peptide purity comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-08-09. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
Reported pharmacological effects center on reduced anxiety-like behavior in animal models and on measures of memory and learning. Proposed contributing mechanisms include modulation of GABAergic signaling, shifts in monoamine turnover, and changes in the activity of enzymes that degrade neuropeptides. Effects on the expression of genes linked to neuroplasticity have also been described. No single molecular target is widely accepted, and whether the behavioral findings arise from one pathway or several remains an open question.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed as a stabilized analogue of tuftsin, a naturally occurring tetrapeptide fragment derived from the immunoglobulin heavy chain. The additional Pro-Gly-Pro segment at the carboxyl terminus is intended to slow enzymatic cleavage. The compound is usually described in the literature as a synthetic peptide with anxiolytic and cognitive-related activity, a label that reflects a research context rather than an approved therapeutic category.
Most published work on selank originates from a small number of research groups in the Russian Federation. A large share of that record appears in Russian-language journals, which limits access for readers who rely on English-indexed databases. Independent replication by laboratories outside the original research network is sparse in publicly available sources. This concentration of origin and language is a frequently noted feature when the compound is summarized in broader reviews of synthetic peptides.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Tuftsin analogue |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form: TKPRPGP |
| Molecular formula | C33H57N11O9 | Calculated for the free peptide |
| Molecular weight | About 751.9 g/mol | Derived from the sequence |
| Appearance | White to off-white powder | Typical lyophilised form |
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.
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.
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.
=== Sequence similarity === EC categories do not reflect sequence similarity. For instance, two ligases of the same EC number that catalyze exactly the same reaction can have completely different sequences. Independent of their function, enzymes, like any other proteins, have been classified by their sequence similarity into numerous families. These families have been documented in dozens of different protein and protein family databases such as Pfam.
In February 2012, Ontario passed legislation to allow the expansion of an already existing drug-tracking system for publicly funded drugs to include those that are privately insured. This database will function to identify and monitor patient's attempts to seek prescriptions from multiple doctors or retrieve them from multiple pharmacies. Other provinces have proposed similar legislation, while some, such as Nova Scotia, have legislation already in effect for monitoring prescription drug use. These changes have coincided with other changes in Ontario's legislation to target the misuse of painkillers and high addiction rates to drugs such as oxycodone. As of 29 February 2012, Ontario passed legislation delisting oxycodone from the province's public drug benefit program. This was a first for any province to delist a drug based on addictive properties. The new law prohibits prescriptions for OxyNeo except to certain patients under the Exceptional Access Program including palliative care and in other extenuating circumstances. Patients already prescribed oxycodone will receive coverage for an additional year for OxyNeo, and after that, it will be disallowed unless designated under the exceptional access program. Much of the legislative activity has stemmed from Purdue Pharma's decision in 2011 to begin a modification of OxyContin's composition to make it more difficult to crush for snorting or injecting. The new formulation, OxyNeo, is intended to be preventive in this regard and retain its effectiveness as a painkiller.
Polatuzumab vedotin, sold under the brand name Polivy, is an antibody-drug conjugate medication used for the treatment of diffuse large B-cell lymphoma (cancer). Polatuzumab is an antibody that targets CD79b, and vedotin is an agent that inhibits cell division by blocking the polymerisation of tubulin. It was developed by the Genentech subsidiary of Roche. The most common side effects include low levels of white blood cells (neutropenia), platelets (thrombocytopenia) and red blood cells (anemia); nerve damage (peripheral neuropathy); fatigue; diarrhea; fever; decreased appetite; and pneumonia. Polatuzumab vedotin was approved for medical use in the United States in June 2019, in Australia in October 2019, in the European Union in January 2020, and in Canada in November 2020.
The neurons of the raphe nuclei are the principal source of 5-HT release in the brain. There are nine raphe nuclei, designated B1–B9, which contain the majority of serotonin-containing neurons (some scientists chose to group the nuclei raphes lineares into one nucleus), all of which are located along the midline of the brainstem, and centered on the reticular formation. Axons from the neurons of the raphe nuclei form a neurotransmitter system reaching almost every part of the central nervous system. Axons of neurons in the lower raphe nuclei terminate in the cerebellum and spinal cord, while the axons of the higher nuclei spread out in the entire brain. It is the dorsal part of the raphe nucleus that contains neurons projecting to the central nervous system. Serotonin-releasing neurons in this area receive input from a large number of areas, notably from prefrontal cortex, lateral habenula, preoptic area, substantia nigra and amygdala. These neurons are thought to communicate the expectation of rewards in the near future, a quantity called state value in reinforcement learning.
==== Antimicrobial photodynamic therapy ==== PDT may also be utilized to treat multidrug-resistant skin, wound, or other superficial infections. This is known as antimicrobial photodynamic therapy (aPDT) or photodynamic inactivation (PDI). aPDT has been observed to be effective against both gram-positive and gram-negative bacteria such as Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Mycobacterium. aPDT has shown lowered efficacy on some other bacterial species, such as Klebsiella pneumoniae and Acinetobacter baumannii. This is likely due to factors such as cell wall thickness and membrane potential. Many studies utilizing aPDT focus on the application of the photosensitizer through leakage from a hydrogel, which has been found to increase wound healing speed of skin infections through the upregulation of vascular endothelial growth factor (VEGF) and hypoxia inducible factor (HIF). This controlled leakage allows for prolonged but limited generation of ROS, lowering the impact on human cell viability due to ROS cytotoxicity. It is unlikely for drug resistance to photosensitizers to form due to the nontoxic nature of the photosensitizer itself as well as the ROS generation mechanism of action, which cannot be prevented outside of hypoxic environments. Certain dental infections (peri-implantitis, periodontitis) are more difficult to treat with PDT as opposed to photothermal therapy due to the requirement of oxygen, though a significant response is still observed.
Sources: en.wikipedia.org
In 1984, the chain returned to the U.S. with a location in Tonawanda, New York. Starting in the mid-1990s, however, the chain began expanding in the U.S. by acquiring former locations from fast-food chains. In 1996 and 1997, thirty-seven former Rax locations in Ohio, Kentucky, and West Virginia were bought by Wendy's International Inc.; 30 of these were converted to Tim Hortons, while the others became Wendy's franchise locations. Thirty-five closed Hardee's stores in the Detroit area were also purchased with the intention of being converted. By 2004, the chain had also acquired 42 Bess Eaton coffee and donut restaurants in southern New England. Several combination Wendy's/Tim Hortons units were opened in the US; both in the "traditional" markets of Maine and Buffalo, where there were well over 180 locations as of 2011, and in the markets entered through acquisition. In October 2008, Tim Hortons announced a plan to add 82 locations in Tops Markets stores in the United States. On July 13, 2009, Tim Hortons opened stores in New York City at former Dunkin' Donuts locations operated by the Riese Organization. One of the stores is at Madison Square Garden, where Horton played as a member of the New York Rangers from 1969 to 1971. In November 2010, Tim Hortons announced it was closing 36 stores in the northeastern United States due to high competition with New England–based Dunkin' Donuts and Au Bon Pain.
Burroughs found Trump's efforts to freeze billions of dollars of funding for Harvard illegal, writing that the government had infringed upon Harvard's free speech rights and that it was "difficult to conclude anything other than that defendants used antisemitism as a smokescreen for a targeted, ideologically-motivated assault on this country's premier universities".
GSK was fined for promoting Paxil/Seroxat (paroxetine) for treating depression in the under-18s, although the drug had not been approved for pediatric use. Paxil had US$4.97 billion worldwide sales in 2003. The company conducted nine clinical trials between 1994, and 2002, none of which showed that Paxil helped children with depression. From 1998, to 2003, it promoted the drug for the under-18s, paying physicians to go on all-expenses paid trips, five-star hotels and spas. From 2004, Paxil's label, along with those of similar drugs, included an FDA-mandated boxed warning that it might increase the risk of suicidal ideation and behaviour in patients under 18. An internal SmithKline Beecham document said in 1998, about withheld data from two GSK studies: "It would be commercially unacceptable to include a statement that [pediatric] efficacy had not been demonstrated, as this would undermine the profile of paroxetine." The company ghostwrote an article, published in 2001, in the Journal of the American Academy of Child and Adolescent Psychiatry, that misreported the results of one of its clinical trials, Study 329. The article concluded that Paxil was "generally well tolerated and effective for major depression in adolescents." The suppression of the research findings is the subject of the 2008 book Side Effects by Alison Bass. For 10 years GSK marketed Paxil as non-habit forming.
A biosynthetic pathway has been hypothesized based on proposed gene functions (see figure). btmM, with homology to Zn+2 aminopeptidases, is predicted to cleave the N-terminal methionine residue, which is not present in the bottromycin final product. btmE and btmF both contain YcaO-like domains. It is believed that one Although it is unclear which enzyme is responsible for which step, it is hypothesized that one catalyzes macrocyclic amidine formation while the other catalyzes thiazoline formation. btmJ, encoding an enzyme with cytochrome P450 homology, may oxidize the thiazoline to the thiazole. btmH or btmI both have homology to hydrolytic enzymes (α/β hydrolase and metallo-dependent hydrolase, respectively) may catalyze follower peptide hydrolysis. An alternative proposed role for btmH or btmI is to function as a cyclodehydratase in macrocyclization. Gene deletion studies failed to elucidate the function of other proteins within the cluster.
From the mid-1960s onward, Ramachandran continued studying crystallography, including the conformation of peptides including types of β-turns, conformation of prolyl residues, cis-peptide units, occurrence and need for non-planarity of the peptides, NMR coupling constants and peptides containing L and D residues, among other tops. He was awarded the prestigious Jawarharlal Nehru Fellowship in 1968 for research on Protein and Polypeptide Conformation; he was one of its first recipients. Ramachandran can be credited for bringing together into the one field of molecular biophysics the then disparate fields of X-ray crystallography, peptide synthesis, NMR and other optical studies, and physico-chemical experimentation. In 1970, he founded the Molecular Biophysics Unit at the Indian Institute of Science which was later known as the Centre of Advanced Study in Biophysics. Ramachandran and A.V. Lakshminarayanan developed convolution-backprojection algorithms which greatly improved the quality and practicality of results obtainable by x-ray tomography. Compared to previously used methods, their algorithms considerably reduced computer processing time for image reconstruction, as well as providing more numerically accurate images. As a result, commercial manufacturers of x-ray tomographic scanners started building systems capable of reconstructing high resolution images that were almost photographically perfect. In 1971, they published their research in PNAS. In 1981, Ramachandran became a founding member of the World Cultural Council.
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.
Selank is a synthetic analogue built on the tuftsin tetrapeptide Thr-Lys-Pro-Arg. Extra proline residues were added to the C-terminus during design work. That modification is intended to make the peptide less vulnerable to rapid enzymatic degradation.
Transliteration from Russian produces variant spellings such as Selanc. Many suppliers avoid the trade-style name entirely and list the peptide sequence. Comparing sequences rather than names is the reliable way to confirm two entries describe the same molecule.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro, designed as a metabolically stabilized analogue of the endogenous tetrapeptide tuftsin. It has been studied mainly against anxiety-related and cognitive endpoints rather than as an approved medicine in most jurisdictions.