Lyophilisation is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-04-28. Where a claim depends on a specific study, the study is described rather than over-claimed.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
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.
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.
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.
Channelopathies can be categorized based on the organ system they affect. In the cardiovascular system, the electrical impulse required for each heart beat is provided by the electrochemical gradient of each heart cell. Because the beating of the heart depends on the proper movement of ions across the surface membrane, cardiac ion channelopathies form a major group of heart diseases. Cardiac ion channelopathies may explain some of the cases of sudden death syndrome and sudden arrhythmic death syndrome. Long QT syndrome is the most common form of cardiac channelopathy.
Birds have featured in culture and art since prehistoric times, when they were represented in early cave painting and carvings. Some birds have been perceived as monsters, including the mythological Roc and the Māori's legendary Pouākai, a giant bird capable of snatching humans. Birds were later used as symbols of power, as in the magnificent Peacock Throne of the Mughal and Persian emperors. With the advent of scientific interest in birds, many paintings of birds were commissioned for books. Among the most famous of these bird artists was John James Audubon, whose paintings of North American birds were a great commercial success in Europe and who later lent his name to the National Audubon Society. Birds are also important figures in poetry; for example, Homer incorporated nightingales into his Odyssey, and Catullus used a sparrow as an erotic symbol in his Catullus 2. The relationship between an albatross and a sailor is the central theme of Samuel Taylor Coleridge's The Rime of the Ancient Mariner, which led to the use of the term as a metaphor for a 'burden'. Other English metaphors derive from birds; vulture funds and vulture investors, for instance, take their name from the scavenging vulture. Aircraft, particularly military aircraft, are frequently named after birds. The predatory nature of raptors make them popular choices for fighter aircraft such as the F-16 Fighting Falcon and the Harrier Jump Jet, while the names of seabirds may be chosen for aircraft primarily used by naval forces such as the HU-16 Albatross and the V-22 Osprey.
Flavoproteins are proteins that contain a nucleic acid derivative of riboflavin. These proteins are involved in a wide array of biological processes, including removal of radicals contributing to oxidative stress, photosynthesis, and DNA repair. The flavoproteins are some of the most-studied families of enzymes. Flavoproteins have either FMN (flavin mononucleotide) or FAD (flavin adenine dinucleotide) as a prosthetic group or as a cofactor. The flavin is generally tightly bound (as in adrenodoxin reductase, wherein the FAD is buried deeply). About 5-10% of flavoproteins have a covalently linked FAD. Based on the available structural data, FAD-binding sites can be divided into more than 200 different types. 90 flavoproteins are encoded in the human genome; about 84% require FAD and around 16% require FMN, whereas 5 proteins require both. Flavoproteins are mainly located in the mitochondria. Of all flavoproteins, 90% perform redox reactions and the other 10% are transferases, lyases, isomerases, ligases.
Sources: en.wikipedia.org
=== Molecular Separations === The well-defined pore structure of organic cages enables selective molecular separations. Molecular cages can discriminate between molecules based on size, shape, and chemical affinity. Gas separation represents a major application, where cages are incorporated into mixed-matrix membranes for selective gas transport. Studies have demonstrated effective separation of CO2/N2, CO2/CH4, and other industrially relevant gas mixtures. The uniform pore size and chemical environment ensure consistent separation performance. In liquid-phase separations, organic cages show promise for challenging molecular separations. Their solution processability enables incorporation into chromatographic stationary phases. The intrinsic chirality of some cage structures allows for enantioselective separations of racemic mixtures, achieving high separation factors for pharmaceutical and fine chemical applications.
== Benefits == Tracing of an item through various stages of production, manufacturing, processing, handling, transportation, sales and consumption is a widespread practice in today's world. Manufacturers may require purchasers to register ownership of a product to facilitate possible future recall for safety reasons or warranty fulfillment. The Post Office and package delivery companies make widespread use of tracking packages from pickup to delivery, even to destinations on the other side of the world.Some often-recognized benefits of traceability include:
=== Seth Holt === Seth Holt (John Corbett) is Sarah's rocker ex-husband and Amber and Drew's absent father. Seth is a traveling musician and has never made much time for either of his children. Sarah left Seth due to his chronic problems with drugs and alcohol, and she constantly had to lie to her children regarding his long absences, saying he was away on tour. He shares a bond with his son Drew, who visits him during the "Pilot." Seth calls Drew on Thanksgiving after Zeek leaves him a voicemail. Seth comes back to town and bonds with Drew again. After Drew tells Sarah that Seth is back in town, she visits him and the two talk. Seth reveals that he has been sober for the last nine months, and Sarah finally lets Drew and Amber see him. While Drew has a good relationship with Seth, Amber is less forgiving and resents her father for never being there. Eventually, Seth leaves to go back on tour. Seth visits Sarah while he is drunk, and she attempts to help him get sober. Seth finally agrees to admit himself to rehab, and he and Sarah get closer again even though she is in a committed relationship with Mark Cryr. After Seth gets clean, he kisses Sarah, but she breaks it off. Amber asks Seth to leave after overhearing Sarah talk about the kiss. Seth leaves to stay with his cousin Eric in Tahoe, leaving packages of birthday cards for both Amber and Drew to make up for all the birthdays he missed through the years. Later in the season, Sarah calls to tell Seth that she and Mark are trying to have a baby, which upsets him.
Juvenile white sharks typically inhabit shallower water and are limited to feeding on smaller prey. The white shark has a fearsome reputation among the public. It is featured in the 1974 novel Jaws and its 1975 film adaptation, both of which portray it as a ferocious man-eater. In reality, white sharks normally do not prey on humans, and the majority of bites are due to curiosity or possibly mistaken identity. Many attempts have been made to keep the species in captivity, but specimens either ended up dying or being released. White shark aggregations have attracted tourists who may view them from boats or from inside shark cages. The International Union for Conservation of Nature lists the white shark as a vulnerable species globally and critically endangered regionally in European and Mediterranean waters. Major threats have included accidental catching by commercial fisheries, recreational fishing, and entanglement in protective nets near beaches. Several governments have enacted protections for the species, including bans on catching and killing it.
Sources: en.wikipedia.org
A cold trap is a concept in planetary science that describes an area cold enough to freeze (trap) volatiles. Cold traps can exist on the surfaces of airless bodies or in the upper layers of an adiabatic atmosphere. On airless bodies, the ices trapped inside cold traps can potentially remain there for geologic time periods, providing a glimpse into the primordial solar system. In adiabatic atmospheres, cold traps prevent volatiles (such as water) from escaping the atmosphere into space.
Several countries require all travellers, or all foreign travelers, to be fingerprinted on arrival and refuse admission to or arrest travellers who refuse to comply. In some countries, such as America, this may apply even to transit passengers proceeding to a third country. Many countries also require a photo to be taken of people entering the country. The United States, which does not fully implement exit control formalities at its land frontiers (although long mandated by domestic legislation), intends to implement facial recognition for passengers departing from international airports to identify people who overstay their visa. Together with fingerprint and face recognition, iris scanning is one of three biometric identification technologies internationally standardised since 2006 by the International Civil Aviation Organization (ICAO) for use in e-passports and the United Arab Emirates conducts iris scanning on visitors who need to apply for a visa. The Department of Homeland Security has announced plans to increase the biometric data it collects at American borders greatly. In 2018, Singapore began trials of iris scanning at three land and maritime immigration checkpoints.
polyploid (of a cell or organism) Having more than two homologous copies of each chromosome; i.e. any ploidy level that is greater than diploid. Polyploidy may occur as a normal condition of chromosomes in certain cells or even entire organisms, or it may result from errors in cell division or mutations causing the duplication of the entire chromosome set.
Sources: en.wikipedia.org
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.