If you have been reading about nootropic and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-06-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
| 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 |
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
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.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
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.
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.
=== Therapeutic effects === Pain relief: Primarily, fentanyl provides the relief of pain by acting on the brain and spinal μ-receptors. Sedation: Fentanyl produces sleep and drowsiness, as the dosage is increased, and can produce the δ-waves often seen in natural sleep on electroencephalogram. Suppression of the cough reflex: Fentanyl can decrease the struggle against an endotracheal tube and excessive coughing by decreasing the cough reflex, becoming useful when intubating people who are awake and have compromised airways. After receiving a bolus dose of fentanyl, people can also experience paradoxical coughing, which is a phenomenon that is not well understood.
=== Hair loss === LLLT has been studied as a treatment for hair loss; a review in 2012 found little evidence to support the use of lasers to treat hair loss. A 2014 review found tentative evidence for benefit for lasers, while another 2014 review concluded that the results were mixed, had a high risk of bias, and that its effectiveness was unclear. A 2015 review found tentative evidence of benefit. Additionally, a 2017 review of clinical trials found 10 of 11 trials reviewed "demonstrated significant improvement of androgenic alopecia in comparison to baseline or controls when treated with LLLT." LLLT is shown to increase hair density and growth in both genders. The types of devices (hat, comb, helmet) and duration did not alter the effectiveness, with more emphasis to be placed on lasers compared to LEDs. Ultraviolet and infrared light are more effective for alopecia areata, while red light and infrared light is more effective for androgenetic alopecia. Medical reviews suggest that LLLT is as effective or potentially more than other non invasive and traditional therapies such as minoxidil and finasteride but further studies such as RCTs, long term follow up studies, and larger double blinded trials need to be conducted to confirm the initial findings.
=== Role in the onset of Gingival Cyst === Some studies suggest that the gingival cyst may have developed from the odontogenic epithelium or from the surface or sulcular epithelium that has been traumatically implanted in the area.
This article incorporates public domain material from The World Factbook (2025 ed.). CIA. (country: Honk Kong) Hong Kong from BBC News Key Development Forecasts for Hong Kong from International Futures Hong Kong in Transition (1995–2020) Archived 20 March 2025 at the Wayback Machine, an open access photographic archive of recent Hong Kong history Government
Dust mite allergy, also known as house dust allergy, is a sensitization and allergic reaction to the droppings of house dust mites. The allergy is common and can trigger allergic reactions such as asthma, eczema, or itching. The mite's gut contains potent digestive enzymes (notably peptidase 1) that persist in their faeces and are major inducers of allergic reactions such as wheezing. The mite's exoskeleton can also contribute to allergic reactions. Unlike scabies mites or skin follicle mites, house dust mites do not burrow under the skin and are not parasitic. Dust mite-proof encasements to mattress, pillow, and duvet prevent chronic contact with allergens.
Sources: en.wikipedia.org
=== Ari Haswari === Ari Haswari (portrayed by Rudolf Martin) is a terrorist who attacks and wounds both Gibbs and Gerald Jackson when he infiltrates the NCIS morgue during the episode "Bête Noire". NCIS initially identifies him as an undercover Mossad agent in the episode "Reveille", but he is really a rogue agent working for Hamas, and he is later found to be the leader of an Al-Qaeda cell in Washington, D.C., the latter info a correct summation made by Gibbs in "Twilight". Ari is an early archenemy of Agent Gibbs, as well as Eli David's first-born child. Both of his parents were medical doctors; Ari's mother, Hasmia Haswari, was Palestinian and his father, Dr. Benjamin Weinstein (actually Eli David using an alias), was Israeli. He underwent medical training in Scotland at the University of Edinburgh Medical School in order to serve undercover inside the Gaza Strip, where his mother was killed during a retaliatory bombardment by Israel. The event prompted Ari to join the radical Islamic cause. It is shown that he hates his Israeli father since Eli David arranged for the attack on Gaza on a day when Ari was in the city. He preferred to be referred to as Haswari in school instead of Ari. Ari's motivation for his actions is his hatred of his father, who groomed him from birth to be a spy within Al-Qaeda, and was very likely the reason why Gibbs later suspects him in "Twilight" to be the head of an Al-Qaeda cell in Washington, D.C.
The topology of a β-sheet describes the order of hydrogen-bonded β-strands along the backbone. For example, the flavodoxin fold has a five-stranded, parallel β-sheet with topology 21345; thus, the edge strands are β-strand 2 and β-strand 5 along the backbone. Spelled out explicitly, β-strand 2 is H-bonded to β-strand 1, which is H-bonded to β-strand 3, which is H-bonded to β-strand 4, which is H-bonded to β-strand 5, the other edge strand. In the same system, the Greek key motif described above has a 4123 topology. The secondary structure of a β-sheet can be described roughly by giving the number of strands, their topology, and whether their hydrogen bonds are parallel or antiparallel. β-sheets can be open, meaning that they have two edge strands (as in the flavodoxin fold or the immunoglobulin fold) or they can be closed β-barrels (such as the TIM barrel). β-Barrels are often described by their stagger or shear. Some open β-sheets are very curved and fold over on themselves (as in the SH3 domain) or form horseshoe shapes (as in the ribonuclease inhibitor). Open β-sheets can assemble face-to-face (such as the β-propeller domain or immunoglobulin fold) or edge-to-edge, forming one big β-sheet.
=== Entry into bacteria === Penicillin can easily enter bacterial cells in the case of gram-positive species. This is because Gram-positive bacteria do not have an outer cell membrane and are simply enclosed in a thick cell wall. Penicillin molecules are small enough to pass through the spaces of glycoproteins in the cell wall. For this reason Gram-positive bacteria are very susceptible to penicillin (as first evidenced by the discovery of penicillin in 1928). Penicillin, or any other molecule, enters gram-negative bacteria in a different manner. The bacteria have thinner cell walls but the external surface is coated with an additional cell membrane, called the outer membrane. The outer membrane is a lipid layer (lipopolysaccharide chain) that blocks passage of water-soluble (hydrophilic) molecules like penicillin. It thus acts as the first line of defence against any toxic substance, which is the reason for relative resistance to antibiotics compared to gram-positive species. But penicillin can still enter gram-negative species by diffusing through aqueous channels called porins (outer membrane proteins), which are dispersed among the fatty molecules and can transport nutrients and antibiotics into the bacteria. Porins are large enough to allow diffusion of most penicillins, but the rate of diffusion through them is determined by the specific size of the drug molecules. For instance, penicillin G is large and enters through porins slowly; while smaller ampicillin and amoxicillin diffuse much faster.
is the first derivative of concentration with respect to time, i.e. the change in concentration with time. It is derived from a mass balance. Clearance of a substance is sometimes expressed as the inverse of the time constant that describes its removal rate from the body divided by its volume of distribution (or total body water). In steady-state, it is defined as the mass generation rate of a substance (which equals the mass removal rate) divided by its concentration in the blood.
Derived from “the addition of a hydrophilic heterocyclic group to the α-amino group of ampicillin”, the structure consists of a thiazolidine ring conjoined to a β-lactam ring contained within several ring compounds. The addition of this substituent increases the compound's affinity to penicillin-binding protein PBP-3, improving activity against Gram-negative bacteria, and thus broadening its spectrum of activity. Susceptible β-lactamase producing bacteria such as Staphylococcus spp. or Haemophilus influenzae, the combination of tazobactam (which shares a similar structure to sulbactam, another β-lactamase inhibitor), and piperacillin significantly improves the stability of the drug against β-lactamases.
Sources: en.wikipedia.org
=== Americas === In the US, "cider" often refers to sweetened, unfiltered apple juice, traditionally made with a distinct sweet-tart taste, and in these regions, the fermented (alcoholic) beverage is known as "hard cider". In Canada, "cider" usually refers to the alcoholic drink, while the non-alcoholic juice may sometimes be called "apple cider".
== Metabolism == GABA transaminase enzymes catalyze the conversion of 4-aminobutanoic acid (GABA) and 2-oxoglutarate (α-ketoglutarate) into succinic semialdehyde and glutamate. Succinic semialdehyde is then oxidized into succinic acid by succinic semialdehyde dehydrogenase and as such enters the citric acid cycle as a usable source of energy.
In August 2025, Moore's chief of staff, Fagan Harris, announced that he would resign his post at the end of the year to become the next president of the Abell Foundation; he was succeeded by Lester Davis, a CareFirst BlueCross BlueShield executive who worked as an unpaid outside advisor to Moore's 2022 gubernatorial campaign. In October 2025, Roland Butler resigned as secretary of state police and was succeeded by state senator Michael A. Jackson. In November 2025, Paul Monteiro resigned as secretary of Maryland Department of Service and Civic Innovation and was succeeded by Jonny Dorsey, one of Moore's deputy chiefs of staff. In October 2025, Moore appointed Walter Simmons to serve as the secretary of the newly created Department of Social and Economic Mobility. Two of Moore's cabinet secretaries resigned in 2026. Maryland Secretary of Human Services Rafael López, who resigned on February 23, citing health reasons, and was succeeded by deputy secretary Gloria Brown Burnett, who will serve as acting secretary until April 1, when Stacy Rodgers will then take over as acting secretary. In March 2026, Rai announced that he would step down on March 27, and would be succeeded by deputy secretary Elena Quiroz-Livanis, who will serve as acting secretary until a search for a new, permanent secretary is completed.
Birches often form even-aged stands on light, well-drained, particularly acidic soils. They are regarded as pioneer species, rapidly colonizing open ground especially in secondary successional sequences following a disturbance or fire. Birches are early tree species to become established in primary successions, and can become a threat to heathland if the seedlings and saplings are not suppressed by grazing or periodic burning. Birches are generally lowland species, but some species, such as Betula nana, have a montane distribution. In the British Isles, there is some difference between the environments of Betula pendula and Betula pubescens, and some hybridization, though both are "opportunists in steady-state woodland systems". Mycorrhizal fungi, including sheathing (ecto)mycorrhizas, are found in some cases to be beneficial to tree growth. A large number of lepidopteran insects feed on birch foliage.
=== Storing oils and fats === Oils and fats can go rancid quickly if not stored properly. Rancid cooking oils and fats do not often smell rancid until well after they have spoiled. Oxygen, light, and heat all contribute to cooking oils becoming rancid. The higher the level of polyunsaturated fat that an oil contains, the faster it spoils. The percentage of polyunsaturated fat in some common cooking oils is safflower (74%), sunflower (66%), corn (60%), soybean (37%), peanut (32%), canola (29%), olive (8%), and coconut (5%). To help preserve oils from rancidification, they should be stored in a dark place, in oxygen-safe, light-reducing containers (e.g., dark glass or metal). Once opened, oils should be refrigerated and used within a few weeks, when some types begin to go rancid. Unopened oils can have a storage life of up to one year, but some types have a shorter shelf-life even when unopened (such as sesame and flaxseed).
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.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.