Peptidase stability is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-07-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Primary route studied | Intranasal | Also examined parenterally in animal work |
| Reported plasma half-life | Minutes to tens of minutes | Values vary widely between reports |
| Main model systems | Rodent behavioural and cell assays | Human trials are few and small |
| Principal proposed targets | GABA-A receptor, GABA transaminase | Monoamine and neurotrophic pathways also reported |
| Evidence grade | Preliminary | Limited independent replication |
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 not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
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.
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.
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.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
=== DPP-4 inhibitor trials === McGuire served on the executive committees of four cardiovascular outcome trials (CVOTs) evaluating DPP-4 inhibitors: SAVOR-TIMI 53 (saxagliptin), TECOS (sitagliptin), CAROLINA (linagliptin), and CARMELINA (linagliptin). He was co-chair of CARMELINA. These trials were designed to establish non-inferiority for major adverse cardiovascular events (MACE). SAVOR-TIMI 53 reported an increased risk of hospitalization for heart failure with saxagliptin.
== Function == The C-terminal region of the product of the MMACHC gene is similar to TonB, a bacterial protein involved in energy transduction for cobalamin uptake. The MMACHC gene product catalyzes the decyanation of cyanocobalamin as well as the dealkylation of alkylcobalamins including methylcobalamin and adenosylcobalamin. The MMACHC gene product is characterised as a cyanocobalamin reductase (cyanide-eliminating) and a alkylcobalamin reductase. It enables the interconversion of cyano- and alkylcobalamins.
"APS user shares the "Israeli Nobel" for chemistry", from the Argonne National Laboratory Advanced Photon Source (APS), United States Department of Energy The Official Site of Louisa Gross Horwitz Prize Weizmann Institute of Science, Yonath-Site Talk by Ada Yonath at the Origins 2011 congress Ada E. Yonath on Nobelprize.org Ada Yonath at IMDb
Sources: en.wikipedia.org
== Other functions == In Cullen's paper "Granzymes in Cancer and Immunity" he discusses how granzyme A has been known to be found in elevated levels within patients who currently have an infectious disease and/or in a pro-inflammatory state. Granzymes have also been found to help initiate the inflammatory response. "For example, rheumatoid arthritis patients have increased levels of granzyme A in the synovial fluid of swollen joints". When granzymes are in an extracellular state they have the ability to activate macrophages and mast cells to initiate the inflammatory response. The interaction between the granzymes and somatic cells are still unexplainable but advances in understanding the process are being made constantly. Other granzymes like granzyme K have been found in high levels of patients who have gone septic. Granzyme H has been found to have a direct correlation with patients who have a viral infection. Scientists are able to conclude that granzyme H specializes in detecting 'proteolytic degradation' which is found in viral proteins. Cullen further states in his paper that granzymes may have a role in immunomodulation, or the job of maintaining homeostasis in the immune system during an infection. "In humans, loss of perforin function leads to a syndrome called familial hemophagocytic lymphohistiocytosis […]". This syndrome can lead to death because both T cells and macrophages multiply to fight the pathogen, resulting in harmful levels of proinflammatory cytokines.
=== Mechanism of action === Carbetocin works as an oxytocic, antihemorrhagic and uterotonic drug in the peripheral nervous system. The most common causes of postpartum hemorrhage are lack of tone in the uterus from overstretching or the use of an anesthetic. Carbetocin functions as an agonist at peripheral oxytocin receptors, particularly in the myometrium, with lesser affinity for myoepithelial cells. Oxytocin receptors are G protein-coupled and their mechanism of action involves second messengers and the production of inositol phosphates. Carbetocin mimics this mechanism. Binding for carbetocin and other oxytocin agonists has been shown to be nonselective at the extracellular N-terminus and loops E2 and E3. While the oxytocin receptor shows equal affinity for oxytocin and carbetocin, the biological effect of carbetocin is almost 50% that of endogenous or exogenous oxytocin. Carbetocin has a much longer lasting effect than oxytocin, necessitating only a single dose. Carbetocin inhibits endogenous oxytocin release, interrupting the uterine feedback loop with the hypothalamus and decreasing both central and peripheral release of oxytocin. Carbetocin is a biased agonist of the oxytocin receptor. During pregnancy, the synthesis of oxytocin receptors in the uterus greatly increases, reaching a peak during labor and delivery. Consequently, the administration of carbetocin or another oxytocin analog during or immediately following birth will have increased uterotonic and contractile effect.
In December 2019, a Santa hat was placed on the spire. The Cornell Daily Sun speculated the hat was put there by drone, though no one claimed responsibility and this was never proven. On October 20, 2023, 26 years after the first pumpkin, a second pumpkin was noticed on top of the tower. The pumpkin had been placed there during significant renovations which had included the erection of scaffolding. The identity of the person who put it there was verified, though not released, by The Cornell Daily Sun. The prankster came forward after feeling "attacked" by other students falsely claiming responsibility.
Electrons can enter the chain at three levels: at the level of a dehydrogenase, at the level of the quinone pool, or at the level of a mobile cytochrome electron carrier. These levels correspond to successively more positive redox potentials, or to successively decreased potential differences relative to the terminal electron acceptor. In other words, they correspond to successively smaller Gibbs free energy changes for the overall redox reaction. Individual bacteria use multiple electron transport chains, often simultaneously. Bacteria can use a number of different electron donors, a number of different dehydrogenases, a number of different oxidases and reductases, and a number of different electron acceptors. For example, E. coli (when growing aerobically using glucose and oxygen as an energy source) uses two different NADH dehydrogenases and two different quinol oxidases, for a total of four different electron transport chains operating simultaneously. A common feature of all electron transport chains is the presence of a proton pump to create an electrochemical gradient over a membrane. Bacterial electron transport chains may contain as many as three proton pumps, like mitochondria, or they may contain two or at least one.
Sources: en.wikipedia.org
Significant increases in central MP levels were also observed after just two weeks of supplementation. Furthermore, in patients who had an atypical MP distribution in the eye (i.e., they did not have a high concentration of pigment in the centre of the macula), when supplemented with a meso-zeaxanthin-dominant supplement for 8 weeks, the normal pigment profile was reinstated, whereas this was not the case when patients were supplemented with a formulation lacking meso-zeaxanthin. The main findings from the MOST trials in patients with AMD were published in 2013 and 2015. The series of publications from these trials concluded, "Augmentation of the MP optical density across its spatial profile and enhancements in contrast sensitivity were best achieved after supplementation with a formulation containing high doses of meso-zeaxanthin in combination with lutein and zeaxanthin". Also, the final publication from this work, published in 2015, concluded that, "The inclusion of meso-zeaxanthin in a supplement formulation seems to confer benefits in terms of MP augmentation and in terms of enhanced contrast sensitivity in subjects with early AMD.". In 2016 and 2017, the results of two small clinical trials were published. The first trial, the CREST (Central Retinal Enrichment Supplementation Trials) study involved 105 normal healthy volunteers who underwent a series of complex tests of vision and were supplemented over 12 months.
== Products == There are thought to be a number of useful products that can potentially be manufactured in space and result in an economic benefit. Research and development is required to determine the best commodities to be produced, and to find efficient production methods. The following products are considered prospective early candidates:
==== Supranational ==== United Nations: UN Assistance Mission in Afghanistan (UNAMA) urged both nations to cease hostilities and to take steps to prevent harm to civilians. Richard Bennett, the UN Special Rapporteur on the situation of human rights in Afghanistan, expressed concern over airstrikes in Nangarhar and Paktika, calling on the belligerent parties to exercise "maximum restraint". He stated deep concern for "a significant number of children and civilians" who were killed following the hostilities. European Union: In a brief statement, the EU Council called on all actors for immediate de-escalation and a halt of hostilities in the area. It reiterated to the Taliban that Afghan territory must not be used to threaten or attack other countries and calls on them to take effective action against all terrorist groups operating in or from Afghanistan.
=== First measures === Right after taking office on 1 January 2023, Lula and his ministers took several measures to revert Bolsonaro policies and/or create policies announced during the election campaign and the transition of power. This processs, known as "desbolsonarização" (de-'Bolsonarization') or "revogaço" (mass repeal of decrees) by some ministers and party members included a series of federal decrees revoking the previous government's measures involving weapons, environment policies and top officials' data secrecy. Some of the decrees included temporarily suspending new authorizations for shooting clubs, revoking Bolsonaro government policies that allowed "artisan mining" in the Amazon rainforest area and indigenous lands (which were seen as an incentive to illegal miners). and the creation of the "Secretary of Digital Policies", which was to be established under the Secretary of Social Communications with the stated objective of "combatting the spread of disinformation, fake news and hate speech on the internet". On the same week, Environment and Climate Change Minister Marina Silva claimed that another "revogaço" was yet to come. Mostly related to the teto de gastos (debt ceiling) fiscal policy, which was seen as impractical by government officials. This policy was later replaced with another debt limit law following its approval in the Federal Congress.
Bempedoic acid is a prodrug. It is activated to the thioester with coenzyme A by the enzyme acyl-CoA synthetase in the liver. The activated substance inhibits ATP citrate lyase, which is involved in the liver's biosynthesis of cholesterol upstream of HMG-CoA reductase, the enzyme that is blocked by statins. The substance also activates AMP-activated protein kinase, but this effect is likely not relevant in humans.
Sources: en.wikipedia.org
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.
The peptide enters plasma rapidly and is broken down by ordinary proteases into amino acids and shorter fragments. Reported half-lives are short. Whether meaningful amounts of the intact molecule reach the brain is an open question.
Most clinical reports are small, published in Russian and not independently replicated. English-language reviews highlight the absence of large randomised trials. Conclusions about efficacy should be treated as provisional.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.