This is a working overview of lyophilized powder, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-23 and is reviewed periodically as new material appears.
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.
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.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
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.
| 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 |
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.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
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.
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.
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.
Mexico's tequila protection interests were prominent during the Chinese accession negotiations to the World Trade Organization. In accordance with WTO accession regulations, in order to gain considerations for WTO membership, China had to sign bilateral agreements with all existing members, including Mexico. Since China has a climatic condition suitable for blue agave plants, Mexico was worried about rival pseudo tequilas from China. The Mexican authorities took the opportunity of the bilateral negotiations with China to ensure that the latter accepted tequila as a geographically indicated product.
The pharmacokinetics of progesterone are dependent on its route of administration. The medication is approved in the form of oil-filled capsules containing micronized progesterone for oral administration, termed "oral micronized progesterone" ("OMP") or simply "oral progesterone". It is also available in the form of vaginal or rectal suppositories, vaginal gels, oil solutions for intramuscular injection, and aqueous solutions for subcutaneous injection, among others. Routes of administration that progesterone has been used include oral, intranasal, transdermal, vaginal, rectal, intramuscular, subcutaneous, and intravenous injection. Oral progesterone has been found to be inferior to vaginal and intramuscular progesterone in terms of absorption (low) and clearance rate (rapid). Vaginal progesterone is available in the forms of progesterone gel, rings, and suppositories or pessaries. Advantages of intravaginal progesterone over oral administration include high bioavailability, rapid absorption, avoidance of first-pass metabolism, sustained plasma concentrations, and a local endometrial effect, while advantages of intravaginal progesterone relative to intramuscular injection include greater convenience and lack of injection site pain. Intranasal progesterone as a nasal spray is effective in achieving therapeutic levels, and was not associated with nasal irritation, but was associated with an unpleasant taste of the spray. Rectal, intramuscular, and intravenous routes may be inconvenient, especially for long-term treatment.
== Applications == With an expanded genetic code, the unnatural amino acid can be genetically directed to any chosen site in the protein of interest. The high efficiency and fidelity of this process allows a better control of the placement of the modification compared to modifying the protein post-translationally, which, in general, will target all amino acids of the same type, such as the thiol group of cysteine and the amino group of lysine. Also, an expanded genetic code allows modifications to be carried out in vivo. The ability to site-specifically direct lab-synthesized chemical moieties into proteins allows many types of studies that would otherwise be extremely difficult, such as:
{\displaystyle {\begin{aligned}[][a_{0},a_{1},a_{2},a_{3}]&=[0.398942280401,0.159773702775,0.0389687688311,0.00364356495452]\\[][b_{1},b_{2},b_{3},b_{4},b_{5},b_{6}]&=\left[1.653807476138,1.170419428529,0.448892964428,0.0951971709160,0.00931642803836,-6.383774657279\times 10^{-6}\right]\end{aligned}}}
Sources: en.wikipedia.org
=== Cattle === In dairy cattle, ketosis commonly occurs during the first weeks after giving birth to a calf and is sometimes referred to as acetonemia. This is most likely the result of an energy deficit when intake is inadequate to compensate for the increased metabolic demand of lactating. The elevated β-hydroxybutyrate concentrations can depress gluconeogenesis, feed intake and the immune system, as well as have an impact on milk composition. Point of care diagnostic tests can be useful to screen for ketosis in cattle.
== External links == The Journal of Proteolysis is an open access journal that provides an international forum for the electronic publication of the whole spectrum of high-quality articles and reviews in all areas of proteolysis and proteolytic pathways. Proteolysis MAP from Center on Proteolytic Pathways
On February 3, 2004, Kennedy launched his first bid for the U.S. Senate to replace incumbent John Breaux, who was retiring. He ran as a Democrat in the state's jungle primary, losing to Republican David Vitter and Democrat Chris John. Vitter won the election outright.
Similar delays in the MICV program meant the ultimate vehicles descending from their efforts, the M2/M3 Bradley fighting vehicle, did not enter production until 1981, by which point the Bushmaster had matured. Since 1990, there have been several enhancements made upon the weapon, resulting in the enhanced 25 mm gun. To date, more than 10,500 weapons are in service. One of the major reasons for this popularity is the extremely reliable nature of the weapon. It has a rating of 22,000 mean rounds between failure (MRBF), much higher than many comparable devices.
The deep veins of the lower limb include the common femoral vein, femoral vein, and the deep femoral vein; the popliteal vein, the tibial, and fibular veins. In the common femoral vein one valve is located above the saphenofemoral junction called the suprasaphenic valve. There are sometimes two valves in the same tract. In the femoral vein there are often three valves, the most constantly found valve is just below the joining of the deep femoral vein. The deep femoral vein and its perforators have valves. In the popliteal veins there are between one and three valves; in each posterior tibial vein there are between 8 and 19 valves, and in the anterior tibial veins there are between 8 and 11 valves. In the superficial veins there are between one and seven valves along the thigh portion of the great saphenous vein (GSV); two to six below the knee and one to four in the marginal veins of the foot. There is a valve at the termination of the GSV known as the terminal valve to prevent reflux from the femoral vein. A preterminal valve is located just below the openings of the tributaries to prevent reflux form these into the GSV. Incompetence of the GSV is a common cause of varicose veins. The valves also divide the column of blood into segments which helps move the blood unidirectionally to the heart. Their action is supported by the action of skeletal muscle pumps that contract and compress the veins. A skeletal muscle is confined in its fascia and contraction of the muscle which makes it wider results In compression on the vein that pushes the blood forward.
Sources: en.wikipedia.org
Clarke, S (1987). "Propensity for spontaneous succinimide formation from aspartyl and asparaginyl residues in cellular proteins". International Journal of Peptide and Protein Research. 30 (6): 808–821. doi:10.1111/j.1399-3011.1987.tb03390.x. PMID 3440704. Stephenson, RC; Clarke, S (1989). "Succinimide Formation from Aspartyl and Asparaginyl Peptides as a Model for the Spontaneous Degradation of Proteins". The Journal of Biological Chemistry. 264 (11): 6164–6170. doi:10.1016/S0021-9258(18)83327-0. PMID 2703484. Robinson NE, Robinson AB. (2004) Molecular Clocks: Deamidation of Asparaginyl and Glutaminyl Residues in Peptides and Proteins. Althouse Press: Cave Junction, Ore. OCLC 56978028
1 March to August 1971 In the DMZ Campaign (1969-71) the 1st Brigade, 5th Infantry Division (Mechanized) assumed responsibility for the defense of the DMZ from the 3rd Marine Division as it withdrew from South Vietnam.
A Levey–Jennings chart is a graph that quality control data is plotted on to give a visual indication whether a laboratory test is working well. The distance from the mean is measured in standard deviations. It is named after Stanley Levey and E. R. Jennings, pathologists who suggested in 1950 that Shewhart's individuals control chart could be used in the clinical laboratory. The date and time, or more often the number of the control run, is plotted on the x-axis. A mark is made indicating how far the actual result was from the mean, which is the expected value for the control. Lines run across the graph at the mean, as well as one, two and three standard deviations to either side of the mean. This makes it easy to see how far off the result was. Rules such as the Westgard rules can be applied to see whether the results from the samples when the control was done can be released, or if they need to be rerun. The formulation of Westgard rules were based on statistical methods. Westgard rules are commonly used to analyse data in Shewhart control charts. Westgard rules are used to define specific performance limits for a particular assay (test) and can be used to detect both random and systematic errors. Westgard rules are programmed into automated analyzers to determine when an analytical run should be rejected. These rules need to be applied carefully so that true errors are detected while false rejections (of valid results that are outside of range) are minimized. The rules applied to high-volume chemistry and hematology instruments should produce low false rejection rates.
CPA is widely available throughout the world, and is marketed in almost every developed country, with the notable major exceptions of the United States and Japan. In almost all countries in which CPA is marketed, it is available both alone and in combination with an estrogen in birth control pills. CPA is marketed widely in combination with both ethinylestradiol and estradiol valerate. CPA-containing birth control pills are available in South Korea, but CPA as a standalone medication is not marketed in this country. In Japan and South Korea, the closely related antiandrogen and progestin chlormadinone acetate, as well as other medications, are used instead of CPA. Specific places in which CPA is marketed include the United Kingdom, elsewhere throughout Europe, Canada, Australia, New Zealand, South Africa, Latin America, and Asia. CPA is not marketed in most of Africa and the Middle East. It has been said that the lack of availability of CPA in the United States explains why there are relatively few studies of it in the treatment of androgen-dependent conditions such as hyperandrogenism and hirsutism in women.
=== Intravenous injection === Testosterone esters like testosterone enanthate are hydrolyzed into testosterone so rapidly in the blood that testosterone and testosterone enanthate have nearly identical pharmacokinetics when administered via intravenous injection.
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.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.