The short version of blood-brain barrier fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-28. Anything still debated is marked as such rather than presented as settled.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter notation. Its structure consists of the immunomodulatory tetrapeptide tuftsin, Thr-Lys-Pro-Arg, extended at the carboxyl terminus by a Pro-Gly-Pro segment. The molecular formula is commonly given as C33H57N11O9, corresponding to a monoisotopic mass near 751.4 Da and an average molecular mass near 751.9 Da. All seven residues are proteinogenic amino acids, and the molecule carries no modified side chains or non-natural linkages.
The compound was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences during the 1980s and 1990s. The stated design goal was to retain the immunomodulatory and central nervous system activity attributed to tuftsin while improving resistance to enzymatic breakdown. Adding a proline-rich tail to the short parent peptide was a deliberate strategy, because proline residues restrict the conformations available to many peptidases. The same laboratory produced Semax, an ACTH fragment analog, and both compounds were developed in parallel as short, enzymatically stabilized peptides intended for intranasal use.
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.
Published clinical work is concentrated in Russian-language journals and generally involves small samples without independent replication. Systematic reviews in English note the shortage of randomised, placebo-controlled trials and the difficulty of verifying methods from translated reports. Outcome measures vary between studies, which complicates pooling of results. Interest in the compound as a cognitive or anxiolytic agent therefore rests on a thinner evidence base than the volume of citations suggests. Replication in well-powered trials with preregistered endpoints would be needed before firm conclusions about efficacy can be drawn.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
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.
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.
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.
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.
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.
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.
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.
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel forming a blood clot. The process involves activation, adhesion and aggregation of platelets, as well as deposition and maturation of fibrin. Coagulation results in hemostasis, the cessation of blood loss from a damaged vessel, allowing repair. Coagulation begins almost instantly after an injury to the endothelium that lines a blood vessel. Exposure of blood to the subendothelial space initiates two processes: changes in platelets, and the exposure of subendothelial platelet tissue factor to coagulation factor VII, which ultimately leads to cross-linked fibrin formation. Platelets immediately form a plug at the site of injury; this is called primary hemostasis. Secondary hemostasis occurs simultaneously: additional coagulation factors beyond factor VII (listed below) respond in a cascade to form fibrin strands, which strengthen the platelet plug. Coagulation is highly conserved throughout biology. In all mammals, coagulation involves both cellular components (platelets) and proteinaceous components (coagulation or clotting factors). The pathway in humans has been the most extensively researched and is the best understood. Disorders of coagulation can result in problems with hemorrhage, bruising, or thrombosis.
=== Nerve supply === Innervation derives from spinal cord segments S2 to S4, reaching the penis through the pelvic splanchnic nerves and the pudendal nerves. The dorsal nerve of the penis, a branch of the pudendal nerve, runs alongside the dorsal artery and supplies the skin and the glans. It travels deep to Buck's fascia within the dorsal neurovascular bundle, in the groove between the corpora cavernosa. The cavernous nerves carry the parasympathetic fibres that innervate the helicine arteries supplying the erectile tissue.
Twinlab Consolidated Corporation is an American company which manufactures and markets vitamins, minerals, and bodybuilding supplements. Twinlab is based in Boca Raton, Florida. Twinlab currently produces more than 500 different products.
The British policy as stated in the declaration was to face numerous challenges to its implementation in the following years. The first of these was the indirect peace negotiations which took place between Britain and the Ottomans in December 1917 and January 1918 during a pause in the hostilities for the rainy season; although these peace talks were unsuccessful, archival records suggest that key members of the War Cabinet may have been willing to permit leaving Palestine under nominal Turkish sovereignty as part of an overall deal. In October 1919, almost a year after the end of the war, Lord Curzon succeeded Balfour as Foreign Secretary. Curzon had been a member of the 1917 Cabinet that had approved the declaration, and according to British historian Sir David Gilmour, Curzon had been "the only senior figure in the British government at the time who foresaw that its policy would lead to decades of Arab–Jewish hostility". He therefore determined to pursue a policy in line with its "narrower and more prudent rather than the wider interpretation". Following Bonar Law's appointment as Prime Minister in late 1922, Curzon wrote to Law that he regarded the declaration as "the worst" of Britain's Middle East commitments and "a striking contradiction of our publicly declared principles". In August 1920 the report of the Palin Commission, the first in a long line of British Commissions of Inquiry on the question of Palestine during the Mandate period, noted that "The Balfour Declaration ... is undoubtedly the starting point of the whole trouble".
Sources: en.wikipedia.org
{\displaystyle \cos \varphi ={\frac {(\mathbf {b} _{0}\times \mathbf {b} _{1})\cdot (\mathbf {b} _{0}\times \mathbf {b} _{2})}{|\mathbf {b} _{0}\times \mathbf {b} _{1}||\mathbf {b} _{0}\times \mathbf {b} _{2}|}}}
When Abraham Lincoln won the 1860 election on a platform of halting the expansion of slavery, according to the 1860 U.S. census, roughly 400,000 individuals, representing 8% of all U.S. families, owned nearly 4,000,000 slaves. One-third of Southern families owned slaves. The South was heavily invested in slavery. As such, upon Lincoln's election, seven states broke away to form the Confederate States of America. The first six states to secede held the greatest number of slaves in the South. Shortly after, over the issue of slavery, the United States erupted into an all-out Civil War, with slavery legally ceasing as an institution following the war in December 1865. In 1865, the United States ratified the 13th Amendment to the United States Constitution, which banned slavery and involuntary servitude "except as punishment for a crime whereof the party shall have been duly convicted," providing a legal basis for forced labor to continue in the country. This led to the system of convict leasing, which affected primarily African Americans. The Prison Policy Initiative, an American criminal justice think tank, cites the 2020 US prison population as 2.3 million, and nearly all able-bodied inmates work in some fashion. In Texas, Georgia, Alabama and Arkansas, prisoners are not paid at all for their work. In other states, prisoners are paid between $0.12 and $1.15 per hour. Federal Prison Industries paid inmates an average of $0.90 per hour in 2017. Inmates who refuse to work may be indefinitely remanded into solitary confinement or have family visitation revoked.
Glycerol () is a sugar alcohol with chemical formula C3H5(OH)3. It has three carbon atoms with one hydroxyl group on each. Glycerol is a colorless, odorless, sweet-tasting, viscous liquid at Standard Ambient Temperature and Pressure (SATP). Because of its three hydroxyl groups, glycerol is miscible with water and is hygroscopic in nature. The glycerol backbone is found in lipids known as glycerides, where one or more of the hydroxyl groups are esterified with fatty acids. The most abundant of glycerides are triglycerides (found in animal fats and vegetable oils), the form in which glycerol is most commonly found in nature. It is also widely used as a sweetener in the food industry and as a humectant in pharmaceutical formulations. Modern use of the word glycerine (alternatively spelled glycerin) refers to commercial preparations of glycerol that are less than 100% pure, typically 95%.
The freezing point of a solution is lower than that of the pure solvent, and the freezing-point depression (ΔT) is directly proportional to the amount concentration for dilute solutions. When the composition is expressed as a molality, the proportionality constant is known as the cryoscopic constant (Kf) and is characteristic for each solvent. If w represents the mass fraction of the solute in solution, and assuming no dissociation of the solute, the molar mass is given by
== Clinical significance == Chromosomal rearrangements and altered expression of this gene have been implicated in several neurological, neoplastic, and other types of diseases, including Alzheimer's disease, Down syndrome, epilepsy, amyotrophic lateral sclerosis, schwannoma, melanoma, and type I diabetes mellitus. It has been suggested that the regulation of S100B by melittin has potential for the treatment of epilepsy.
Sources: en.wikipedia.org
=== Ionization processes === Thermospray ionization has three possible processes by which it can occur. The first involved direct desorption of analyte, where evaporation of the more volatile solvent allows the less volatile liquid sample ions to enter gas phase. The second type of ionization is an acid-base transfer such that solvent ions exchange a proton with ionic components of a buffer. This form of ionization is most commonly used with reverse phase high performance liquid chromatography (RP-HPLC). The third process through which ionization can occur is termed plasmaspray ionization, where electron ionization is applied to the solvent flow under ambient conditions to produce a plasma source. This plasma source then chemically ionizes solvent reagent ions. (Also called filament-on operation.)
Director, Chuckling Goat. For services to Charity and to Innovation in Wales. Evelyn Mary Joy. Agent, Buckingham Conservative Association. For Political and Public Service. James Michael Keggen. Coxswain, Port St Mary Lifeboat Station, Royal National Lifeboat Institution. For voluntary services to Maritime Safety. Sharon Elaine Kelly. Project Manager, Royston Youth Action. For services to Young People. Lindsey Kemp. Officer, National Crime Agency. For services to Law Enforcement. Maurice Joseph Kennedy. Volunteer, Transport Training Board. For services to the Transport and Logistics Industries of Northern Ireland and Great Britain. Christine Anne Kenyon. Deputy Principal, The Manchester College, Greater Manchester. For services to Further Education. Michael Kettle. Explosives Officer, Metropolitan Police Service. For services to Bomb Disposal. Helen Morag Keys. Entrepreneur, Queen's University's Students' Union. For services to Entrepreneurship and Innovation in Farming. Jasdeep Hari Bhajan Singh Khalsa. Founder, The Sikher Project. For charitable services to the Sikh Community. Professor Saye Hock Khoo. Professor of Pharmacology and Therapeutics, University of Liverpool. For services to Infectious Diseases and Pharmacology. Virginia Kiddle. Officer, National Crime Agency. For services to Law Enforcement. Amy Kilby. UK Representative, International Project Management Organisation. For services to Military Communications. James Kilpatrick. Chair, RVH Liver Support Group. For services to People with Liver Disease and their Carers in Northern Ireland. Charline Zephoria King.
A bound system is typically at a lower energy level than its unbound constituents because its mass must be less than the total mass of its unbound constituents. For systems with low binding energies, this "lost" mass after binding may be fractionally small, whereas for systems with high binding energies, the missing mass may be an easily measurable fraction. This missing mass may be lost during the process of binding as energy in the form of heat or light, with the removed energy corresponding to the removed mass through Einstein's equation E = mc2. In the process of binding, the constituents of the system might enter higher energy states of the nucleus/atom/molecule while retaining their mass, and because of this, it is necessary that they are removed from the system before its mass can decrease. Once the system cools to normal temperatures and returns to ground states regarding energy levels, it will contain less mass than when it first combined and was at high energy. This loss of heat represents the "mass deficit", and the heat itself retains the mass that was lost (from the point of view of the initial system). This mass will appear in any other system that absorbs the heat and gains thermal energy. For example, if two objects are attracting each other in space through their gravitational field, the attraction force accelerates the objects, increasing their velocity, which converts their potential energy (gravity) into kinetic energy.
== Further reading == May RM, Anderson RM (1991). Infectious diseases of humans: dynamics and control. Oxford: Oxford University Press. ISBN 0-19-854040-X. Vynnycky E, White RG, eds. (2010). An Introduction to Infectious Disease Modelling. Oxford: Oxford University Press. ISBN 978-0-19-856576-5. Capasso V (2008). Mathematical Structures of Epidemic Systems. 2nd Printing. Heidelberg: Springer. ISBN 978-3-540-56526-0. Carlson CS, Rubin DM, Heikkilä V, Postema M (2021). "Extracting transmission and recovery parameters for an adaptive global system dynamics model of the COVID-19 pandemic". 2021 IEEE Africon (PDF). pp. 456–459. doi:10.1109/AFRICON51333.2021.9570946. ISBN 978-1-6654-1984-0. S2CID 239899862.
=== Electrochemical skin conductance === Electrochemical skin conductance (ESC) is an objective, quantitative, non-invasive method for the assessment of sudomotor function that utilizes chronoamperometry (the application of rectangular direct current (DC) pulses of varying voltage amplitudes) to electrically stimulate eccrine sweat glands, and reverse iontophoresis (the migration of electrolytes from the human sweat to the electrodes) for quantitative measurement of the resulting flow of Cl- ions. ESC can be measured with the use of a medical device called Sudoscan. A novel electrochemical model of the skin was devised, reproducing the behavior of chloride ions and the properties of their ion channel to develop a computational tool for measuring chloride ion flow through a sweat gland in response to an imposed voltage. In vitro electrochemical studies were then carried out in conventional three-electrode cells to identify the origin of currents measured upon the application of low voltage potentials with variable amplitudes to stainless steel electrodes applied to the skin during clinical tests. These studies also evaluated the influence of different parameters in sweat (e.g., urea, lactate) on the obtained currents. These studies formed the basis for the ESC methodology of measuring sudomotor function. The flow of Cl− ions in the sweat secreted from the activated sweat glands are captured by the anode. This process is repeated twice for the feet and twice for the hands with the right and left electrodes alternating as the anode and cathode.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
Reports describe modulation of GABA signalling, changes in monoamine turnover and effects on neurotrophic factor expression. These observations come mainly from animal and cell studies. A single unifying mechanism has not been demonstrated.