certificate of analysis 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 2025-09-17. Where a claim depends on a specific study, the study is described rather than over-claimed.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
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.
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.
Selank is a hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
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.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
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.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
University-based ophthalmologists in the US and Canada further refined the use of botulinum toxin as a therapeutic agent. By 1985, a scientific protocol of injection sites and dosage had been empirically determined for treatment of blepharospasm and strabismus. Side effects in treatment of this condition were deemed to be rare, mild and treatable. The beneficial effects of the injection lasted only four to six months. Thus, blepharospasm patients required re-injection two or three times a year. In 1986, Scott's micromanufacturer and distributor of Botox was no longer able to supply the drug because of an inability to obtain product liability insurance. People became desperate, as supplies of Botox were gradually consumed, forcing him to abandon people who would have been due for their next injection. For a period of four months, American blepharospasm patients had to arrange to have their injections performed by participating doctors at Canadian eye centers until the liability issues could be resolved. In December 1989, Botox was approved by the US FDA for the treatment of strabismus, blepharospasm, and hemifacial spasm in people over 12 years old. In the case of treatment of infantile esotropia in people younger than 12 years of age, several studies have yielded differing results.
Most of the supporters also stated that the death sentence should be deployed for drug crimes due to its strong deterrent effect. Shen's death sentence was subsequently upheld after he lost his appeal on 1 March 2024. When CNN covered the topic of Singapore's death penalty and Changi Prison in October 2024, it was noted that the death penalty continued to thrive with huge public support, and there were about 40 inmates on death row as of the time when CNN covered the issue exclusively. An inmate, a former schoolteacher who introduced himself as Matthew, stated he believed in the deterrent effect of the death penalty for drug trafficking; Matthew was then serving a seven-year jail term for non-capital drug charges. However, his sentiments were not shared by the family members of death row inmates who spoke to CNN. Haslinda Ismail, whose son Muhammed Izwan bin Borhan was sentenced to death for diamorphine trafficking, stated that she was devastated over the outcome and felt resentful towards the government for not giving her son a second chance; Izwan remained on death row awaiting to be hanged as of the time of writing. Similarly, Nazeri Lajim's sister, Nazira Lajim, who was an anti-death penalty activist, stated that she was sad and angry that her brother was executed despite her push for a life sentence, and likely due to her brother's hanging in 2022, Nazira encouraged her adult children to permanently leave Singapore and emigrate to Australia.
Surgical or internal medicine Age range of patients Diagnostic or therapeutic Organ-based or technique-based Throughout history, the most important has been the division into surgical and internal medicine specialties. The surgical specialties are those in which an important part of diagnosis and treatment is achieved through major surgical techniques. The internal medicine specialties are the specialties in which the main diagnosis and treatment is never major surgery. In some countries, anesthesiology is classified as a surgical discipline, since it is vital in the surgical process, though anesthesiologists never perform major surgery themselves. Many specialties are organ-based. Many symptoms and diseases come from a particular organ. Others are based mainly around a set of techniques, such as radiology, which was originally based around X-rays. The age range of patients seen by any given specialist can be quite variable. Pediatricians handle most complaints and diseases in children that do not require surgery, and there are several subspecialties (formally or informally) in pediatrics that mimic the organ-based specialties in adults. Pediatric surgery may or may not be a separate specialty that handles some kinds of surgical complaints in children. A further subdivision is the diagnostic versus therapeutic specialties. While the diagnostic process is of great importance in all specialties, some specialists perform mainly or only diagnostic examinations, such as pathology, clinical neurophysiology, and radiology.
==== Mixed ==== A mixed inhibitor binds to an allosteric site and the binding of the substrate and the inhibitor affect each other. The enzyme's function is reduced but not eliminated when bound to the inhibitor. This type of inhibitor does not follow the Michaelis–Menten equation.
Sources: en.wikipedia.org
== Morphology and histological staining == Hematoxylin and eosin staining (H&E) shows that the cytoplasm of active osteoblasts is slightly basophilic due to the substantial presence of rough endoplasmic reticulum. The active osteoblast produces substantial collagen type I. About 10% of the bone matrix is collagen with the balance mineral. The osteoblast's nucleus is spherical and large. An active osteoblast is characterized morphologically by a prominent Golgi apparatus that appears histologically as a clear zone adjacent to the nucleus. The products of the cell are mostly for transport into the osteoid, the non-mineralized matrix. Active osteoblasts can be labeled by antibodies to Type-I collagen, or using naphthol phosphate and the diazonium dye fast blue to demonstrate alkaline phosphatase enzyme activity directly.
Another synonymous mutation (c.3156C>T) was proposed to introduce a cryptic donor site, resulting in aberrant splicing, a theory which subsequently was confirmed in several families with ERED from different countries.
==== Central nervous system ==== The presence of ColVI in the brain was originally discovered in meningeal cells. ColVI has also been linked to the development of Alzheimer's disease. When treated with AB-peptides, mice without the COL6A1 gene were observed to have an increase in apoptosis compared to wild type mice, suggesting that ColVI plays a neuroprotective role against AB-peptide toxicity. Further, ColVI has been suggested to play an anti-apoptotic role in other parts of the nervous system, as seen in studies analyzing the effects of UV-induced apoptosis.
Despite the anomalous electron configuration for gaseous thorium atoms, metallic thorium shows significant 5f involvement. A hypothetical metallic state of thorium that had the [Rn]6d27s2 configuration with the 5f orbitals above the Fermi level should be hexagonal close packed like the group 4 elements titanium, zirconium, and hafnium, and not face-centred cubic as it actually is. The actual crystal structure can only be explained when the 5f states are invoked, proving that thorium is metallurgically a true actinide. Tetravalent thorium compounds are usually colourless or yellow, like those of silver or lead, as the Th4+ ion has no 5f or 6d electrons. Thorium chemistry is therefore largely that of an electropositive metal forming a single diamagnetic ion with a stable noble-gas configuration, indicating a similarity between thorium and the main group elements of the s-block. Thorium and uranium are the most investigated of the radioactive elements because their radioactivity is low enough not to require special handling in the laboratory.
D-Phenylalanine (DPA, D-Phe), sold under the brand names Deprenon, Sabiben, and Sabiden, is an enantiomer of phenylalanine which is described as an antidepressant and is marketed as a prescription drug for medical use in Argentina. The medication has been marketed since at least the 1970s and continued to be available by the 2000s. D-Phenylalanine has been found to act as an enkephalinase inhibitor, an inhibitor of enkephalinase enzymes that break down endogenous opioid peptides called enkephalins. It has been found to produce anti-inflammatory, analgesic, and anti-craving effects in animal studies.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.