tuftsin 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 2026-06-04. Numbers and descriptions here follow the published literature rather than marketing material.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For lyophilized powder, long term |
| Common analytical method | Reverse-phase HPLC | Usually paired with mass spectrometry |
| Typical reported purity | At or above 95 percent by area | Research-grade material |
| Aqueous solubility | High | Solutions used in laboratory assays |
| Moisture sensitivity | Hydrolyzes in solution | Aseptic handling reduces degradation |
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.
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.
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.
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.
=== Vomiting === The vomiting center in the medulla, called the area postrema, contains low concentrations of Substance P and its receptor, in addition to other neurotransmitters such as choline, histamine, dopamine, serotonin, and endogenous opioids. Their activation stimulates the vomiting reflex. Different emetic pathways exist, and Substance P/NK1R appears to be within the final common pathway to regulate vomiting.
Thyroid nodules are often found on the gland, with a prevalence of 4–7%. The majority of nodules do not cause any symptoms, thyroid hormone secretion is normal, and they are non-cancerous. Non-cancerous cases include simple cysts, colloid nodules, and thyroid adenomas. Malignant nodules, which only occur in about 5% of nodules, include follicular, papillary, medullary carcinomas and metastasis from other sites. Nodules are more likely in females, those who are exposed to radiation, and in those who are iodine deficient. When a nodule is present, thyroid function tests determine whether the nodule is secreting excess thyroid hormones, causing hyperthyroidism. When the thyroid function tests are normal, an ultrasound is often used to investigate the nodule, and provide information such as whether the nodule is fluid-filled or a solid mass, and whether the appearance is suggestive of a benign or malignant cancer. A needle aspiration biopsy may then be performed, and the sample undergoes cytology, in which the appearance of cells is viewed to determine whether they resemble normal or cancerous cells. The presence of multiple nodules is called a multinodular goitre; and if it is associated with hyperthyroidism, it is called a toxic multinodular goitre.
== P == Paraphilic Disorder Peritoneum disorders Personality disorders Pervasive developmental disorders Post-traumatic stress disorders Psychiatric disorders, i.e., mental illness Psychoactive substance abuse disorders Psychological disorders, i.e., mental illness Psychotic disorders Puerperal disorders
== Anatomy == Flaps can contain many different combination of layers of tissue, from skin to bone (see § Classification). The main goal of a flap is to maintain blood flow to tissue to maintain survival, and understanding the anatomy in flap design is key to a successful flap surgery.
=== Adhesion molecules of the immune system === Springer began his research career in immunology by studying the molecular basis for cellular immunity using as an example the interaction of cytotoxic T lymphocytes with antigen-bearing target cells. None of the molecules involved in this interaction had yet been defined, including the long postulated antigen-specific T cell receptor. However, it was known that Mg2+ was required for immune cell-cell interactions, and that interaction between fibroblasts and the extracellular matrix was similarly Mg2+-dependent. Postulating that adhesion receptors were likely to be similar to antibodies and were unlikely to require magnesium, Springer hypothesized that other molecules must be required for antigen-specific interactions. He immunized animals with cytotoxic T lymphocytes and screened for monoclonal antibodies that blocked antigen-specific killing. Using this functional assay, his laboratory identified a set of lymphocyte function-associated (LFA) antigens required for cytotoxic T-cell-mediated killing and other T cell-dependent responses, including LFA-1 (CD11a/CD18), LFA-2 (CD2), and LFA-3 (CD58). Springer's group then identified ICAM-1 as a ligand for LFA-1, demonstrating that this interaction is required for efficient antigen recognition by cytotoxic T cells, and later discovered ICAM-2 (CD102) and ICAM-3 (CD50), which have two to five immunoglobulin (Ig)-like domains and comprise a subfamily of the Ig superfamily.
Sources: en.wikipedia.org
== 90Sr contamination in the environment == 90Sr is not quite as likely as 137Cs to be released as a part of a nuclear reactor accident because it is much less volatile, but is probably the most dangerous component of the radioactive fallout from a nuclear weapon. A study of hundreds of thousands of deciduous teeth, collected by Dr.Louise Reiss and her colleagues as part of the Baby Tooth Survey, found a large increase in 90Sr levels through the 1950s and early 1960s. The study's final results showed that children born in St. Louis, Missouri, in 1963 had levels of 90Sr in their deciduous teeth that was 50 times higher than that found in children born in 1950, before the advent of large-scale atomic testing. Reviewers of the study predicted that the fallout would cause increased incidence of disease in those who absorbed 90Sr into their bones. However, no follow up studies of the subjects have been performed, so the claim is untested. An article with the study's initial findings was circulated to U.S. President John F. Kennedy in 1961, and helped convince him to sign the Partial Nuclear Test Ban Treaty with the United Kingdom and Soviet Union, ending the above-ground nuclear weapons testing that placed the greatest amounts of nuclear fallout into the atmosphere. The Chernobyl disaster released roughly 10 PBq, or about 5% of the core inventory, of 90Sr into the environment. The Kyshtym disaster released 90Sr and other radioactive material into the environment. It is estimated to have released 20 MCi (800 PBq) of radioactivity.
==== Apolipoprotein B ==== Apolipoprotein B can exist in two forms: B-100 and B-48. Apolipoprotein B-100 is present on several lipoproteins, including very low-density lipoproteins (VLDL), intermediate density lipoproteins (IDL) and low density lipoproteins (LDL), and can assemble VLDL particles in the liver. Apolipoprotein B-100 has been linked to the development of atherosclerosis. ApoB is ancestrally universal to all animals, as homologs are found in choanoflagellates. The insect homolog is called apolipophorin I/II.
== Publications == Essays 1782 Recherches sur la trajectoire des projectiles dans les milieux résistants (prize on projectiles offered by the Berlin Academy) Books Eléments de géométrie, textbook 1794 Essai sur la Théorie des Nombres 1797-8 ("An VI"), 2nd ed. 1808, 3rd ed. in 2 vol. 1830 Nouvelles Méthodes pour la Détermination des Orbites des Comètes, 1805 Exercices de Calcul Intégral, book in three volumes 1811, 1817, and 1819 Traité des Fonctions Elliptiques, book in three volumes 1825, 1826, and 1830 Memoires in Histoire de l'Académie Royale des Sciences 1783 Sur l'attraction des Sphéroïdes homogènes (work on Legendre polynomials) 1784 Recherches sur la figure des Planètes p. 370 1785 Recherches d'analyse indéterminée p. 465 (work on number theory) 1786 Mémoire sur la manière de distinguer les Maxima des Minima dans le Calcul des Variations p. 7 (as Legendre) 1786 Mémoire sur les Intégrations par arcs d'ellipse p. 616 (as le Gendre) 1786 Second Mémoire sur les Intégrations par arcs d'ellipse p.
=== Hoechst stains === Hoechst is a bis-benzimidazole derivative compound that binds to the minor groove of DNA. Often used in fluorescence microscopy for DNA staining, Hoechst stains appear yellow when dissolved in aqueous solutions and emit blue light under UV excitation. There are two major types of Hoechst: Hoechst 33258 and Hoechst 33342. The two compounds are functionally similar, but with a little difference in structure. Hoechst 33258 contains a terminal hydroxyl group and is thus more soluble in aqueous solution, however this characteristics reduces its ability to penetrate the plasma membrane. Hoechst 33342 contains an ethyl substitution on the terminal hydroxyl group (i.e. an ethylether group) making it more hydrophobic for easier plasma membrane passage
Sources: en.wikipedia.org
In 1962, Stanier and van Niel published an influential definition of bacteria, proposing that bacteria be defined as prokaryotic cellular entities; they also specified three differences between prokaryotes and eukaryotes: presence or absence of internal membranes, division by fission or mitosis, and presence or absence of a cell wall. A major step forward in the study of bacteria came in 1977 when Carl Woese recognised that archaea have a separate line of evolutionary descent from bacteria. This new phylogenetic taxonomy came from the sequencing of 16S ribosomal RNA and divided prokaryotes into two evolutionary domains as part of the three-domain system.
Among the Ancient Greeks before Hippocrates, all blood vessels were called Φλέβες, phlebes. The word arteria then referred to the windpipe. Herophilos was the first to describe anatomical differences between the two types of blood vessel. While Empedocles believed that the blood moved to and fro through the blood vessels, there was no concept of the capillary vessels that join arteries and veins, and there was no notion of circulation. Diogenes of Apollonia developed the theory of pneuma, originally meaning just air but soon identified with the soul itself, and thought to co-exist with the blood in the blood vessels. The arteries were thought to be responsible for the transport of air to the tissues and to be connected to the trachea. This was as a result of finding the arteries of cadavers devoid of blood. In medieval times, it was supposed that arteries carried a fluid, called "spiritual blood" or "vital spirits", considered to be different from the contents of the veins. This theory went back to Galen. In the late medieval period, the trachea, and ligaments were also called "arteries". William Harvey described and popularized the modern concept of the circulatory system and the roles of arteries and veins in the 17th century. Alexis Carrel at the beginning of the 20th century first described the technique for vascular suturing and anastomosis and successfully performed many organ transplantations in animals; he thus actually opened the way to modern vascular surgery that was previously limited to vessels' permanent ligation.
== Abiogenic (opposite) == An abiogenic substance or process does not result from the present or past activity of living organisms. Abiogenic products may, e.g., be minerals, other inorganic compounds, as well as simple organic compounds (e.g. extraterrestrial methane, see also abiogenesis).
Sources: en.wikipedia.org
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.
Lyophilized powder is usually kept frozen and protected from moisture. Solutions are less stable and are often used promptly or divided into aliquots to avoid repeated freeze-thaw cycles. Exact shelf-life values depend on purity and handling.
No. A purity figure derived from chromatographic area does not prove the amino acid sequence. Identity requires an orthogonal method such as mass spectrometry or sequencing. Truncated or isomerized peptides can co-elute with the target compound.
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.