freeze-thaw 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.
Updated 2025-11-13. Numbers and descriptions here follow the published literature rather than marketing material.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
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.
| Property | Value | Notes |
|---|---|---|
| Route studied | Intranasal | Predominant route in published reports |
| Circulation stability | Short, minutes scale | Peptidases cleave it; the tail slows the process |
| Analytical method | RP-HPLC with mass spectrometry | Used for identity and purity assessment |
| Reported outcome domains | Anxiety and cognitive measures | Derived from small, mostly regional trials |
| Regulatory status | Marketed in Russia | Availability outside that market is limited |
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.
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.
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.
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.
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.
The inverted repeat regions are highly conserved in land plants, and accumulate few mutations. Similar inverted repeats exist in the genomes of cyanobacteria and the other two chloroplast lineages (glaucophyta and rhodophyceae), suggesting that they predate the chloroplast. Some chloroplast genomes have since lost or flipped the inverted repeats (making them direct repeats). It is possible that the inverted repeats help stabilize the rest of the chloroplast genome, as chloroplast genomes which have lost some of the inverted repeat segments tend to get rearranged more.
==== Emotional health ==== Researcher Dianne Hales described an emotionally healthy person as someone who exhibits flexibility and adaptability to different circumstances, a sense of meaning and affirmation in life, an "understanding that the self is not the center of the universe", compassion and the ability to be unselfish, an increased depth and satisfaction in intimate relationships, and a sense of control over the mind and body.
Those men that were stigmatic were non-ordained, including Saint Francis. Harrison argues that in many cases the stigmata was a consequence of the intense personal mystical ministries practiced by those excluded from the priesthood. Only in the twentieth century have cases of stigmatic priests appeared. One suggestion is that painful bruising syndrome may explain rare cases of non self-induced stigmata. Skeptical investigator Joe Nickell who investigated recent cases of stigmata such as Katya Rivas, as well as stigmatics throughout history, commented that the cases are indistinguishable from hoaxing. In 2002, a psychoanalytic study of stigmatic Therese Neumann suggested her stigmata resulted from post-traumatic stress symptoms expressed in unconscious self-mutilation through abnormal autosuggestibility. According to a study of the French theologian Joachim Bouflet, in the 21st century there were 200 stigmatics all over the world. Most of them reached the third age without having particular health problems. The oldest stigmatic was Marie-Julie Jahenny who died in 1941 at the age of 91. As of 1997, the stigmatics who had been declared saints by the Roman Catholic Church were only 7.
Total activity (or just activity), A, is the number of decays per unit time of a radioactive sample. Number of particles, N, in the sample. Specific activity, a, is the number of decays per unit time per amount of substance of the sample at time set to zero (t = 0). "Amount of substance" can be the mass, volume or moles of the initial sample. These are related as follows:
Much of the Gulf states' food is imported – for example, over 90 per cent in Qatar. These factors have led to fears of food insecurity not only in Gulf states, but around the world. As of 28 March, analysts fear that another hard oil crisis is unfolding that is expected to be very decisive to the global economy. Oil prices increased on September 13 due to market stability after recent declines. Investors are awaiting potential U.S.-Iran talks at the UN General Assembly. Analysts believe the price rise may result from traders adjusting their positions rather than a change in market trends.
Sources: en.wikipedia.org
The history of smallpox extends into pre-history. Genetic evidence suggests that the smallpox virus emerged 3,000 to 4,000 years ago. Prior to that, similar ancestral viruses circulated, but possibly only in other mammals, and possibly with different symptoms. Only a few written reports dating from about 500–1000 CE are considered reliable historical descriptions of smallpox, so understanding of the disease prior to that has relied on genetics and archaeology. However, during the second millennium, especially starting in the 16th century, reliable written reports become more common. The earliest physical evidence of smallpox is found in the Egyptian mummies of people who died some 3,000 years ago. Smallpox has had a major impact on world history, not least because indigenous populations of regions where smallpox was non-native, such as the Americas and Australia, were rapidly and greatly reduced by smallpox (along with other introduced diseases) during periods of initial foreign contact, which helped pave the way for conquest and colonization. During the 18th century, the disease killed an estimated 400,000 Europeans each year, including five reigning monarchs, and was responsible for a third of all blindness. Between 20 and 60% of all those infected—and over 80% of infected children—died from the disease. During the 20th century, it is estimated that smallpox was responsible for 250–500 million deaths. In the early 1950s, an estimated 50 million cases of smallpox occurred in the world each year.
Glucose is a sugar with the molecular formula C6H12O6. It is the most abundant monosaccharide, a subcategory of carbohydrates. It is made from water and carbon dioxide during photosynthesis by plants and most algae. It is used by plants to make cellulose, the most abundant carbohydrate in the world, for use in cell walls, and by all living organisms to make adenosine triphosphate (ATP), which is used by the cell as energy. Glucose is often abbreviated as Glc. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is stored as a polymer, in plants mainly as amylose and amylopectin, and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form is d-glucose, while its stereoisomer l-glucose is produced synthetically in comparatively small amounts and is less biologically active. Glucose is a monosaccharide containing six carbon atoms and an aldehyde group, and is therefore an aldohexose. The glucose molecule can exist in an open-chain (acyclic) as well as ring (cyclic) form. Glucose is naturally occurring and is found in its free state in fruits and other parts of plants. In animals, it is released from the breakdown of glycogen in a process known as glycogenolysis. Glucose, as intravenous sugar solution, is on the World Health Organization's List of Essential Medicines. It is also on the list in combination with sodium chloride (table salt). The name glucose is derived from Ancient Greek γλεῦκος (gleûkos) 'wine, must', from γλυκύς (glykýs) 'sweet'.
==== Microspheres ==== An aqueous suspension of progesterone encapsulated in microspheres is marketed for use by intramuscular injection under the brand name ProSphere in Mexico. It is administered once weekly or once monthly, depending on the indication. For instance, the medication is administered at a dose of 100 to 300 mg by intramuscular injection once every 7 days for the treatment of threatened miscarriage. The microspheres range in size from 33 to 75 μg and are delivered using pre-filled syringes with a 20-gauge 38 mm needle. Peak levels of progesterone after a single 100 or 200 mg intramuscular injection of ProSphere occur after about 1.5 days. The elimination half-life of progesterone with this formulation is about 8 days. A single 200 mg intramuscular injection maintains progesterone levels of more than 10 ng/mL for 5 to 7 days. ProSphere is well tolerated in terms of injection site reactions. A combination of both estradiol and progesterone encapsulated within microspheres as an aqueous suspension for use by intramuscular injection has been marketed under the brand name Juvenum in Mexico. Studies of this formulation have been published. Estradiol and progesterone encapsulated in microspheres has been studied for use as a once-a-month combined injectable contraceptive but has not been further developed nor introduced for medical use.
=== 2 August === The SAF and the JDF claimed to have killed an RSF commander who held Colombian citizenship in El Fasher during a failed RSF attack on the city. Fifteen people trying to flee El Fasher to Garni were killed by the RSF.
== History == The sign is named after American physician John Benjamin Murphy (1857–1916), a Chicago surgeon from the 1880s to the early 1900s, who first described the hypersensitivity to deep palpation in the subcostal area when a patient with gallbladder disease takes a deep breath.
Sources: en.wikipedia.org
The stream of protonated water clusters acts as a secondary ionizing species and generates analytes ions by chemical ionization mechanisms at atmospheric pressure. Here protonation, deprotonation, direct charge transfer and adduct ion formation may occur.
=== Conversion of UDP-galactose to UDP-glucose === GALE inverts the configuration of the 4' hydroxyl group of UDP-galactose through a series of 4 steps. Upon binding UDP-galactose, a conserved tyrosine residue in the active site abstracts a proton from the 4' hydroxyl group. Concomitantly, the 4' hydride is added to the si-face of NAD+, generating NADH and a 4-ketopyranose intermediate. The 4-ketopyranose intermediate rotates 180° about the pyrophosphoryl linkage between the glycosyl oxygen and β-phosphorus atom, presenting the opposite face of the ketopyranose intermediate to NADH. Hydride transfer from NADH to this opposite face inverts the stereochemistry of the 4' center. The conserved tyrosine residue then donates its proton, regenerating the 4' hydroxyl group.
=== Diver's telephone === The communications equipment is relatively straightforward and may be of the two-wire or four-wire type. Two wire systems use the same wires for surface to diver and diver to surface messages, whereas four wire systems allow the diver's messages and the surface operator's messages to use separate wire pairs. In a two wire system the standard arrangement for diver communications is to have the diver's side normally on, so that the surface team can hear anything from the diver at all times except when the surface is sending a message. In a four-wire system the diver's side is always on, even when the surface operator is talking. This is considered an important safety feature, as the surface team can monitor the diver's breathing sounds, which can give early warning of problems developing, and confirms that the diver is alive. Heliox divers may need a decoder system (unscrambler) which reduces the frequency of the sound to make it more intelligible.
=== Properties === Cyanuric acid can be viewed as the cyclic trimer of the elusive chemical species cyanic acid, HOCN. The ring can readily interconvert between several structures via lactam–lactim tautomerism. Although the triol tautomer may have aromatic character, the keto form predominates in solution. The hydroxyl (-OH) groups assume phenolic character. Deprotonation with base affords a series of cyanurate salts:
Sources: en.wikipedia.org
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.
Intranasal delivery is the route described in most published work. It is used because the peptide is degraded quickly once it reaches circulation. Direct evidence of brain penetration in humans is lacking.
Most trials are small, regionally concentrated, and often lack rigorous blinding or placebo control. Independent replication is limited. Reviews in English generally rate the evidence as preliminary.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.