The short version of Peptidase stability fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Modeled on tuftsin |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues |
| Approximate molecular mass | Around 750 Da | Depends on counter-ion and hydration |
| Common forms | Lyophilized powder | Also described as aqueous solution |
| Primary origin of research | Russian laboratories | Mid-1990s onward |
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.
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.
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.
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.
=== 241Am === Americium-241 is a candidate isotope with much greater availability than 238Pu. Though 241Am has a half-life of 432 years, which is about five times longer than that of 238Pu and could hypothetically power a device for centuries, missions with more than 10 years were not the subject of the research until 2019. The power density of 241Am is only one-fourth that of 238Pu, and 241Am produces more penetrating radiation through decay chain products than 238Pu and needs more shielding. Its shielding requirements in a RTG are the third lowest: only 238Pu and 210Po require less. With a current global shortage of 238Pu, 241Am is being studied as RTG fuel by ESA and in 2019, UK's National Nuclear Laboratory announced the generation of usable electricity. An advantage over 238Pu is that it is produced as nuclear waste and is nearly isotopically pure. Prototype designs of 241Am RTGs expect 2–2.2 We/kg for 5–50 We RTGs design but in practical testing dropped to 1.3–1.9 We/kg. Americium-241 is currently used in small quantities in household smoke detectors and thus its handling and properties are well-established. However, it decays to neptunium-237, the most chemically mobile among the actinides.
These studies, albeit limited in the quality of their findings, reported no benefit of progestogens on breast development in transgender women. This has also been the case in limited clinical experience. Progestogens have some antiestrogenic effects in the breasts, for instance decreasing expression of the estrogen receptor and increasing expression of estrogen-metabolizing enzymes, and for this reason, have been used to treat breast pain and benign breast disorders. Progesterone levels during female puberty do not normally increase importantly until near the end of puberty in cisgender girls, a point by which most breast development has already been completed. In addition, concern has been expressed that premature exposure to progestogens during the process of breast development is unphysiological and might compromise final breast growth outcome, although this notion presently remains theoretical. Though the role of progestogens in pubertal breast development is uncertain, progesterone is essential for lobuloalveolar maturation of the mammary glands during pregnancy. Hence, progestogens are required for any transgender woman who wishes to lactate or breastfeed. A study found full lobuloalveolar maturation of the mammary glands on histological examination in transgender women treated with an estrogen and high-dose cyproterone acetate. However, lobuloalveolar development reversed with discontinuation of cyproterone acetate, indicating that continued progestogen exposure is necessary to maintain the tissue.
== History == Bromley is first recorded in an Anglo-Saxon charter of 862 as Bromleag and means 'woodland clearing where broom grows'. It shares this Old English etymology with Great Bromley in eastern Essex, but not with the Bromley in the East End of London. The history of Bromley is closely connected with the See of Rochester. In AD 862 Ethelbert, the King of Kent, granted land to form the Manor of Bromley. In 1185 Bromley Palace was built by Gilbert Glanvill, Bishop of Rochester. Pilgrims came to the town to visit St. Blaise's Well. The Palace was held by the Bishops until 1845, when Coles Child, a wealthy local merchant and philanthropist, purchased Bromley Palace and became lord of the manor. The town was an important coaching stop on the way to Hastings from London, and the Royal Bell Hotel (which has recently been reopened as of January 2026 and is just off Market Square) is referred to in Jane Austen's Pride and Prejudice. It was a quiet rural village until the arrival of the railway in 1858 in Shortlands, which led to rapid growth, and outlying suburban districts such as Bickley (which later overflowed into Bromley Common) were developed to accommodate those wishing to live so conveniently close to London. Bromley, also known as Bromley St Peter and St Paul, formed an ancient parish in the Bromley and Beckenham hundred and the Sutton-at-Hone lathe of Kent. In 1840 it became part of the expanded Metropolitan Police District. The parish adopted the Local Government Act 1858 and a local board was formed in 1867.
Sources: en.wikipedia.org
=== MeSH D12.644.468 – opioid peptides === MeSH D12.644.468.180 – dynorphins MeSH D12.644.468.241 – endorphins MeSH D12.644.468.241.030 – alpha-endorphin MeSH D12.644.468.241.080 – beta-endorphin MeSH D12.644.468.241.360 – gamma-endorphin MeSH D12.644.468.281 – enkephalins MeSH D12.644.468.281.075 – enkephalin, ala(2)-mephe(4)-gly(5)- MeSH D12.644.468.281.231 – enkephalin, leucine MeSH D12.644.468.281.231.300 – enkephalin, leucine-2-alanine MeSH D12.644.468.281.381 – enkephalin, methionine MeSH D12.644.468.281.381.300 – d-ala(2),mephe(4),met(0)-ol-enkephalin MeSH D12.644.468.281.600 – enkephalin, d-penicillamine (2,5)-
=== Brand names === It is sold under the brand names Heartgard, Sklice, and Stromectol in the United States, Ivomec worldwide by Merial Animal Health, Mectizan in Canada by Merck, Iver-DT in Nepal by Alive Pharmaceutical and Ivexterm in Mexico by Valeant Pharmaceuticals International. In Southeast Asian countries, it is marketed by Delta Pharma Ltd. under the trade name Scabo 6. The formulation for rosacea treatment is sold under the brand name Soolantra. While in development, it was assigned the code MK-933 by Merck.
In patients with non-severe asymptomatic aortic valve stenosis, increased age- and sex adjusted N-terminal pro-brain natriuretic peptide (NT-proBNP) levels alone and combined with a 50% or greater increase from baseline had been found associated with increased event rates of aortic valve stenosis related events (cardiovascular death, hospitalization with heart failure due to progression of aortic valve stenosis, or aortic valve replacement surgery). In patients with non-severe asymptomatic aortic valve stenosis and no overt coronary artery disease, the increased troponin T (above 14 pg/mL) was found associated with an increased 5-year event rate of ischemic cardiac events (myocardial infarction, percutaneous coronary intervention, or coronary artery bypass surgery).
== Preparation == Divinyl sulfone is prepared from the diacetate bis(2-hydroxyethyl)sulfide. Oxidation of this diester with hydrogen peroxide gives the sulfone. The sulfone is then pyrolyzed to induce elimination of two equivalents of acetic acid:
Sources: en.wikipedia.org
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.
It originates from research in Russia, associated with the Institute of Molecular Genetics of the Russian Academy of Sciences. The first descriptions date to the mid-1990s. Most published studies come from Russian laboratories.
No, Selank itself does not occur naturally. Its backbone is based on tuftsin, which is produced in the body, but the seven-residue version is a synthetic construct. It is supplied as a manufactured peptide.
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.