If you have been reading about freeze-thaw 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 2026-04-14. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 |
|---|---|---|
| Identity confirmation | Reversed-phase HPLC retention time versus reference standard | Retention depends on column, gradient, and ion-pairing agent |
| Mass confirmation | Electrospray or MALDI mass spectrometry | Doubly protonated ion near m/z 377 is consistent with about 752 Da |
| Typical purity specification | 95 percent or higher by chromatographic peak area | Lower values suggest truncated or modified peptide species |
| Storage of lyophilized powder | -20 °C, desiccated, protected from light | Powder tolerates long storage better than solution |
| Storage of solution | 2-8 °C for short periods | Freeze-thaw cycling promotes aggregation and surface adsorption |
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.
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.
Reversed-phase high-performance liquid chromatography is the standard technique for estimating peptide purity. The result is a peak-area percentage, which describes how much of the detected material elutes as the main peak in one run. Mass spectrometry confirms the molecular mass and can reveal truncated, adducted, or otherwise modified species. Amino acid analysis or tandem mass spectrometry can address sequence fidelity when identity is in doubt. None of these measurements, taken alone, establishes that a sample is fit for any specific purpose.
Lyophilized selank is normally supplied as a dry powder and is considered stable for extended periods when kept cold and dry. Moisture uptake is the main practical threat, because absorbed water promotes both hydrolysis and aggregation in the solid state. Vials are usually warmed to room temperature before opening so that condensation does not form on the powder. Supplier documentation commonly specifies -20 °C for routine storage, with -80 °C used for material intended to be archived for years.
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.
This combined testing of OQ and PQ phases is sanctioned by the European Commission Enterprise Directorate-General within ‘Annex 15 to the EU Guide to Good Manufacturing Practice guide’ (2001, p. 6) which states that:
=== Global expansion === The company elected to expand globally, and acquired other entities. In March 2002, Dr. Reddy's acquired BMS Laboratories, Beverley, and its wholly owned subsidiary Meridian Healthcare, for €14.81 million. These companies deal in oral solids, liquids and packaging, with manufacturing facilities in London and Beverley in the UK. Recently, Dr. Reddy's entered into an R&D and commercialisation agreement with Argenta Discovery Ltd., a private drug development company based in the UK, for the treatment of chronic obstructive pulmonary disease (COPD). Dr. Reddy's entered into a 10-year agreement with Rheoscience A/S of Denmark for the joint development and commercialisation of Balaglitazone (DRF-2593), a molecule for the treatment of type-2 diabetes. Rheoscience holds this product's marketing rights for the European Union and China, while the rights for the US and the rest of the world will be held by Dr. Reddy's. Dr. Reddy's conducted clinical trials of its cardiovascular drug RUS 3108 in Belfast, Northern Ireland, in 2005. The trials were conducted to study the safety and the pharmacokinetic profiles of the drug, which is intended for the treatment of atherosclerosis, a major cause of cardiovascular disorders. Dr. Reddy's entered into a marketing agreement with Eurodrug Laboratories, a pharmaceutical company based in Netherlands, for improving its product portfolio for respiratory diseases. It introduced a second-generation xanthine bronchodilator, doxofylline, which is used for the treatment of asthma and COPD patients.
Although previous studies proposed that Komodo dragon saliva contains a variety of highly septic bacteria that would help to bring down prey, research in 2013 suggested that the bacteria in the mouths of Komodo dragons are ordinary and similar to those found in other carnivores. Komodo dragons have good mouth hygiene. To quote Bryan Fry: "After they are done feeding, they will spend 10 to 15 minutes lip-licking and rubbing their head in the leaves to clean their mouth ... Unlike people have been led to believe, they do not have chunks of rotting flesh from their meals on their teeth, cultivating bacteria." They do have a slashing bite, which normally includes a dose of their neurotoxic venom and anticoagulant saliva. Komodo dragons do not wait for prey to die and track it at a distance, as vipers do; observations of them hunting deer, boar and in some cases buffalo reveal that they kill prey in less than half an hour during successful hunts, and usually in a matter of a few minutes, similar to large mammalian carnivores. The observation of prey dying of sepsis is instead likely based on misinterpretations of failed predation attempts caused by the natural instinct of water buffalo, which are not native to the islands where the Komodo dragon lives, to run into water after escaping an attack. The warm, faeces-filled water would then cause the infections. The study used samples from 16 captive dragons (10 adults and six neonates) from three US zoos.
== Extracellular NAMPT == Extracellular NAMPT (eNAMPT) is functionally different from intracellular NAMPT (iNAMPT), and less well understood (which is why the enzyme has been given so many names: NAMPT, PBEF and visfatin). iNAMPT is secreted by many cell types (nobably adipocytes) to become eNAMPT. The sirtuin 1 (SIRT1) enzyme is required for eNAMPT secretion from adipose tissue. eNAMPT may act more as a cytokine, although its receptor (possibly TLR4) has not been proven. It has been demonstrated that eNAMPT could bind to and activate TLR4. eNAMPT can exist as a dimer or as a monomer, but is normally a circulating dimer. As a monomer, eNAMPT has pro-inflammatory effects that are independent of NAD+, whereas the dimeric form of eNAMPT protects against these effects. eNAMPT/PBEF/visfatin was originally cloned as a putative cytokine shown to enhance the maturation of B cell precursors in the presence of Interleukin-7 (IL-7) and stem cell factor, it was therefore named "pre-B cell colony-enhancing factor" (PBEF). When the gene encoding the bacterial nicotinamide phosphoribosyltransferase (nadV) was first isolated in Haemophilus ducreyi, it was found to exhibit significant homology to the mammalian PBEF gene. Rongvaux et al. demonstrated genetically that the mouse PBEF gene conferred Nampt enzymatic activity and NAD-independent growth to bacteria lacking nadV. Revollo et al. determined biochemically that the mouse PBEF gene product encodes an eNAMPT enzyme, capable of modulating intracellular NAD levels. Others have since confirmed these findings.
=== Turnover === Research suggests that, at least in the United States, vegetarianism has a high turnover rate, with less than 20% of adopters persisting for more than a year. Research shows that lacking social support contributes to lapses. A 2019 analysis found that adhering to any kind of restricted diet (gluten-free, vegetarian, kosher, teetotal) was associated with feelings of loneliness and increased social isolation. Vegetarians or vegans who adopted their diet abruptly might be more likely to eventually abandon it when compared to individuals adopting their diet gradually with incremental changes.
Sources: en.wikipedia.org
=== Other drugs === Certain medications can decrease the absorption of orally consumed vitamin B12, including colchicine, extended-release potassium products, and antibiotics such as gentamicin, neomycin and tobramycin. Anti-seizure medications phenobarbital, pregabalin, primidone and topiramate are associated with lower than normal serum vitamin concentration. However, serum levels were higher in people prescribed valproate. In addition, certain drugs may interfere with laboratory tests for the vitamin, such as amoxicillin, erythromycin, methotrexate and pyrimethamine.
== Prevention == In the past, the prophylactic use of dantrolene was recommended for MH-susceptible patients undergoing general anesthesia. However, multiple retrospective studies have demonstrated the safety of trigger-free general anesthesia in these patients in the absence of prophylactic dantrolene administration. The largest of these studies looked at the charts of 2214 patients who underwent general or regional anesthesia for an elective muscle biopsy. About half (1082) of the patients were muscle biopsy positive for MH. Only five of these patients exhibited signs consistent with MH, four of which were treated successfully with parenteral dantrolene, and the remaining one recovered with only symptomatic therapy. After weighing its questionable benefits against its possible adverse effects (including nausea, vomiting, muscle weakness and prolonged duration of action of nondepolarizing neuromuscular blocking agents), experts no longer recommend the use of prophylactic dantrolene prior to trigger-free general anesthesia in MH-susceptible patients.
AD 250) gives one of the earliest references regarding the plausible centenarian longevity given by a scientist, the astronomer Hipparchus of Nicaea (c. 185 – c. 120 BC), who, according to the doxographer, said that the philosopher Democritus of Abdera (c. 470/460 – c. 370/360 BC) lived 109 years. Other ancient accounts of Democritus agree that the philosopher lived at least 90 years. The case of Democritus differs from those of, for example, Epimenides of Crete (7th and 6th centuries BC), who is said to have lived an implausible 154, 157, or 290 years, depending on the source. Other ancient Greek philosophers thought to have lived beyond the age of 90 include Xenophanes of Colophon (c. 570/565 – c. 475/470BC), Pyrrho of Ellis (c. 360 – c. 270 BC), Gorgias of Leontinoi, and Eratosthenes of Cirene (c. 285 – c. 190 BC). Also, the Greek rhetorician Isocrates of Athens (436–338 BC) lived 97/98 years and the famous Greek tragedian Sophocles (497/496-406/405 BC) lived at least 90 years. Hosius of Córdoba, the man who convinced Constantine the Great to call the First Council of Nicaea, reportedly lived to age 102. A rare record of an ordinary person who lived to be a centenarian is the tombstone of Roman British legionary veteran Julius Valens, inscribed "VIXIT ANNIS C". It is believed the 7th century Pope Agatho lived to 103-104, making him the longest lived pope to this day as well as the only pope to become a centenarian. In the medieval period, Albert Azzo II, Margrave of Milan (d. 1097) is said by Bernold of Constance to have lived past 100 years (iam maior centenario).
=== Research === A major thread of Bumpus' research is determining how antiviral drugs used to treat HIV-1 are metabolized and how genetic variations in drug-processing enzymes may impact these drugs' efficacy. One antiviral commonly used to treat and prevent HIV is tenofovir (Viread). Tenofovir is a nucleotide analog reverse transcriptase inhibitor that prevents the HIV virus from replicating. Tenofovir is given in an inactive form – it has to be phosphorylated twice to become active, and this phosphorylation is carried out in two steps by separate kinases. Bumpus and her team identified which kinases do this and found that the enzymes responsible varied by cell type, so administration route (e.g. orally or topically) could affect how effectively the drug is processed. They also sequenced the genes of these kinases from different patients and found that some people have genetic variants in the kinases that may affect how effectively the drug is processed. Tenofovir can be given prophylactically, and Bumpus collaborated with researchers from around the world in a study of the use of tenofovir for HIV pre-exposure prophylaxis (PrEP) to prevent HIV infection in heterosexual men and women. Bumpus has also researched nonnucleoside reverse transcriptase inhibitors. Her lab was the first to publish the P450-catalyzed phase 1 and phase 2 metabolic pathways of two nonnucleoside reverse transcriptase inhibitors, rilpivirine and etravirine and was first to characterize the metabolism of the nonnucleoside reverse transcriptase inhibitor dapivirine.
Sources: en.wikipedia.org
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.
Lyophilized powder is normally stored desiccated at -20 °C, protected from light and moisture. Powder kept under these conditions is generally stable for long periods. Solutions are less stable and are usually prepared immediately before use.
A purity value from one chromatographic method does not capture every possible impurity. Related peptides with similar retention behavior, counterions, and residual solvents may not appear in the same analysis. Independent testing with an orthogonal method provides stronger assurance of identity and content.
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.