The short version of lyophilized powder fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2025-12-14 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
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.
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.
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.
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.
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.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
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.
It is an optical analytical technique that analyzes the interference pattern of white light reflected from two surfaces: a layer of immobilized protein on the biosensor tip, and an internal reference layer. Any change in the number of molecules bound to the biosensor tip causes a shift in the interference pattern that can be measured in real-time, providing detailed information regarding the kinetics of association and dissociation of the two molecules as well as the affinity constant for the protein interaction (ka, kd and Kd). Due to sensor configuration, the technique is highly amenable to both purified and crude samples as well as high throughput screening experiments. The detection method can also be used to determine the molar concentration of analytes. Protein activity determination by NMR multi-nuclear relaxation measurements, or 2D-FT NMR spectroscopy in solutions, combined with nonlinear regression analysis of NMR relaxation or 2D-FT spectroscopy data sets. Whereas the concept of water activity is widely known and utilized in the applied biosciences, its complement—the protein activity which quantitates protein–protein interactions—is much less familiar to bioscientists as it is more difficult to determine in dilute solutions of proteins; protein activity is also much harder to determine for concentrated protein solutions when protein aggregation, not merely transient protein association, is often the dominant process.
The presence of ethanol can lead to the formations of non-lamellar phases also known as non-bilayer phases. Ethanol has been recognized as being an excellent solvent in an aqueous solution for inducing non-lamellar phases in phospholipids. The formation of non-lamellar phases in phospholipids is not completely understood, but it is significant that this amphiphilic molecule is capable of doing so. The formation of non-lamellar phases is significant in biomedical studies which include drug delivery, the transport of polar and non-polar ions using solvents capable of penetrating the biomembrane, increasing the elasticity of the biomembrane when it is being disrupted by unwanted substances (viruses, bacteria, solvents, etc.) and functioning as a channel or transporter of biomaterial.
== Biochemical functions == Oxaloacetate is an intermediate of the citric acid cycle, where it reacts with acetyl-CoA to form citrate, catalyzed by citrate synthase. It is also involved in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, and fatty acid synthesis. Oxaloacetate is also a potent inhibitor of complex II.
American ethnobotanist Jonathan Ott and colleagues subsequently showed in 2001 that bufotenin is in fact a psychedelic and does not necessarily produce major adverse effects, although marked nausea and vomiting are prominent. The related psychedelic 5-MeO-DMT was first synthesized by Japanese chemists Toshio Hoshino and Kenya Shimodaira in 1936. It was later isolated from Dictyoloma incanescens in 1959. Subsequently, 5-MeO-DMT was isolated from numerous other plants and fungi. The compound was isolated from the skin of toads, specifically the Colorado River toad (Incilius alvarius, formerly Bufo alvarius), by Italian chemist and pharmacologist Vittorio Erspamer in 1967. A 1984 pamphlet by Albert Most (real name Ken Nelson), titled Bufo Alvarius: the Psychedelic Toad of the Sonoran Desert, described how to obtain and use Colorado River toad secretions as a psychedelic drug, and this started its recreational use.
Sources: en.wikipedia.org
== Further reading == Martin, Christopher S.; Chung, Tammy; Langenbucher, James W. (2017). "Part 1: Defining and Characterizing the Nature and Extent of Substance Use Disorders – Historical and Cultural Perspectives on Substance Use and Substance Use Disorders". In Sher, Kenneth J. (ed.). The Oxford Handbook of Substance Use and Substance Use Disorders: Volume 1. Oxford Library of Psychology. Oxford and New York: Oxford University Press. pp. 27–59. doi:10.1093/oxfordhb/9780199381678.013.001. ISBN 978-0-19-938167-8. LCCN 2016020729. Anthony, James; Barondess, David A.; Radovanovic, Mirjana; Lopez-Quintero, Catalina (2017). "Part 1: Psychiatric Comorbidity – Polydrug Use: Research Topics and Issues". In Sher, Kenneth J. (ed.). The Oxford Handbook of Substance Use and Substance Use Disorders: Volume 2. Oxford Library of Psychology. Oxford and New York: Oxford University Press. pp. 27–59. doi:10.1093/oxfordhb/9780199381708.013.006. ISBN 978-0-19-938170-8. LCCN 2016020729. Hernández-Serrano, Olga; Gras, Maria E.; Font-Mayolas, Sílvia; Sullman, Mark J. M. (2016). "Part VI: Dual and Polydrug Abuse – Chapter 83: Types of Polydrug Usage". In Preedy, Victor R. (ed.). Neuropathology of Drug Addictions and Substance Misuse, Volume 3: General Processes and Mechanisms, Prescription Medications, Caffeine and Areca, Polydrug Misuse, Emerging Addictions and Non-Drug Addictions. Cambridge, Massachusetts: Academic Press, imprint of Elsevier. pp. 839–849. doi:10.1016/B978-0-12-800634-4.00083-4. ISBN 978-0-12-800634-4.
=== Indirect size measurement of intact complexes === Sedimentation-velocity analytical ultracentrifugation (measures the translational diffusion constant) Dynamic light scattering (measures the translational diffusion constant) Pulsed-gradient protein nuclear magnetic resonance (measures the translational diffusion constant) Fluorescence polarization (measures the rotational diffusion constant) Dielectric relaxation (measures the rotational diffusion constant) Dual polarisation interferometry (measures the size and the density of the complex) Methods that measure the mass or volume under unfolding conditions (such as MALDI-TOF mass spectrometry and SDS-PAGE) are generally not useful, since non-native conditions usually cause the complex to dissociate into monomers. However, these may sometimes be applicable; for example, the experimenter may apply SDS-PAGE after first treating the intact complex with chemical cross-link reagents.
== Definition == According to the United Nations Statistics Division, wholesale is the resale of new and used goods to retailers, to industrial, commercial, institutional or professional users, or to other wholesalers, or involves acting as an agent or broker in buying merchandise for, or selling merchandise to, such persons or companies. Wholesalers frequently physically assemble, sort, and grade goods in large lots, break-bulk, repack, and redistribute in smaller lots. While wholesalers of most products usually operate from independent premises, wholesale marketing for foodstuffs can take place at specific wholesale markets where all traders are congregated. In the International Standard Industrial Classification (ISIC Rev.4), wholesale trade is primarily Division 46 ("Wholesale trade, except of motor vehicles and motorcycles"). In the NAICS, wholesale trade is Sector 42, commonly separated into merchant wholesalers and agents/brokers (including electronic markets). A common way to distinguish wholesale from retail is by the main customer:
In 1992, DiCaprio had a brief role in the first installment of the Poison Ivy film series, and was handpicked by Robert De Niro from a shortlist of 400 young actors to co-star with him in This Boy's Life. Adapted from the memoir by Tobias Wolff, the film focuses on the relationship between a rebellious teenager, Toby (DiCaprio), and his mother (Ellen Barkin) and abusive stepfather (De Niro). Director Michael Caton-Jones said that DiCaprio did not know how to behave on set; accordingly, Caton-Jones used a strict mentoring style, after which DiCaprio's behavior began to improve. Bilge Ebiri of Rolling Stone found that the powerful bond between Barkin and DiCaprio elevated the film, praising DiCaprio's portrayal of his character's complex growth from a rebellious teen to an independent young man. This Boy's Life was the first film that gained him recognition. DiCaprio's first talk show appearance was in 1992 on the Looseleaf Report, hosted by Victoria Looseleaf, who later wrote a 1998 (unauthorized) biography on him. DiCaprio played the developmentally disabled brother of Johnny Depp's character in What's Eating Gilbert Grape (1993), a comedy-drama about a dysfunctional Iowa family. Caton-Jones recommended DiCaprio to director Lasse Hallström who was initially skeptical, as he considered DiCaprio too good-looking for the part. Hallström cast DiCaprio after he emerged as "the most observant" auditionee.
The spray is a combination of local anaesthetics lidocaine and prilocaine in a metered-dose aerosol that is sprayed directly on the penis to numb sensations. It was developed by the same group that invented the erectile dysfunction drug sildenafil. The drug was approved in Europe and was released in the UK market in November 2016 and within the EU will be marketed by, early in 2017 In the United States, the Food and Drug Administration (FDA) is expected to approve the drug in 2018.
Sources: en.wikipedia.org
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.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.