Enkephalinase 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 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
Once dissolved, the peptide is markedly less stable than the dry powder. Aqueous solutions are subject to backbone hydrolysis and to microbial growth when they are handled without sterile technique. Buffered solutions near neutral pH are common for short-term laboratory work, while acidic conditions are sometimes used to improve solubility. Analytical laboratories generally prepare working solutions fresh rather than storing them, and a residual water film left in a reopened vial can seed degradation even when the container appears dry.
| 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 |
Tuftsin, the parent structure, is a naturally occurring immunomodulatory tetrapeptide released from the Fc region of immunoglobulin G by spleen enzymes. Selank extends this four-residue sequence with three additional amino acids. The stated rationale is that the added tail slows enzymatic breakdown and may influence receptor interactions. How the full heptapeptide behaves at the molecular level is not firmly established, and proposed mechanisms often involve indirect modulation of neurotransmitter or immune signaling rather than a single defined target.
Selank is a synthetic heptapeptide developed in Russia. Its sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, a seven-residue chain built around the natural tetrapeptide tuftsin. Researchers at the Institute of Molecular Genetics of the Russian Academy of Sciences first described the compound in the mid-1990s. The design combined the tuftsin core with an added Pro-Gly-Pro tail, a modification intended to extend the molecule's stability in biological fluids. Published work on the peptide has appeared mainly in Russian-language journals.
The compound has a calculated molecular weight near 751.9 daltons and carries a net positive charge at physiological pH because of its arginine residue. It dissolves freely in water and in common aqueous buffers, and typically appears as a white or off-white lyophilized powder. The amide backbone makes the molecule susceptible to peptidases, which limits oral use and favors intranasal or parenteral routes. Nomenclature in the literature varies: the substance is also described by the sequence abbreviation TP-7 and by a Russian trade designation.
Regulatory status differs sharply by region. Selank holds a Russian marketing authorization, where it is supplied mainly as nasal drops, while authorities elsewhere have not approved it for medical use. Material sold internationally is therefore usually labeled as a research chemical rather than a medicine. Peer-reviewed publications come predominantly from Russian laboratories, and sample sizes are generally small. Whether the compound produces comparable effects under independent, well-controlled replication remains an open question that the broader literature has not settled.
Selank is a synthetic heptapeptide developed in Russia as a structural analogue of tuftsin, a naturally occurring immunomodulatory tetrapeptide. Its sequence, Thr-Lys-Pro-Arg-Pro-Gly-Pro, keeps the tuftsin core at the N-terminus and appends a Pro-Gly-Pro tail. Researchers at the Institute of Molecular Genetics in Moscow synthesized the compound during the 1990s while searching for peptides with combined anxiolytic and immunomodulatory activity. The added tail was intended to resist enzymatic cleavage and prolong the molecule's presence in circulation.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. It was designed at the Institute of Molecular Genetics of the Russian Academy of Sciences as a structural analogue of tuftsin, a naturally occurring tetrapeptide fragment of the immunoglobulin heavy chain. The added Pro-Gly-Pro tail was intended to slow enzymatic degradation and extend biological activity. In Russia it is registered as an anxiolytic nasal preparation, while regulators elsewhere have not approved it for clinical use.
Proposed mechanisms centre on modulation of the GABAergic system, with reports of altered expression of genes related to GABA-A receptor subunits and changed monoamine turnover. Some studies describe inhibition of enkephalinase, the enzyme that degrades endogenous enkephalins, which may prolong opioid peptide signalling. Effects on brain-derived neurotrophic factor and on cytokine expression have also been reported. These findings come largely from animal models and small human studies, and the precise primary target remains unresolved.
In 2019, Mahathir said that Malaysians should learn from the hard work of China's citizens, which enabled their nation to achieve technological advancement within a few decades. In 2025, he said that China would overtake the United States and remain the world's top power in the long term, while downplaying India's potential to compete with China on a global scale. Mahathir has advocated for a balance between environmental protection and natural resource use for economic growth in developing countries. He referred to the outcomes of the Earth Summit as "eco-imperialism", arguing that Global North countries put an undue burden on Global South countries for environmental degradation. In response to international scrutiny, he said in 2019 that linking palm oil production to deforestation was "baseless, unfair and unjustified" and that the Malaysian palm oil sector had developed sustainably. In the aftermath of the 2020 Nice stabbing and murder of Samuel Paty, Mahathir posted remarks on his blog. Mahathir said that the attacks were wrong and against Islam, but also argued that Muslims had a right to be angry and kill French people for past massacres committed by the French. Mahathir's post was later circulated on his Twitter account, where it was labelled for "glorifying violence". Mahathir was criticised for stoking tensions and hatred by the former Australian ambassador to France Brendan Berne, Australian prime minister Scott Morrison, and French secretary of state for digital affairs Cédric O.
=== Hypersensitivity syndrome === Hypersensitivity to abacavir is strongly associated with a specific allele at the human leukocyte antigen B locus namely HLA-B*5701. The mechanism for this hypersensitivity reaction is due to abacavir binding in the antigen-binding cleft of HLA-B*57:01, allowing alternative peptides to bind, which appear as "non-self" when presented to T cells. There is an association between the prevalence of HLA-B*5701 and ancestry. The prevalence of the allele is estimated to be 3.4 to 5.8 percent on average in populations of European ancestry, 17.6 percent in Indian Americans, 3.0 percent in Hispanic Americans, and 1.2 percent in Chinese Americans. There is significant variability in the prevalence of HLA-B*5701 among African populations. In African Americans, the prevalence is estimated to be 1.0 percent on average, 0 percent in the Yoruba from Nigeria, 3.3 percent in the Luhya from Kenya, and 13.6 percent in the Masai from Kenya, although the average values are derived from highly variable frequencies within sample groups. Common symptoms of abacavir hypersensitivity syndrome include fever, malaise, nausea, and diarrhea. Some patients may also develop a skin rash. Symptoms of AHS typically manifest within six weeks of treatment using abacavir, although they may be confused with symptoms of HIV, immune reconstitution syndrome, hypersensitivity syndromes associated with other drugs, or infection. The U.S.
=== Drug-drug interactions === Clinafloxacin inhibits multiple CYP450 drug metabolizing enzymes, especially CYP1A2. Clinafloxacin has induced the accumulation of CYP1A2 substrates, including theophylline, at therapeutic doses. This can also affect the metabolism of caffeine, another CYP1A2 substrate. Caffeine consumption must be limited while taking clinafloxacin to prevent caffeine accumulation and overdose. There is also a known interaction of clinafloxacin with phenytoin, resulting in a decrease in the clearance of phenytoin from the body. The increase in INR seen in patients taking both clinafloxacin and the anticoagulant warfarin has yet to be fully elucidated.
GLaDOS was built to control the facility and monitor the tests, but researchers found that the computer had villainous tendencies, threatening to kill the entire staff before it was shut down in time. The Aperture researchers constructed a number of "personality cores" that would fit onto GLaDOS to prevent her from turning against them. Despite this, on the day she was officially activated (coincidentally on "Take Your Daughter to Work Day"), she turned against the researchers and killed nearly everyone in the facility with lethal doses of neurotoxin gas. In the games and the comic Lab Rat, one employee Doug Rattmann survived due to his schizophrenia and distrust of GLaDOS. In trying to find a way to defeat GLaDOS, he finds that Chell, one of the human subjects kept in cryogenic storage within Aperture, has a high level of tenacity, and arranges for the events of Portal to occur by moving her to the top of GLaDOS' testing list. GLaDOS remains driven to test human subjects despite the lack of humans.
== Medical uses == Sitagliptin is used to treat type 2 diabetes. It is generally less preferred than metformin or sulfonylureas. It is taken by mouth. It is also available as the fixed-dose combinations of sitagliptin/metformin (Janumet, Janumet XR) and sitagliptin/simvastatin (Juvisync). Sitagliptin should not be used to treat type 1 diabetes. In December 2020, the US Food and Drug Administration (FDA) approved labeling changes stating that Januvia (sitagliptin), Janumet (sitagliptin and metformin hydrochloride), and Janumet XR (sitagliptin and metformin hydrochloride extended-release) are not proven to improve glycemic (blood sugar) control in children aged 10 to 17 with type 2 diabetes. The drugs are approved to improve blood sugar control in adults aged 18 and older with type 2 diabetes.
Sources: en.wikipedia.org
==== Age limits on purchase ==== In the United States, over-the-counter nicotine replacement therapy products are only available to people aged 18 and above, and it is not for sale in vending machines or from any source where proof of age cannot be verified. The minimum age to purchase tobacco products in the US is 21 at the federal level. In the European Union, the minimum age to purchase nicotine products is 18 in all member states except Latvia, where it is 20. However, there is no minimum age requirement to use tobacco or nicotine products. In the United Kingdom, the minimum age to purchase tobacco products is 18.
Chemical burns can be caused by over 25,000 substances, most of which are either a strong base (55%) or a strong acid (26%). Most chemical burn deaths are secondary to ingestion. Common agents include: sulfuric acid as found in toilet cleaners, sodium hypochlorite as found in bleach, and halogenated hydrocarbons as found in paint remover, among others. Hydrofluoric acid can cause particularly deep burns that may not become symptomatic until some time after exposure. Formic acid may cause the breakdown of significant numbers of red blood cells.
For theories obtained by quantization of a classical theory, each stationary point of the energy in the configuration space gives rise to a single vacuum. String theory is believed to have a huge number of vacua –the so-called string theory landscape.
Port Talbot Steelworks is allocated up to £500m by the UK government in a bid to keep the plant open and produce steel using greener methods. Marks & Spencer becomes the latest high street retailer to announce it is scrapping plastic bags in favour of paper ones. 16 September Comedian and actor Russell Brand is accused by four women of rape, sexual assaults, and emotional abuse between 2006 and 2013, following a joint investigation by the Sunday Times and Channel 4's Dispatches. Brand releases a video denying "serious criminal allegations". Christine Middlemiss, the UK's Chief Veterinary Officer, says there will not be a cull of American bully XL dogs following Sunak's announcement that the breed is to be banned. Solicitors representing convicted killer nurse Lucy Letby announce that she will be applying for permission to appeal against her convictions. 18 September COVID-19 vaccination in the UK: New booster vaccines begin rolling out for people aged 65 and over in England, as a precaution against a highly mutated new COVID-19 variant called Pirola. A new palm oil substitute called PALM-ALT is presented by researchers at Queen Margaret University in Scotland. The plant-based ingredient is shown to be 70% better for the environment than conventional palm oil and is described as "the holy grail to replace it." Conservative MP Dehenna Davison resigns as a levelling up minister, saying "chronic migraines" have made it "impossible" to do her job.
The National Institutes of Health has defined a biomarker as "a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention." Understanding the proteome, the structure and function of each protein and the complexities of protein–protein interactions are critical for developing the most effective diagnostic techniques and disease treatments in the future. For example, proteomics is highly useful in the identification of candidate biomarkers (proteins in body fluids that are of value for diagnosis), identification of the bacterial antigens that are targeted by the immune response, and identification of possible immunohistochemistry markers of infectious or neoplastic diseases. An interesting use of proteomics is using specific protein biomarkers to diagnose disease. A number of techniques allow to test for proteins produced during a particular disease, which helps to diagnose the disease quickly. Techniques include western blot, immunohistochemical staining, enzyme linked immunosorbent assay (ELISA) or mass spectrometry. Secretomics, a subfield of proteomics that studies secreted proteins and secretion pathways using proteomic approaches, has recently emerged as an important tool for the discovery of biomarkers of disease.
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.
Sealed, desiccated storage at -20 °C or colder is the standard recommendation for research-grade material. Vials should reach room temperature before they are opened, which limits condensation. Repeated temperature cycling is discouraged.