Intranasal delivery 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 2025-10-14. Numbers and descriptions here follow the published literature rather than marketing material.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Analog of the tetrapeptide tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Reported consistently across pharmacopoeial descriptions |
| Appearance | White to off-white lyophilized powder | Typical form of research-grade material |
| Solubility | Freely soluble in water | Aqueous buffers; poor in nonpolar solvents |
| Typical storage temperature | -20 degrees Celsius | Lyophilized powder; protect from moisture |
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.
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.
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.
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.
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.
PD-1 is a type I membrane protein of 288 amino acids. PD-1 is a member of the extended CD28/CTLA-4 family of T cell regulators. The protein's structure includes an extracellular IgV domain followed by a transmembrane region and an intracellular tail. The intracellular tail contains two phosphorylation sites located in an immunoreceptor tyrosine-based inhibitory motif and an immunoreceptor tyrosine-based switch motif, which suggests that PD-1 negatively regulates T-cell receptor TCR signals. This is consistent with binding of SHP-1 and SHP-2 phosphatases to the cytoplasmic tail of PD-1 upon ligand binding. In addition, PD-1 ligation up-regulates E3 ubiquitin ligases CBL-b and c-CBL that trigger T cell receptor down-modulation. PD-1 is expressed on the surface of activated T cells, B cells, and macrophages, suggesting that compared to CTLA-4, PD-1 more broadly negatively regulates immune responses.
== Gastropod mucus == Mucus is the viscoelastic, biological secretions from gastropods like snails and slugs. Gastropod mucus serves as a lubricant and survival mechanism, facilitating movement on wet surfaces and preventing dehydration. These functions are attributed to the unique cross-linking and electrostatic interactions as well as the combination of glycoproteins, amino acids, and divalent metal ions, gastropod mucus, that allow it to adhere to surfaces even in wet environments.
==== Anti-viral ==== In 2021, SLR14 was reported to prevent infection in the lower respiratory tract and severe disease in an interferon type I (IFN-I)–dependent manner in mice. Immunodeficient mice with chronic SARS-CoV-2 infection experienced near-sterilizing innate immunity with no help from the adaptive immune system.
Molybdenum is an essential element in most organisms; a 2008 research paper speculated that a scarcity of molybdenum in the Earth's early oceans may have strongly influenced the evolution of eukaryotic life (which includes all plants and animals). At least 50 molybdenum-containing enzymes have been identified, mostly in bacteria. Those enzymes include aldehyde oxidase, sulfite oxidase and xanthine oxidase. With one exception, Mo in proteins is bound by molybdopterin to give the molybdenum cofactor. The only known exception is nitrogenase, which uses the FeMoco cofactor, which has the formula Fe7MoS9C. In terms of function, molybdoenzymes catalyze the oxidation and sometimes reduction of certain small molecules in the process of regulating nitrogen, sulfur, and carbon. In some animals, and in humans, the oxidation of xanthine to uric acid, a process of purine catabolism, is catalyzed by xanthine oxidase, a molybdenum-containing enzyme. The activity of xanthine oxidase is directly proportional to the amount of molybdenum in the body. An extremely high concentration of molybdenum reverses the trend and can inhibit purine catabolism and other processes. Molybdenum concentration also affects protein synthesis, metabolism, and growth. Mo is a component in most nitrogenases. Among molybdoenzymes, nitrogenases are unique in lacking the molybdopterin. Nitrogenases catalyze the production of ammonia from atmospheric nitrogen:
Sources: en.wikipedia.org
Immunohistochemical and immunofluorescence examinations located KRT81 within the cytoplasm. Additionally, in KRT81-knockdown MDA-MB231 cells, zymography illustrated decreased MMP9 activity, while scratch and invasion assays demonstrated diminished cell migration and invasion capabilities. This presents the first evidence of complete KRT81 expression in both normal breast epithelial cells and breast cancer cells. Furthermore, the findings suggest that KRT81 plays a role in the migration and invasion of breast cancer cells.
=== Production and secretion === During pregnancy, the syncytiotrophoblast cells of the placenta produce a polypeptide hormone, human placental lactogen (hPL), also known as human chorionic somatomammotropin (hCS). in six weeks of gestation, production of hPL in maternal plasma is detected, then the concentration of hPL keeps increasing until week 30 of pregnancy. The secretion rate of hPL is one gram per day, which is the highest rate compared to other hormones.
A gunshot wound (GSW) is a penetrating injury caused by a projectile (e.g., a bullet) shot from a gun. Damage may include bleeding, bone fractures, organ damage, wound infection, and loss of the ability to move part of the body. Damage depends on the part of the body hit, the path the bullet follows through (or into) the body, and the type and speed of the bullet, and can be fatal. Long-term complications can include bowel obstruction, failure to thrive, neurogenic bladder and paralysis, recurrent cardiorespiratory distress and pneumothorax, hypoxic brain injury leading to early dementia, amputations, chronic pain and pain with light touch (hyperalgesia), deep venous thrombosis with pulmonary embolus, limb swelling and debility, and lead poisoning. Factors that determine rates of gun violence vary by country. These factors may include the illegal drug trade, easy access to firearms, substance misuse including alcohol, mental health problems, firearm laws, social attitudes, economic differences, and occupations such as being a police officer. Where guns are more common, altercations more often end in death; however, firearm laws, particularly background checks and permit to purchase, can decrease this risk. Safer firearm storage may decrease the risk of firearm-related deaths in children. Before management begins, the area must be verified as safe. This is followed by stopping major bleeding, then assessing and supporting the airway, breathing, and circulation. In 2015, about a million gunshot wounds occurred from interpersonal violence.
Sources: en.wikipedia.org
Enhanced mobility – components are described as "familiar, performance-enhancing, eat-out-of-hand" foods that require little or no preparation by the soldier. The beverages are reconstituted (CamelBak compatible) and consumed right out of the pouch. No water is needed for food preparation, only for the beverage mix. The food takes the form of pocket sandwiches to be eaten by hand. Lightweight – when compared to three Meals, Ready-to-Eat, the FSR reduces the weight and volume of one day's subsistence by approximately 50%. Characteristics – has a minimum two-year shelf life at 80 °F (27 °C) and provides an average of 2,900 calories per day. The FSR has nine meals per shipping container consisting of three each of three different menus up through 2010. Since 2011 there are 9 different meal combinations per shipping container. Meals – Each pouch contains items for a breakfast, lunch, and a dinner, although there is no requirement to consume the items in any specific order.
=== Red blood cells === Vitamin A may be needed for normal red blood cell formation; deficiency causes abnormalities in iron metabolism. Vitamin A is needed to produce the red blood cells from stem cells through retinoid differentiation.
The survival of Franz Joseph was also commemorated in Prague by erecting a new statue of St. Francis of Assisi, the patron saint of the emperor, on Charles Bridge. It was donated by Count Franz Anton von Kolowrat-Liebsteinsky, the first minister-president of the Austrian Empire.
==== Mechanical properties ==== The mechanical properties of iron and its alloys are extremely relevant to their structural applications. Those properties can be evaluated in various ways, including the Brinell test, the Rockwell test, and the Vickers hardness test. The properties of pure iron are often used to calibrate measurements or to compare tests. However, the mechanical properties of iron are significantly affected by the sample's purity: pure, single crystals of iron are actually softer than aluminium, and the purest industrially produced iron (99.99%) has a hardness of 20–30 Brinell. Very pure iron (99.9%～99.999%) called electrolytic iron is industrially produced by electrolytic refining. An increase in the carbon content will cause a significant increase in the hardness and tensile strength of iron. Maximum hardness of 65 Rc is achieved with a 0.6% carbon content, although the alloy has low tensile strength. Because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium.
Sources: en.wikipedia.org
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.
The first four residues of Selank reproduce the tuftsin sequence Thr-Lys-Pro-Arg. A Pro-Gly-Pro extension at the C-terminus was added to slow enzymatic breakdown and extend residence time.
It holds marketing authorization in Russia, where nasal drop formulations are sold. No equivalent approval exists in the European Union, the United States, or most other countries.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.