If you have been reading about Reversed-phase HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-06-06. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised solid form |
| Solubility class | Freely soluble in water | Hydrophilic heptapeptide |
| Dry storage temperature | -20 degrees Celsius or lower | Sealed, desiccated, protected from light |
| Solution storage | 2 to 8 degrees Celsius short term | Avoid repeated freeze-thaw cycles |
| Common identification method | Reversed-phase HPLC with mass spectrometry | Confirms purity and molecular mass |
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.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, 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.
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.
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.
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Subfamily ABCC contains thirteen members and nine of these transporters are referred to as the Multidrug Resistance Proteins (MRPs). The MRP proteins are found throughout nature and they mediate many important functions. They are known to be involved in ion transport, toxin secretion, and signal transduction. Of the nine MRP proteins, four of them, MRP4, 5, 8, 9, (ABCC4, 5, 11, and 12), have a typical ABC structure with four domains, comprising two membrane spanning domains, with each spanning domain followed by a nucleotide binding domain. These are referred to as short MRPs. The remaining 5 MRP's (MRP1, 2, 6, 7) (ABCC1, 2, 3, 6 and 10) are known as long MRPs and feature an additional fifth domain at their N terminus. CFTR, the transporter involved in the disease cystic fibrosis, is also considered part of this subfamily. Cystic fibrosis occurs upon mutation and loss of function of CFTR. The sulfonylurea receptors (SUR), involved in insulin secretion, neuronal function, and muscle function, are also part of this family of proteins. Mutations in SUR proteins are a potential cause of Neonatal diabetes mellitus. SUR is also the binding site for drugs such as sulfonylureas and potassium-channel openers activators such as diazoxide.
Heteroduplex analysis (HDA) is a method in biochemistry used to detect point mutations in DNA (Deoxyribonucleic acid) since 1992. Heteroduplexes are dsDNA molecules that have one or more mismatched pairs, on the other hand homoduplexes are dsDNA which are perfectly paired. This method of analysis depend up on the fact that heteroduplexes shows reduced mobility relative to the homoduplex DNA. heteroduplexes are formed between different DNA alleles. In a mixture of wild-type and mutant amplified DNA, heteroduplexes are formed in mutant alleles and homoduplexes are formed in wild-type alleles. There are two types of heteroduplexes based on type and extent of mutation in the DNA. Small deletions or insertion create bulge-type heteroduplexes which is stable and is verified by electron microscope. Single base substitutions creates more unstable heteroduplexes called bubble-type heteroduplexes, because of low stability it is difficult to visualize in electron microscopy. HDA is widely used for rapid screening of mutation of the 3 bp p.F508del deletion in the CFTR gene.
Research in 2018 into the treatment of central nervous system infections caused by free-living amoebae such as Naegleria fowleri and Acanthamoeba castellanii, tested the effectiveness of existing drugs as well as the effectiveness of the same drugs when they were conjugated with silver nanoparticles. In vitro tests demonstrated more potent amoebicidal effects for the drugs when conjugated with silver nanoparticles as compared to the same drugs when used alone. They also found that conjugating the drugs with silver nanoparticles enhanced their anti-acanthamoebic activity. Silver-halide imaging plates used with X-ray imaging were the standard before digital techniques arrived; these function essentially the same as other silver-halide photographic films, although for x-ray use the developing process is very simple and takes only a few minutes. Silver x-ray film remains popular for its accuracy, and cost effectiveness, particularly in developing countries, where digital X-ray technology is usually not available.
Sources: en.wikipedia.org
Gary J. Patti is an American biochemist known for his research in metabolism and for using mass spectrometry to characterize biological processes. He is the Michael and Tana Powell Professor at Washington University in St. Louis. He is co-founder and Chief Scientific Officer of Panome Bio and an Associate Editor for Clinical & Translational Metabolism. Biemann Medal, 2024 ACS Midwest Award, 2023 Academy of Science Innovation Award, 2016 Edward Mallinckrodt Jr. Scholar Award, 2016 Pew Biomedical Scholars Award, 2015 Alfred P. Sloan Award, 2014 Camille Dreyfus Teacher-Scholar Award, 2014 Gary Patti publications indexed by Google Scholar
Case report forms are manually filled at site and mailed to the company for which trial is being performed. The data on forms is transferred to the CDMS tool through data entry. The most popular method being double data entry where two different data entry operators enter the data in the system independently and both the entries are compared by the system. In case the entry of a value conflicts, system alerts and a verification can be done manually. Another method is Single Data Entry. The data in CDMS are then transferred for the data validation. Also, in these systems during validation the data clarification from sites are done through paper forms, which are printed with the problem description and sent to the investigator site and the site responds by answering on forms and mailing them back.
Mouse MA-10 cells respond to 5-oxo-ETE but lack OXER1. It has been suggested that these cells' responses to 5-oxo-ETE are mediated by an ortholog to OXER1, mouse niacin receptor 1, Niacr1, which is a G protein-coupled receptor for niacin, or, alternatively, by one or more of the mouse hydroxycarboxylic acid (HCA) family of the G protein-coupled receptors, HCA1 (GPR81), HCA2 (GPR109A), and HCA3 (GPR109B), which are G protein-coupled receptors for fatty acids.
Reactions of acids are often generalized in the form HA ⇌ H+ + A−, where HA represents the acid and A− is the conjugate base. This reaction is referred to as protolysis. The protonated form (HA) of an acid is also sometimes referred to as the free acid. Acid–base conjugate pairs differ by one proton, and can be interconverted by the addition or removal of a proton (protonation and deprotonation, respectively). The acid can be the charged species and the conjugate base can be neutral in which case the generalized reaction scheme could be written as HA+ ⇌ H+ + A. In solution there exists an equilibrium between the acid and its conjugate base. The equilibrium constant K is an expression of the equilibrium concentrations of the molecules or the ions in solution. Brackets indicate concentration, such that [H2O] means the concentration of H2O. The acid dissociation constant Ka is generally used in the context of acid–base reactions. The numerical value of Ka is equal to the product (multiplication) of the concentrations of the products divided by the concentration of the reactants, where the reactant is the acid (HA) and the products are the conjugate base and H+.
Sources: en.wikipedia.org
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.
Reversed-phase HPLC establishes purity, while mass spectrometry confirms the expected molecular mass. Sequence confirmation may use tandem mass spectrometry or peptide mapping. A certificate of analysis typically reports these results alongside the analytical method applied.
In Russia it is a registered medicine available by prescription. In many other countries it is not approved for human use and is supplied only as a research chemical. Import and possession rules differ by jurisdiction, and buyers are responsible for checking local requirements.
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.