Everything below concerns pharmacokinetics. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 |
|---|---|---|
| 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 |
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
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.
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.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
=== Biosynthesis === Cannabinoid production begins with an enzyme combining geranyl pyrophosphate and olivetolic acid to form CBGA. CBGA is converted to THCA, CBDA, or CBCA by separate synthases, FAD-dependent dehydrogenase enzymes that diverged from a promiscuous common ancestor. There is no enzymatic conversion of CBDA or CBD to THCA or THC. Propyl homologues (CBGVA, THCVA, CBDVA, CBCVA) follow an analogous pathway from divarinolic acid.
== References == Aagaard et al.: "An inflammatory role for the mammalian carboxypeptidase inhibitor latexin: relationship to cystatins and the tumor suppressor TIG1." Structure 13(2), 309–317, 2005. Cho et al.: "Hypermethylation of CpG island loci and hypomethylation of LINE-1 and Alu repeats in prostate adenocarcinoma and their relationship to clinicopathological features." J Pathology 211(3), 269–277, 2007. Gautron et al.: "Ovacalyxin-32, a novel chicken eggshell matrix protein." J Biol Chem 276(42), 39243–39252, 2001. Jing et al.: "Tazarotene-Induced Gene 1 (TIG1) expression in prostate carcinomas and its relationship to tumorigenicity" J Natl Cancer Institute 94(7), 482–490, 2002. Liang et al.: "The quantitative trait gene latexin influences the size of the hematopoietic stem cell population in mice." Nature Genetics 39(2), 178–188, 2007. So et al.: "Multiple tumor suppressor genes are increasingly methylated with age in non-neoplastic gastric epithelia." Cancer Sci 97(11), 1155–1158, 2006.
Thus, the 9s and 9p1/2 orbitals in essence replace the 8s and 8p1/2 ones, making elements 157–172 probably chemically analogous to groups 3–18: for example, element 164 would appear two places below lead in group 14 under the usual pattern, but is calculated to be very analogous to palladium in group 10 instead. Thus, it takes fifty-four elements rather than fifty to reach the next noble element after 118. However, while these conclusions about elements 157 through 172's chemistry are generally agreed by models, there is disagreement on whether the periodic table should be drawn to reflect chemical analogies, or if it should reflect likely formal electron configurations, which should be quite different from earlier periods and are not agreed between sources. Discussion about the format of the eighth row thus continues. Beyond element 172, calculation is complicated by the 1s electron energy level becoming imaginary. Such a situation does have a physical interpretation and does not in itself pose an electronic limit to the periodic table, but the correct way to incorporate such states into multi-electron calculations is still an open question, which would need to be answered to calculate the periodic table's structure beyond this point. Nuclear stability will likely prove a decisive factor constraining the number of possible elements. It depends on the balance between the electric repulsion between protons and the strong force binding protons and neutrons together.
Sources: en.wikipedia.org
TFA is the precursor to trifluoroacetic anhydride, trifluoroperacetic acid, and 2,2,2-trifluoroethanol. It is a reagent used in organic synthesis because of a combination of convenient properties: volatility, solubility in organic solvents, and its strength as an acid. TFA is also less oxidizing than sulfuric acid but more readily available in anhydrous form than many other acids. One complication to its use is that TFA forms an azeotrope with water (b. p. 105 °C). TFA is used as a strong acid to remove protecting groups such as Boc used in organic chemistry and peptide synthesis. At a low concentration, TFA is used as an ion pairing agent in liquid chromatography (HPLC) of organic compounds, particularly peptides and small proteins. TFA is a versatile solvent for NMR spectroscopy (for materials stable in acid). It is also used as a calibrant in mass spectrometry. TFA is used to produce trifluoroacetate salts. TFA is a high-production chemical and has wide applicationos in organic synthesis, e.g., in rearrangements, functional group deprotections, oxidations, reductions, condensations, hydroarylations, and trifluoromethylations.
In addition to its well-explored interactions with NMDA receptors, PCP has also been shown to inhibit dopamine reuptake, and thereby leads to increased extracellular levels of dopamine and hence increased dopaminergic neurotransmission. However, PCP has little affinity for the human monoamine transporters, including the dopamine transporter (DAT). Instead, its inhibition of monoamine reuptake may be mediated by interactions with allosteric sites on the monoamine transporters. PCP is notably a high-affinity ligand of the PCP site 2 (Ki = 154 nM), a not-well-characterized site associated with monoamine reuptake inhibition. Studies on rats indicate that PCP interacts indirectly with opioid receptors (endorphin and enkephalin) to produce analgesia. A binding study assessed PCP at 56 sites including neurotransmitter receptors and transporters and found that PCP had Ki values of >10,000 nM at all sites except the dizocilpine (MK-801) site of the NMDA receptor (Ki = 59 nM), the σ2 receptor (PC12) (Ki = 136 nM), and the serotonin transporter (Ki = 2,234 nM). The study notably found Ki values of >10,000 nM for the D2 receptor, the opioid receptors, the σ1 receptor, and the dopamine and norepinephrine transporters. These results suggest that PCP is a highly selective ligand of the NMDAR and σ2 receptor. However, PCP may also interact with allosteric sites on the monoamine transporters to produce inhibition of monoamine reuptake.
In June 2021, Biden took his first trip abroad as president, visiting Belgium, Switzerland, and the United Kingdom. He attended a G7 summit, a NATO summit, and an EU summit, and held one-on-one talks with Russian president Vladimir Putin. In September 2021, Biden announced AUKUS, a defense pact between Australia, the United Kingdom and the United States, to ensure "peace and stability in the Indo-Pacific". In February 2021, the Biden administration announced that the United States was ending its support for the Saudi-led bombing campaign in Yemen and revoked the designation of Yemen's Houthis as terrorists. In early February 2022, Biden ordered the counterterrorism raid in northern Syria that resulted in the death of Abu Ibrahim al-Hashimi al-Qurashi, the second leader of the Islamic State. In late July, Biden approved the drone strike that killed Ayman al-Zawahiri, the second leader of Al-Qaeda, and an integral member in the planning of the September 11 attacks. The 2022 OPEC+ oil production cut caused a diplomatic spat with Saudi Arabia, threatening a longstanding alliance. In August 2024, Biden negotiated and oversaw the 2024 Ankara prisoner exchange, the largest prisoner exchange since the end of the Cold War. It involved the release of 26 people, including journalist Evan Gershkovich and former Marine Paul Whelan. In November 2024, the Biden administration announced that it had helped broker a ceasefire agreement in the Israel–Hezbollah conflict.
=== Effects on ozone layer === Sulfur dioxide aerosols in the stratosphere can contribute to ozone depletion in the presence of chlorofluorocarbons and other halogenated ozone-depleting substances. The effects of volcanic eruptions containing sulfur dioxide aerosols on the ozone layer are complex, however. In the absence of anthropogenic or biogenic halogenated compounds in the lower stratosphere, depletion of dinitrogen pentoxide in the middle stratosphere associated with its reactivity to the aerosols can promote ozone formation. Injection of sulfur dioxide and large amounts of water vapor into the stratosphere following the 2022 eruption of Hunga Tonga-Hunga Haʻapai resulted in altered atmospheric circulation that promoted a decrease in ozone in the southern latitudes but an increase in the tropics. The additional presence of hydrochloric acid in eruptions can result in net ozone depletion.
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.
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.