This is a working overview of Reversed-phase HPLC, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-10-08 and is reviewed periodically as new material appears.
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 synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
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.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
| 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 |
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.
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.
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.
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.
A modified variant of the atractylenolide carries an additional carboxyl group at the C4 atom of the atractyligenin, which is then referred to as carboxy-atractyloside (CATR), sometimes referred to as "gummiferin". The ATR/CATR chemical structure on the right indicates this difference between compounds.
==== Yolk sac ==== The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle. In humans, the yolk sac is important in early embryonic blood supply.
Pharmacokinetics is often studied using mass spectrometry because of the complex nature of the matrix (often blood or urine) and the need for high sensitivity to observe low dose and long time point data. The most common instrumentation used in this application is LC-MS with a triple quadrupole mass spectrometer. Tandem mass spectrometry is usually employed for added specificity. Standard curves and internal standards are used for quantitation of usually a single pharmaceutical in the samples. The samples represent different time points as a pharmaceutical is administered and then metabolized or cleared from the body. Blank or t=0 samples taken before administration are important in determining background and ensuring data integrity with such complex sample matrices. Much attention is paid to the linearity of the standard curve; however it is not uncommon to use curve fitting with more complex functions such as quadratics since the response of most mass spectrometers is less than linear across large concentration ranges. There is currently considerable interest in the use of very high sensitivity mass spectrometry for microdosing studies, which are seen as a promising alternative to animal experimentation. Recent studies show that secondary electrospray ionization (SESI) is a powerful technique to monitor drug kinetics via breath analysis. Because breath is naturally produced, several datapoints can be readily collected. This allows for the number of collected data-points to be greatly increased. In animal studies, this approach SESI can reduce animal sacrifice.
The Kisrawan campaigns were a series of Mamluk military expeditions against the mountaineers of the Kisrawan, as well as the neighboring areas of Byblos and the Jurd, in Mount Lebanon. The offensives were launched in 1292, 1300 and 1305. The mountaineers were Shia Muslim, Alawite, Maronite and Druze tribesmen who historically acted autonomously of any central authority. The Maronites in particular had maintained close cooperation with the last Crusader state, the County of Tripoli. After the fall of Tripoli to the Mamluks in 1289, the mountaineers would often block the coastal road between Tripoli and Beirut, prompting the first Mamluk expedition in 1292 under the viceroy of Egypt, Baydara. During that campaign, the Mamluks, spread along the coastal road and cut off from each other at various points, were constantly harried by the mountaineers, who confiscated their weapons, horses and money. Baydara withdrew his men only after paying off the mountain chiefs. In modern Lebanese historical narratives, the Kisrawan campaigns have been a source of controversy by historians from different religious groups. Maronite, Shia and Druze historians have each sought to emphasize the roles of their respective confessional group, over each other, in defending the autonomy of the Kisrawan from Mamluk outsiders. In writings by Sunni Muslim authors, the Mamluks are portrayed as the legitimate Muslim state working to incorporate Mount Lebanon into the rest of the Islamic realm.
In the 1970s, Judi Sheppard Missett helped create the market for commercial aerobics with her Jazzercise program, at the same time as Jacki Sorensen was expanding her system of aerobic dancing. In the 1980s, Richard Simmons hosted an aerobic exercise show on television, and followed Jane Fonda's lead by releasing a series of exercise videos. In the 1990s, Billy Blanks's Tae Bo helped popularize cardio-boxing workouts that incorporated martial arts movements. Reebok shoes popularized step aerobics with their Reebok Step device and training program.
Sources: en.wikipedia.org
NAD+-β-hydroxybutyrate dehydrogenase hydroxybutyrate oxidoreductase β-hydroxybutyrate dehydrogenase D-β-hydroxybutyrate dehydrogenase D-3-hydroxybutyrate dehydrogenase D-(−)-3-hydroxybutyrate dehydrogenase β-hydroxybutyric acid dehydrogenase 3-D-hydroxybutyrate dehydrogenase β-hydroxybutyric dehydrogenase
Protein production is the biotechnological process of generating a specific protein. It is typically achieved by the manipulation of gene expression in an organism such that it expresses large amounts of a recombinant gene. This includes the transcription of the recombinant DNA to messenger RNA (mRNA), the translation of mRNA into polypeptide chains, which are ultimately folded into functional proteins and may be targeted to specific subcellular or extracellular locations. Protein production systems (also known as expression systems) are used in the life sciences, biotechnology, and medicine. Molecular biology research uses numerous proteins and enzymes, many of which are from expression systems; particularly DNA polymerase for PCR, reverse transcriptase for RNA analysis, restriction endonucleases for cloning, and to make proteins that are screened in drug discovery as biological targets or as potential drugs themselves. There are also significant applications for expression systems in industrial fermentation, notably the production of biopharmaceuticals such as human insulin to treat diabetes, and to manufacture enzymes.
=== GDGT-1 – GDGT-4 === GDGT-1, GDGT-2, and GDGT-3 have one, two, and three cyclopentane rings respectively within their isoprenoid biphytane carbon structures, respectively. Nitrososphaerota are the largest producers of these groups in marine and lacustrine environments. Methanogens are not thought to be large synthesizers of these molecules, with the exception of Methanopyrus kandleri, which does produce them. These classes are lower in abundance than GDGT-0 and GDGRT-4. They are used in the TEX86 paleothermometer. GDGT-4 refers to the version with four cyclopentane rings. It is quite abundant (although not easy to differentiate from crenarchaeol on GC/MS, see below). Nitrososphaerota also makes GDGT-4.
Hours later, White House press secretary Karoline Leavitt said that acquiring Greenland was "a national security priority of the United States", "vital to deter our adversaries in the Arctic region", and added: "The president and his team are discussing a range of options to pursue this important foreign policy goal, and of course, utilizing the US military is always an option at the commander in chief's disposal." Rubio emphasized that any acquisition of Greenland by the US would be negotiated rather than resort to military force, saying Trump's threats were mainly rhetorical and an effort to push Denmark into approving a US-friendly deal. In the following days Trump said the US is "going to do something [there] whether they like it or not", that "We're not going to have Russia or China occupy Greenland. That's what they're going to do if we don't. So we're going to be doing something with Greenland, either the nice way or the more difficult way" and "I would like to make a deal, you know, the easy way. But if we don't do it the easy way, we're going to do it the hard way," that "the fact that they had a boat land there 500 years ago doesn't mean that they own the land. [I'm] sure we had lots of boats go there also." Asked if obtaining Greenland or preserving NATO was his higher priority, he said "it may be a choice."
The first MP, installed at Yale in 1963, operated consistently at 10–11 megavolts; a later installation at Strasbourg reached 18. At these energies, electron stripping becomes highly efficient. A uranium ion passing through the terminal can lose more than 20 electrons, enabling heavy-ion fusion experiments impossible with earlier machines. Advances in gamma-ray spectroscopy combined with MP tandems enabled precision measurements of nuclear structure. HVEC manufactured 10 MP units between 1965 and 1973 for institutions including the University of Minnesota, Chalk River, and the Max Planck Institute in Heidelberg. The XTU ("Holy Roman Emperor") was designed for superheavy element synthesis. Theoretical models predicted an "island of stability" beyond element 110 where nuclei would resist rapid decay. The XTU's 20-megavolt rating would accelerate uranium ions to nearly one billion electron volts—enough to overcome Coulomb barriers in heavy-element fusion. Two prototypes operated solely on a test basis at Burlington before the project was cancelled. One later sold to Italy's national laboratory at Legnaro in 1979.
Sources: en.wikipedia.org
== Adverse effects == Adverse effects, especially with higher doses, include dizziness, drowsiness, fatigue, diarrhea, unusual dreams, trouble sleeping, depression, and vision problems such as blurred vision or dry eyes. β-blockers, including metoprolol, reduce salivary flow via inhibition of the direct sympathetic innervation of the salivary glands. Metoprolol may also cause the hands and feet to feel cold. Due to the high penetration across the blood–brain barrier, lipophilic beta blockers such as propranolol and metoprolol are more likely than other less lipophilic beta blockers to cause sleep disturbances such as insomnia, vivid dreams and nightmares. Patients should be cautious while driving or operating machinery due to its potential to cause decreased alertness. There may also be an impact on blood sugar levels, and it can potentially mask signs of low blood sugar. The safety of metoprolol during pregnancy is not fully established.
=== Coagulation === During the fermentation process, once sufficient lactic acid has been developed, rennet is added to cause the casein to precipitate. Rennet contains the enzyme chymosin which converts κ-casein to para-κ-caseinate (the main component of cheese curd, which is a salt of one fragment of the casein) and glycomacropeptide, which is lost in the cheese whey. As the curd is formed, milk fat is trapped in a casein matrix. After adding the rennet, the cheese milk is left to form curds over a period of time.
Cellulose acetate and cellulose triacetate are film- and fiber-forming materials that find a variety of uses. Nitrocellulose was initially used as an explosive and was an early film forming material. When plasticized with camphor, nitrocellulose gives celluloid. Cellulose Ether derivatives include:
In biochemistry, the Luebering–Rapoport pathway (also called the Luebering–Rapoport shunt) is a metabolic pathway in mature erythrocytes involving the formation of 2,3-bisphosphoglycerate (2,3-BPG), which regulates oxygen release from hemoglobin and delivery to tissues. 2,3-BPG, the reaction product of the Luebering–Rapoport pathway was first described and isolated in 1925 by the Austrian biochemist Samuel Mitja Rapoport and his technical assistant Jane Luebering.
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.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.