This is a working overview of pharmacokinetics, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-14 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
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.
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.
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.
In September 2014, the company acquired Innopharma for $225 million, plus up to $135 million in milestone payments, in a deal that expanded Pfizer's range of generic and injectable drugs. On January 5, 2015, the company announced it would acquire a controlling interest in Redvax, expanding its vaccine portfolio targeting human cytomegalovirus. In February 2015, the company received approval from the Food and Drug Administration for palbociclib (Ibrance) for treatment of certain types of breast cancer. In March 2015, the company announced it would restart its collaboration with Eli Lilly and Company surrounding the Phase III trial of Tanezumab. In May 2015, Pfizer and a Bar-Ilan University laboratory announced a partnership based on the development of medical DNA nanotechnology. In June 2015, the company acquired Nimenrix and Mencevax, meningococcal vaccines, from GlaxoSmithKline for around $130 million. In September 2015, Pfizer acquired Hospira for $17 billion, including the assumption of debt. Hospira was the largest producer of generic injectable pharmaceuticals in the world. On November 23, 2015, Pfizer and Allergan announced a planned $160 billion merger, in the largest pharmaceutical deal ever and the third largest corporate merger in history. The proposed transaction contemplated that the merged company maintain Allergan's Republic of Ireland domicile, resulting in the new company being subject to corporation tax at the relatively low rate of 12.5%.
=== European Union === Ractopamine has not been allowed in the European Union, based on the 2009 EU's Food Safety Authority's opinion on its safety evaluation, which concluded that available data were insufficient to derive a maximum residue limit as a 'safe residue level for human consumption'. The uncertainty was particularly great for people who might be thought to be more susceptible than most to an increase in β adrenergic stimulation from consuming the additive, such as children or people with cardiovascular disease, and that simply increasing the "uncertainty factor" built into the calculation as a safety factor would rapidly become arbitrary.
Robert Shonov, who worked in the US consulate in Vladivostok before being subcontracted to summarize Russian media reports for the embassy in Moscow was arrested, charged with cooperating "on a confidential basis with a foreign state, [or] international or foreign organisation", and detained at Lefortovo Prison. The State Department said the allegations were without merit. The FSB later said it had charged Shonov for “confidential collaboration” with a foreign state, allegedly collecting information on the Russian war effort in Ukraine, its military draft and protest activities in the run-up to the 2024 presidential elections. Hungary blocked the disbursement of an upcoming tranche of military support for Ukraine provided under the European Union's European Peace Facility (EPF), arguing that the fund was too focused on Ukraine and that the funds could be used elsewhere. Hungarian Foreign Minister Peter Szijjarto previously said that the country would block the disbursement as well as any new sanctions package on Russia until Ukraine removed OTP Bank, Hungary's largest commercial bank, in the list of sponsors of the war in Ukraine due to the position of the bank's management to continue operations in Russia and its client republics in the Donbas, which itself was based on a decision by the National Agency for the Prevention of Corruption of Ukraine. Hungary also demanded the removal of three people from a new sanctions list proposed by the European Commission as part of the 11th package of sanctions against Russia.
Sources: en.wikipedia.org
=== Beginning === Most early progress in tissue engineering research was done in the US. This is due to less strict regulations regarding stem cell research and more available funding than in other countries. This leads to the creation of academic startups many of them coming from Harvard or MIT. Examples are BioHybrid Technologies whose founder, Bill Chick, went to Harvard Medical School and focused on the creation of artificial pancreas. Another example would be Organogenesis Inc. whose founder went to MIT and worked on skin engineering products. Other companies with links to the MIT are TEI Biosciences, Therics and Guilford Pharmaceuticals. The renewed interest in biotechnologies in the 1980s leads to many private investors investing in these new technologies even though the business models of these early startups were often not very clear and did not present a path to long term profitability. Government sponsors were more restrained in their funding as tissue engineering was considered a high-risk investment. In the UK the market got off to a slower start even though the regulations on stem cell research were not strict as well. This is mainly due to more investors being less willing to invest in these new technologies which were considered to be high-risk investments. Another problem faced by British companies was getting the NHS to pay for their products. This especially because the NHS runs a cost-effectiveness analysis on all supported products. Novel technologies often do not do well in this respect. In Japan, the regulatory situation was quite different.
=== Shrinkage and swelling === Shrinkage and swelling may occur in wood when the moisture content is changed. Shrinkage occurs as moisture content decreases, while swelling takes place when it increases. Volume change is not equal in all directions. The greatest dimensional change occurs in a direction tangential to the growth rings. Shrinkage from the pith outwards, or radially, is usually considerably less than tangential shrinkage, while longitudinal (along the grain) shrinkage is so slight as to be usually neglected. The longitudinal shrinkage is 0.1% to 0.3%, in contrast to transverse shrinkages, which is 2% to 10%. Tangential shrinkage is often about twice as great as in the radial direction, although in some species it is as much as five times as great. The shrinkage is about 5% to 10% in the tangential direction and about 2% to 6% in the radial direction. Differential transverse shrinkage of wood is related to:
The liquid containing the analytes of interest (typically 10−6 - 10−4 M needed ) is dispersed by electrospray, into a fine aerosol. Because the ion formation involves extensive solvent evaporation (also termed desolvation), the typical solvents for electrospray ionization are prepared by mixing water with volatile organic compounds (e.g. methanol acetonitrile). To decrease the initial droplet size, compounds that increase the conductivity (e.g. acetic acid) are customarily added to the solution. These species also act to provide a source of protons to facilitate the ionization process. Large-flow electrosprays can benefit from nebulization of a heated inert gas such as nitrogen or carbon dioxide in addition to the high temperature of the ESI source. The aerosol is sampled into the first vacuum stage of a mass spectrometer through a capillary carrying a potential difference of approximately 3000 V, which can be heated to aid further solvent evaporation from the charged droplets. The solvent evaporates from a charged droplet until it becomes unstable upon reaching its Rayleigh limit. At this point, the droplet deforms as the electrostatic repulsion of like charges, in an ever-decreasing droplet size, becomes more powerful than the surface tension holding the droplet together. At this point the droplet undergoes Coulomb fission, whereby the original droplet 'explodes' creating many smaller, more stable droplets. The new droplets undergo desolvation and subsequently further Coulomb fissions.
Despite the fearsome reputation, aggression toward humans usually only arises from an individual inadvertently exposing itself or being cornered; encounters happen through chance, including negative interactions. Threatened by habitat destruction, it has been listed as Vulnerable on the IUCN Red List since 2010. Regarded as the national reptile of India, it has an eminent position in the mythology and folk traditions of India, Bangladesh, Sri Lanka and Myanmar.
Sources: en.wikipedia.org
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While the first transfusions had to be made directly from donor to receiver before coagulation, it was discovered that by adding anticoagulant and refrigerating the blood it was possible to store it for some days, thus opening the way for the development of blood banks. John Braxton Hicks was the first to experiment with chemical methods to prevent the coagulation of blood at St Mary's Hospital, London in the late-19th century. His attempts, using phosphate of soda, however, proved unsuccessful. The Belgian doctor Albert Hustin performed the first non-direct transfusion on March 27, 1914, though this involved a diluted solution of blood. The Argentine doctor Luis Agote used a much less diluted solution in November of the same year. Both used sodium citrate as an anticoagulant. The First World War (1914–1918) acted as a catalyst for the rapid development of blood banks and transfusion techniques. Francis Peyton Rous and Joseph R. Turner at the Rockefeller University (then The Rockefeller Institute for Medical Research) made the first important discoveries that blood typing was necessary to avoid blood clumping (coagulation) and blood samples could be preserved using chemical treatment. Their first report in March 1915 showed that gelatine, agar, blood serum extracts, starch and beef albumin proved to be useless preservatives.
cis-dominant mutation A mutation occurring within a cis-regulatory element (such as an operator) which alters the functioning of a nearby gene or genes on the same chromosome. Cis-dominant mutations affect the expression of genes because they occur at sites that control transcription rather than within the genes themselves.
Sources: en.wikipedia.org
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.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
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.