Everything below concerns Semax. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-14. Numbers and descriptions here follow the published literature rather than marketing material.
Solubility behavior is a practical concern for handling. Selank dissolves readily in water and in common aqueous buffers, which simplifies preparation of working solutions. The choice of solvent, ionic strength, and pH can influence aggregation over time, particularly at higher concentrations. Aqueous solutions are typically sterile-filtered before use. Because stability depends on several variables, storage and handling notes should be treated as general guidance rather than fixed rules, and specific values are best confirmed against a certificate of analysis for each batch.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Also in aqueous buffers |
| Typical purity (HPLC) | 95 percent or higher | Lot-dependent |
| Dry powder storage | Minus 20 degrees Celsius | Sealed, dry, protected from light |
| Solution storage | 2 to 8 degrees Celsius | Short-term use |
| Identity confirmation | Mass spectrometry | ESI or MALDI-TOF |
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.
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.
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.
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.
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.
Protein + drug ⇌ Protein-drug complex Notably, it is the unbound fraction which exhibits pharmacologic effects. It is also the fraction that may be metabolized and/or excreted. For example, the "fraction bound" of the anticoagulant warfarin is 97%. This means that out of the amount of warfarin in the blood, 97% is bound to plasma proteins. The remaining 3% (the fraction unbound) is the fraction that is actually active and may be excreted. Protein binding can influence the drug's biological half-life. The bound portion may act as a reservoir or depot from which the drug is slowly released as the unbound form. Since the unbound form is being metabolized and/or excreted from the body, the bound fraction will be released in order to maintain equilibrium. Since albumin is alkalotic, acidic and neutral drugs will primarily bind to albumin. If albumin becomes saturated, then these drugs will bind to lipoprotein. Basic drugs will bind to the acidic alpha-1 acid glycoprotein. This is significant because various medical conditions may affect the levels of albumin, alpha-1 acid glycoprotein, and lipoproteins.
Around 90% of the protein structures available in the Protein Data Bank have been determined by X-ray crystallography. This method allows one to measure the three-dimensional (3-D) density distribution of electrons in the protein, in the crystallized state, and thereby infer the 3-D coordinates of all the atoms to be determined to a certain resolution. Roughly 7% of the known protein structures have been obtained by nuclear magnetic resonance (NMR) techniques. For larger protein complexes, cryo-electron microscopy can determine protein structures. The resolution is typically lower than that of X-ray crystallography, or NMR, but the maximum resolution is steadily increasing. This technique is still a particularly valuable for very large protein complexes such as virus coat proteins and amyloid fibers. General secondary structure composition can be determined via circular dichroism. Vibrational spectroscopy can also be used to characterize the conformation of peptides, polypeptides, and proteins. Two-dimensional infrared spectroscopy has become a valuable method to investigate the structures of flexible peptides and proteins that cannot be studied with other methods. A more qualitative picture of protein structure is often obtained by proteolysis, which is also useful to screen for more crystallizable protein samples. Novel implementations of this approach, including fast parallel proteolysis (FASTpp), can probe the structured fraction and its stability without the need for purification.
By choosing porous graphitic carbon as a stationary phase for liquid chromatography, even non derivatized glycans can be analyzed. Electrospray ionisation (ESI) is frequently used for this application.
== Applications == Stability constant values are exploited in a wide variety of applications. Chelation therapy is used in the treatment of various metal-related illnesses, such as iron overload in β-thalassemia sufferers who have been given blood transfusions. The ideal ligand binds to the target metal ion and not to others, but this degree of selectivity is very hard to achieve. The synthetic drug deferiprone achieves selectivity by having two oxygen donor atoms so that it binds to Fe3+ in preference to any of the other divalent ions that are present in the human body, such as Mg2+, Ca2+ and Zn2+. Treatment of poisoning by ions such as Pb2+ and Cd2+ is much more difficult since these are both divalent ions and selectivity is harder to accomplish. Excess copper in Wilson's disease can be removed by penicillamine or Triethylene tetramine (TETA). DTPA has been approved by the U.S. Food and Drug Administration for treatment of plutonium poisoning. DTPA is also used as a complexing agent for gadolinium in MRI contrast enhancement. The requirement in this case is that the complex be very strong, as Gd3+ is very toxic. The large stability constant of the octadentate ligand ensures that the concentration of free Gd3+ is almost negligible, certainly well below toxicity threshold. In addition the ligand occupies only 8 of the 9 coordination sites on the gadolinium ion. The ninth site is occupied by a water molecule which exchanges rapidly with the fluid surrounding it and it is this mechanism that makes the paramagnetic complex into a contrast reagent.
Sources: en.wikipedia.org
A pharmacologically important aspect of the contraction-reducing properties of ingested salvinorin A on gut tissue is that it is only pharmacologically active on inflamed and not normal tissue, thus reducing possible side-effects.
Prodine (trade names Prisilidine and Nisentil) is an opioid analgesic that is an analog of pethidine (meperidine). It was developed in Germany in the late 1940s. There are two isomers of the trans form of prodine, alphaprodine and betaprodine. Both exhibit optical isomerism and alphaprodine and betaprodine are racemates. Alphaprodine is closely related to desomorphine in steric configuration. The cis form also has active isomers but none are used in medicine. Betaprodine is around five times more potent than alphaprodine but is metabolized more rapidly, and only alphaprodine was developed for medicinal use. It has similar activity to pethidine, but with a more rapid onset and shorter duration of effects. Betaprodine produces more euphoria and side effects than alphaprodine at all dose levels, and it was found that 5 to 10 mg of betaprodine is equivalent to 25 to 40 mg of alphaprodine. Testing in rats showed alphaprodine to be 97% the strength of morphine via the subcutaneous route and 140% the strength of oral methadone. Betaprodine was 550% stronger than morphine SC, the laevorotatory cis isomer was 350% stronger, and the dextrorotatory cis isomer was 790% stronger. Betaprodine taken orally was 420% stronger than oral methadone, the cis form was 390% stronger for the laevorotatory and 505% stronger for the dextrorotatory isomers.
A lipopeptide is a molecule consisting of a lipid connected to a peptide. They are able to self-assemble into different structures. Many bacteria produce these molecules as a part of their metabolism, especially those of the genus Bacillus, Pseudomonas and Streptomyces. Certain lipopeptides are used as antibiotics. Due to the structural and molecular properties such as the fatty acid chain, it poses the effect of weakening the cell function or destroying the cell. Other lipopeptides are toll-like receptor agonists. Certain lipopeptides can have strong antifungal and hemolytic activities. It has been demonstrated that their activity is generally linked to interactions with the plasma membrane, and sterol components of the plasma membrane could play a major role in this interaction. It is a general trend that adding a lipid group of a certain length (typically C10–C12) to a lipopeptide will increase its bactericidal activity. Lipopeptides with a higher amount of carbon atoms, for example 14 or 16, in its lipid tail will typically have antibacterial activity as well as anti-fungal activity. Therefore, an increase in the alkyl chain can make lipopeptides soluble in water. As well, it opens the cell membrane of the bacteria, so antimicrobial activity can take place. Lipopeptide detergents (LPDs) are composed of amphiphiles and two alkyl chains which are located on the last part of the peptide backbone. They were designed to mimic the architecture of the native membranes in which two alkyl chains in a lipid molecule facially interact with the hydrophobic segment of MPs.
Sources: en.wikipedia.org
=== Aging === Tissue homeostasis generally declines with age, in part because stem/progenitor cells fail to self-renew or differentiate. Skin aging is caused in part by TGF-β by blocking the conversion of dermal fibroblasts into fat cells which provide support. Common changes in the skin as a result of aging range from wrinkles, discoloration, and skin laxity, but can manifest in more severe forms such as skin malignancies. Moreover, these factors may be worsened by sun exposure in a process known as photoaging.
== History == The idea of the creatine phosphate shuttle was suggested as an explanation for altered blood glucose levels in exercising diabetic patients. The change in blood glucose levels were very similar to the alterations that would occur if a diabetic patient would receive a shot of Insulin. It was then proposed that contraction of myofibrils during rigorous exercise freed creatine which imitated the effects of Insulin by consumption of ATP and releasing ADP. With the discovery of the mitochondrial isozyme of creatine kinase which participates in the shuttle, the other isozyme in the cytosol, Samuel Bessman further contributed to the creatine phosphate shuttle and proposed that the reversible properties of the creatine kinase enzyme was why exercise in diabetic patients can imitate the effects of Insulin.
=== Natural Killer T-cells === Natural killer T-cells (NKT cells) can also be visualized with tetramer technology. NKT cells bind to proteins that present lipid or glycolipid antigens. The antigen presenting complex that NKT cells bind to involves CD1 proteins, so tetramers made of CD1 can be used to stain for NKT cells.
Sources: en.wikipedia.org
Reverse-phase HPLC is the usual method and gives a percentage purity value. Mass spectrometry then confirms the molecular mass. Together they provide a basic identity and purity profile for a lot.
Freeze-dried material is kept frozen, often at minus 20 degrees Celsius, and protected from light and moisture. Dissolved peptide is refrigerated for short-term use. Repeated freeze-thaw cycles are avoided.
A certificate of analysis typically lists purity by HPLC, the confirmed mass, appearance, and sometimes water or counter-ion content. It documents results for a specific batch. Details vary by supplier.
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.