A practical reference on freeze-thaw: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-09. Anything still debated is marked as such rather than presented as settled.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
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.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
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.
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.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
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.
dissimilatory process Any exergonic process of microbial catabolism by which redox-active chemical species participate in oxidation-reduction reactions (exchange of electrons) to provide the cell with energy needed for sustaining metabolic activities. Exogenous substances are absorbed by the cell from its environment and then decomposed to release energy, with the byproducts subsequently excreted out of the cell. This is in contrast to an assimilatory process, in which the atoms of the exogenous substances are reused in the synthesis of biomolecules or the fabrication of cellular components.
Carbonaceous chondrites at The Encyclopedia of Astrobiology, Astronomy, and Spaceflight Gilmour, I.; Wright, I.; Wright, J. (1997). Origins of earth and life. Bletchley: The Open University. ISBN 978-0-7492-8182-3.
=== Elemental analysis === The ICP-MS allows determination of elements with atomic mass ranges 7 to 250 (Li to U), and sometimes higher. Some masses are prohibited, such as 40 Da, due to the abundance of argon in the sample. Other interference regions may include mass 80 (due to the argon dimer) and mass 56 (due to ArO), the latter of which greatly hinders Fe detection unless the instrument is fitted with a reaction chamber. Such interferences can be reduced by using a high resolution ICP-MS (HR-ICP-MS) which uses two or more slits to constrict the beam and distinguish between nearby peaks. This comes at the cost of sensitivity. For example, distinguishing iron from argon requires a resolving power of about 10,000, which may reduce the iron sensitivity by around 99%. Interfering species can alternatively be distinguished through the use of a collision chamber, which can filter gasses by either chemical reaction or physical collision. A single collector ICP-MS may use a multiplier in pulse counting mode to amplify very low signals, an attenuation grid or a multiplier in analogue mode to detect medium signals, and a Faraday cup/bucket to detect larger signals. A multi-collector ICP-MS may have more than one of any of these, typically Faraday buckets which are more cost-effective than other collectors. With this combination, a dynamic range of 12 orders of magnitude, from 1 part per quadrillion (ppq) to 100 parts per million (ppm) is possible. ICP-MS is a common method for the determination of cadmium in biological samples.
== Adverse events related to red blood cell transfusion == Adverse events related to transfusion in general may include allergic reactions such as anaphylaxis, infection, volume overload, and lung injury. With current screening methods, the risk of viral infections such as hepatitis C and HIV/AIDS are less than one in a million. With current testing methods in high-income countries the prevalence of transfusion-transmissible infections in blood donations is very low (median: HIV 0.002%, hepatitis B 0.02%, hepatitis C 0.007% and syphilis 0.02% in 2024). However, in low-income countries the risk of a blood donation being positive for HIV, hepatitis C or syphilis is up to 1%, and the risk of it being hepatitis B positive was approximately 2.8% in 2024. The differences relate to variations in eligible blood donors, whether the donation is paid or voluntary, non-remunerated, and the effectiveness of the system of educating and selecting donors. Adverse events related to transfusion of red blood cells are mainly linked to incompatibility issues or other transfusion reactions. Incompatible AB0 transfusion can be fatal. For patients with a previous transfusion reaction history, the risk of repeated adverse events can be mitigated by choosing the proper processing modification and/or red blood cell phenotype combination.
Millimoles per liter (mmol/L) is the SI standard unit used in most countries around the world. Milligrams per deciliter (mg/dL) is used in some countries such as the United States, Japan, France, Egypt, and Colombia. Scientific journals are moving toward using mmol/L; some journals now use mmol/L as the primary unit but quote mg/dL in parentheses. Glucose levels vary before and after meals, and at various times of day; the definition of "normal" varies among medical professionals. In general, the normal range for most people (fasting adults) is about 4 to 6 mmol/L or 80 to 110 mg/dL. (where 4 mmol/L or 80 mg/dL is "optimal".) A subject with a consistent range above 7 mmol/L or 126 mg/dL is generally held to have hyperglycemia, whereas a consistent range below 4 mmol/L or 70 mg/dL is considered hypoglycemic. In fasting adults, blood plasma glucose should not exceed 7 mmol/L or 126 mg/dL. Sustained higher levels of blood sugar cause damage to the blood vessels and to the organs they supply, leading to the complications of diabetes. Chronic hyperglycemia can be measured via the HbA1c test. The definition of acute hyperglycemia varies by study, with mmol/L levels from 8 to 15 (mg/dL levels from 144 to 270). Defects in insulin secretion, insulin action, or both, results in hyperglycemia. Chronic hyperglycemia can be measured by clinical urine tests which can detect sugar in the urine or microalbuminuria which could be a symptom of diabetes.
Sources: en.wikipedia.org
Over 100 different genetic defects leading to Wilson's disease have been described and are available on the Internet at [1]. Some of the mutations have geographic clustering. Many Wilson's patients carry different mutations on each chromosome 13 (i.e., they are compound heterozygotes). Even in individuals who are homozygous for a mutation, onset and severity of the disease may vary. Individuals homozygous for severe mutations (e.g., those truncating the protein) have earlier disease onset. Disease severity may also be a function of environmental factors, including the amount of copper in the diet or variability in the function of other proteins that influence copper homeostasis. It has been suggested that heterozygote carriers of the Wilson's disease gene mutation may be potentially more susceptible to elevated copper intake than the general population. A heterozygotic frequency of 1/90 people has been estimated in the overall population. However, there is no evidence to support this speculation. Further, a review of the data on single-allelic autosomal recessive diseases in humans does not suggest that heterozygote carriers are likely to be adversely affected by their altered genetic status.
Hadi's election on 24 February 2012 peacefully introduced a new government in Yemen, with only a small percentage of voters spoiling their ballots in the single-candidate contest. Hadi, a southerner, especially enjoyed support in former South Yemen, quieting the murmurs of separatism, although the Southern Movement boycotted the presidential election, as did the Houthis. Hadi did not give the restive Houthis any seats in his cabinet.
== Health aspects == Fruits that are rich in polyphenol oxidase activity may affect the polyphenol content of other fruits consumed in the same meal. In particular mixed fruit juices and smoothies are at risk, as different fruits (and their cellular content) are mixed long time before digestion enzymes can inactivate the polyphenol oxidase. Thus, these beverages contain considerably less bioactive polyphenoles compared to fruit juices made entirely of low-PPO fruits or whole fruits.
=== Ostwald ripening === Ostwald ripening is a process in which large particles grow at the expense of the smaller particles as a result of dissolution of small particles and deposition of the dissolved molecules on the surfaces of the larger particles. It occurs because smaller particles have a higher surface energy than larger particles. This process is typically undesirable in nanoparticle synthesis as it negatively impacts the functionality of nanoparticles.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.