This is a working overview of Pro-Gly-Pro, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-03 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
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.
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.
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.
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.
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
Selank is studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
Some analyses of traditional preparations of San Pedro cactus have found doses ranging from 34 mg to 159 mg of total alkaloids, a relatively low and barely psychoactive amount. It appears that patients who receive traditional treatments with San Pedro ingest sub-psychoactive doses and do not experience psychedelic effects. The onset of the effects of mescaline given orally is 0.5 to 0.9 hours on average with a range of 0.1 to 2.7 hours. Its effects peak after 1.9 to 4.0 hours with a range of 0.5 to 8.0 hours. The duration of mescaline appears to be dose-dependent, varying from 6.4 hours on average (range 3.0–10 hours) at a dose of 100 mg, 9.7 to 11 hours on average (range 5.6–22 hours) at moderate doses of 300 to 500 mg, and 14 hours on average (range 7.2–22 hours) at a dose of 800 mg. Cases of mescaline having unusually prolonged or delayed effects have also been described. Given intravenously, mescaline has been reported to have an onset of several minutes or within 10 minutes, a time to peak of 1 to 2 hours, and a duration of approximately 4 to 9 hours in different studies. Mescaline induces a psychedelic state comparable to those produced by LSD and psilocybin, but with unique characteristics. Subjective effects may include altered thinking processes, an altered sense of time and self-awareness, and closed- and open-eye visual phenomena. In PiHKAL, Shulgin described the effects of mescaline based on a collection of experience reports.
P3 peptides are thought to have a role in neuronal death and in the enhanced inflammatory response in AD and DS, as it has been demonstrated that the treatment of cells with the p3 fragment, induced by the c-Jun N-terminal kinases (JNK) phosphorylation, is involved in neuronal cells apoptosis and causes the death of SH-SY5Y and IMR‐32 human neuroblastoma cells.
== External links == Histology image: 00801ooa – Histology Learning System at Boston University - "Connective Tissue elastic fibers " UIUC Histology Subject 328 Anatomy photo: TermsCells&Tissues/connective/elastic/elastic2 - Comparative Organology at University of California, Davis - "Connective tissue, elastic (LM, High)"
Interstitial fibrosis, described in cases of congestive heart failure and hypertension, and as part of normal cellular aging. Replacement fibrosis, indicating tissue damage from previous myocardial infarction.
In one pathway, arginine is converted into agmatine. The conversion is catalyzed by the enzyme arginine decarboxylase (ADC). Agmatine is transformed into N-carbamoylputrescine by agmatine imino hydroxylase (AIH). Finally, N-carbamoylputrescine is hydrolyzed to give putrescine. In the second pathway, arginine is converted into ornithine and then ornithine is converted into putrescine by ornithine decarboxylase (ODC). Putrescine, via metabolic intermediates including N-acetylputrescine, γ-aminobutyraldehyde (GABAL), N-acetyl-γ-aminobutyric acid (N-acetyl-GABAL), and N-acetyl-γ-aminobutyric acid (N-acetyl-GABA), biotransformations mediated by diamine oxidase (DAO), monoamine oxidase B (MAO-B), aminobutyraldehyde dehydrogenase (ABALDH), and other enzymes, can act as a minor biological precursor of γ-aminobutyric acid (GABA) in the brain and elsewhere. In 2021, it was discovered that MAO-B does not mediate dopamine catabolism in the rodent striatum but instead participates in striatal GABA synthesis and that synthesized GABA in turn inhibits dopaminergic neurons in this brain area. It has been found that MAO-B, via the putrescine pathway, importantly mediates GABA synthesis in astrocytes in various brain areas, including in the hippocampus, cerebellum, striatum, cerebral cortex, and substantia nigra pars compacta (SNpc).
Sources: en.wikipedia.org
For 2026 and subsequent years, qualified overtime compensation must be reported on Form W-2, box 12, code TT. Employers must report all qualified overtime compensation without regard to the tax limit of $12,500 ($25,000 if married filing jointly). An employee who is actively engaged in the management of their employer and owns at least a 20-percent equity interest in it is not eligible to take the tax deduction. Overtime compensation is not excluded or exempt from gross income. Employers continue to be required to withhold income taxes, social security taxes, and Medicare taxes from workers' overtime pay. An employee is allowed, however, to give their employer an updated Form W-4 that includes their acticipated tax deduction for qualified overtime compensation in Step 4(b).
After its expulsion from Malaysia, Singapore became independent as the "Republic of Singapore" on 9 August 1965, with Lee Kuan Yew and Yusof bin Ishak as the first prime minister and president respectively. In 1967, the country co-founded the Association of Southeast Asian Nations (ASEAN). Race riots erupted again in 1969 as a spillover from the 13 May incident in Malaysia. On this occasion, the unrest was more firmly contained. Lee's emphasis on rapid economic growth, racial integration, promotion of business entrepreneurship and curbs on democratic freedoms by governing with extensive legal powers shaped Singapore's policies for the next half century. Economic growth continued throughout the 1980s, with the unemployment rate falling to 3% and real GDP growth averaging at about 8% up until 1999. During the 1980s, Singapore began to shift towards high-tech industries, such as the wafer fabrication sector, in order to remain competitive as neighbouring countries began manufacturing with cheaper labour. Singapore Airlines was formed in 1972 and Changi Airport was opened in 1981, replacing the international airport at Paya Lebar. Lee's government capitalised on Singapore's favourable geographical position to develop the Port of Singapore into one of the world's busiest ports, while the service and tourism industries also expanded significantly during this period. The PAP has remained in power since 1959.
Felines, especially domestic cats, are well known for having penile spines. Upon withdrawal of a cat's penis, the spines rake the walls of the female's vagina, which may serve as a trigger for ovulation. Many other felid species have penile spines, but they are relatively small in jaguars and pumas, and do not occur in margays. Penile spines in chimpanzees and mice are small surface projections made by the piling up of keratinized cell layers in the outermost skin surface. They occur in wombats, koalas, spotted hyenas, fossas, echidnas, primates, bats, and several rodent species. Penile spines are often found in primate species that form copulatory plugs after mating. In galagos, penile spines may form a "genital lock" during copulation.
=== Pharmacology research === Pharmacological studies on synephrine date back to the late 1920s, when it was observed that injected synephrine raised blood pressure, constricted peripheral blood vessels, dilated pupils, stimulated the uterus, and relaxed the intestines in experimental animals. Representative of this early work is the paper by Tainter and Seidenfeld, who were the first researchers to systematically compare the different effects of the two synephrine enantiomers, d- and l- synephrine, as well as of the racemate, d,l-synephrine, in various animal assays. In experiments on anesthetized cats, Tainter and Seidenfeld confirmed earlier reports of the increase in blood pressure produced by intravenous doses of synephrine, showing that the median pressor doses for the isomers were: l-synephrine: 0.5 mg/kg; d,l-synephrine: 1.0 mg/kg; and d-synephrine: 2–20 mg/kg. These effects lasted 2–3 minutes, peaking at ~30 seconds after administration. l-Synephrine was thus the more potent enantiomer, with about 1/60x the potency of the standard pressor l-epinephrine in the same assay. A later study, by Lands and Grant, showed that a dose of ~0.6 mg/kg of racemic synephrine, given intravenously to anesthetized dogs, produced a rise in blood pressure of 34 mmHg lasting 5–10 minutes, and estimated that this pressor activity was about 1/300x that of epinephrine. Using cats and dogs, Tainter and Seidenfeld observed that neither d- nor l-synephrine caused any changes in the tone of normal bronchi, in situ, even at "maximum" doses.
=== Independent Grand Lodge of Colon === At the insistence of Albert Pike (after he had been allowed to return from exile to the United States), in 1867, the Grand Lodge of Colon under the leadership of Grand Master Andrés Puente, established its own constitution. Even though they recognized the sovereignty of the Supreme Council, their new constitution established that the Grand Lodge of Colon held the exclusive authority to enact its own bylaws, issue charters, and regulate its own Lodges. Albert Pike gave his staunch support and approval in the new autonomy of the Grand Lodge. The Supreme Council of the Scottish Rite in Cuba, however, outright refused to recognize any independent authority of the Grand Lodge of Colon. They dissolved the Grand Lodge and assumed all of its orders. On September 20, 1867, the Grand Lodge of Colon agreed to suspend their constitution until a joint meeting of the Supreme Council and the Grand Lodge could occur, where the parties were scheduled to discuss the situation. That meeting was scheduled to happen on November 25, 1868. That meeting never took place, due to the outbreak of the Ten Years' War.
Sources: en.wikipedia.org
=== Indoor ward === In second phase in April 2014, SIUT Chablani Medical center was upgraded to a full-fledged hospital, having 36-bed in its indoor ward. The indoor facilities reported 1,256 indoor admissions in same year and 33,918 patients went to the thrice-a-week outpatient clinic, 16,403 dialysis sessions were performed with 16 Hemodialysis machines, 2,400 patients received lithotripsy, the laboratory carried out 111,913 tests and 4,254 surgeries.
Whereas increasing the dose of opioid can be an effective way to overcome tolerance, doing so to compensate for opioid-induced hyperalgesia may worsen the patient's condition by increasing sensitivity to pain while escalating physical dependence. This "uncommon but important phenomenon [can be] seen with high-dose opioid therapy." However, the conclusion of a report published in the Journal of Pain and Palliative Care Pharmacotherapy suggests that "[h]yperalgesia shares a common mechanism with tolerance and it may be that hyperalgesia is a manifestation of tolerance itself."
=== Scaffolding === In 2013, using a 3D scaffolding of Matrigel in various configurations, substantial pancreatic organoids was produced in vitro. Clusters of small numbers of cells proliferated into 40,000 cells within one week. The clusters transform into cells that make either digestive enzymes or hormones like insulin, self-organizing into branched pancreatic organoids that resemble the pancreas. The cells are sensitive to the environment, such as gel stiffness and contact with other cells. Individual cells do not thrive; a minimum of four proximate cells was required for subsequent organoid development. Modifications to the medium composition produced either hollow spheres mainly composed of pancreatic progenitors, or complex organoids that spontaneously undergo pancreatic morphogenesis and differentiation. Maintenance and expansion of pancreatic progenitors require active Notch and FGF signaling, recapitulating in vivo niche signaling interactions. The organoids were seen as potentially offering mini-organs for drug testing and for spare insulin-producing cells. Aside from Matrigel 3D scaffolds, other collagen gel systems have been developed. Collagen/hyaluronic acid scaffolds have been used for modeling the mammary gland In Vitro while co-coculturing epithelial and adipocyte cells. The HyStem kit is another 3D platform containing ECM components and hyaluronic acid that has been used for cancer research. Additionally, hydrogel constituents can be chemically modified to assist in crosslinking and enhance their mechanical properties.
=== Clipfish === Over the centuries, several variants of dried fish have evolved. Stockfish, dried as fresh fish and not salted, is often confused with clipfish, in which the fish is salted before drying. After 2–3 weeks in salt the fish has saltmatured and is transformed from wet salted fish to clipfish through a drying process. The salted fish was earlier dried on rocks (clips) on the foreshore. The production method for clipfish (or bacalhau in Portuguese) was developed by the Portuguese, who first mined salt near the brackish water of Aveiro and brought it to Newfoundland, where cod was available in tremendous quantities. Salting was not economically feasible until the 17th century, when cheap salt from southern Europe became available to the maritime nations of northern Europe. Stockfish is cured in a process called fermentation in which cold-adapted bacteria matures the fish, similar to the maturing process of cheese. Clipfish is processed in a chemical curing process called saltmaturing, similar to the maturing processes of other saltmatured products like Parma ham.
Sources: en.wikipedia.org
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.