The short version of reversed-phase HPLC fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Derived from the seven-residue sequence |
| Molecular weight | About 751.9 g/mol | Average mass; the monoisotopic value is slightly lower |
| Residue count | Seven amino acids | Thr-Lys-Pro-Arg-Pro-Gly-Pro |
| Parent compound | Tuftsin (Thr-Lys-Pro-Arg) | Selank extends tuftsin at the C-terminus |
| Compound class | Synthetic short peptide | Studied in a research setting; not a licensed drug in most markets |
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
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.
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.
is its oven dry mass (the attainment of constant mass generally after drying in an oven set at 103±2 °C (218±4 °F) for 24 hours as mentioned by Walker et al., 1993). The equation can also be expressed as a fraction of the mass of the water and the mass of the oven dry wood rather than a percentage. For example, 0.59 kg/kg (oven dry basis) expresses the same moisture content as 59% (oven dry basis).
== History == Sodium thiopental was discovered in the early 1930s by Ernest H. Volwiler and Donalee L. Tabern, working for Abbott Laboratories. It was first used in human beings on March 8, 1934, by Dr. Ralph M. Waters in an investigation of its properties, which were short-term anesthesia and surprisingly little analgesia. Three months later, Dr. John S. Lundy started a clinical trial of thiopental at the Mayo Clinic at the request of Abbott. Abbott continued to make the drug until 2004, when it spun off its hospital-products division as Hospira. Thiopental is famously associated with a number of anesthetic deaths in victims of the attack on Pearl Harbor. These deaths, relatively soon after the drug's introduction, were said to be due to excessive doses given to shocked trauma patients. However, evidence available through the freedom of information legislation suggested that the story was exaggerated. Of the 344 wounded that were admitted to the Tripler Army Hospital, only 13 did not survive, and it is unlikely that thiopentone overdose was responsible for more than a few of them.
Nescafé is a brand of instant coffee sold by the multinational food and drink corporation Nestlé. It comes in many different forms. The name is a portmanteau of the words "Nestlé" and "café". Nestlé first introduced their flagship coffee brand in Switzerland on April 1, 1938.
Sources: en.wikipedia.org
===== Pharmacodynamics ===== Cyproterone acetate suppresses libido by directly reducing the level of active androgen, testosterone, in males. The suppression of testosterone level results from its inhibition of the release of luteinizing hormone (LH) from the anterior section of the pituitary gland, interfering with testosterone production from the testes as LH stimulates testosterone production. It also blocks the conversion of testosterone to dihydrotestosterone for action. In addition to this mechanism, it also competes for the androgen receptors against testosterone and dihydrotestosterone, causing interference with the androgen-receptor interaction on the reproductive organ, thereby lowering sexual desire.
map of cold seeps in the Monterey Bay Additionally, seeps have been discovered offshore southern California in the inner California Borderlands along several fault systems including the San Clemente fault, San Pedro fault, and San Diego Trough fault. Fluid flow at the seeps along the San Pedro and San Diego Trough faults appears controlled by localized restraining bends in the faults.
This is to ensure that no new infections have been acquired or have developed during the period of donation. Providing the result is negative, the sperm samples can be released from quarantine and used. Common reasons for sperm rejection include suboptimal semen quality and STDs. Chromosomal abnormalities are also a cause for semen rejection, but are less common. Children conceived through sperm donation had a birth defect rate of almost a fifth compared with the general population in a 1983 study. The sperm will be checked to ensure its fecundity and also to ensure that motile sperm will survive the freezing process. If a man is accepted as a sperm donor, his sperm will generally be constantly monitored, and samples of his blood will be taken at regular intervals. A sperm bank may provide a donor with dietary supplements containing herbal or mineral substances such as maca, zinc, vitamin E, and arginine which are designed to improve the quality and quantity of the donor's semen, as well as reduce the refractory time.
DszB, the final enzyme in the pathway, is also one of the slowest with a turnover rate of 1.7 ± 0.2 min−1, becoming a major bottleneck of the 4S pathway. A computational rational design approach determined a set of mutations that could accelerate the charge transfer occurring in the active site during DszB reaction mechanism, reducing the activation energy for the reaction and potentially increasing its turnover rate. DszB's catalytic efficiency and thermostability was also addressed in an experimental mutagenesis approach, the Y63F/Q65H double mutant revealed an increase in the enzyme's thermostability without loss of catalytic efficiency. DszD has also been targeted for rate enhancing mutation on the Thr62 residue. Mutation of Thr62 by Asn and Ala residues managed to increase its activity 5- and 7-fold, respectively. A computational study demonstrated that substitutions in position 62 of DszD sequence have a major impact in the activation energy for the hydride transfer reaction from NADH to FAD. The Thr62 mutation by an Asp residue returns the lowest activation energy from all possible mutants at this position due to the stabilization effect induced by Asp negative charge.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.
Tuftsin contains four residues, while selank carries an additional Pro-Gly-Pro segment at the carboxyl end. That extension is intended to reduce enzymatic cleavage. Comparative pharmacokinetic data in humans remain limited.
No single receptor target is widely accepted as the definitive mediator of the reported effects. Proposed contributors include GABAergic modulation, shifts in monoamine turnover, and altered neuropeptide degradation. The mechanism is treated in the literature as unresolved.
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.