Research chemical raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2025-11-22. Anything still debated is marked as such rather than presented as settled.
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.
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Common route | Intranasal | Also injected in some animal work |
| Solubility class | Freely soluble in water | Solid form is hygroscopic |
| Typical storage | About -20 degrees Celsius | Keep desiccated and dark |
| Purity method | Reverse-phase HPLC | Reported as area percent |
| Confirmatory method | Mass spectrometry | Verifies expected molecular mass |
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.
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.
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.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
Although the precise mechanisms driving the chronic neurodegeneration caused by mutant glycyl-tRNA synthetase (GlyRS) remain unclear, one proposed theory involves disrupted vascular endothelial growth factor (VEGF) signaling. The mutant GlyRS aberrantly interacts with neuronal transmembrane receptors, such as neuropilin 1 (Nrp1) and VEGF receptors, interfering with normal signaling pathways and contributing to the development of neuropathy. GARS-CMT2D mutations alter GlyRS and allow it to bind to the Nrp1 receptor, interfering with the normal binding of Nrp1 to VEGF. While enhanced expression of VEGF improves motor function, reduced expression of Nrp1 worsens CMT2D; because Nrp1 binds to mutant GlyRS in mutant GARS1-CMT2D individuals, Nrp1 expression is reduced, in turn worsening motor function. Mice with deficient VEGF demonstrate motor neuron disease over time. Thus, the VEGF/Nrp1 pathway is considered to be targetable for CMT2D treatment.
On 16 March, Pakistan said that its forces launched multiple airstrikes against Taliban military installations in Kabul and Nangarhar, and claimed that it destroyed ammo storages and "technical support infrastructure". Taliban claimed that Pakistani strikes on Khost province killed four civilians and wounded nine, and destroyed civilian infrastructure in Kunar and Paktika province with 43 rounds being fired into Shkin district. A militant attack on a police post in Bannu District was repulsed by police forces. Following the strikes, Afghanistan claimed that a Pakistani airstrike struck the Omid Addiction Treatment Hospital in Kabul, reportedly killing over 200 people, mostly drug addicts undergoing treatment at the drug rehabilitation facility. Pakistan denied the claims and said that it had only targeted Taliban military installations. While the health ministry spokesperson maintained that there were "more than 200 martyrs and more than 200 injured," deputy government spokesperson Hamdullah Fitrat claimed death toll was at least "double" that, with 250 wounded. Zabihullah Mujahid declared it a "crime against humanity". On 17 March, five Pakistani soldiers were killed and three wounded in a skirmish at Ghulam Khan border crossing in North Waziristan District. A militant attack in Badaber injured two policemen. On 18 March, Pakistani missile strikes in Asadabad wounded six civilians. According to Taliban, Pakistan conducted 63 missile strikes on Nari District, 33 on Manogai, 13 on Sarkani, six on Shultan and six on Asadabad.
Development of the human body is the process of growth to maturity. The process begins with fertilisation, where an egg released from the ovary of a female is penetrated by sperm. The egg then lodges in the uterus, where an embryo and later fetus develop until birth. Growth and development occur after birth, and include both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. Development and growth continue throughout life, through childhood, adolescence, and through adulthood to old age, and are referred to as the process of aging.
Further, the method lacks the capability to distinguish between positive and negative nonsynonymous substitutions. Some amino acids are chemically similar to one another, whereas other substitutions may place an amino acid with wildly different properties to its precursor. In most situations, a smaller chemical change is more likely to allow the protein to continue to function, and a large chemical change is likely to disrupt the chemical structure and cause the protein to malfunction. However, incorporating this into a model is not straightforward as the relationship between a nucleotide substitution and the effects of the modified chemical properties is very difficult to determine. An additional concern is that the effects of time must be incorporated into an analysis, if the lineages being compared are closely related; this is because it can take a number of generations for natural selection to "weed out" deleterious mutations from a population, especially if their effect on fitness is weak. This limits the usefulness of the Ka/Ks ratio for comparing closely related populations.
Instead of only one player winning the round, the team with the higher score wins. If friendly fire is enabled, one point is deducted each time a teammate is killed. If the player selected a Resistance model for his character, and they are taken to the Combine team, they will get a random model from the list of Combine models. Nevertheless, if the player dislikes that character, they are able to choose another one from the list. If the teams are unbalanced, the team with fewer players won't get players from the other team, (unless the server owner had 'Auto-Balance' enabled) instead, they will get new players connected to the server.
Sources: en.wikipedia.org
==== Recombinant DNA ==== Biotechnology in the modern sense of genetic engineering began in the 1970s, with the invention of recombinant DNA techniques. Restriction enzymes were discovered and characterized in the late 1960s, following on the heels of the isolation, then duplication, then synthesis of viral genes. Beginning with the lab of Paul Berg in 1972 (aided by EcoRI from Herbert Boyer's lab, building on work with ligase by Arthur Kornberg's lab), molecular biologists put these pieces together to produce the first transgenic organisms. Soon after, others began using plasmid vectors and adding genes for antibiotic resistance, greatly increasing the reach of the recombinant techniques. Wary of the potential dangers (particularly the possibility of a prolific bacteria with a viral cancer-causing gene), the scientific community as well as a wide range of scientific outsiders reacted to these developments with both enthusiasm and fearful restraint. Prominent molecular biologists led by Berg suggested a temporary moratorium on recombinant DNA research until the dangers could be assessed and policies could be created. This moratorium was largely respected, until the participants in the 1975 Asilomar Conference on Recombinant DNA created policy recommendations and concluded that the technology could be used safely. Following Asilomar, new genetic engineering techniques and applications developed rapidly. DNA sequencing methods improved greatly (pioneered by Frederick Sanger and Walter Gilbert), as did oligonucleotide synthesis and transfection techniques.
In June 2010, Mohannad al-Hassani, head of the Syrian Organisation for Human Rights (Swasiya) and winner of the 2010 Martin Ennals Award for Human Rights Defenders, was convicted of "weakening national morale" and "conveying within Syria false news that could debilitate the morale of the nation." He was sentenced to three years in prison. Sednaya Prison alone housed more than 600 political prisoners. The authorities have kept many for years behind bars, often well past their legal sentence. Mass graves across the country were also discovered by forces from the Syrian transitional government after the fall of the Assad regime in December 2024. In a 2006 report, Human Rights Watch reported on the continued detention of "thousands" of political prisoners in Syria, "many of them members of the banned Muslim Brotherhood and the Communist Party." According to the Syrian Human Rights Committee that there were 4,000 political prisoners held in Syrian jails in 2006.
== Standards == A LIMS covers standards such as 21 CFR Part 11 from the Food and Drug Administration (United States), ISO/IEC 17025, ISO 15189, ISO 20387, Good Clinical Practice (GCP), Good Laboratory Practice (GLP), Good Manufacturing Practice (GMP), FDA Food Safety Modernization Act (FSMA), HACCP, and ISBER Best Practices.
=== Forms === As of 2010, methylnaltrexone is supplied as an injection in trays containing seven one-dose vials containing 0.6 mL of solution. Each tray also contains seven 12 mm (0.47 in) 1 mL 27 gauge needles with retractable tips, and alcohol wipes for home use. A single vial can treat someone who weighs as much as 115 kilograms (254 lb). For hospital use, vials are available separately. It is also now available in 150 mg oral tablets, taken 3 to 5 times daily.
Sources: en.wikipedia.org
The equilibrium constant for this dissociation reaction is known as a dissociation constant. The liberated proton combines with a water molecule to give a hydronium (or oxonium) ion H3O+ (naked protons do not exist in solution), and so Arrhenius later proposed that the dissociation should be written as an acid–base reaction:
Historians sometimes define a nineteenth century historical era from 1815 (the Congress of Vienna) to 1914 (the outbreak of World War I). Alternatively, Eric Hobsbawm defined the "long nineteenth century" as spanning from the French Revolution in 1789, to 1914. During this century, the Spanish, Portuguese, and Ottoman Empires began to decline. The Ottoman Empire suffered territorial losses in the eastern Mediterranean and Balkans. The Holy Roman Empire was dissolved in 1806 by Emperor Francis II. The Mughal Empire effectively ended after the Indian Rebellion of 1857.
Cases of stigmatism fall into two categories: self-inflicted wounds, which may be either cases of fraud or of unconscious self-infliction, and those that are caused by emotional states ... Self-induced (through autosuggestion) itching and subsequent scratching of which the individual is unaware is likely to occur in suggestible persons if the stimulus is a mental or actual picture of the Crucifixion used during meditation and if the main motive is to receive the stigmata. The motive behind that may be unconscious conflict and a desire to escape from an intolerable situation into invalidism where one's needs are taken care of. It then becomes a case of hysterical conversion reaction. Many cases of stigmatism can be explained as fraud or unconsciously self-inflicted wounds. In his Stigmata: A Medieval Phenomenon in a Modern Age, Ted Harrison suggests that there is no single mechanism whereby the marks of stigmata were produced. Harrison found no evidence from a study of contemporary cases that the marks were supernatural in origin. He concluded, however, that marks of natural origin need not be hoaxes. Some stigmatics marked themselves in attempt to suffer with Christ as a form of piety. Others marked themselves accidentally and their marks were noted as stigmata by witnesses. Often marks of human origin produced profound and genuine religious responses. Harrison also noted that after Saint Francis of Assisi, the stigmata was "seen as a predominantly female experience" with the female-to-male ratio of stigmatics being 7 to 1.
Iodine-129 (129I; half-life 16.1 million years) is a product of cosmic ray spallation on various isotopes of xenon in the atmosphere, in cosmic ray muon interaction with tellurium-130, and also uranium and plutonium fission, both in subsurface rocks and nuclear reactors. Artificial nuclear processes, in particular nuclear fuel reprocessing and atmospheric nuclear weapons tests, have now swamped the natural signal for this isotope. Nevertheless, it now serves as a groundwater tracer as indicator of nuclear waste dispersion into the natural environment. In a similar fashion, 129I was used in rainwater studies to track fission products following the Chernobyl disaster. In some ways, 129I is similar to 36Cl. It is a soluble halogen, exists mainly as a non-sorbing anion, and is produced by cosmogenic, thermonuclear, and in-situ reactions. In hydrologic studies, 129I concentrations are usually reported as the ratio of 129I to total I (which is virtually all 127I). As is the case with 36Cl/Cl, 129I/I ratios in nature are quite small: the pre-nuclear ratio was nearly 10−12, but as mentioned artificial sources are normally now much greater. 129I differs from 36Cl in that its half-life is longer (16.1 vs. 0.301 million years), it is highly biophilic, and occurs in multiple ionic forms (commonly, I− and IO3−), which have different chemical behaviors. This makes it fairly easy for 129I to enter the biosphere as it becomes incorporated into vegetation, soil, milk, animal tissue, etc.
== Structure == The human CRHR1 gene contains 14 exons over 20 kb of DNA, and its full gene product is a peptide composed of 444 amino acids. Excision of exon 6 yields in the mRNA for the primary functional CRF1, which is a peptide composed of 415 amino acids, arranged in seven hydrophobic alpha-helices. The CRHR1 gene is alternatively spliced into a series of variants. These variants are generated through deletion of one of the 14 exons, which in some cases causes a frame-shift in the open reading frame, and encode corresponding isoforms of CRF1. Though these isoforms have not been identified in native tissues, the mutations of the splice variants of mRNA suggest the existence of alternate CRF receptors, with differences in intracellular loops or deletions in N-terminus or transmembrane domains. Such structural changes suggest that the alternate CRF1 receptors have different degrees of capacity and efficiency in binding CRF and its agonists. Though the functions of these CRF1 receptors is yet unknown, they are suspected to be biologically significant. CRF1 is 70% homologous with the second human CRF receptor family, CRF2; the greatest divergence between the two lies at the N-terminus of the protein.
Sources: en.wikipedia.org
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.
Reported human trials are few, brief and originate mainly from one country. They describe effects on anxiety-related measures, but sample sizes are small and reporting is limited. The results are widely regarded as preliminary rather than confirmed.
Reverse-phase liquid chromatography is used to assess purity and separation of related impurities. Mass spectrometry confirms that the observed molecular mass matches the expected peptide. A certificate of analysis from the supplier is the usual document of record.
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.