A practical reference on Pro-Gly-Pro: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-01-02. Anything still debated is marked as such rather than presented as settled.
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 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.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
| 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 |
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.
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.
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.
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.
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.
=== Pathology associated with ACTA1 === ACTA1 is the gene that codes for the α-isoform of actin that is predominant in human skeletal striated muscles, although it is also expressed in heart muscle and in the thyroid gland. Its DNA sequence consists of seven exons that produce five known transcripts. The majority of these consist of point mutations causing substitution of amino acids. The mutations are in many cases associated with a phenotype that determines the severity and the course of the affliction.
=== Dose uniformity === Good flow properties of granules and powders are important in the manufacturing of tablets and capsules. The distribution of particles should be uniform in terms of number and weight. Very small particle size causes attraction, which in turn destabilises the suspension by coagulating.
=== Metallurgical uses === Metal carbonyls are used in several industrial processes. Perhaps the earliest application was the extraction and purification of nickel via nickel tetracarbonyl by the Mond process (see also carbonyl metallurgy). By a similar process carbonyl iron, a highly pure metal powder, is prepared by thermal decomposition of iron pentacarbonyl. Carbonyl iron is used inter alia for the preparation of inductors, pigments, as dietary supplements, in the production of radar-absorbing materials in the stealth technology, and in thermal spraying.
== Technology == MA/MH technology is achieved by combining proprietary blends of polymers to obtain the desired MVTR and then manipulating the oxygen (O2) and carbon dioxide (CO2) transmission rates of the polymer by laser and/or mechanical microperforations. The result is a film which is tailored to provide the optimum modified atmosphere and modified humidity for the produce to be packaged. "Film composition and extent of microperforation are tailored in accordance with the respiratory activity and weight of the produce packaged, anticipated temperature fluctuations during storage and shipment, and expected physiological and pathological responses of the produce to CO2/O2 concentrations and humidity levels inside the package. ... [MA/MH] packaging allow[s] the formation of a desirable modified atmosphere, retarding ripening and senescence of the produce. Additional beneficial effects ... include reduction of decay, chilling injury, leaf elongation, leaf sprouting, tissue discoloration, peel blemishes, and formation of off-odors, and inhibition of bacterial growth on the produce surface."
==== Potential distinction ==== For clarification, a distinction between the two corresponding cases is needed. With reference to a phase diagram, the sublimation that occurs left of the solid–gas boundary, the triple point or the solid–liquid boundary (corresponding to evaporation in vaporization) may be called gradual sublimation; and the substance sublimes gradually, regardless of rate. The sublimation that occurs at the solid–gas boundary (critical sublimation point) (corresponding to boiling in vaporization) may be called rapid sublimation, and the substance sublimes rapidly. The words "gradual" and "rapid" have acquired special meanings in this context and no longer describe the rate of sublimation.
Sources: en.wikipedia.org
=== February–April 1881 === On 14 February Carrington captured Ramokoatsi, which overlooked the main road to Morija. The following day, a force of 370 cavalry, 100 infantry, 50 native levies, and three artillery pieces under Brabant was sent out in search of a new camping ground. Upon crossing a spruit in the Ramibidikwa area, a CMR scout reported a massed formation of Basuto horsemen. Brabant ordered his soldiers to form a square; soon afterwards the Basuto commenced an attack on its front and two flanks. A combination of rifle and case shot fire kept the Basuto at bay in the center and the right flank. On the left, the Basuto managed to almost reach melee range before being likewise driven off. The artillery continued to fire on the retreating Basuto, who suffered 138 casualties in the engagement. One month later Clarke assumed personal command of the force, moving the camp to Ramibidikwa, 20 miles (32 km) from Morija. On 22 March, Carrington was heavily wounded in the vicinity of the new camp. By early April, Sprigg's conduct of the war was being heavily criticized in the Cape Parliament, whose opposition members were pushing for a vote of no confidence. Using Letsie as an intermediary, Robinson organized a meeting between Griffith and Lerotholi outside Maseru on 17 April. The two sides signed an armistice, although Lerotholi was unwilling to surrender his weapons, as the motion would be too unpopular among his tribesmen. On 29 April, Robinson announced the peace settlement, known as the Award.
==== Azetidine based compounds ==== Informations for this group of inhibitors are quite restricted. Azetidine-based DPP-4 inhibitors can roughly be grouped into three main subcategories: 2-cyanoazetidines, 3-fluoroazetidines, and 2-ketoazetidines. The most potent ketoazetidines and cyanoazetidines have large hydrophobic amino acid groups bound to the azetidine nitrogen and are active below 100nM.
==== Less frequent ==== Hb H (β4) Hb Barts (γ4) Hb O (α2βO2) Hb Bassett Hb Kansas Hb D-Punjab Hb O-Arab Hb G-Philadelphia Hb Hasharon Hb Kirklareli Hb Lepore Hb M Hb Hope Hb Pisa Hb J Hb N-Baltimore Hemoglobin Chesapeake Hemoglobin Louisville Hemoglobin Vanvitelli
== Diagnosis == Hypophosphatemia is diagnosed by measuring the concentration of phosphate in the blood. Concentrations of phosphate less than 0.81 mmol/L (2.5 mg/dL) are considered diagnostic of hypophosphatemia, though additional tests may be needed to identify the underlying cause of the disorder.
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.
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.