reversed-phase HPLC raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-11-28 and is reviewed periodically as new material appears.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
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.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
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.
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.
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.
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.
== Normal levels == Progesterone is used as part of hormone replacement therapy in people who have low progesterone levels, and for other reasons. For purposes of comparison with normal physiological circumstances, luteal phase levels of progesterone are 4 to 30 ng/mL, while follicular phase levels of progesterone are 0.02 to 0.9 ng/mL, menopausal levels are 0.03 to 0.3 ng/mL, and levels of progesterone in men are 0.12 to 0.3 ng/mL. During pregnancy, levels of progesterone in the first 4 to 8 weeks are 25 to 75 ng/mL, and levels are typically around 140 to 200 ng/mL at term. Production of progesterone in the body in late pregnancy is approximately 250 mg per day, 90% of which reaches the maternal circulation.
There are six conditionally essential amino acids whose synthesis can be limited under special pathophysiological conditions, such as prematurity in the infant or individuals in severe catabolic distress: arginine, cysteine, glycine, glutamine, proline and tyrosine. Dietary sources of protein include grains, legumes, nuts, seeds, meats, dairy products, fish, and eggs.
The US military used depleted uranium in tank kinetic energy penetrators and 20–30 mm (0.79–1.18 in) cannon ordnance. Significant controversy regarding the long term safety of depleted uranium exists, including claims of pyrophoric, genotoxic, and teratogenic heavy metal effects. Many have cited its use during the war as a contributing factor to a number of major health issues in veterans and in surrounding civilian populations, including in birth defects and child cancer rates. Scientific opinion on the risk is mixed. In 2004, Iraq had the highest mortality rate due to leukemia of any country. Depleted uranium has 40% less radioactivity than natural uranium. Depleted uranium is not a significant health hazard unless it is taken into the body. External exposure to radiation from depleted uranium is generally not a major concern because the alpha particles emitted by its isotopes travel only a few centimeters in air or can be stopped by a sheet of paper. Also, the uranium-235 that remains in depleted uranium emits only a small amount of low-energy gamma radiation. However, if allowed to enter the body, depleted uranium, like natural uranium, has the potential for both chemical and radiological toxicity with the two important target organs being the kidneys and the lungs.
Sources: en.wikipedia.org
=== Gold's deep-hot biosphere === In the 1970s, Thomas Gold proposed the theory that life first developed not on the surface of the Earth, but several kilometers below the surface. It is claimed that the discovery of microbial life below the surface of another body in our Solar System would lend significant credence to this theory.
=== Candidacy for mayorship of Porto Alegre in 2016 === In 2016, Melo was the candidate for the mayorship of PMDB, with state deputy Juliana Brizola, of the PDT, as the vice-mayoral candidate on the ticket. In the first round, they received 185,655 votes (25.93%). They came in second place behind Nelson Marchezan Júnior, and both qualified for the second round. Melo received a diverse array of support, including from the PCdoB, the PMN, and from the PV's candidate, Marcelo Chiodo, even as his party supported Marchezan Júnior. He also positioned himself as more to the left, announcing his support for the fight against PEC 241, which established a ceiling for public spending for twenty years in Brazil, also going against the national position of his party. Along with this, he affirmed his position against proposed laws inspired by Escola sem Partido, a conservative movement. Melo declared that he had an "identity of struggles" with the left, since he came from the "old MDB", as the party was the main political force against the military dictatorship. As a candidate, he had shown opposition against the privatization of public companies, such as DMAE, Procempa and Carris, and defended participatory budgeting. After a tense campaign with constant trading of accusations between him and Marchezan Júnior, Melo was defeated in the second round, receiving 262,601 votos (39.50%). After the election, on analyzing his defeat in an interview, Melo criticized the possibility that the MDB would become a part of his adversary's administration.
=== Comparison with other expression systems === In standard molecular biology research, the bacterium Escherichia coli is the most frequently used organism for expression system, to produce heterologous proteins, due to its features of fast growth rate, high protein production rate, as well as undemanding growth conditions. Protein production in E. coli is usually faster than that in Komagataella, with reasons: Competent E. coli cells can be stored frozen, and thawed before use, whereas Komagataella cells have to be produced immediately before use. Expression yields in Komagataella vary between different clones, so that a large number of clones has to be screened for protein production, to find the best producer. The biggest advantage of Komagataella over E. coli is that Komagataella is capable of forming disulfide bonds and glycosylations in proteins, but E. coli cannot. E. coli might produce a misfolded protein when disulfides are included in final product, leading to inactive or insoluble forms of proteins. The well-studied Saccharomyces cerevisiae is also used as an expression system with similar advantages over E. coli as Komagataella. However Komagataella has two main advantages over S. cerevisiae in laboratory and industrial settings:
=== NNR === Research overview: This study involves creating a combination of model membranes which contain 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-distearoly-sn-glycero-3-phosphocholine (DSPC) referred to as the "host membranes", phospholipids labeled as 1,2,& 3 referred to as "exchanging molecules" or "reporting molecules" and varied cholesterol mole percentages in the presence of an aqueous solution containing 5% ethanol (v/v). The host membranes were chosen because their phase diagrams are well understood and have been extensively characterized by different analytical techniques.6 The nearest neighbor recognition technique is being applied to the formation of the modeled membranes to observe the association between cholesterol and phospholipids as well as the effects that the presence of ethanol has against this interaction. Researchers are observing whether or not ethanol enhances or disrupts the liquid-ordered phase by reorganizing this formation into a liquid-disordered phase. The liquid-ordered phase is similar to a lamellar phase and the liquid-disordered phase represents the non-lamellar phases but the exact type of each phase (hexagonal, cubic, etc.) is not described. As previously mentioned several different combinations of the host membranes, exchanging molecules, and cholesterol are created to form the model membranes. It is important to mention that the exchanging molecules selected have similar properties to the host membranes.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
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.