mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-11-23. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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 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 |
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
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.
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.
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.
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.
The expected results for external quality assessment samples are not disclosed to the laboratory. External quality assessment programs have been widely adopted in North America and western Europe, and laboratories are often required to participate in these programs to maintain accreditation. Logistical issues may make it difficult for laboratories in under-resourced areas to implement external quality assessment schemes.
Esketamine inhibits the dopamine transporter about 8-fold more potently than does arketamine, and so is about 8 times more potent as a dopamine reuptake inhibitor. Arketamine and esketamine possess similar potency for interaction with the muscarinic acetylcholine receptors.
Paracetamol, also known as acetaminophen, is a medication used to treat pain and fever. It is typically used for mild to moderate pain. In combination with opioid pain medication, paracetamol is now used for more severe pain such as cancer pain and after surgery. It is typically used either by mouth or rectally but is also available intravenously. Effects last between two and four hours. Paracetamol is classified as a mild analgesic, and is generally safe at recommended doses.
with sufficient accuracy for most practical purposes. In effect there is no need to define pKb separately from pKa, but it is done here as often only pKb values can be found in the older literature. For a hydrolyzed metal ion, Kb can also be defined as a stepwise dissociation constant
=== Equipment === KFC initially used stove-top covered cooking pots to fry its chicken. In the 1960s, the officially recommended model was the L S Hartzog developed "KFC 20-Head Cooker", a large device that cost $16,000. The Hartzog model had no oil filtration system, meaning that filtering had to be done manually, and the pressure fryers occasionally exploded often harming employees. In 1969, inventor and engineer Winston L. Shelton developed the "Collectramatic" pressurized fryer to overcome the problems KFC faced in quickly frying chicken to meet growing customer demand. The Collectramatic used precision time and temperature controls and self-filtered the cooking oil – all while meeting Colonel Sanders' high standards. Fred Jeffries, then vice president of purchasing at KFC, claimed that the invention helped fuel the company's rapid expansion and success:
Sources: en.wikipedia.org
Norleucine (abbreviated as Nle) is an amino acid with the formula CH3(CH2)3CH(NH2)CO2H. A systematic name for this compound is 2-aminohexanoic acid. The compound is an isomer of the more common amino acid leucine. Like most other α-amino acids, norleucine is chiral. It is a white, water-soluble solid.
While genome annotation is primarily based on sequence similarity (and thus homology), other properties of sequences can be used to predict the function of genes. In fact, most gene function prediction methods focus on protein sequences as they are more informative and more feature-rich. For instance, the distribution of hydrophobic amino acids predicts transmembrane segments in proteins. However, protein function prediction can also use external information such as gene (or protein) expression data, protein structure, or protein–protein interactions. Evolutionary biology is the study of the origin and descent of species, as well as their change over time. Informatics has assisted evolutionary biologists by enabling researchers to:
These employ the same radioligands and have the same uses as SPECT scanning, but are able to provide even finer 3-D localization of high-uptake tissues, in cases where finer resolution is needed. An example is the sestamibi parathyroid scan which is performed using the 99mTc radioligand sestamibi, and can be done in either SPECT or SPECT/CT machines.
== As a performance-enhancing drug == The possibility of using insulin in an attempt to improve athletic performance was suggested as early as the 1998 Winter Olympics in Nagano, Japan, as reported by Peter Sönksen in the July 2001 issue of Journal of Endocrinology. The question of whether non-diabetic athletes could legally use insulin was raised by a Russian medical officer. Whether insulin would actually improve athletic performance is unclear, but concerns about its use led the International Olympic Committee to ban use of the hormone by non-diabetic athletes in 1998. The book Game of Shadows (2001), by reporters Mark Fainaru-Wada and Lance Williams, included allegations that baseball player Barry Bonds used insulin (as well as other drugs) in the apparent belief that it would increase the effectiveness of the growth hormone he was alleged to be taking. Bonds eventually testified in front of a federal grand jury as part of a government investigation of BALCO. Bodybuilders in particular are claimed to be using exogenous insulin and other drugs in the belief that they will increase muscle mass. Bodybuilders have been described as injecting up to 10 IU of regular synthetic insulin before eating sugary meals. A 2008 report suggested that insulin is sometimes used in combination with anabolic steroids and growth hormone (GH), and that "Athletes are exposing themselves to potential harm by self‐administering large doses of GH, IGF‐I and insulin". Insulin abuse has been mentioned as a possible factor in the deaths of bodybuilders Ghent Wakefield and Rich Piana.
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.
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.