A practical reference on blood-brain barrier: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-01-28. Anything still debated is marked as such rather than presented as settled.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
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.
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.
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 |
|---|---|---|
| Dry storage temperature | -20 C or below | Sealed, desiccated, protected from light |
| Solution stability | Hours to days at 2-8 C | Depends on buffer and microbial load |
| Preferred pH range | Near neutral to slightly acidic | Alkaline pH accelerates hydrolysis |
| Main degradation routes | Hydrolysis and deamidation | No cysteine or methionine in sequence |
| Identity confirmation | Electrospray mass spectrometry | Observed mass compared with 751.9 Da |
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
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.
=== Australia === Fuel prices at the petrol and diesel stations started soaring in early March in Australia, partly driven by panic buying. More critical to overall inflationary forces though, is the supply of diesel to drive heavy machinery. Australia's diesel is largely dependent on refineries in Singapore, South Korea, Malaysia, Taiwan and India. Experts have warned that the increased price of diesel would lead to much higher food prices, threatening both food security and the "just-in-time" logistics infrastructure that serves food retailers.Australia holds around 29 to 36 days' reserves of fuel, and a large proportion of this was released to support retailers in regional areas. If the Strait of Hormuz continues to be blocked, the Liquid Fuel Emergency Act 1984 could be triggered, which allows for formal transaction limits and rationing of fuel. This act was passed in response to the 1970s fuel crisis, and has not been triggered since then. In the meantime, the government has lowered the standard for the flash point for both diesel and petrol, which will make it easier for the country's two refineries to produce more fuel. In mid-March, the state governments of Victoria and Tasmania made public transport free to all users, for differing fixed time periods. On 30 March 2026, the Australian Government under Prime Minister Anthony Albanese, after a meeting of National Cabinet, announced a National Fuel Security Plan, to coordinate responses across all states and territories of Australia.
A bowel obstruction is generally a mechanical obstruction of the gastrointestinal tract and can occur anywhere from the Ligament of Treitz to the anus. When the obstruction affects only the small intestine, it is generally referred to as a small bowel obstruction to distinguish it from a colonic obstruction, which may or may not affect the small intestine. The distinction helps to narrow the possible causes and treatment. Common causes of small bowel obstruction include post-operative adhesions, hernias, intussusception, and intraabdominal tumors. Common causes of colonic obstruction include primary colon cancer, volvulus and post-operative adhesions. When the ileocecal valve is competent, colonic obstruction may manifest as gaseous distention of the colon, but not the small intestine; when the ileocecal valve is incompetent, it does not prevent retrograde passage of air and stool and a colonic obstruction will cause dilation of both large and small bowel. Bowel obstructions can be partial or complete. They can be differentiated on imaging by the intestinal gas pattern. Partial obstructions will have gas distal to the obstruction, whereas a complete obstruction will not. Sounds of "rushes and tinkles" are associated with partial obstructions and represent brief passages of fluid and gas (respectively) through the partial obstruction. Complete obstructions do not make these sounds.
== Synthesis == Fumaric acid is produced based on catalytic isomerisation of maleic acid in aqueous solutions at low pH. It precipitates from the reaction solution. Maleic acid is accessible in large volumes as a hydrolysis product of maleic anhydride, produced by catalytic oxidation of benzene or butane.
Minimizing the number of hydrophobic side-chains exposed to water is an important driving force behind the folding process. The hydrophobic effect is the phenomenon in which the hydrophobic chains of a protein collapse into the core of the protein (away from the hydrophilic environment). In an aqueous environment, the water molecules tend to aggregate around the hydrophobic regions or side chains of the protein, creating water shells of ordered water molecules. An ordering of water molecules around a hydrophobic region increases order in a system and therefore contributes a negative change in entropy (less entropy in the system). The water molecules are fixed in these water cages which drives the hydrophobic collapse, or the inward folding of the hydrophobic groups. The hydrophobic collapse introduces entropy back to the system via the breaking of the water cages which frees the ordered water molecules. The multitude of hydrophobic groups interacting within the core of the globular folded protein contributes a significant amount to protein stability after folding, because of the vastly accumulated van der Waals forces (specifically London Dispersion forces). The hydrophobic effect exists as a driving force in thermodynamics only if there is the presence of an aqueous medium with an amphiphilic molecule containing a large hydrophobic region. The strength of hydrogen bonds depends on their environment; thus, H-bonds enveloped in a hydrophobic core contribute more than H-bonds exposed to the aqueous environment to the stability of the native state.
== Recognition == In August 2024, Dei BioPharma was awarded "Best Pharma Company" at the African Excellence Awards hosted by MEA Markets in London. Members of the Ugandan Parliament commended the company for pioneering drug development in underrepresented areas such as oncology and vaccine production.
Sources: en.wikipedia.org
== Physiology == The activation of protein C is strongly promoted by thrombomodulin and endothelial protein C receptor (EPCR), the latter of which is found primarily on endothelial cells (cells on the inside of blood vessels). The presence of thrombomodulin accelerates activation by several orders of magnitude, and EPCR speeds up activation by a factor of 20. If either of these two proteins is absent in murine specimens, the mouse dies from excessive blood-clotting while still in an embryonic state. On the endothelium, APC performs a major role in regulating blood clotting, inflammation, and cell death (apoptosis). Because of the accelerating effect of thrombomodulin on the activation of protein C, the protein may be said to be activated not by thrombin but the thrombin–thrombomodulin (or even thrombin–thrombomodulin–EPCR) complex. Once in active form, APC may or may not remain bound to EPCR, to which it has approximately the same affinity as the protein zymogen. Protein C in zymogen form is present in normal adult human blood plasma at concentrations between 65 and 135 IU/dL. Activated protein C is found at levels approximately 2000 times lower than this. Mild protein C deficiency corresponds to plasma levels above 20 IU/dL, but below the normal range. Moderately severe deficiencies describe blood concentrations between 1 and 20 IU/dL; severe deficiencies yield levels of protein C that are below 1 IU/dL or are undetectable. Protein C levels in a healthy term infant average 40 IU/dL.
=== Schizophrenic behavior of UCST-LCST diblock copolymers === A more complex scenario can be found in the case of diblock copolymers that feature two orthogonally thermo-responsive blocks, i.e., an UCST and an LCST-type block. By applying a temperature stimulus, the individual polymer blocks show different phase transitions, e.g. by increasing the temperature, the UCST-type block features an insoluble-soluble transition, while the LCST-type block undergoes a soluble-insoluble transition. The order of the individual phase transitions depends on the relative positions of the UCST and LCST. Thus, upon temperature change the roles of the soluble and insoluble polymer blocks are reversed and this structural inversion is typically called 'schizophrenic' in the literature. Besides the fundamental interest in the mechanism of this behavior, such block copolymers have been proposed for application in smart emulsification, drug delivery, and rheology control. Schizophrenic diblock copolymer have also been applied as thin films for potential use as sensors, smart coatings or nanoswitches, and soft robotics.
== External links == Quips article describing E3 Ligase function Archived 2012-11-30 at the Wayback Machine at PDBe Ubiquitin-Protein+Ligases at the U.S. National Library of Medicine Medical Subject Headings (MeSH) EC 6.3.2.19
{\displaystyle {\begin{aligned}{\frac {\mathbf {D} m}{\mathbf {Dt} }}&={\iiint \limits _{V}}\left({{\frac {\mathbf {D} \rho }{\mathbf {Dt} }}+\rho (\nabla \cdot \mathbf {u} )}\right)dV\\{\frac {\mathbf {D} \rho }{\mathbf {Dt} }}+\rho (\nabla \cdot {\mathbf {u} })&={\frac {\partial \rho }{\partial t}}+({\nabla \rho })\cdot {\mathbf {u} }+{\rho }(\nabla \cdot \mathbf {u} )={\frac {\partial \rho }{\partial t}}+\nabla \cdot ({\rho \mathbf {u} })=0\end{aligned}}}
This led the researchers to conclude that although there was little evidence for one technique being less painful than the other at the time of application, freeze branding did produce much less inflammation in the heifers' skin one week out from their brandings. In 1998 the same researchers followed up with a similar study comparing the effectiveness of thermal imagery to behavioral cues like tail flicking and vocalizing as a proxy for pain in steers. Unsurprisingly they found that thermography was far more reliable and its results more statistically significant than human-mediated behavioral study.
Sources: en.wikipedia.org
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.
Hydrolysis of peptide bonds and deamidation of arginine and proline residues are the main degradation routes. Alkaline pH and higher temperatures accelerate both processes. Buffered, near-neutral solutions stored cold generally degrade more slowly than unbuffered ones.
Reverse-phase chromatography gives the clearest single view of related impurities and truncated sequences. Mass spectrometry then confirms that the main peak carries the expected mass. Neither test detects enantiomeric impurities, which require a separate chiral assay.
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.