A practical reference on reversed-phase HPLC: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-05 and is reviewed periodically as new material appears.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
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.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
| Property | Value | Notes |
|---|---|---|
| Typical purity report | 95% or higher by HPLC | Area percentage at 214 nm |
| Identity confirmation | Mass spectrometry | Electrospray or MALDI |
| Powder storage | -20 C, desiccated | Protect from light |
| Solution storage | 2-8 C short term | Freeze aliquots for longer |
| Quality document | Certificate of analysis | States method and value |
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.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
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.
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.
== History == Paniz-Mondolfi was born in Caracas, Venezuela in 1976. His mother is a pediatrician and his father an architect. His grandfather, Edgardo Mondolfi Otero, a biologist and zoologist. Two of his uncles were physicians with special ambitions in the field of sciences and research. His childhood was shared between Caracas and Kenya. Paniz-Mondolfi has a master's degree in parasitology and tropical diseases; he did international fellowships in microbiology, molecular genetics, and skin disease. He also did a second medical residency in the United States in pathology. He isolated and described a new species of parasite that had infected a NY resident, and a new mycobacterium that sickened two people in Connecticut. He earned an MD and PhD and studied under Jacinto Convit the leprosy researcher. He was a pathologist at the IDB Biomedical Research Institute in Barquisimeto, Venezuela until 2019 when he fled to the United States. He is the founder of the Venezuelan Science Incubator, an independent health research organization. Paniz-Mondolfi is assistant professor of pathology, molecular and cell-based medicine at the Mount Sinai Icahn School of Medicine. He is also affiliated with the Yale Cancer Center. In 2020 he focused his research on the COVID-19 pandemic and the effects the virus had on minority children. His research findings have been published in several medical journals including: the European Society of Clinical Microbiology and Infectious Diseases, The American Association for the Advancement of Science, and The Lancet.
Unit I – Bonthapally: The primary manufacturing hub situated in Bonthapally village, Medak District, Telangana, with multiple production blocks including kilo labs and quality assurance laboratories. It holds approvals from major regulatory agencies and supports commercial API production. Unit II – Pashamylaram: A large-scale manufacturing facility comprising multiple production blocks, an engineering workshop, and warehouses. Unit III – Gaddapotharam: A multi-product facility designed for advanced intermediates and APIs, with analytical development and pilot plant capabilities. R&D Centre – Bonthapally: Research and development centre with a team of approximately 360 scientists, pilot labs, and analytical capabilities to catalyze process development and technology transfer.
=== Structure === Scaffolds are used in tissue engineering to create an environment with similar mechanical properties of the native tissue. Scaffolds must be biocompatible and have high compressive strength. Scaffolds can be created from hydrogels, polymers or other material. Hydrogels are lightly cross-linked polymer networks swollen with water. Degree of crosslinking, porosity, and polymer composition can be tuned to create a hydrogel with similar properties to native cartilage. Researchers have been exploring the use of hydrogels as a cartilage substitute since the 1970s.
Sources: en.wikipedia.org
It was also found that 48Ca and 58Fe projectiles had a similar yield for the fusion-fission pathway, suggesting possible future use of 58Fe projectiles in making superheavy elements. It has also been suggested that a neutron-rich flerovium isotope can be formed by quasifission (partial fusion followed by fission) of a massive nucleus. Recently it has been shown that multi-nucleon transfer reactions in collisions of actinide nuclei (such as uranium and curium) might be used to make neutron-rich superheavy nuclei in the island of stability, though production of neutron-rich nobelium or seaborgium is more likely. Theoretical estimates of alpha decay half-lives of flerovium isotopes, support the experimental data. The fission-survived isotope 298Fl, long expected to be doubly magic, is predicted to have alpha decay half-life ~17 days. Making 298Fl directly by a fusion–evaporation pathway is currently impossible: no known combination of target and stable projectile can give 184 neutrons for the compound nucleus, and radioactive projectiles such as 50Ca (half-life 14 s) cannot yet be used in the needed quantity and intensity.
The Guardian described the situation as a "dual blockade", saying that while the US Navy could blockade Iranian ports, it had been unable to stop Iran's blockade and open the strait to allies. Israel and Lebanon agreed a three-week extension of their ceasefire. On 8 June, the IDF announced that it struck military sites in Iran, with explosions reported in Tehran, Isfahan, and Tabriz. This triggered an exchange between the two countries. Two Iranian soldiers were killed in an Israeli attack. Iran afterwards said it had ceased military actions against Israel. Israel stopped strikes at Trump's request. On 9 June, The New York Times reported that American crew was rescued after a helicopter went down near the strait. CENTCOM said they were rescued by a US Navy drone boat for the first time. Trump said Iranians had shot down the helicopter and pledged to respond. A US official said a Shahed one-way attack drone downed the helicopter. Iran said it did not deliberately target the helicopter. CENTCOM later said that it launched "self-defense" strikes in retaliation. One attack damaged water reservoir tanks in Sirik; Iran stated that 20,000 people had lost access to drinking water. On 14 June, Iran said that the draft US deal included Tehran agreeing not to produce or acquire nuclear weapons, and the US agreeing to allow Tehran to dilute its highly enriched uranium stockpile in Iran. Trump and Iran announced they had reached an agreement to end the war and reopen the strait. Trump said he had authorized the lifting of the US blockade.
==== Eulipotyphlan research ==== Valenzuela et al. (2026) study the evolution of the postcranial skeleton in the lineage of Nesiotites from the Pliocene to the Holocene, reporting that members of the studied lineage underwent a size shift throughout their evolutionary history but retained adaptations to terrestrial generalist locomotion. A study on the composition and evolution of Miocene erinaceid assemblages from the Daroca-Calamocha area (Spain) is published by Cailleux et al. (2026). Cailleux (2026) identifies common dental pathologies in the fossil material of Galerix stehlini from the Miocene strata from La Grive-Saint-Alban (France), and interprets their recurrence as possibly linked to small population size linked to habitat fragmentation.
Sources: en.wikipedia.org
Purity is usually reported as an HPLC area percentage, most often measured at 214 nm. Identity is confirmed separately by mass spectrometry. A certificate of analysis should state both the method and the observed value.
Dry powder is kept frozen, desiccated, and shielded from light. Dissolved material is aliquoted and frozen to limit freeze-thaw cycles. Short-term refrigerated storage is common for working solutions.
Russia registers it as a prescription nasal product. Most other markets classify it as a research chemical with no approved medical use. Oversight of purity and labeling is consequently minimal in those markets.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.