The short version of mass spectrometry fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-05-09. Anything still debated is marked as such rather than presented as settled.
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.
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.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
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.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
=== Economics === In the UK, trastuzumab emtansine was not recommended for use by the National Health Service by advisory body NICE, reportedly because an acceptable pricing agreement could not be reached with Roche. Originally it cost £5,900 a month. and NICE estimated it cost £166,000 per QALY (well over the usual maximum). It has been funded by the English NHS Cancer Drugs Fund but in January 2015 it was proposed to remove it from the approved list. After a secret discount was agreed by Roche the Cancer Drugs Fund will continue to fund it. In June 2017, the NHS Confederation and NHS Chief Executive Simon Stevens announced that the NHS would be offering trastuzumab emtansine to a limited number of women after striking a deal with Roche on the price.
In their first major declaration on the issue since 2016, global leaders also committed to raising $100 million to update and implement AMR action plans. However, the final draft of the declaration omitted an earlier target to reduce antibiotic use in animals by 30% by 2030, due to opposition from meat-producing countries and the farming industry. Critics argue this omission is a major weakness, as livestock accounts for around 73% of global sales of antimicrobial agents, including antibiotics, antivirals, and antiparasitics.
=== Role in tumor growth === Endothelial progenitor cells are likely important in tumour growth and are thought to be critical for metastasis and the angiogenesis. A large amount of research has been done on CFU-Hill bone marrow-derived putative EPCs. Ablation of the endothelial progenitor cells in the bone marrow lead to a significant decrease in tumour growth and vasculature development. This indicates that endothelial progenitor cells present novel therapeutic targets. Inhibitor of DNA Binding 1 (ID1) has been used as a marker for these cells; this allows for tracking EPCs from the bone marrow to the blood to the tumour-stroma and even incorporated in tumour vasculature. Recently it has been found that miRNAs regulate EPC biology and tumour angiogenesis. This work by Plummer et al. found that in particular targeting of the miRNAs miR-10b and miR-196b led to significant defects in angiogenesis-mediated tumor growth by decreasing the mobilization of proangiogenic EPCs to the tumour. These findings indicate that directed targeting these miRNAs in EPCs may result in a novel strategy for inhibiting tumor angiogenesis. Studies have shown ECFCs and human umbilical vein endothelial cells (HUVECs) to have a capacity for tumor migration and neoangiogenesis even greater than that of other CD34+ hematopoietic cells when implanted in immunodeficient mice, suggesting the endothelial progenitors play a key role, but further supporting the importance of both cell types as targets for pharmacological therapy.
Further shell closures beyond the main island of stability in the vicinity of Z = 112–114 may give rise to additional islands of stability. Although predictions for the location of the next magic numbers vary considerably, two significant islands are thought to exist around heavier doubly magic nuclei; the first near 354126 (with 228 neutrons) and the second near 472164 or 482164 (with 308 or 318 neutrons). Nuclides within these two islands of stability might be especially resistant to spontaneous fission and have alpha decay half-lives measurable in years, thus having comparable stability to elements in the vicinity of flerovium. Other regions of relative stability may also appear with weaker proton shell closures in beta-stable nuclides; such possibilities include regions near 342126 and 462154. Substantially greater electromagnetic repulsion between protons in such heavy nuclei may greatly reduce their stability, and possibly restrict their existence to localized islands in the vicinity of shell effects. This may have the consequence of isolating these islands from the main chart of nuclides, as intermediate nuclides and perhaps elements in a "sea of instability" would rapidly undergo fission and essentially be nonexistent. It is also possible that beyond a region of relative stability around element 126, heavier nuclei would lie beyond a fission threshold given by the liquid drop model and thus undergo fission with very short lifetimes, rendering them essentially nonexistent even in the vicinity of greater magic numbers.
Sources: en.wikipedia.org
The first and most important step in sample preparation for mass spectrometry is determining what phase the sample needs to be in. Different ionization methods require different sample phases. Solid phase samples can be ionized through methods such as field desorption, plasma-desorption, fast atom bombardment, and secondary-ion ionization. Liquids with the analyte dissolved in them, or solutions, can be ionized through methods such as matrix-assisted laser desorption, electrospray ionization, and atmospheric-pressure chemical ionization. Both solid and liquid samples may be ionized with ambient ionization techniques. Gas samples, or volatile samples, can be ionized using methods such as electron ionization, photoionization, and chemical ionization. These lists are the most commonly used state of matter for each ionization method, but the ionization methods are not necessarily limited to these states of matter. For example, fast atom bombardment ionization is typically used to ionize solid samples, but this method is typically used on solids dissolved into solutions, and can also be used to analyze components that have entered the gas phase.
Since about 2005, body scanners have been used primarily at airports for security (passenger) screening. Passive scanners detect the natural radiation emitted by a person's body and use it to locate objects worn or concealed on the body. Active systems also use artificial radiation to improve detection by analyzing the backscatter. A distinction is made between body scanners that use ionizing radiation (usually X-rays) and those that use non-ionizing radiation (terahertz radiation).
Organic cages function as molecular containers through specific host-guest interactions. The defined cavity can encapsulate guest molecules of appropriate size and chemical compatibility. The binding process often induces measurable changes in cage properties, enabling their use as molecular sensors. Selective binding of specific analytes can trigger optical, electronic, or structural responses that provide detection signals. These features enable applications in environmental monitoring and chemical detection. The host-guest chemistry extends to selective capture of environmental pollutants and valuable chemicals. The tunable cavity size and surface chemistry allow targeting specific molecules, while some cages demonstrate stimuli-responsive guest release for controlled delivery applications.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.