intranasal delivery comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-08-05. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
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.
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.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
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.
Ascites is a build-up of fluid in the peritoneal cavity in the abdomen An enlarged spleen in 35–50% of cases Esophageal varices and gastric varices result from collateral circulation in the esophagus and stomach (a process called portacaval anastomosis). When the blood vessels in this circulation become enlarged, they are called varices. Varices are more likely to rupture at this point. Variceal rupture often leads to severe bleeding, which can be fatal. Caput medusae are dilated paraumbilical collateral veins due to portal hypertension. Blood from the portal venous system may be forced through the paraumbilical veins and ultimately to the abdominal wall veins. The created pattern resembles the head of Medusa, hence the name. Cruveilhier-Baumgarten bruit is bruit in the epigastric region (on examination by stethoscope). It is due to extra connections forming between the portal system and the paraumbilical veins.
==== Premenstrual syndrome ==== Historically, progesterone has been widely used in the treatment of premenstrual syndrome. A 2012 Cochrane review found insufficient evidence for or against the effectiveness of progesterone for this indication. Another review of 10 studies found that progesterone was not effective for this condition, although it stated that insufficient evidence is available currently to make a definitive statement on progesterone in premenstrual syndrome.
Bacterial and mitochondrial N-formyl peptides such as FMLP – pro-inflammatory (though possibly less physiologically significant than lipid-derived ligands); Hp(2–20), from Helicobacter pylori – pro-inflammatory; HIV-1-derived peptides: T21/DP107 and N36 (from gp41), F peptide (from gp120), and V3 peptide (from the MN strain) – unknown effects; CCL23β (amino acids 22–137), a splice variant of CCL23, and SHAAGtide, a proteolytic product – pro-inflammatory; Annexin A1-derived peptides (Ac2–26 and Ac9–25) – dose-dependent; anti-inflammatory at low concentrations, pro-inflammatory at high concentrations; Amyloid β(1–42) and PrP(106–126) (from prion protein) – pro-inflammatory, suggesting roles in Alzheimer's disease, Parkinson's disease, Huntington's disease, and prion diseases such as Creutzfeldt–Jakob disease and Kuru; Humanin, a neuroprotective peptide – anti-inflammatory, counteracting amyloid-induced inflammation; Cleaved fragments of UPARAP (uPAR): D2D3(88–274) and uPAR(84–95) – pro-inflammatory; Antimicrobial peptides: LL-37 and CRAMP (human/rat cathelicidins), Pleurocidins (from fish), and Temporin A (frog-derived) – pro-inflammatory; Pituitary adenylate cyclase-activating polypeptide 27 – pro-inflammatory; Long-chain ceramides (C14–C20) – bind FPR2 in beige and brown adipocytes to inhibit thermogenesis.
Sources: en.wikipedia.org
extein Any part of an amino acid sequence which is retained within a precursor polypeptide, i.e. not excised by post-translational protein splicing, and is therefore present in the mature protein, analogous to the exons of RNA transcripts. Contrast intein.
Elements of the morphine structure have been used to create completely synthetic drugs such as the morphinan family (levorphanol, dextromethorphan and others) and other groups that have multiple members with morphine-like qualities. The modification of morphine and the aforementioned synthetics has also given rise to non-narcotic drugs with other uses such as emetics, stimulants, antitussives, anticholinergics, muscle relaxants, local anaesthetics, general anaesthetics, and others. Morphine-derived agonist–antagonist drugs have also been developed.
=== Wound healing and cell guidance === One of the best-understood roles for bioelectric gradients is at the tissue-level endogenous electric fields utilized during wound healing. It is challenging to study wound-associated electric fields, because these fields are weak, less fluctuating, and do not have immediate biological responses when compared to nerve pulses and muscle contraction. The development of the vibrating and glass microelectrodes, demonstrated that wounds indeed produced and, importantly, sustained measurable electric currents and electric fields. These techniques allow further characterization of the wound electric fields/currents at cornea and skin wounds, which show active spatial and temporal features, suggesting active regulation of these electrical phenomena. For example, the wound electric currents are always the strongest at the wound edge, which gradually increased to reach a peak about 1 hour after injury. At wounds in diabetic animals, the wound electric fields are significantly compromised. Understanding the mechanisms of generation and regulation of the wound electric currents/fields is expected to reveal new approaches to manipulate the electrical aspect for better wound healing. How are the electric fields at a wound produced? Epithelia actively pump and differentially segregate ions. In the cornea epithelium, for example, Na+ and K+ are transported inwards from tear fluid to extracellular fluid, and Cl− is transported out of the extracellular fluid into the tear fluid.
Sources: en.wikipedia.org
Aflatoxin B1 and B2 (AFB), produced by A. flavus and A. parasiticus Aflatoxin G1 and G2 (AFG), produced by some Group II A. flavus and Aspergillus parasiticus Aflatoxin M1 (AFM1), metabolite of aflatoxin B1 in humans and animals (exposure in ng levels may come from a mother's milk) Aflatoxin M2, metabolite of aflatoxin B2 in milk of cattle fed on contaminated foods Aflatoxicol (AFL): metabolite produced by breaking down the lactone ring Aflatoxin Q1 (AFQ1), major metabolite of AFB1 in in vitro liver preparations of other higher vertebrates AFM, AFQ, and AFL retain the possibility of becoming an epoxide. Nevertheless, they appear much less capable of causing mutagenesis than the unmetabolized ABM.
The cycle is present in microorganisms that cause disease but is absent in mammals, for example humans. There is a strong plausibility of the development of antibiotics that would attack the glyoxylate cycle, which would kill the disease-causing microorganisms that depend on the cycle for their survival, yet would not harm humans where the cycle, and thus the enzymes that the antibiotic would target, are absent.
After its inception, the group grew quickly and, by late summer in 1943, It was claimed to have 15,000 to 20,000 active men and women military fighters and 50,000 more in reserve. These fighters' weaponry was obtained primarily by stealing it from battlefields and downed planes left behind by the Japanese, Filipinos, and Americans. They fought Japanese troops, worked to subvert the Japanese tax-collection service, intercepted food and supplies to the Japanese troops, and created a training school where they taught political theory and military tactics based on Marxist ideas. In areas that the group controlled, they set up local governments (Sandatahang Tanod ng Bayan, Barrio United Defense Corps) and instituted land reforms, dividing up the largest estates equally among the peasants and often killing the landlords. In some cases, however, landlords were welcomed as participants in Huk resistance, swayed by anti-Japanese sympathies. PKP organizers quickly went to work to set up BUDCs in Huk controlled barrios, which contributed to its success as a resistance army, although in reality there was an overlap between independently formed barrio governments, "neighborhood committees" set up by the Japanese, and BUDCs. The Huk movement was notable for its inclusion of women peasants, who advocated for inclusion in the movement in resistance to the word of Japanese war atrocities against women, including rape and mutilation. Many of these women fought, but the majority of the resistance remained in villages, collecting supplies and intelligence.
Usually the largest workers in the colony develop into repletes; and, if repletes are removed from the colony, other workers become repletes, demonstrating the flexibility of this particular polymorphism. This polymorphism in morphology and behaviour of workers initially was thought to be determined by environmental factors such as nutrition and hormones that led to different developmental paths; however, genetic differences between worker castes have been noted in Acromyrmex sp. These polymorphisms are caused by relatively small genetic changes; differences in a single gene of Solenopsis invicta can decide whether the colony will have single or multiple queens. The Australian jack jumper ant (Myrmecia pilosula) has only a single pair of chromosomes (with the males having just one chromosome as they are haploid), the lowest number known for any animal, making it an interesting subject for studies in the genetics and developmental biology of social insects.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.