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.
Updated 2026-02-11. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 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.
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.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
Purity assessment relies mainly on reverse-phase high-performance liquid chromatography with ultraviolet detection. Because the peptide lacks a strong chromophore, detection often uses backbone absorbance near 214 nm. Identity is confirmed by mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, comparing the measured mass against the expected value. Amino acid analysis can verify composition after acid hydrolysis. Diastereomer content and residual counterions are reported less often, although both can influence biological assays.
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.
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.
== Occurrence == Trace amounts of plutonium-238, plutonium-239, plutonium-240, and plutonium-244 can be found in nature. Small traces of plutonium-239, a few parts per trillion, and its decay products are naturally found in some concentrated ores of uranium, such as the natural nuclear fission reactor in Oklo, Gabon. The ratio of plutonium-239 to uranium at the Cigar Lake Mine uranium deposit ranges from 2.4×10−12 to 44×10−12. These trace amounts of 239Pu originate in the following fashion: on rare occasions, 238U undergoes spontaneous fission, and in the process, the nucleus emits one or two free neutrons with some kinetic energy. When one of these neutrons strikes the nucleus of another 238U atom, it is absorbed by the atom, which becomes 239U. With a relatively short half-life, 239U decays to 239Np, which decays into 239Pu. Finally, exceedingly small amounts of plutonium-238, attributed to the extremely rare double beta decay of uranium-238, have been found in natural uranium samples. Due to its relatively long half-life of about 80 million years, it was suggested that plutonium-244 occurs naturally as a primordial nuclide, but early reports of its detection could not be confirmed. Based on its likely initial abundance in the Solar System, present experiments as of 2022 are likely about an order of magnitude away from detecting live primordial 244Pu. However, its long half-life ensured its circulation across the Solar System before its extinction, and indeed, evidence of the spontaneous fission of extinct 244Pu has been found in meteorites.
=== Distribution === Estradiol is rapidly distributed throughout the body, with a distribution phase of about 6 minutes following intravenous injection. Estradiol is taken up into cells via passive diffusion due to its lipophilicity. Due to binding to the ERs, estradiol is preferentially concentrated in tissues with the highest ER content. In animals, these tissues have included the uterus, vagina, mammary glands, pituitary gland, hypothalamus, other brain regions, adipose tissue, liver, and adrenal glands, among other tissues. In contrast to estradiol, due to its low affinities for the ERs, estrone is not accumulated in target tissues. Estradiol has been found to cross the blood–brain barrier in rhesus monkeys. The volume of distribution of estradiol has been found to be 0.85 to 1.17 L/kg. In another study however, its volume of distribution was only 0.082 ± 0.015 L/kg (4.8 L in women of average weight 58.4 kg). In terms of plasma protein binding, estradiol is bound loosely to albumin and tightly to SHBG, with approximately 97 to 98% of estradiol bound to plasma proteins. In the circulation, approximately 38% of estradiol is bound to SHBG and 60% is bound to albumin, with 2 to 3% free or unbound. However, with oral estradiol, there is an increase in hepatic SHBG production and hence SHBG levels (e.g., +50%), and this results in a relatively reduced fraction of free estradiol. As only free estradiol that is not bound to plasma proteins or SHBG is biologically active, this may reduce the potency of oral estradiol by some degree.
== Function == Androgens that bind to and activate the androgen receptor have numerous physiological functions which can broadly divided into androgenic (male sexual development) and anabolic (building muscle and bone). The anabolic effects are important in both males and females, although females have lower circulating levels of androgens. The physiologically most important androgens are testosterone (T) and dihydrotestosterone (DHT), which are considered classical androgens because their role in human health was discovered in 1930s. However, much later, in 2010s, the role in human health of 11-oxygenated androgens was established, namely, of 11-ketotestosterone (11KT) and 11-ketodihydrotestosterone (11KDHT), that both bind and activate the human androgen receptor with affinities, potencies, and efficacies that are similar to that of testosterone (T) and DHT, respectively, although 11-oxygenated androgens were long known to be principal androgens in teleost fishes. The main biochemical route to T and DHT is the canonical (classical) pathway that proceeds from pregnenolone (P5). Alternatively, DHT but not T can be produced through a backdoor pathway that proceeds from 17α-hydroxyprogesterone (17OHP) or progesterone (P4). The function of androgen backdoor pathways is to produce physiologically significant androgens in normal conditions where the conventional pathway is insufficient, such as in male early sexual differentiation. Sexual differentiation is a process by which hormones determine anatomic phenotype, mainly the development of the reproductive organs.
Sources: en.wikipedia.org
== Structure == Alginic acid is a linear copolymer with homopolymeric blocks of (1→4)-linked β-D-mannuronate (M) and α-L-guluronate (G) residues, respectively, covalently linked together in different sequences or blocks. The monomers may appear in homopolymeric blocks of consecutive G-residues (G-blocks), consecutive M-residues (M-blocks) or alternating M and G-residues (MG-blocks). α-L-guluronate is the C-5 epimer of β-D-mannuronate.
== Development and spread of the Tiselius apparatus == The apparatus designed by Arne Tiselius in 1931 enabled a range of new applications of electrophoresis in analyzing chemical mixtures. Its development, significantly funded by the Rockefeller Foundation, was an extension of Tiselius' earlier PhD studies. With more assistance from the Rockefeller Foundation, the expensive Tiselius apparatus was built at a number of major centers of chemical research.
T4 (levothyroxine) is almost always preferred over T3 (liothyronine) when treating hypothyroidism. Treatment with T3 alone is not recommended, as it causes increased and potentially unsafe blood levels of free T3 (FT3). Combination treatment of hypothyroidism with T4 and T3 is generally only considered when treatment with T4 alone does not sufficiently resolve symptoms. As there is no evidence showing that combination treatment with T4 and T3 benefits patients, this approach is controversial, but it is supported by current guidelines of the European Thyroid Association and the British Thyroid Association for patients who do not respond at all to treatment with T4 alone.
Sources: en.wikipedia.org
=== Indolin derivatives === Indolin derivatives on the market are Sunitinib and Intedanib. Two indol derivatives that target the VEGF pathway, semaxanib and sunitinib, have been developed. The former is potent but was inefficient in clinical trials and the latter has many side effects. There is need for a drug with pharmacological effects similar to semaxanib and sunitinib, but it needs to be less toxic. MPEG3-9-semaxanib is semaxanib with an additional water-soluble, non-peptidic oligomer attached to it via a spacer moiety. MPEG3-9-semaxanib derivatives are 10 times more active against VEGFR-2 than sunitinib. Compounds with sunitinib heterocyclic moiety but different amide side chains inhibit VEGFR-1 and VEGFR-2 and regulate disorders. Another compound with sunitinib heterocyclic moiety and a pyrrole side chain has very good VEGFR-2 potency, with an IC50 of 65 nM. N-indol-1-amide compound is a possible anti-tumor drug in combination with other anticancer treatment and has an IC50 value of 31 nM. There are many indol derivatives with different side chains that target multiple kinases and take part in several pathways in tumor development. Intedanib is a multiple tyrosine kinase inhibitor and is the first drug to treat idiopathic pulmonary fibrosis. Indol derivatives with 1-NH of 2-indolinone motif that is an H-bond donor, and 2-carbonyl oxygen that acts as an H-bond acceptor, bind with Glu915 and Cys917, respectively. These compounds have basic amine side chains or nitrogen heterocycles and provide ideal solubility and pharmacokinetics.
Prohibitin-targeting peptide 1 (also known as prohibitin-TP01 and TP01; trade name Adipotide) is a peptidomimetic with sequence CKGGRAKDC-GG-D(KLAKLAK)2. It is an experimental proapoptotic drug that has been shown to cause rapid weight loss in mice and rhesus monkeys. Its mechanism of action is to target specific blood vessels supplying adipose tissue with blood, cause the vessels to shrink and the fat cells fed by those vessels to undergo apoptosis. TP01 is designed to bind to two receptors, ANXA2 and prohibitin, that are specific to blood vessels supplying white adipose tissue. As of 2019, clinical development has been discontinued.
=== Traumatic === Traumatic vertebral dissection may follow blunt trauma to the neck, such as in a traffic collision, direct blow to the neck, strangulation, or whiplash injury. 1–2% of those with major trauma may have an injury to the carotid or vertebral arteries. In many cases of vertebral dissection, people report recent very mild trauma to the neck or sudden neck movements, e.g. in the context of playing sports. Others report a recent infection, particularly respiratory tract infections associated with coughing. Trauma has been reported to have occurred within a month of dissection in 40% with nearly 90% of the traumas being minor. It has been difficult to prove the association of vertebral artery dissection with mild trauma and infections statistically. It is likely that many "spontaneous" cases may in fact have been caused by such relatively minor insults in someone predisposed by other structural problems to the vessels. A more likely theory, also as yet unproven, is that the low-energy traumatic dissections are actually spontaneous dissections brought to medical attention by the onset of neurological symptoms. These neurological events represent embolic phenomena due to loosening or breakdown of the clot at the site of the dissection, which can be triggered by low energy trauma or even occur spontaneously. The fragments travel within the arterial system downstream to the brain to cause stroke or stroke-like symptoms. Vertebral artery dissection has also been reported in association with some forms of neck manipulation.
The IATA code for John Glenn Columbus International Airport in Columbus, Ohio The National Rail station code for Cwmbach railway station in Rhondda Cynon Taf, Wales CMH Records Cambridge Military Hospital Canadian Mountain Holidays Canadian Museum of History United States Army Center of Military History Central Middlesex Hospital Ceramic discharge metal-halide lamp Children's Memorial Hospital Children's Museum of Houston Cohen Modal Haplotype Combined Military Hospital Combined Military Hospital (Dhaka) Community mental health Congressional Medal of Honor Consolidated Media Holdings Creatine monohydrate Cochran–Mantel–Haenszel statistics
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
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.