mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-10-01. Anything still debated is marked as such rather than presented as settled.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue with a C-terminal Pro-Gly-Pro tail |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Abbreviated TKPRPGP in most catalogues |
| Molecular mass | About 752 Da | Value for the free peptide |
| Solubility | Freely soluble in water | Aqueous solutions are kept cold and used promptly |
| Typical storage | -20 °C, dry, protected from light | Applies to the lyophilised powder before reconstitution |
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.
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.
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.
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.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
== Isotopic abundance == The monoisotopic peak is sometimes not observable for two primary reasons. First, the monoisotopic peak may not be resolved from the other isotopic peaks. In this case, only the average molecular mass may be observed. In some cases, even when the isotopic peaks are resolved, such as with a high-resolution mass spectrometer, the monoisotopic peak may be below the noise level and higher isotopes may dominate completely. If a piece of iron was put into a mass spectrometer to be analyzed, the mass spectra of iron (Fe) would result in multiple mass spectral peaks due to the existence of the iron isotopes, 54Fe, 56Fe, 57Fe, 58Fe. The mass spectrum of Fe represents that the monoisotopic mass is not always the most abundant isotopic peak in a spectrum despite it containing the most abundant isotope for each atom. This is because as the number of atoms in a molecule increases, the probability that the molecule contains at least one heavy isotope atom also increases. If there are 100 carbon atoms 12C in a molecule, and each carbon has a probability of approximately 1% of being a heavy isotope 13C, the whole molecule is highly likely to contain at least one heavy isotope atom of carbon-13 and the most abundant isotopic composition will no longer be the same as the monoisotopic peak.
=== Availability === Chlorprothixene is widely available throughout Europe and elsewhere in the world. The drug was previously available in the United States under the brand name Taractan, but this formulation has since been discontinued and the drug is no longer available in this country.
=== In the military === An estimated 16% percent of active duty U.S. military personnel were obese in 2004, with the cost of remedial bariatric surgery for the military reaching US$15 million in 2002. Obesity is currently the largest single cause for the discharge of uniformed personnel. A financial analysis published in 2007 further showed that the treatment of diseases and disorders associated with obesity costs the military $1.1 billion annually. Moreover, the analysis found that the increased absenteeism of obese or overweight personnel amounted to a further 658,000 work days lost per year. This lost productivity is higher than the productivity loss in the military due to high alcohol consumption which was found to be 548,000 work days. Problems associated with obesity further manifested itself in early discharge due to inability to meet weight standards. Approximately 1200 military enlistees were discharged due to this reason in 2006. The rise in obesity has led to fewer citizens able to join the military and therefore more difficulty in recruitment for the armed forces. In 2005, 9 million adults aged 17 to 24, or 27%, were too overweight to be considered for service in the military. For comparison, just 6% of military aged men in 1960 would have exceeded the current weight standards of the U.S. military. Excess weight is the most common reason for medical disqualification and accounts for the rejection of 23.3% of all recruits to the military.
=== Advantages and disadvantages of displacement mode === In contrast to elution chromatography, solutes separated in displacement mode form sharp-edged zones rather than spreading peaks. Zone boundaries in displacement chromatography are self-sharpening: if a molecule for some reason gets ahead of its band, it enters a zone in which it is more strongly retained, and will then run more slowly until its zone catches up. Furthermore, because displacement chromatography takes advantage of the non-linearity of the isotherms, loadings are deliberately high; more material can be separated on a given column, in a given time, with the purified components recovered at significantly higher concentrations. Retention conditions can still be adjusted, but the displacer controls the migration rate of the solutes. The displacer is selected to have higher affinity for the stationary phase than does any of the solutes being separated, and its concentration is set to approach saturation of the stationary phase and to give the desired migration rate of the concentration wave. High-retention conditions can be employed without gradient operation, because the displacer ensures removal of all solutes of interest in the designed run time. Because of the concentrating effect of loading the column under high-retention conditions, displacement chromatography is well suited to purify components from dilute feed streams.
Sources: en.wikipedia.org
ABRF Next Generation Sequencing Group (ABRF-NGS) Antibody Technology Research Group (ARG) Biomedical 'Omics Research Group (BORG) DNA Sequencing Research Group (DSRG) Flow Cytometry Research Group (FCRG) Genomics Research Group (GVRG) Glycoprotein Research Group (gPRG) Light Microscopy Research Group (LMRG) Metabolomics Research Group (MRG) Metagenomics Research Group (MGRG) Molecular Interactions Research Group (MIRG) Nucleic Acids Research Group (NARG) Protein Expression Research Group (PERG) Protein Sequencing Research Group (PSRG) Proteomics Research Group (PRG) Proteome Informatics Research Group (iPRG) Proteomics Standards Research Group (sPRG)
Primary hypercortisolism (Cushing's syndrome): excessive levels of cortisol Secondary hypercortisolism (pituitary tumor resulting in Cushing's disease, pseudo-Cushing's syndrome) Primary hypocortisolism (Addison's disease, Nelson's syndrome): insufficient levels of cortisol Secondary hypocortisolism (pituitary tumor, Sheehan's syndrome)
== Viscoelasticity == Viscoelasticity is the phenomena of time-dependent strain exhibited by amorphous materials such as polymers or glasses. The viscoelasticity of materials depend on the viscosity and can be mechanically modelled using mechanical elements known as springs and dashpots. In turn, constitutive equations can relate the mechanical interpretation of viscoelasticity to the materials properties and strain rate.
=== Examining what occurs at the cellular level of NL. === Tissue Architecture in NL Lesions A lesion is a tissue that has been altered or injured. They can occur as wounds or, in the case of progressive NL, ulcers. The tissue architecture of NL is characterized by degeneration of collagen in the dermis and subcutaneous layers. The lesions exhibit granulomatous inflammation, palisading granulomas, and thickened blood vessels. Palisading granulomas are significant because they show an immune cell ring around degenerated tissue, commonly seen in autoimmune and chronic inflammatory diseases. Thickened blood vessels occur due to an accumulation of immune cells. Together, all these structural features indicate NL as a chronic, inflammatory response. Fibroblasts and endothelial cells are malfunctioning, and there is an imbalance in tissue homeostasis. Fibroblast and collagen remodeling Fibroblasts contribute to the formation of connective tissue, collagen, and elastin. Failure in fibroblasts causes skin to atrophy and degenerate. Increased uptake of GLUT-1 (a glucose transporter) is observed in NL cases. When up-regulated: glycolysis, oxidative stress, and fibroblast proliferation all increase. Despite the metabolic increase, fibroblasts in NL dysfunction. This suggests that in NL tissue decay and dysfunction are linked to both structural and immunological tissue components. The tissue is observed to have increased GLUT-1 and decreased pro-collagen mRNA. A predominance of Type 1 collagen is observed in PL.
Stirring of a given sample of amylose is said to form fibrillar crystals which are said to precipitate out of the mother liquor. These long fibrils can be imaged using electron microscopy revealing transverse striations resembling a shish-kebab. Amylose fibrils are categorized with having one of two morphologies: ones with small rodlike fibrils and others with lath-shaped crystals.
Sources: en.wikipedia.org
Selank is a seven-amino-acid peptide built from the tuftsin sequence plus a Pro-Gly-Pro tail. It is produced by chemical synthesis rather than extracted from a natural source. The free peptide is usually supplied as a lyophilised powder or in an aqueous formulation.
Tuftsin is a natural tetrapeptide derived from the Fc portion of immunoglobulin G. Selank retains that tetrapeptide at its N-terminus and adds three residues to improve resistance to enzymatic breakdown. The relationship is structural, and the two molecules are not interchangeable in experimental work.
It holds a product registration in Russia for intranasal use as an anxiolytic. Registrations of that kind are not automatically accepted by regulators elsewhere. In most other countries it is treated as an unapproved substance or a research material.
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.