Everything below concerns tuftsin. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-26. Numbers and descriptions here follow the published literature rather than marketing material.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
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.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
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.
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.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
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.
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.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
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.
The first group of Directives create a range of individual rights in EU employment relationships. The Employment Information Directive 1991 requires that every employee (however defined by member state law) has the right to a written statement of their employment contract. While there is no wage regulation, the Institutions for Occupational Retirement Provision Directive 2003 requires that pension benefits are protected through a national insurance fund, that information is provided to beneficiaries, and minimum standards of governance are observed. Most member states go far beyond these requirements, particularly by requiring a vote for employees in who manages their money. Reflecting basic standards in the Universal Declaration of Human Rights and ILO Conventions, the Working Time Directive 2003 requires a minimum of 4 weeks (totalling 28 days) paid holidays each year, a minimum of 20-minute paid rest breaks for 6-hour work shifts, limits on night work or time spent on dangerous work, and a maximum 48-hour working week unless a worker individually consents. The Parental Leave Directive 2010 creates a bare minimum of 4 months of unpaid leave for parents (mothers, fathers, or legal guardians) to care for children before they turn 8 years old, and the Pregnant Workers Directive 1992 creates a right for mothers to a minimum of 14 weeks' paid leave to care for children.
=== Healthcare === On 11 January, Lula signed into law the "National Policy for the Prevention of Self-Mutilation and Suicide", created by the Health Ministry with the objective of giving mental health support for public security agents. On 20 January, Lula signed a bill, classifying community and disease control agents as health professionals. Also on 20 January, under pressure from religious entities, Lula created the "Department of Support for Therapeutic Communities", aimed at treating drug addicts; after the measure was criticized by human rights organizations, the Ministry of Social Development and Fight against Hunger announced that it would review the decision. The Brazilian Association of Mental Health had also spoken out against the measure in a repudiation note. On 8 March, International Women's Day, Lula announced the creation of the "Programme for the Protection and Promotion of Menstrual Dignity", which provides distribution of menstrual pads by the Sistema Único de Saúde (SUS) to people in vulnerable situations, below the Poverty threshold. The document regulates the Law nº 14.214/2021, which had been vetoed by Jair Bolsonaro in 2021. 8 million people will benefit from the initiative, according to specialists, with an investment of 418 million reals per year, according to the Ministry of Health.
carbamylation the addition of Isocyanic acid to a protein's N-terminus or the side-chain of Lys. carbonylation the addition of carbon monoxide to other organic/inorganic compounds. glycation, the addition of a sugar molecule to a protein without the controlling action of an enzyme. glutarylation, the addition of a glutaryl group to lysine residues malonylation, the addition of a malonyl group to lysine residues methylmalonylation, the addition of a methylmalonyl group to lysine residues spontaneous isopeptide bond formation, between lysine and aspartic acid or asparagine, as found in many surface proteins of Gram-positive bacteria. succinylation, addition of a succinyl group to lysine
Sources: en.wikipedia.org
Before automated cell counters were introduced, complete blood count tests were performed manually: white and red blood cells and platelets were counted using microscopes. The first person to publish microscopic observations of blood cells was Antonie van Leeuwenhoek, who reported on the appearance of red cells in a 1674 letter to the Proceedings of the Royal Society of London. Jan Swammerdam had described red blood cells some years earlier, but did not publish his findings at the time. Throughout the 18th and 19th centuries, improvements in microscope technology such as achromatic lenses allowed white blood cells and platelets to be counted in unstained samples. The physiologist Karl Vierordt is credited with performing the first blood count. His technique, published in 1852, involved aspirating a carefully measured volume of blood into a capillary tube and spreading it onto a microscope slide coated with egg white. After the blood dried, he counted every cell on the slide; this process could take more than three hours to complete. The hemocytometer, introduced in 1874 by Louis-Charles Malassez, simplified the microscopic counting of blood cells. Malassez's hemocytometer consisted of a microscope slide containing a flattened capillary tube. Diluted blood was introduced to the capillary chamber by means of a rubber tube attached to one end, and an eyepiece with a scaled grid was attached to the microscope, permitting the microscopist to count the number of cells per volume of blood.
Acetylfentanyl (acetyl fentanyl) is an opioid analgesic drug that is an analog of fentanyl. Studies have estimated acetylfentanyl to be 15 times more potent than morphine, which would mean that despite being somewhat weaker than fentanyl, it is nevertheless still several times stronger than pure heroin. It has never been licensed for medical use and instead has only been sold on the illicit drug market. Acetylfentanyl was discovered at the same time as fentanyl itself and had only rarely been encountered on the illicit market in the late 1980s. However, in 2013, Canadian police seized 3 kilograms of acetylfentanyl. As a μ-opioid receptor agonist, acetylfentanyl may serve as a direct substitute for oxycodone, heroin or other opioids. Common side effects of fentanyl analogs are similar to those of fentanyl itself, which include itching, nausea, and potentially fatal respiratory depression. Fentanyl analogs have killed hundreds of people throughout Europe and the former Soviet republics since the most recent resurgence in use began in Estonia in the early 2000s, and novel derivatives continue to appear.
== Practice of therapeutic drug monitoring == Automated analytical methods such as enzyme multiplied immunoassay technique or fluorescence polarization immunoassay are widely available in medical laboratories for drugs frequently measured in practice. Nowadays, most other drugs can be readily measured in blood or plasma using versatile methods such as liquid chromatography–mass spectrometry or gas chromatography–mass spectrometry, which progressively replaced high-performance liquid chromatography. Yet, TDM is not limited to the provision of precise and accurate concentration measurement results, it also involves appropriate medical interpretation, based on robust scientific knowledge. In order to guarantee the quality of this clinical interpretation, it is essential that the sample be taken under good conditions: i.e., preferably under a stable dosage, at a standardized sampling time (often at the end of a dosing interval), excluding any source of bias (sample contamination or dilution, analytical interferences) and having carefully recorded the sampling time, the last dose intake time, the current dosage and the influential patient's characteristics.
== Signs and symptoms == Signs and symptoms of TIA are widely variable and can mimic other neurologic conditions, making the clinical context and physical exam crucial in ruling in or out the diagnosis. The most common presenting symptoms of TIA are focal neurologic deficits, which can include, but are not limited to:
Sources: en.wikipedia.org
=== Commensals === The word "commensalism" is derived from the word "commensal", meaning "eating at the same table" and all plants and animals are colonised by commensal bacteria. In humans and other animals, trillions of them live on the skin, the airways, the gut and other orifices. Referred to as "normal flora", or "commensals", these bacteria usually cause no harm but may occasionally invade other sites of the body and cause infection. Escherichia coli is a commensal in the human gut but can cause urinary tract infections. Similarly, streptococci, which are part of the normal flora of the human mouth, can cause heart disease.
== Weak and strong ion exchangers == A "strong" ion exchanger will not lose the charge on its matrix once the column is equilibrated and so a wide range of pH buffers can be used. "Weak" ion exchangers have a range of pH values in which they will maintain their charge. If the pH of the buffer used for a weak ion exchange column goes out of the capacity range of the matrix, the column will lose its charge distribution and the molecule of interest may be lost. Despite the smaller pH range of weak ion exchangers, they are often used over strong ion exchangers due to their having greater specificity. In some experiments, the retention times of weak ion exchangers are just long enough to obtain desired data at a high specificity. Resins (often termed 'beads') of ion exchange columns may include functional groups such as weak/strong acids and weak/strong bases. There are also special columns that have resins with amphoteric functional groups that can exchange both cations and anions. Some examples of functional groups of strong ion exchange resins are quaternary ammonium cation (Q), which is an anion exchanger, and sulfonic acid (S, -SO2OH), which is a cation exchanger. These types of exchangers can maintain their charge density over a pH range of 0–14. Examples of functional groups of Weak ion exchange resins include diethylaminoethyl (DEAE, -C2H4N(C2H5)2), which is an anion exchanger, and carboxymethyl (CM, -CH2-COOH), which is a cation exchanger. These two types of exchangers can maintain the charge density of their columns over a pH range of 5–9.
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This regulates the reaction catalyzing fructose 2,6-bisphosphate (a potent activator of phosphofructokinase-1, the enzyme that is the primary regulatory step of glycolysis) by slowing the rate of its formation, thereby inhibiting the flux of the glycolysis pathway and allowing gluconeogenesis to predominate. This process is reversible in the absence of glucagon (and thus, the presence of insulin). Glucagon stimulation of PKA inactivates the glycolytic enzyme pyruvate kinase, inactivates glycogen synthase, and activates hormone-sensitive lipase, which catabolizes glycerides into glycerol and free fatty acid(s), in hepatocytes. Glucagon also inactivates acetyl-CoA carboxylase (ACC), which creates malonyl-CoA from acetyl-CoA, through cAMP-dependent and/or cAMP-independent kinases. Malonyl-CoA is a product formed by ACC during denovo synthesis and an allosteric inhibitor of carnitine palmitoyltransferase I (CPT1), a mitochondrial enzyme important for bringing fatty acids into the intermembrane space of the mitochondria for β-oxidation. Glucagon decreases malonyl-CoA through inhibition of acetyl-CoA carboxylase and through reduced glycolysis through its aforementioned reduction in Fructose 2,6-bisphosphate. Thus, reduction in malonyl-CoA is a common regulator for the increased fatty acid metabolism effects of glucagon.
=== Veterinary use === The use of progesterone tests in dog breeding to pinpoint ovulation is becoming more widely used. There are several tests available, the most reliable being a blood test with the blood sample drawn by a veterinarian and sent to a lab for processing. Results can usually be obtained within 24 to 72 hours. The rationale for using progesterone tests is that increased numbers begin close to the preovulatory surge in gonadotrophins and continue through ovulation and estrus. When progesterone levels reach certain levels they can signal the stage of estrus the female is. Prediction of birth date of the pending litter can be accurate if ovulation date is known. Puppies deliver within a day or two of nine weeks gestation in most cases. Determining pregnancy using progesterone tests once a breeding has taken place is not possible, however. This limitation is due to the fact that, in dogs, progesterone levels remain elevated throughout the estrus period.
Sources: en.wikipedia.org
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.