The short version of Certificate of analysis fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-06-24 and is reviewed periodically as new material appears.
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.
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.
Peptide bonds in selank are susceptible to hydrolysis under strongly acidic or basic conditions, and the terminal proline residues are vulnerable to exopeptidase activity in biological samples. Lyophilized powder stored dry at -20 °C typically remains stable for extended periods, whereas aqueous solutions degrade faster and may lose measurable purity within days to weeks depending on pH, temperature, and microbial load. Repeated freeze-thaw cycles promote aggregation and adsorption to container surfaces. For analytical work, solutions are usually prepared fresh, kept cold, and used within a single working day.
| 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 |
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 Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
=== Lymphoproliferative diseases === Hyperactive mTOR pathways have been identified in certain lymphoproliferative diseases such as autoimmune lymphoproliferative syndrome (ALPS), multicentric Castleman disease, and post-transplant lymphoproliferative disorder (PTLD).
== Function == 3-hydroxyisobutyrate dehydrogenase is a tetrameric mitochondrial enzyme that catalyzes the NAD+-dependent, reversible oxidation of 3-hydroxyisobutyrate, an intermediate of valine catabolism, to methylmalonate semialdehyde.
Surface anatomy, or superficial anatomy, is the study of anatomical landmarks that can be identified readily from the contours or other reference points on the surface of the body. It is important in human anatomy: with knowledge of superficial anatomy, physicians gauge the position and anatomy of deeper structures. Common names of parts of the human body, from top to bottom:
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Lord Robert Cecil on 2 December 1917, assured an audience that the government fully intended that "Judea [was] for the Jews." Yair Auron opines that Cecil, then a deputy Foreign Secretary representing the British Government at a celebratory gathering of the English Zionist Federation, "possibly went beyond his official brief" in saying (he cites Stein) "Our wish is that Arabian countries shall be for the Arabs, Armenia for the Armenians and Judaea for the Jews". The following October Neville Chamberlain, while chairing a Zionist meeting, discussed a "new Jewish State." At the time, Chamberlain was a Member of Parliament for Ladywood, Birmingham; recalling the event in 1939, just after Chamberlain had approved the 1939 White Paper, the Jewish Telegraph Agency noted that the Prime Minister had "experienced a pronounced change of mind in the 21 years intervening" A year later, on the Declaration's second anniversary, General Jan Smuts said that Britain "would redeem her pledge ... and a great Jewish state would ultimately rise." In similar vein, Churchill a few months later stated:
Sources: en.wikipedia.org
Cystathionine is an intermediate in the synthesis of cysteine from homocysteine. It is produced by the transsulfuration pathway and is converted into cysteine by cystathionine gamma-lyase (CTH). Biosynthetically, cystathionine is generated from homocysteine and serine by cystathionine beta synthase (upper reaction in the diagram below). It is then cleaved into cysteine and α-ketobutyrate by cystathionine gamma-lyase (lower reaction). An excess of cystathionine in the urine is called cystathioninuria.
During the trial of alleged 9/11 conspirator Zacarias Moussaoui, the U.S. government identified five people as having been completely aware of the operation's details; bin Laden, Mohammed, Mohammed Atef, Abu Turab al-Urduni, and bin al-Shibh. The attacks were conceived by Khalid Sheikh Mohammed, who first presented it to bin Laden in 1996. Many targets were listed that al-Qaeda hijackers could crash planes into, including the Library Tower (now the U.S. Bank Tower) in Los Angeles. Bin Laden rejected the plan for being too elaborate. Al-Qaeda's first attacks against the U.S. after Bin Laden's 1998 fatwa were the 1998 African embassy bombings. In late 1998 or early 1999, bin Laden approved Mohammed to go forward with a new version of the 1996 plan. Bin Laden provided leadership and financial support, and was involved in selecting participants. Atef provided operational support, including target selections and helping arrange travel for the hijackers. He initially selected Nawaf al-Hazmi and Khalid al-Mihdhar, both experienced jihadists who had fought in the Bosnian war. The two arrived in the United States in mid-January 2000. In early 2000, they took flying lessons in San Diego, California. Both spoke little English. They performed poorly in flying lessons, and so they eventually served as secondary "muscle" hijackers. The Hamburg cell in Germany included Islamists who were key operatives in the 9/11 attacks. In late 1999, cell members bin al-Shibh, Mohamed Atta, Marwan al-Shehhi, and Ziad Jarrah arrived to meet al-Qaeda in Afghanistan.
=== Manufacturing costs === The raw material consumption and the conversion cost are the two elements that establish the manufacturing cost for a particular fine chemical. The former is determined primarily by the unit consumption and the purchasing cost of the materials used; the latter, by the throughput in kilograms per day in a given production bay. A precise calculation of the conversion cost is a demanding task. Different products with widely differing throughputs are produced in campaigns in multipurpose plants, occupying the equipment to different extents. Therefore, both the production capacity and the equipment utilization for a specific fine chemical are difficult to determine. Moreover, cost elements such as labor, capital, utilities, maintenance, waste disposal, and quality control cannot be allocated unambiguously. An approximative calculation can be done by an experienced process development or pilot plant chemist on the basis of the laboratory synthesis procedure and by breaking down the process into unit operations, the standard costs of which have been determined previously. Controlling has to be involved for a more in-depth costing. It must fairly allocate costs for production capacity which is not used, whether because part of a production bay is idle, because of lack of demand or because a reactor is not required for a particular process. Manufacturing costs usually are reported on a per kilogram product basis. For the purpose of benchmarking (both internal and external), the volume x time/output (VTO) is a useful aid.
Boltovsky, T., Bernardo Abiahy, Viviana A. Alder, Martin V. Angel, Renate Bernstein, Dennis Binet, Demetrio Boltovsky, Jean Bouillon, Janet Bradford-Grieve, John-Paul Casanova, Paul Cornelius, Jose R. Dadon, Christina Deponte, Graciela B. Esnal, Maria Alamo, Adilson Fransozo, Mark Gibbons, Ray Gibson, and Cristoph Helemben. "Marine Species Identification Portal : Catostylus tagi." Marine Species Identification Portal : Catostylus tagi. UNESCO, n.d. Web. 24 Sept. 2014.
=== Fibrosis quantization === Collagen (particular case, but widely studied in SHG microscopy), can exist in various forms : 28 different types, of which 5 are fibrillar. One of the challenge is to determine and quantify the amount of fibrillar collagen in a tissue, to be able to see its evolution and relationship with other non-collagenous materials. To that end, a SHG microscopy image has to be corrected to remove the small amount of residual fluorescence or noise that exist at the SHG wavelength. After that, a mask can be applied to quantify the collagen inside the image. Among other quantization techniques, it is probably the one with the highest specificity, reproductibility and applicability despite being quite complex.
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.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.