blood-brain barrier comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-12-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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 a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
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.
A number of former Wildcats have gone on to pursue successful professional NBA careers (especially during the Lute Olson era), including Gilbert Arenas, Richard Jefferson, Mike Bibby, Jason Terry, Sean Elliott, Damon Stoudamire, Khalid Reeves, Luke Walton, Hassan Adams, Salim Stoudamire, Andre Iguodala, Channing Frye, Brian Williams (later known as Bison Dele), Sean Rooks, Jud Buechler, Michael Dickerson, Chase Budinger, Jordan Hill, Jerryd Bayless, Derrick Williams, Kadeem Allen, Aaron Gordon, Solomon Hill, Rondae Hollis-Jefferson, Stanley Johnson, T.J McConnell, Lauri Elias Markkanen, Kobi Simmons, Steve Kerr, Deandre Ayton, Rawle Alkins, and Allonzo Trier. Kenny Lofton, now best known as a former Major League Baseball star, was a four-year letter winner as a Wildcat basketball player (and was on the 1988 Final Four team), before one year on the Arizona baseball team. Another notable former Wildcat basketball player is Eugene Edgerson, who played on the 1997 and 2001 Final Four squads, and spent some of his professional careers as one of the Harlem Globetrotters as "Wildkat" Edgerson.
==== Actions ==== Compound 22 is a low-potency antagonist of the trace amine-associated receptor 1 (TAAR1). It has shown significant inhibition of TAAR1 signaling at a concentration of 100 μM in vitro. The drug's IC50Tooltip half-maximal inhibitory concentration value for TAAR1 antagonism is unknown but is greater than 100 μM. Compound 22 was also screened for off-target activity at 47 targets at a concentration of 10 μM. The screened targets included monoamine receptors, monoamine transporters, histamine receptors, muscarinic acetylcholine receptors, glutamate receptors, GABA receptors, opioid receptors, and sigma receptors. There were five hits (>50% binding inhibition), which included the serotonin transporter (SERT), dopamine transporter (DAT), and norepinephrine transporter (NET), as well as the sigma σ1 and σ2 receptors. Its affinities (Ki) were 1,800 nM for the SERT, 1,053 nM for the DAT, 1,902 nM for the NET, 276 nM for the sigma σ1 receptor, and 412 nM for the sigma σ2 receptor. Although compound 22 bound with significant affinity to the DAT, it did not inhibit dopamine reuptake and did not interfere with cocaine-induced dopamine reuptake inhibition at concentrations of up to 100 μM.
=== High population densities === Since sea ice pockets are confined and highly-concentrated ecosystems, they are able to house several orders of magnitude greater population densities of bacteria and protists than are found in the open ocean (up to thousands of individuals per liter for protists). This high abundance of organisms can pose challenges, as different bacteria and protists will compete for resources. A high density of microorganisms can result in the accumulation of metabolic byproducts, such as oxygen, dissolved organic matter, ammonia, and dimethylsulfoniopropionate (DMSP). Some organisms can gain a selective advantage within brine pockets as the high population density can result in increased rates of horizontal gene transfer because organisms are in close proximity. Horizontal gene transfer can allow certain organisms to obtain genes from bacteria that may be advantageous in a light-limited, extremely cold environment.
Sources: en.wikipedia.org
The bacterial outer membrane is found in gram-negative bacteria. Gram-negative bacteria form two lipid bilayers in their cell envelopes - an inner membrane (IM) that encapsulates the cytoplasm, and an outer membrane (OM) that encapsulates the periplasm. The composition of the outer membrane is distinct from that of the inner cytoplasmic cell membrane - among other things, the outer leaflet of the outer membrane of many gram-negative bacteria includes a complex lipopolysaccharide whose lipid portion acts as an endotoxin - and in some bacteria such as E. coli it is linked to the cell's peptidoglycan by Braun's lipoprotein. Porins can be found in this layer.
In evolutionary biology, sequence space is a way of representing all possible sequences (for a protein, gene or genome). The sequence space has one dimension per amino acid or nucleotide in the sequence leading to highly dimensional spaces. Most sequences in sequence space have no function, leaving relatively small regions that are populated by naturally occurring genes. Each protein sequence is adjacent to all other sequences that can be reached through a single mutation. It has been estimated that the whole functional protein sequence space has been explored by life on the Earth. Evolution by natural selection can be visualised as the process of sampling nearby sequences in sequence space and moving to any with improved fitness over the current one.
== Historical uses == Following its discovery by Marie and Pierre Curie in 1898, radium (principally 226Ra) has had a number of uses. In the early 20th century, when the hazards of radiation were not well-known, radium was commonly used in consumer items such as toothpaste and hair creams. Radium was also formerly used as a radiation source for cancer treatment, but has since been replaced in this role by safer and more easily available alternatives. Until the 1960s, radium was used in luminous paint for watch dials and aircraft instruments.
Computational neuroscientists show that people with higher intelligence scores in HCP cognitive tests took more time to solve difficult problems and that their higher synchrony between brain areas allowed for better integration of evidence (or progress) from preceding working memory sub-problem processing. Reducing synchrony in "avatar" simulations, that were adjusted and tuned towards personalization, "led decision-making circuits to quickly jump to conclusions". Their codified results may be useful for an understanding of cognition to replicate or imitate in bio-inspired computing. Researchers report trends in reasons for HPV vaccine hesitancy during 2010–20. 24 May Scientists show how gene 'FAAH'-related disruption via genetic or epigenome editing can enable pain insensitivity (see also 10 March 2021). Their analyses, mainly about long non-coding RNA 'FAAH-OUT', following from decade-long study of a woman who can't feel pain or anxiety, could also enable novel therapeutic developments against other neurological problems. One of the first empirical studies on what real users are shown during their typical use of popular Web search engines interprets its results to show that choices for unreliable news sources for their queries are driven primarily by users' own choices and less by the engine's algorithms. The Web scientists link their findings to the concept of filter bubbles which emphasizes the role of design- and personalization algorithms.
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.