If you have been reading about Certificate of analysis and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-04-11. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| 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 |
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
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.
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, frequently abbreviated as TKPRPGP. It was designed as a structural analogue of tuftsin, a naturally occurring tetrapeptide released by enzymatic cleavage of the immunoglobulin heavy chain. The two additional proline residues at the C-terminal end extend the parent chain and change how the molecule behaves in solution. The free peptide has a calculated molecular mass of approximately 751.9 g/mol and is generally supplied as a lyophilised white to off-white powder.
Development work on the compound began in the 1980s and 1990s at the Institute of Molecular Genetics in Moscow, within the same research programme that produced the peptide Semax. Early investigators sought a tuftsin derivative with improved resistance to enzymatic breakdown and with activity in the central nervous system after peripheral administration. Most of the primary literature from this period was published in Russian, a factor that still shapes how easily the findings can be checked by outside groups.
Collagen primary structure and collagen processing: ADAMTS2, COL1A1, COL1A2, COL3A1, COL5A1, COL5A2 Collagen folding and collagen cross-linking: PLOD1, FKBP14 Structure and function of myomatrix: TNXB, COL12A1 Glycosaminoglycan biosynthesis: B4GALT7, B3GALT6, CHST14, DSE Complement pathway: C1R, C1S Intracellular processes: SLC39A13, ZNF469, PRDM5 Variations in these genes usually alter the structure, production, or processing of collagen or proteins that interact with collagen. Collagen provides structure and strength to connective tissue. A defect in collagen can weaken connective tissue in the skin, bones, blood vessels, and organs, resulting in the features of the disorder. Inheritance patterns depend on the specific syndrome. Most forms of EDS are inherited in an autosomal dominant pattern, which means only one of the two copies of the gene in question must be altered to cause a disorder. A few are inherited in an autosomal recessive pattern, which means both copies of the gene must be altered for a person to be affected. It can also be an individual (de novo or "sporadic") variation. Sporadic variations occur without any inheritance.
== Notable works == The Saxxy awards were given to a total of 33 winners, ranging from comedic or action shorts to extended short films across a variety of genres. Longer films produced with the software include Darkest Days, an hour-long jukebox musical based on Left 4 Dead 2, and Emesis Blue, a 108-minute psychological horror feature film based on Team Fortress 2.
=== Hypersensitivity === Prior to the advent of the "human" lente insulins, the lente insulins (semi-lente, lente, and ultra-lente) were a combination of porcine and bovine insulin products that were filtered and combined with zinc to form the suspension. Even with product filtering, due to the animal origin, the human body might recognize the foreign protein as such and form antibodies against it. These reactions were slightly more likely with lente insulins than insulins derived from a solely porcine source, as bovine insulin was more immunogenic than porcine insulin.
Sources: en.wikipedia.org
signaling PRRs that activate gene transcriptional mechanisms that lead to cellular activation, endocytic PRRs that function in pathogen binding and phagocytosis, and secreted PRRs that usually function as opsonins or activators of complement. The recognition and clearance of invading microorganisms occurs through both opsonin-dependent and opsonin–independent pathways. The molecular mechanisms facilitating opsonin-dependent phagocytosis are different for specific opsonin/receptor pairs. For example, phagocytosis of IgG-opsonized pathogens occurs through the Fcγ receptors (FcγR), and involves phagocyte extensions around the microbe, resulting in the production of pro-inflammatory mediators. Conversely, complement receptor-mediated pathogen ingestion occurs without observable membrane extensions (particles just sink into the cell) and does not generally results in an inflammatory mediator response. Following internalization, the microbe is enclosed in a vesicular phagosome which then undergoes fusion with primary or secondary lysosomes, forming a phagolysosome. There are various mechanisms that lead to intracellular killing; there are oxidative processes, and others independent of the oxidative metabolism. The former involves the activation of membrane enzyme systems that lead to a stimulation of oxygen uptake (known as the respiratory burst), and its reduction to reactive oxygen intermediates (ROIs), molecular species that are highly toxic for microorganisms.
=== Effects of Temperature === All enzymes work within a range of temperature specific to the organism. Increases in temperature generally lead to increases in reaction rates. There is a limit to the increase because higher temperatures lead to a sharp decrease in reaction rates. This is due to the denaturating (alteration) of protein structure resulting from the breakdown of the weak ionic and hydrogen bonding that stabilize the three-dimensional structure of the enzyme active site. The "optimum" temperature for human enzymes is usually between 35 and 40 °C. The average temperature for humans is 37 °C. Human enzymes start to denature quickly at temperatures above 40 °C. Enzymes from thermophilic archaea found in the hot springs are stable up to 100 °C. However, the idea of an "optimum" rate of an enzyme reaction is misleading, as the rate observed at any temperature is the product of two rates, the reaction rate and the denaturation rate. If you were to use an assay measuring activity for one second, it would give high activity at high temperatures, however if you were to use an assay measuring product formation over an hour, it would give you low activity at these temperatures.
As a result, people with a history of cardiovascular disease may derive benefit from statins irrespective of their cholesterol levels (total cholesterol below 5.0 mmol/L [193 mg/dL]), and in men without cardiovascular disease, there is benefit from lowering abnormally high cholesterol levels ("primary prevention"). Primary prevention in women was originally practiced only by extension of the findings in studies on men, since, in women, none of the large statin trials conducted prior to 2007 demonstrated a significant reduction in overall mortality or in cardiovascular endpoints. Meta-analyses have demonstrated significant reductions in all-cause and cardiovascular mortality, without significant heterogeneity by sex.
=== Non-nutrients === Ethanol (C2H5OH) is not an essential nutrient, but it does supply approximately 29 kilojoules (7 kilocalories) of food energy per gram. For spirits (vodka, gin, rum, etc.) a standard serving in the United States is 44 millilitres (1+1⁄2 US fluid ounces), which at 40% ethanol (80 proof) would be 14 grams and 410 kJ (98 kcal). At 50% alcohol, this would be 17.5 g and 513 kJ (122.5 kcal). Wine and beer contain a similar amount of ethanol in servings of 150 and 350 mL (5 and 12 US fl oz), respectively, but these beverages also contribute to food energy intake from components other than ethanol. A 150 mL (5 US fl oz) serving of wine contains 420 to 540 kJ (100 to 130 kcal). A 350 mL (12 US fl oz) serving of beer contains 400 to 840 kJ (95 to 200 kcal). According to the U.S. Department of Agriculture, based on NHANES 2013–2014 surveys, women ages 20 and up consume on average 6.8 grams of alcohol per day and men consume on average 15.5 grams per day. Ignoring the non-alcohol contribution of those beverages, the average ethanol contributions to daily food energy intake are 200 and 450 kJ (48 and 108 kcal), respectively. Alcoholic beverages are considered empty calorie foods because, while providing energy, they contribute no essential nutrients. By definition, phytochemicals include all nutritional and non-nutritional components of edible plants. Included as nutritional constituents are provitamin A carotenoids, whereas those without nutrient status are diverse polyphenols, flavonoids, and lignans that are present in numerous plant foods.
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.
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.