Peptidase stability raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-12-09. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
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.
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.
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.
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.
== Applications == One of the potent applications of siRNAs is the ability to distinguish the target versus non-target sequence with a single-nucleotide difference. This approach has been considered therapeutically crucial for silencing dominant gain-of-function (GOF) disorders, where the mutant allele causing disease differs from the wild-type allele by a single nucleotide (nt). These types of siRNAs, which are capable of distinguishing a single-nucleotide difference, are termed allele-specific siRNAs. ASP-RNAi is an innovative category of RNAi with the objective of suppressing the dominant mutant allele while sparing expression of the corresponding normal allele with the specificity of single-nucleotide differences between the two. ASP-siRNAs are potentially a novel and better remedial alternative for the treatment of autosomal dominant genetic disorders, especially in cases where wild-type allele expression is crucial for organism survival, such as Huntington disease (HD), DYT1 dystonia (Gonzalez-Alegre et al. 2003, 2005), Alzheimer's disease (AD) (Sierant et al. 2011), Parkinson's disease (PD) (Takahashi et al. 2015), amyotrophic lateral sclerosis (ALS) (Schwarz et al. 2006), and Machado-Joseph disease (MJD) (Alves et al. 2008). Their therapeutic potential has also been assessed for various skin disorders like epidermolysis bullosa simplex (Atkinson et al. 2011), epidermolytic palmoplantar keratoderma (EPPK) (Lyu et al. 2016), and lattice corneal dystrophy type I (LCDI) (Courtney et al. 2014).
In December 2025, the Food and Drug Administration announced that it would offer "agentic AI capabilities" to its staff for "meeting management, pre-market reviews, review validation, post-market surveillance, inspections and compliance and administrative functions." That same month, the United States Department of Defense launched GenAI.mil, an internal platform for American military personnel to use generative AI-based applications based on Google Gemini, including "intelligent agentic workflows". Defense Secretary Pete Hegseth listed applications such as "[conducting] deep research, [formatting] documents and even [analyzing] video or imagery at unprecedented speed." In December 2025, the United States Immigration and Customs Enforcement agency signed a contract with a company for its Enforcement and Removal Operations department to use AI agents for skip tracing.
FDA issued a public health advisory to warn health care providers of the potential toxicity of this synthetic dye in enteral feeding solutions. The following legal limits apply in the EU (E 133) and other countries: 150–300 mg/kg depending on the type of food. Safety limit for foods and drugs: 0.1 mg/day per kg body weight. The acceptable daily intake for brilliant blue FCF is 6 mg/kg.
Sources: en.wikipedia.org
Ibogaine's hallucinogenic effects not being mediated by serotonin 5-HT2A receptor activation has been said to be in accordance with its hallucinogenic effects in humans being qualitatively distinct from and unlike those of serotonergic psychedelics but instead similar to those of harmala alkaloids. It is also in accordance with the fact that unlike serotonergic psychedelics like LSD, neither ibogaine nor harmala alkaloids cause pupil dilation or increase blood pressure in humans. Conversely, unlike serotonergic psychedelics, ibogaine and harmaline are said to cause balance disturbances and vomiting to a greater extent than any other psychoactive drug besides alcohol. Ibogaine shows appreciable affinity for the NMDA receptor. However, the NMDA receptor antagonists phencyclidine (PCP) and dizocilpine (MK-801) fail to substitute for ibogaine and ibogaine fails to substitute for these NMDA receptor antagonists in rodents and/or monkeys. Hence, NMDA receptor antagonism does not appear to be involved in the subjective effects of ibogaine. Neither μ-opioid receptor agonists nor κ-opioid receptor agonists like U-50,488 substitute for ibogaine. In addition, the opioid antagonist naloxone did not substitute for ibogaine. However, naltrexone partially substitutes for ibogaine. In addition, the mixed opioid agonists and antagonists pentazocine, diprenorphine, and nalorphine partially substituted for ibogaine and this could be antagonized by naloxone. The preceding findings suggest a role of opioid receptors but not the NMDA receptor in the effects of ibogaine.
== Other uses == The nutrition-rich nature of yeast extract lends it to a variety of uses. It was historically popular as a vitamin supplement for humans. Rich in proteins and nucleotides, it currently finds use in animal feed and microbiology (see yeast extract agar) as nutritional supplements. It also finds use in cosmetics and skincare products due to its alleged moisturizing and antioxidant properties.
1946: Shimpei Fukuye, who killed four prisoners of war during the Selarang Barracks incident, was executed on 27 April 1946. 1947: Oishi Masayuki, commander of the 2nd Field Kempeitai, and Kawamura Saburo, commander of the Syonan Defence Garrison. Both men were sentenced to death in 1947 for initiating the Sook Ching massacre, and executed the same year. Lieutenant-Colonel Sumida Haruzo, Warrant Officer Monai Tadamori, Sergeant Major Makizono Masuo, Sergeant Major Terada Takao, Sergeant Nozawa Toichiro, Sergeant Major Tsujio Shigeo, Sergeant Major Morita Shozo and army interpreter Toh Swee Koon, the eight defendants who were sentenced to death after their conviction for war crimes at the 1946 Double Tenth incident trial.
The HGSA is governed by a council, presided over by the president. The day-to-day strategic decision making is undertaken by an executive of council, consisting of the president, vice-president, treasurer and secretary. The Society employs a chief executive officer to run the administrative functions of the organization. Executive members of HGSA council are elected to their positions by popular vote from the membership. The remainder of the council is representative of the membership. The jurisdictions are represented by the chairpersons of HGSA branches, while the special interest groups are represented by their chairs. Council has the capacity to establish committees to undertake long-term high-level activities of the society. Longstanding committees include the Scientific Programme Committee; Annual Scientific Meeting Local Organising Committee; and the Education, Ethics and Social Issues Committee.
Sources: en.wikipedia.org
In land plants, chloroplasts are generally lens-shaped, 3–10 μm in diameter and 1–3 μm thick. Corn seedling chloroplasts are ≈20 μm3 in volume. Greater diversity in chloroplast shapes exists among the algae, which often contain a single chloroplast that can be shaped like a net (e.g., Oedogonium), a cup (e.g., Chlamydomonas), a ribbon-like spiral around the edges of the cell (e.g., Spirogyra), or slightly twisted bands at the cell edges (e.g., Sirogonium). Some algae have two chloroplasts in each cell; they are star-shaped in Zygnema, or may follow the shape of half the cell in order Desmidiales. In some algae, the chloroplast takes up most of the cell, with pockets for the nucleus and other organelles, for example, some species of Chlorella have a cup-shaped chloroplast that occupies much of the cell. All chloroplasts have at least three membrane systems—the outer chloroplast membrane, the inner chloroplast membrane, and the thylakoid system. The two innermost lipid-bilayer membranes that surround all chloroplasts correspond to the outer and inner membranes of the ancestral cyanobacterium's gram negative cell wall, and not the phagosomal membrane from the host, which was probably lost. Chloroplasts that are the product of secondary endosymbiosis may have additional membranes surrounding these three. Inside the outer and inner chloroplast membranes is the chloroplast stroma, a semi-gel-like fluid that makes up much of a chloroplast's volume, and in which the thylakoid system floats.
==== Youth development ==== Positive youth development focuses on the promotion of healthy development rather than viewing youth as prone to problems needing to be addressed. This is accomplished through programs and efforts by communities, schools, and government agencies.
Agonist: A drug with a fast association and a fast dissociation. Partial-agonist: A drug with an intermediate association and an intermediate dissociation. Antagonist: A drug with a fast association & slow dissociation
=== Jordan Hampton === Dr. Jordan Hampton (Torri Higginson) first appears in the episode "Identity Crisis". When a "John Doe" is donated to science and Ducky finds mercury in his brain, he is outraged that the medical examiner who performed the autopsy did not think to check his brain before donating him. As he and Gibbs go to confront "him" (Ducky mistakenly assumed that Dr. Hampton was male), he asks Gibbs to think no less of him for giving the M.E. a piece of his mind. After finding out that Dr. Hampton was not male, Ducky was visibly placated. Jordan came back to Ducky's autopsy room to help him find anything else she might have missed, and decodes the tattoo on his arm, helping Gibbs and his team eventually solve the case. She also reveals in this episode that she likes things neat and clean. She made a reappearance in the episode "Broken Bird" to help Ducky overcome grief and guilt for euthanizing a tortured Afghan when he was a doctor in the military. The two show some romantic interest in both episodes. Also, although she did not appear in the episode, she gave Ducky the autopsy report for La Grenouille in the episode "Internal Affairs".
=== Initial chemical classification === In the periodic table published by Dmitri Mendeleev in 1869, thorium and the rare-earth elements were placed outside the main body of the table, at the end of each vertical period after the alkaline earth metals. This reflected the belief at that time that thorium and the rare-earth metals were divalent. With the later recognition that the rare earths were mostly trivalent and thorium was tetravalent, Mendeleev moved cerium and thorium to group IV in 1871, which also contained the modern carbon group (group 14) and titanium group (group 4), because their maximum oxidation state was +4. Cerium was soon removed from the main body of the table and placed in a separate lanthanide series; thorium was left with group 4 as it had similar properties to its supposed lighter congeners in that group, such as titanium and zirconium.
Sources: en.wikipedia.org
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.