A practical reference on RP-HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-12-27 and is reviewed periodically as new material appears.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For lyophilized powder, long term |
| Common analytical method | Reverse-phase HPLC | Usually paired with mass spectrometry |
| Typical reported purity | At or above 95 percent by area | Research-grade material |
| Aqueous solubility | High | Solutions used in laboratory assays |
| Moisture sensitivity | Hydrolyzes in solution | Aseptic handling reduces degradation |
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 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.
Selank is a synthetic heptapeptide developed in Russia during the 1990s. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences designed it as a stabilized analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The compound has been studied primarily for its reported anxiolytic and nootropic effects. It remains largely unknown in Western pharmacology and is not approved as a medicine by major regulators such as the FDA or the EMA.
The primary structure of Selank is Thr-Lys-Pro-Arg-Pro-Gly-Pro, corresponding to the molecular formula C33H57N11O9 and a monoisotopic mass of roughly 751.9 daltons. The N-terminal threonine and the arginine residue in the fourth position are shared with tuftsin, which carries the sequence Thr-Lys-Pro-Arg. The three additional residues at the C-terminus, Pro-Gly-Pro, extend the chain and are associated with greater resistance to enzymatic degradation. This extension also separates Selank from the shorter parent peptide.
Naming conventions place Selank in the same research family as Semax, another Russian-developed peptide investigated for cognitive effects. The two compounds share a lineage but differ in sequence and in the biological systems proposed as their targets. Semax descends from ACTH fragments, whereas Selank descends from tuftsin. Publications sometimes identify Selank by its full peptide sequence or by laboratory codes rather than one uniform trade name. Because replication outside Russia is limited, reports on its properties are best read alongside the study design and the purity of the material tested.
The Treuhand's operations drew criticism for unnecessarily closing allegedly profitable businesses, misuse and waste of funds, and layoffs that were claimed to be unnecessary. It also drew substantial protest from the workforces affected, as 2.5 million employees in state-owned enterprises (out of 4 million in total) were laid off in the early 1990s. Supporters argued that not placing the former state-owned enterprises into private hands would have caused the loss of many more jobs and slowed economic recovery. On 1 April 1991, chairman of the Treuhand Detlev Karsten Rohwedder was shot dead by an unknown assassin (possibly the Red Army Faction). He was succeeded by Birgit Breuel. The trust itself was extraordinarily unprofitable, such that, when its operations ended in 1994, it had amassed 260 to 270 billion DM in debt, equal to around 350 billion United States dollars in 2025.
== Disadvantages == Handling of small quantities is not always simple. Higher accuracy of weighing is necessary (e.g. use of accurate balance). Sample surface preparation can have a major impact on measurement results.
The association of bacterial species with the production of the toxin is unequivocal – Lago and coworkers state, "[e]ndocellular symbiotic bacteria have been proposed as a possible source of eukaryotic TTX by means of an exogenous pathway", and Chau and coworkers note that the "widespread occurrence of TTX in phylogenetically distinct organisms... strongly suggests that symbiotic bacteria play a role in TTX biosynthesis" – although the correlation has been extended to most but not all animals in which the toxin has been identified. To the contrary, there has been a failure in a single case, that of newts (Taricha granulosa), to detect TTX-producing bacteria in the tissues with highest toxin levels (skin, ovaries, muscle), using PCR methods, although technical concerns about the approach have been raised. Critically for the general argument, Takifugu rubripes puffers captured and raised in laboratory on controlled, TTX-free diets "lose toxicity over time", while cultured, TTX-free Takifugu niphobles puffers fed on TTX-containing diets saw TTX in the livers of the fishes increase to toxic levels. Hence, as bacterial species that produce TTX are broadly present in aquatic sediments, a strong case is made for ingestion of TTX and/or TTX-producing bacteria, with accumulation and possible subsequent colonization and production.
Sources: en.wikipedia.org
== Contraindications == Contraindications of elagolix include pregnancy, known osteoporosis, severe hepatic impairment, and concomitant use with strong organic anion-transporting polypeptide (OATP) 1B1 inhibitors such as ciclosporin and gemfibrozil. Elagolix may increase the risk of miscarriage in early pregnancy. Women should avoid pregnancy while taking elagolix, for instance by using birth control, and should discontinue the medication if they become or wish to become pregnant. Elagolix should not be used in women with osteoporosis because it may increase the risk of further bone loss. Severe hepatic impairment is associated with 7-fold increased exposure to elagolix, which may increase the risk of bone loss. In women with moderate hepatic impairment, which is associated with 3-fold increased exposure to elagolix, the medication at 200 mg twice per day should not be used, while 150 mg once per day should be used for no more than 6 months. OATP1B1 inhibitors are likely to greatly increase exposure to elagolix similarly to moderate to severe hepatic impairment. Combined birth control is not contraindicated with elagolix, but because of the estrogen component, is expected to decrease the effectiveness of elagolix in the treatment of endometriosis, and hence is not recommended. Other forms of birth control, such as non-hormonal birth control, can be used instead. Elagolix is not contraindicated in women who are breastfeeding, but it is unknown whether the medication is excreted in breast milk or if it has adverse effects on milk production or the breastfed child.
=== Folk medicine === In myths and folk medicine, honey was used both orally and topically to treat various ailments including gastric disturbances, ulcers, skin wounds, and skin burns by ancient Greeks and Egyptians, and in Ayurveda and traditional Chinese medicine.
=== Australia === Pizza Hut expanded to Australia in 1970, opening its first dine-in restaurant in Belfield in April 1970. In September 2016, private equity firm Allegro Funds and a local management team bought the master franchise agreement for Pizza Hut in Australia from Yum! Brands. In November 2016, Pizza Hut acquired Australian pizza chain Eagle Boys. Half of the Eagle Boys stores were converted to Pizza Hut stores by Christmas 2016 while the remainder were converted by April 2017. In June 2023, Allegro sold Pizza Hut Australia to US franchise operator Flynn Restaurant Group. As of June 2023, there are about 260 Pizza Hut stores in Australia. In May 2024, Australian franchisee Pizza Pan Group was penalized with a AU$2.5 million fine for sending 10 million marketing spam messages over four months in violation of Australian spam laws. It had been directed to report regularly to the Australian Communications and Media Authority.
== Origin == The first symptoms of apitoxin (bee venom), that are now thought to be caused by apamin, were described back in 1936 by Hahn and Leditschke. Apamin was first isolated by Habermann in 1965 from Apis mellifera, the Western honey bee. Apamin was named after this bee. Bee venom contains many other compounds, like histamine, phospholipase A2, hyaluronidase, MCD peptide, and the main active component melittin. Apamin was separated from the other compounds by gel filtration and ion exchange chromatography.
Sources: en.wikipedia.org
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.
Lyophilized powder is usually kept frozen and protected from moisture. Solutions are less stable and are often used promptly or divided into aliquots to avoid repeated freeze-thaw cycles. Exact shelf-life values depend on purity and handling.
No. A purity figure derived from chromatographic area does not prove the amino acid sequence. Identity requires an orthogonal method such as mass spectrometry or sequencing. Truncated or isomerized peptides can co-elute with the target compound.
Identity is confirmed by matching the retention time in reversed-phase chromatography against a reference standard and by measuring the molecular mass with mass spectrometry. Tandem mass spectrometry or amino acid analysis can verify the sequence of the seven residues. Because the peptide contains no aromatic amino acids, detection at 280 nm is not useful.