peptide purity raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-10-14. Anything still debated is marked as such rather than presented as settled.
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.
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.
Animal studies have examined behaviour in tests of anxiety, memory retention and stress response, and several report changes in neurotrophic or neurotransmitter-related markers. The human evidence base is much smaller, consisting mainly of short trials conducted in Russia with limited reporting in English-language journals. Sample sizes are modest and outcome measures vary between studies, so the findings are best described as preliminary. Independent replication under modern trial standards has not been widely reported.
Outside its country of origin the compound is generally handled as a research chemical rather than an approved medicine. No regulatory approval from the United States Food and Drug Administration or the European Medicines Agency has been granted for human use. Identity and purity are normally checked by reverse-phase high-performance liquid chromatography, with mass spectrometry used to confirm the molecular mass. Lyophilised material is stored cold and desiccated, and repeated freeze-thaw cycles are avoided.
| 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 |
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
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.
Handling follows standard practice for research peptides. Material is weighed in a low-humidity environment because the powder absorbs atmospheric moisture. Purity is reported as the percentage area of the main peak in a chromatogram, with specifications commonly set at 95 percent or higher; values below that threshold indicate the presence of truncated or modified species. Residual trifluoroacetate from purification is often present and may affect mass balance. Certificates of analysis should state the analytical method, the column and gradient used, and the lot-specific retention time so that results can be compared across suppliers.
Identity and purity of selank are established with reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The peptide elutes from C18 columns with acetonitrile gradients in water containing trifluoroacetic acid or formic acid, and detection is usually performed by ultraviolet absorbance near 214 nm. Electrospray ionization in positive mode gives a doubly protonated ion near m/z 377, consistent with a mass of about 752 Da. Amino acid analysis or tandem mass spectrometry of fragment ions confirms the sequence. Because the molecule has no aromatic residues, it lacks a usable 280 nm chromophore, so low-wavelength detection or mass spectrometry is required.
=== Surface modification improving cell adhesion === Surface modification can also affect properties that promote cell adhesion. One particular research in 2005 studied the mammalian cell adhesion on the modified surfaces of porous silicon. The research used rat PC12 cells and Human Lens Epithelial (HLE) cells cultured for four hours on the surface modified porous silicon. Cells were then stained with vital dye FDA and observed under fluorescence microscopy. The research concluded that "amino silanisation and coating the pSi surface with collagen enhanced cell attachment and spreading".
In December 2021, Newsom announced his intention to make California a "sanctuary" for abortion, which included possibly paying for procedures, travel, and lodging for out-of-state abortion seekers, if the procedure is banned in Republican-led states. In March 2022, he signed a bill requiring private health insurance plans in the state to fully cover abortion procedures by eliminating associated co-pays and deductibles and increasing insurance premiums. In February 2023, Newsom organized the Reproductive Freedom Alliance of state governors supportive of abortion and reproductive rights. After Walgreens announced in March 2023 that it would refuse to dispense abortion pills in the 21 states where it is illegal, Newsom tweeted, "California won't be doing business with @walgreens – or any company that cowers to the extremists and puts women's lives at risk, we're done." He also said that Walgreens was giving in to "right-wing bullies" and that he would determine how California could cut ties with it. He indicated that he wanted to cancel Walgreens's $54 million contract with the California state prison system. Walgreens also receives $1.5 billion for filling prescriptions for the 15 million people enrolled in the state's Medi-Cal program (California's version of Medicaid). Legal experts said that federal Medicaid laws do not allow health plans to disqualify providers for reasons other than fraud or contract violations, provisions that have prevented conservative states from blocking Medicaid spending to Planned Parenthood clinics.
=== Tourism === Tourism is a major part of Hong Kong's economy, accounting for 5% of its GDP. In 2016, 26.6 million visitors contributed HK$258 billion (US$32.9 billion) to the territory, making Hong Kong the 14th-most popular destination for international tourists. It is the most popular Chinese city for tourists, receiving over 70% more visitors than its closest competitor Macau. The city is ranked as one of the most expensive cities for expatriates. However, since 2020, there has been a sharp decline in incoming visitors due to tight COVID-19 travel restrictions. In an attempt to attract tourists back to Hong Kong, the Hong Kong government announced plans to give away 500,000 free airline tickets in 2023. Hong Kong was the second most visited city in the world with 23.2 million visitors in 2025.
=== Crowding of the border === After hearing the 9 November broadcast, East Germans began gathering at the Wall, at the six checkpoints between East and West Berlin, demanding that border guards immediately open the gates. The surprised and overwhelmed guards made many hectic telephone calls to their superiors about the problem. At first, they were ordered to find the "more aggressive" people gathered at the gates and stamp their passports with a special stamp that barred them from returning to East Germany—in effect, revoking their citizenship. However, this still left thousands of people demanding to be let through "as Schabowski said we can". It soon became clear that no one among the East German authorities would take personal responsibility for issuing orders to use lethal force, so the vastly outnumbered soldiers had no way to hold back the huge crowd of East German citizens. Mary Elise Sarotte in a 2009 Washington Post story characterized the series of events leading to the fall of the Wall as an accident, saying "One of the most momentous events of the past century was, in fact, an accident, a semicomical and bureaucratic mistake that owes as much to the Western media as to the tides of history".
Sources: en.wikipedia.org
== Career == While attending the University of Hawaiʻi, Nickson was a model in Honolulu, where she appeared in her first play, The Winter's Tale. After acting classes, community theater, and roles on Magnum, P.I., she appeared as the female lead in Rambo: First Blood Part II (1985). She appeared with Chuck Norris in Sidekicks (1992). Her other film appearances have included roles in Glitch! (1988), China Cry (1991), K2 (1992), Double Dragon (1994), White Tiger (1996), Devil in the Flesh (1998), Ethan Mao (2004), Half-Life (2008), Dim Sum Funeral (2008), and One Kine Day (2011). Nickson guest starred in the final episode of seaQuest 2032 as Lieutenant Commander Heiko Kimura, a role that would have been a main character had the series continued, and in two Star Trek series: The Next Generation episode "The Arsenal of Freedom" as Enterprise-D crewmember Ensign Lian T'su, and the Deep Space Nine episode "Paradise" as Cassandra, a villager who attempts to seduce Commander Benjamin Sisko. She played Catherine Sakai, Commander Jeffrey Sinclair's love-interest, in the first season of Babylon 5. She had a recurring role as Dr. Susan Lee on the television series Walker, Texas Ranger (reuniting her with Chuck Norris), and as Princess Aouda in the 1989 miniseries version of Around the World in 80 Days opposite Pierce Brosnan and Eric Idle. She had a supporting role in the television version of the novel Noble House, again opposite Brosnan. Julia retired from acting for personal reasons on March 29, 2025
=== Pharmacokinetics === Metformin has an oral bioavailability of 50–60% under fasting conditions, and is absorbed slowly. Peak plasma concentrations (Cmax) are reached within 1–3 hours of taking immediate-release metformin and 4–8 hours with extended-release formulations. The plasma protein binding of metformin is negligible, as reflected by its very high apparent volume of distribution (300–1000 L after a single dose). Steady state is usually reached in 1–2 days. Metformin has acid dissociation constant values (pKa) of 2.8 and 11.5, so it exists very largely as the hydrophilic cationic species at physiological pH values. The metformin pKa values make it a stronger base than most other basic medications with less than 0.01% nonionized in blood. Furthermore, the lipid solubility of the nonionized species is slight as shown by its low logP value (log(10) of the distribution coefficient of the nonionized form between octanol and water) of −1.43. These chemical parameters indicate low lipophilicity and, consequently, rapid passive diffusion of metformin through cell membranes is unlikely. As a result of its low lipid solubility, it requires the transporter SLC22A1 for it to enter cells. The logP of metformin is less than that of phenformin (−0.84) because two methyl substituents on metformin impart lesser lipophilicity than the larger phenylethyl side chain in phenformin. More lipophilic derivatives of metformin are presently under investigation to produce prodrugs with superior oral absorption than metformin. Metformin is not metabolized.
Recombinant myoglobin for faux meat (Motif Foodworks) Recombinant leghemoglobin for faux meat (Impossible Foods) Recombinant whey protein for dairy replacement (Perfect Day) Recombinant casein protein for dairy replacements (Those Vegan Cowboys) Recombinant egg white (EVERY) Heme proteins such as myoglobin and hemoglobin give meat its characteristic texture, flavor, color, and aroma. The myoglobin and leghemoglobin ingredients can be used to replicate this property, despite them coming from a vat instead of meat.
== Mechanism of action == Isoniazid is a prodrug that inhibits the formation of the mycobacterial cell wall. Isoniazid must be activated by KatG, a bacterial catalase-peroxidase enzyme in Mycobacterium tuberculosis. KatG catalyzes the formation of the isonicotinic acyl radical, which spontaneously couples with NADH to form the nicotinoyl-NAD adduct. This complex binds tightly to the enoyl-acyl carrier protein reductase InhA, thereby blocking the natural enoyl-AcpM substrate and the action of fatty acid synthase. This process inhibits the synthesis of mycolic acids, which are required components of the mycobacterial cell wall. A range of radicals are produced by KatG activation of isoniazid, including nitric oxide, which has also been shown to be important in the action of another antimycobacterial prodrug pretomanid.
=== Cancer === While serum low 25-hydroxyvitamin D status has been associated with a higher risk of cancer in observational studies, the general conclusion is that there is insufficient evidence for an effect of vitamin D supplementation on the risk of cancer, although there is some evidence for reduction in cancer mortality.
Sources: en.wikipedia.org
In his psychological theory—which is not necessarily linked to a particular theory of social structure—the persona appears as a consciously created personality or identity, fashioned out of part of the collective psyche through socialisation, acculturation and experience. Jung applied the term persona because, in Latin, it means both personality and the masks worn by Roman actors of the classical period, expressive of the individual roles played. The persona, he argues, is a mask for the "collective psyche", a mask that 'pretends' individuality so that both self and others believe in that identity, even if it is really no more than a well-played role through which the collective psyche is expressed. It has also been referred to as the social archetype or the conformity archetype. Jung regarded the "persona-mask" as a complicated system that mediates between individual consciousness and the social community: it is "a compromise between the individual and society as to what a man should appear to be". But he also makes it quite explicit that it is, in substance, a character mask in the classical sense known to theatre, with its double function: both intended to make a certain impression on others and to hide (part of) the true nature of the individual, which he calls the 'shadow'. The therapist then aims to assist the individuation process through which the client (re)gains their "own self"—by liberating the self, both from the deceptive cover of the persona and from the power of unconscious impulses.
== Further reading == Harary, Isaac; Korey, Saul R.; Ochoa, Severo (August 1953). "Biosynthesis of dicarboxylic acids by carbon dioxide fixation. VII. Equilibrium of malic enzyme reaction". The Journal of Biological Chemistry. 203 (2): 595–604. doi:10.1016/S0021-9258(19)52329-8. PMID 13084629. Ochoa S, Mehler AH, Kornberg A (July 1948). "Biosynthesis of dicarboxylic acids by carbon dioxide fixation; isolation and properties of an enzyme from pigeon liver catalyzing the reversible oxidative decarboxylation of 1-malic acid". The Journal of Biological Chemistry. 174 (3): 979–1000. doi:10.1016/S0021-9258(18)57307-5. PMID 18871257. Rutter WJ, Lardy HA (August 1958). "Purification and properties of pigeon liver malic enzyme". The Journal of Biological Chemistry. 233 (2): 374–82. doi:10.1016/S0021-9258(18)64768-4. PMID 13563505. Stickland RG (December 1959). "Some properties of the malic enzyme of pigeon liver. 1. Conversion of malate into pyruvate". The Biochemical Journal. 73 (4): 646–54. doi:10.1042/bj0730646. PMC 1197115. PMID 13834656. Stickland RG (December 1959). "Some properties of the malic enzyme of pigeon liver. 2. Synthesis of malate from pyruvate". The Biochemical Journal. 73 (4): 654–9. doi:10.1042/bj0730654. PMC 1197116. PMID 13834657. Walker DA (February 1960). "Physiological studies on acid metabolism. 7. Malic enzyme from Kalanchoe crenata: effects of carbon dioxide concentration". The Biochemical Journal. 74 (2): 216–23. doi:10.1042/bj0740216. PMC 1204145. PMID 13842495.
The first reference in the literature to a commercially available protein A chromatography resin appeared in 1976. Today, chromatographic separation using protein A immobilized on porous substrates is the most widely established method for purifying monoclonal antibodies (mAbs) from harvest cell culture supernatant. The choice of protein A as the preferred method is due to the high purity and yield which are easily and reliably achieved. This forms the basis for a general antibody purification "platform" which simplifies manufacturing operations and reduces the time and effort required to develop purification processes. A typical mAb purification process is shown at right. Albeit the long history of protein A chromatography for the production of antibodies, the process is still being improved today. Continuous chromatography, more precisely periodic counter-current chromatography, enormously increases the productivity of the purification step.
QM (quantum-mechanical) methods are very powerful. However, they are computationally expensive, while the MM (classical or molecular mechanics) methods are fast but suffer from several limits (require extensive parameterization; energy estimates obtained are not very accurate; cannot be used to simulate reactions where covalent bonds are broken/formed; and are limited in their abilities for providing accurate details regarding the chemical environment). A new class of method has emerged that combines the good points of QM (accuracy) and MM (speed) calculations. These methods are termed mixed or hybrid quantum-mechanical and molecular mechanics methods (hybrid QM/MM). The most important advantage of hybrid QM/MM method is the speed. The cost of doing classical molecular dynamics (MM) in the most straightforward case scales O(n2), where n is the number of atoms in the system. This is mainly due to electrostatic interactions term (every particle interacts with every other particle). However, use of cutoff radius, periodic pair-list updates and more recently the variations of the particle-mesh Ewald's (PME) method has reduced this to between O(n) to O(n2). In other words, if a system with twice as many atoms is simulated then it would take between two and four times as much computing power. On the other hand, the simplest ab initio calculations typically scale O(n3) or worse (restricted Hartree–Fock calculations have been suggested to scale ~O(n2.7)).
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.
Most published work uses intranasal application, either as drops or as a nasal spray. Injection routes appear in a smaller set of animal experiments. Oral use is uncommon in the literature because peptide breakdown and poor absorption limit this route.