. Some organisms, such as Staphylococcus or Streptococcus, can cause skin infections, pneumonia, meningitis and sepsis, a systemic inflammatory response producing shock, massive vasodilation and death. Yet these organisms are also part of the normal human flora and usually exist on the skin or in the nose without causing any disease at all. Other organisms invariably cause disease in humans, such as Rickettsia, which are obligate intracellular parasites able to grow and reproduce only within the cells of other organisms. One species of Rickettsia causes typhus, while another causes Rocky Mountain spotted fever. Chlamydia, another phylum of obligate intracellular parasites, contains species that can cause pneumonia or urinary tract infection and may be involved in coronary heart disease. Some species, such as Pseudomonas aeruginosa, Burkholderia cenocepacia, and Mycobacterium avium, are opportunistic pathogens and cause disease mainly in people who are immunosuppressed or have cystic fibrosis. Some bacteria produce toxins, which cause diseases. These are endotoxins, which come from broken bacterial cells, and exotoxins, which are produced by bacteria and released into the environment. The bacterium Clostridium botulinum for example, produces a powerful exotoxin that cause respiratory paralysis, and Salmonellae produce an endotoxin that causes gastroenteritis. Some exotoxins can be converted to toxoids, which are used as vaccines to prevent the disease.
The boom of Ion exchange chromatography primarily began between 1935 and 1950 during World War II and applications and IC were significantly extended through the Manhattan Project. Ion chromatography was originally introduced by two English researchers, agricultural Sir Thompson and chemist J T Way. The works of Thompson and Way involved the action of water-soluble fertilizer salts, ammonium sulfate and potassium chloride. These salts could not easily be extracted from the ground due to the rain. They performed ion methods to treat clays with the salts, resulting in the extraction of ammonia in addition to the release of calcium. In the 1950s and 1960s, theoretical models were developed for IC for further understanding, and in the 1970s continuous detectors were utilized, paving the path for the development from low-pressure to high-performance chromatography. In 1975, "ion chromatography" was established as a name in reference to the techniques, and was thereafter used as a name for marketing purposes. Today, IC is important for investigating aqueous systems, such as drinking water. It is a popular method for analyzing anionic elements or complexes that help solve environmentally relevant problems. Likewise, it also has great uses in the semiconductor industry. Because of the abundant separating columns, elution systems, and detectors available, chromatography has developed into the main method for ion analysis. When this technique was initially developed, it was primarily used for water treatment.
Flay opened a second Mesa Grill at Caesars Palace in Las Vegas in 2004, and in 2005 he opened Bar Americain, an American Brasserie, in Midtown Manhattan. He continued to expand his restaurants by opening Bobby Flay Steak in the Borgata Hotel Casino & Spa in Atlantic City, New Jersey. This was followed by a third Mesa Grill in the Bahamas, located in The Cove at Atlantis Paradise Island, which opened on March 28, 2007. The Las Vegas Mesa Grill earned Flay his only Michelin Star in 2008, which was taken away in the 2009 edition. Michelin did not publish a 2010 or 2011 Las Vegas edition, so the star could not be re-earned. Bolo Bar & Restaurant closed its doors on December 31, 2007, to make way for a condominium. Aside from his restaurants and television shows, Flay has been a master instructor and visiting chef at the French Culinary Institute. Although he is not currently teaching classes, he occasionally visits when his schedule permits. Flay established the Bobby Flay Scholarship in 2003. This full scholarship to the French Culinary Institute is awarded annually to a student in the Long Island City Culinary Arts Program. Flay personally helps select the awardee each year. Flay opened his first Bobby's Burger Palace (BBP) at the Smith Haven Mall in Lake Grove, Long Island, on July 15, 2008. At its peak, BBP had nineteen locations in eleven states and the District of Columbia. The original Mesa Grill in New York closed in September 2013 following a proposed rent increase by the landlord.
. Determining the disposition index on the basis of an FSIGT requires fitting the timeseries of insulin and glucose concentrations to the minimal model of insulin-glucose homeostasis. The disposition index is then calculated as
Sources: en.wikipedia.org
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.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.