Everything below concerns Pro-Gly-Pro. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-17. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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 hydrophilic peptide and dissolves readily in water and in aqueous buffers. The lyophilised powder is typically a white to off-white solid. Because short peptides are prone to hydrolysis and oxidation, handling benefits from limiting exposure to heat, moisture and strong light. Working solutions are commonly prepared in sterile water or saline, and repeated freeze-thaw cycles are avoided to reduce aggregation and loss of activity. These practices reflect general laboratory convention rather than published stability specifications.
Dry powder is normally held at -20 degrees Celsius or lower, in a sealed container with desiccant and protection from light. Reconstituted solutions are usually kept at 2 to 8 degrees Celsius for short periods and frozen for longer ones. Proline residues at several positions are generally associated with some resistance to peptidase attack, but chemical stability still declines at neutral to alkaline pH and at elevated temperature. Exact shelf-life figures are product-specific and are not standardised across suppliers.
| 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 |
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Development took place at the Institute of Molecular Genetics of the Russian Academy of Sciences, where a series of short peptides were designed in the 1980s and 1990s. Selank was selected from variants of tuftsin that showed resistance to plasma peptidases. Russian regulatory approval covers it as an anxiolytic agent given intranasally. Outside that market the compound is normally handled as a research chemical rather than a medicine, and no widely recognised international pharmacopoeial monograph exists. The name Selank is a coined trade designation rather than a systematic chemical name.
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.
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.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
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.
== Growth conditions == External conditions such as acidity and temperature affect the growth rates of F. sanfranciscensis. A temperature of 33 °C (91 °F) leads to maximum growth rates, whereas temperatures over 41 °C (105 °F) completely inhibit the bacteria growth. And in terms of pH, most strains can tolerate levels as low as 3.6, but the optimal range for growth is slightly higher (around 4–5) as it is also the optimum pH for some of the key proteins involved—for example, those involved in maltose transport function optimally at 5.2–5.6. However, there is lots of intraspecies diversity within Fructilactobacillus sanfranciscensis, so the optimal temperature and pH for growth will vary from strain to strain, and depend on a variety of factors—namely, the type of carbon source for metabolism, and the resulting proteins involved. For instance, a common yeast in sourdough, K. humilis, prefers 27 °C (81 °F) and will not grow above 36 °C (97 °F).
=== Sleep, tobacco, and alcohol === Inadequate/irregular sleep and untreated obstructive sleep apnoea increase metabolic and CV risk. Smoking increases insulin resistance and CV risk; cessation reduces adverse outcomes. High alcohol intake raises BP, TGs, and hepatic steatosis; moderation is advised.
Progesterone converts the endometrium to its secretory stage to prepare the uterus for implantation. At the same time progesterone affects the vaginal epithelium and cervical mucus, making it thick and impenetrable to sperm. Progesterone is anti-mitogenic in endometrial epithelial cells, and as such, mitigates the tropic effects of estrogen. If pregnancy does not occur, progesterone levels will decrease, leading to menstruation. Normal menstrual bleeding is progesterone-withdrawal bleeding. If ovulation does not occur, and the corpus luteum does not develop, levels of progesterone may be low, leading to anovulatory dysfunctional uterine bleeding. During implantation and gestation, progesterone appears to decrease the maternal immune response to allow for the acceptance of the pregnancy. Progesterone decreases contractility of the uterine smooth muscle. This effect contributes to prevention of preterm labor. Studies have shown that in individuals who are pregnant with a single fetus, asymptomatic in the prenatal stage, and at a high risk of giving pre-term birth spontaneously, vaginal progesterone medication has been found to be effective in preventing spontaneous pre-term birth. Individuals who are at a high risk of giving pre-term birth spontaneously are those who have a short cervix of less than 25 mm or have previously given pre-term birth spontaneously. Although pre-term births are generally considered to be less than 37 weeks, these studies found that vaginal progesterone is associated with fewer pre-term births of less than 34 weeks.
Sources: en.wikipedia.org
On the morning of 21 December, Ceaușescu addressed an assembly of approximately 100,000 people to condemn the uprising in Timișoara. Party officials took great pains to make it appear that Ceaușescu was still immensely popular. Several busloads of workers, under threat of being fired, arrived in Bucharest's Piața Palatului (Palace Square, now Piața Revoluției – Revolution Square) and were given red flags, banners and large pictures of Ceaușescu. They were augmented by bystanders who were rounded up on Calea Victoriei.
=== Isomerisation === In dilute sodium hydroxide or other dilute bases, the monosaccharides mannose, glucose, and fructose interconvert (via a Lobry de Bruyn–Alberda–Van Ekenstein transformation), so that a balance between these isomers is formed. This reaction proceeds via an enediol:
With oral administration, progesterone is rapidly metabolized in the gastrointestinal tract and liver. As many as 30 different metabolites have been found to be formed from progesterone with oral ingestion. Regardless of the route of administration, 5α-reductase is the major enzyme involved in the metabolism of progesterone and is responsible for approximately 60 to 65% of its metabolism. 5β-Reductase is also a major enzyme in the metabolism of progesterone. 5α-Reduction of progesterone occurs predominantly in the intestines (specifically the duodenum), whereas 5β-reduction occurs almost exclusively in the liver. The metabolites of progesterone produced by 5α-reductase and 5β-reductase (after further transformation by 3α-hydroxysteroid dehydrogenase) are allopregnanolone and pregnanolone, respectively. With oral administration of progesterone, they occur in circulation at very high and in fact supraphysiological concentrations that are well in excess of those of progesterone itself (peak concentrations of 30 ng/mL for allopregnanolone and 60 ng/mL for pregnanolone versus 12 ng/mL for progesterone at 4 hours after a single 200-mg oral dose of progesterone). In one study, a single 200-mg oral dose of progesterone resulted in peak levels of 20α-dihydroprogesterone of around 1 ng/mL after 2 hours. The percentage constitutions of progesterone and its metabolites as reflected in serum levels have been determined for a single 100 mg dose of oral or vaginal progesterone.
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.
Dry powder is normally held at -20 degrees Celsius or below in a sealed, light-protected container with desiccant. Brief room-temperature handling during weighing is generally tolerated. Storage instructions vary between suppliers, so the accompanying certificate of analysis should be followed.