A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-03-29. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic heptapeptide | Stabilized analog of tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Monoisotopic mass about 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as lyophilized solid |
| Solubility | Freely soluble in water | Also soluble in common polar solvents |
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, with mass spectrometry used to confirm molecular mass and sequence information. Amino acid analysis and peptide mapping may supplement these methods. Certified reference standards are scarce, and many commercial lots are sold as research chemicals without a pharmacopoeial monograph. Regulatory treatment differs by country: Selank is a registered prescription medicine in Russia, while in the European Union and the United States it is not an approved drug and may fall under research-chemical or unapproved-product frameworks.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
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.
Furthermore, the NP protein plays a crucial role in enhancing primary transcription. Without newly synthesized NP protein, early transcription occurs at minimal levels, while its presence restores normal transcriptional activity. These findings indicate that the synthesis of these proteins facilitates the transition from preliminary to efficient transcription, underscoring their importance in the viral life cycle.
=== Bronchoalveolar lavage === Bronchoalveolar lavage (BAL) is a well-tolerated diagnostic procedure in ILD. BAL cytology analyses (differential cell counts) should be considered in the evaluation of patients with IPF at the discretion of the treating physician based on availability and experience at their institution. BAL may reveal alternative specific diagnoses: malignancy, infections, eosinophilic pneumonia, histiocytosis X, or alveolar proteinosis. In the evaluation of patients with suspected IPF, the most important application of BAL is in the exclusion of other diagnoses. Prominent lymphocytosis (>30%) generally allows excluding a diagnosis of IPF.
== Regulation == Some of the strategies for regulating retinal dehydrogenases are only now becoming more clear after in vivo regulation remained mysterious for some time, though much of the current research on regulation has focused on the modulation of gene expression rather than direct protein regulation. Dendritic cells in the gut help in modulating immune tolerance through the activity of retinal dehydrogenase; expression in these cells may be driven by a TNF receptor, 4-1-BB. It was also shown that the expression of a certain retinal dehydrogenase found in humans, retinal short-chain dehydrogenase/reductase (retSDR1), is increased by tumor-suppressor proteins p53 and p63, suggesting that retSDR1 may have tumor-preventing activities. Expression of retinal dehydrogenase types 1 and 2 genes is enhanced by the addition of cholesterol or cholesterol derivatives. Disulfiram is a drug used to artificially regulate aldehyde dehydrogenase activity in patients with alcoholism by inhibiting the activity of aldehyde dehydrogenases, though it is not specific to retinal dehydrogenase. Other exogenous molecules have also been found to inhibit retinal dehydrogenase activity including nitrofen, 4-biphenyl carboxylic acid, bisdiamine, and SB-210661.
=== Amyloid formation === Although ELPs generally form reversible spherical aggregates due to their proline and glycine content, there is a possibility that, under certain conditions such as exceedingly high temperatures, ELPs will form amyloids, or irreversible aggregates of insoluble protein. It is also believed that changes in the ELP backbone leading to a reduction in the proline and glycine content may lead to ELPs with a greater propensity for the amyloid state. As amyloids are implicated in the progression of Alzheimer's disease as well as in prion-based diseases, such as Creutzfeldt-Jakob disease (CJD), modeling of ELP amyloid formation may be useful from a biomedical standpoint.
=== Distillation === Since liquids often have different boiling points, mixtures or solutions of liquids or gases can typically be separated by distillation, using heat, cold, vacuum, pressure, or other means. Distillation can be found in everything from the production of alcoholic beverages, to oil refineries, to the cryogenic distillation of gases such as argon, oxygen, nitrogen, neon, or xenon by liquefaction (cooling them below their individual boiling points).
Sources: en.wikipedia.org
Some experts noted that the Maduro government had previously attempted to offer the US access to these minerals in a failed attempt to stave off military action, with the ongoing operations marking a return to "resource imperialism". Trump stated on the day of the military operation that US oil companies would invest billions to increase oil production in the country; ExxonMobil, ConocoPhillips, and Chevron Corporation (the US oil majors) reportedly had no prior knowledge of the operation to remove Maduro and unnamed sources said they had no discussions with the Trump administration before the operation about investing in the country if Maduro was removed. Trump further stated that US oil companies would invest $100 billion in Venezuelan oil production; in a meeting between Trump and two dozen oil company executives on 9 January, ExxonMobil CEO Darren Woods stated that Venezuela was "uninvestable" due to the legal framework in the country while the majority of the executives in attendance did not make firm investment commitments. ExxonMobil and ConocoPhillips left Venezuela after their assets were expropriated in 2007, while Chevron continued its operations. Two days after the meeting, Trump told reporters that he was "inclined" to keep ExxonMobil out of Venezuela because he "didn't like Exxon's response" to his proposed investments for the country and thought that "They're playing too cute." Unlike Congress, Trump claimed to have spoken with oil companies both "before and after".
There were other witnesses for the defense who did not show up. Several scientists who had been listed as potential witnesses for the state, backed out because of what Clark termed "peer pressure." Another state witness, Dr. Dean Kenyon, a biophysicist at San Francisco State University, mysteriously disappeared on the eve of his day in court. He had flown into Little Rock on a Sunday evening, but when one of Clark's assistants went to take his deposition he could not find him. Kenyon had checked out of the hotel and flown back home. Bird had encouraged Kenyon not to testify, although Kenyon taught evolution theory for 16 years until three years ago when he became a creationist. Bird, who is general counsel to Institute for Creation Research, said he attempted to get other defense witnesses not to testify after he perceived the trial as botched by Clark.
Even more surprising, the researchers determined that the girl's mother's genome was more closely related to Western European Neanderthal DNA, excavated thousands of miles away at the Vindija Cave, Croatia, than the Neanderthals who lived in the Siberian cave where her daughter's remains were found. This finding suggests that Neanderthals migrated in multiple waves from Western Europe to Central Eurasia and encountered the Denisovans several times over a span of tens of thousands of years, and possibly coexisted with them for periods of time.
=== Veterinary use === An SSRI (fluoxetine) has been approved for veterinary use in treatment of canine separation anxiety. Like in human medicine, fluoxetine is extensively used off-label in animal medicine. In dogs and cats, it is mainly prescribed off-label for behavior problems.
Sources: en.wikipedia.org
Selank is a synthetic heptapeptide designed as a stabilized analog of the natural tetrapeptide tuftsin. It has been investigated mainly for anxiolytic and cognitive effects. It is not an approved pharmaceutical in most countries.
It was developed in Russia, at the Institute of Molecular Genetics of the Russian Academy of Sciences, during the 1990s. Most published research originates from Russian institutions. Independent international replication remains limited.
Tuftsin is a natural tetrapeptide with the sequence Thr-Lys-Pro-Arg that participates in immune signaling. Selank extends that sequence with Pro-Gly-Pro at the C-terminus. The added residues are linked to greater resistance to enzymatic breakdown.
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.