A practical reference on mass spectrometry: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-26 and is reviewed periodically as new material appears.
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.
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 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 |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
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.
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.
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.
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.
=== Pharmacodynamics === MMDA has been shown to act as a non-neurotoxic serotonin releasing agent, with no effects on release of dopamine or probably norepinephrine, and as a serotonin 5-HT2A receptor agonist. The latter property is thought to be responsible for its psychedelic effects, whereas the former action may be involved in its entactogenic effects.
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== P == Pacinian corpuscle A type of rapidly adapting mechanoreceptor located deep in the skin, responsible for detecting vibration and pressure. Pain An unpleasant sensory and emotional experience associated with actual or potential tissue damage. In neuroscience, pain is studied through nociception, pain pathways, and perception. Paralysis The loss of voluntary muscle function, often caused by damage to the brain, spinal cord, or peripheral nerves. Paraneoplastic syndrome A rare disorder triggered by an immune response to cancer that affects the nervous system. Can lead to sensory, motor, or cognitive symptoms. Parietal lobe A region of the cerebral cortex located near the top and back of the brain, involved in processing somatosensory information, spatial orientation, and body awareness. Parkinson’s disease A neurodegenerative disorder characterized by tremors, rigidity, bradykinesia, and postural instability. Caused by loss of dopaminergic neurons in the substantia nigra. Parvocellular pathway A visual processing stream originating in small ganglion cells of the retina, responsible for high-acuity and color vision. Projects to the lateral geniculate nucleus. Periaqueductal gray (PAG) A midbrain region involved in pain modulation, defensive behavior, and autonomic regulation. Contains opioid receptors and descending pain control pathways. Peripheral nervous system (PNS) All nerves and ganglia outside the brain and spinal cord. It includes sensory and motor neurons as well as autonomic nerves. Periventricular Located near or surrounding the brain’s ventricular system.
Sources: en.wikipedia.org
== Structure == Azalides feature a nitrogen atom in their 15-membered macrolide ring, resulting in improved pharmacokinetic properties and greater stability when compared to earlier-generation macrolides. Replacement of the ketone group in traditional macrolides with a tertiary amine group confers greater acid stability. See Beckmann rearrangement.
== U == Ultrasound attenuation spectroscopy UPS – UV-photoelectron spectroscopy USANS – Ultra small-angle neutron scattering USAXS – Ultra small-angle X-ray scattering UT – Ultrasonic testing UV-Vis – Ultraviolet–visible spectroscopy
Also, biodegradable polymers often require special composting conditions to properly degrade. Normal sealed landfill conditions do not promote biodegradation. Biodegradable plastics include biodegradable films and coatings synthesized from organic materials and microbial polymers. Some package materials are edible. For example, pharmaceuticals are sometimes in capsules made of gelatin, starch, potato, or other materials. Newer bioplastics, films and products are being developed. There is an increasing development and production of food packaging materials containing substances and realizing systems intended to extend shelf life: carbon dioxide (CO2) emitters; antioxidants (e.g. butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tocopherols, hinokitiol); antimicrobial enzymes (e.g. lysozyme), polymers (e.g. ε-polylysine, chitosan) and nanoparticles (e.g. silver, copper, gold, platinum, titanium dioxide, zinc oxide, magnesium oxide, organically modified nanoclays); bacteriocins (e.g. nisin, natamycin); and essential oils. In the last decades, the use of modified atmosphere packaging (MAP) and other variation of this technology has shown growing interest and application in the food packaging industry. The use of a specific gas mixture inside the packaging headspace has proven to be ideal to slow down the metabolic process of food products, thus prolonging the shelf-life of meat, fish, fruits and vegetables.
Sources: en.wikipedia.org
=== Other common diseases === EpiVacCorona, a peptide-based vaccine against COVID-19. IC41 is a peptide vaccine candidate against the Hepatitis C virus. It consists of five synthetic peptides along with the synthetic adjuvant called poly-l-arginine. Multimeric-001 is the most efficient peptide vaccine candidate against influenza. It contains B- and T-cell epitopes from Hemagglutinin. Matrix I and nucleoprotein are combined into a single recombinantly-expressed polypeptide. Alzheimer peptide vaccines: CAD106, UB311, Lu, AF20513, ABvac40, ACI-35, AADvac-1.
== Principle of the method == ZooMS identifies species based on differences in the amino acid composition of the collagen protein. The amino acid sequence of a species' collagen protein is determined by its DNA and as a result like DNA, the amino acid sequence reflects a species' evolutionary history. The greater the evolutionary distance between two species, the more different their collagen proteins will be. ZooMS typically can identify a sample up to genus level, though in some cases the identification can be more or less specific. A good understanding of the archaeological context of the sample can be used to further refine the resolution of the species identification.
== Contraindications == Gabapentin should be used carefully and at lower doses in people with kidney problems due to possible accumulation and toxicity. It is unclear if it is safe during pregnancy or breastfeeding.
Unlike the highly phosphorylated forms of thiamine, ThMP and free thiamine are capable of crossing cell membranes. Calcium and magnesium have been shown to affect the distribution of thiamine in the body and magnesium deficiency has been shown to aggravate thiamine deficiency. Thiamine contents in human tissues are less than those of other species. The half-life of thiamine content stored in tissues of human body is about 9–18 days, while after intake in high doses, the half-life of thiamine in circulating blood is about one to 12 hours. Additionally, thiamine pyrophosphate derived from pyrimidines supports lipid synthesis and adipogenesis, highlighting its role in energy storage and cellular differentiation. Thiamine and its metabolites (2-methyl-4-amino-5-pyrimidine carboxylic acid, 4-methyl-thiazole-5-acetic acid, and others) are excreted principally in the urine.
Sources: en.wikipedia.org
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.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
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.