electrospray ionization 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 2026-03-16. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
Characterization of Selank in laboratory settings relies on standard peptide analytical techniques. Reverse-phase high-performance liquid chromatography separates the peptide from related impurities and degradation products, while mass spectrometry confirms molecular identity through accurate mass measurement. Amino acid analysis and peptide sequencing verify the primary structure when reference material is unavailable. Because Selank is a short chain, fragmentation-based analysis produces a diagnostic ion pattern that supports confident identification.
| Property | Value | Notes |
|---|---|---|
| Typical purity specification | 95 percent or higher by RP-HPLC | Area percentage of the main peak |
| Identity confirmation | Electrospray ionization mass spectrometry | Observed mass compared with the theoretical value near 751.9 Da |
| Recommended dry storage | -20 °C, desiccated | -80 °C for multi-year archival material |
| Solution handling | Prepare fresh; avoid long storage | Sterile filtration reduces microbial load |
| Common synonyms | TKPRPGP; TP-7 | Sequence code and laboratory designation used interchangeably |
Laboratory work relies on standard behavioral paradigms. Rodents are tested in the elevated plus maze, open field, and passive avoidance tasks, with outcomes compared against diazepam or vehicle controls. Intranasal dosing is used most often because it bypasses first-pass metabolism, though intraperitoneal and intravenous routes also appear in published protocols. Biochemical endpoints include tissue BDNF concentrations, cytokine levels, and monoamine metabolites. Human data are limited to small Russian trials reporting reduced anxiety scores; most were not prospectively registered, and few employed independent outcome assessment.
Measuring peptide exposure inside the brain is technically difficult. Selank is degraded rapidly in plasma, and assays must separate intact peptide from fragments, which favors targeted mass spectrometry over immunoassays alone. Reported half-lives are short, on the order of minutes, so effects observed hours later are attributed to downstream signaling rather than to the parent compound. Blood-brain barrier permeability is debated and rarely quantified directly. Gaps include absent dose-response characterization, inconsistent reporting of purity, and almost no pharmacokinetic data from human participants.
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.
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.
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.
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.
That's exactly what I didn't want to happen." One of Staley's last shows with Alice in Chains was the MTV Unplugged performance in New York on April 10, 1996. The recording of Unplugged came after a long period of inactivity for the band; it was their first concert in two-and-a-half years. Staley made his last performance on July 3, 1996, in Kansas City, Missouri, while Alice in Chains was touring with Kiss.
The majority of mummies recovered in the Czech Republic come from underground crypts. While there is some evidence of deliberate mummification, most sources state that desiccation occurred naturally due to unique conditions within the crypts. The Capuchin Crypt in Brno contains three hundred years of mummified remains directly below the main altar. Beginning in the 18th century when the crypt was opened, and continuing until the practice was discontinued in 1787, the Capuchin friars of the monastery would lay the deceased on a pillow of bricks on the ground. The unique air quality and topsoil within the crypt naturally preserved the bodies over time. Approximately fifty mummies were discovered in an abandoned crypt beneath the Church of St. Procopius of Sázava in Vamberk in the mid-1980s. Workers digging a trench accidentally broke into the crypt, which began to fill with waste water. The mummies quickly began to deteriorate, though thirty-four were able to be rescued and stored temporarily at the District Museum of the Orlické Mountains until they could be returned to the monastery in 2000. The mummies range in age and social status at time of death, with at least two children and one priest. The majority of the Vamberk mummies date from the 18th century. The Klatovy catacombs currently house an exhibition of Jesuit mummies, alongside some aristocrats, that were originally interred between 1674 and 1783. In the early 1930s, the mummies were accidentally damaged during repairs, resulting in the loss of 140 bodies.
A study that follows a group of people over time who have, or are at risk of developing, a specific medical condition or disease. A natural history study collects health information in order to understand how the medical condition or disease develops and how to treat it. (NCI) Study of the natural development of something (such as an organism or a disease) over a period of time. (NLM) New Drug Application (NDA)
Malaysia is a federation of 13 states and three federal territories. Out of these, 11 states and two federal territories are in Peninsular Malaysia, whereas the other two states and one federal territory comprise East Malaysia. The country has three tiers of government—federal, state, and local. Governance of the states is divided between the federal and the state governments, with different powers reserved for each, and the federal government has direct administration of the federal territories. Each state has a unicameral State Legislative Assembly whose members are elected from single-member constituencies. State governments are led by Chief Ministers, who are state assembly members from the majority party in the assembly. In each of the states with a hereditary ruler, the Chief Minister is normally required to be a Malay, appointed by the ruler upon the recommendation of the Prime Minister. Until 2018, state elections were held concurrently with the general election by convention, except for those in Sarawak. Following the 2020–2022 political crisis, only Pahang, Perak and Perlis opted to conduct their state elections simultaneously with the general elections. Positioned below the federal and state governments, local governments represent the lowest tier of governance in Malaysia. As of 2024, Malaysia is divided between 19 cities, 40 municipalities, 91 district-level councils, and four statutory agencies.
=== Francis Crick Graduate Lectures === The University of Cambridge Graduate School of Biological, Medical and Veterinary Sciences hosts The Francis Crick Graduate Lectures. The first two lectures were by John Gurdon and Tim Hunt.
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Preeclampsia A condition that some women with diabetes have during the late stages of pregnancy. Two signs of this condition are high blood pressure and swelling because the body cells are holding extra water. Prevalence rate of happening of something. Example: there is a high prevalence of sleeping amongst humans. Previous abnormality of glucose tolerance (PrevAGT) People who have had above-normal levels of blood glucose (sugar) when tested for diabetes in the past but who show as normal on a current test. PrevAGT used to be called either "latent diabetes" or "prediabetes." Prognosis Telling a person now what is likely to happen in the future because of having a disease. Proinsulin The substance made first in the pancreas that is then made into insulin. Proliferative retinopathy damage to the retina caused by growth of small blood vessels. the proliferative variety is dangerous to sight. Prosthesis a replacement for a body part. For instance, a foot or leg. Protein a class of biochemicals made from amino acids in specific sequences. Proteins can be very large molecules with very specific shapes in folds and sheets, etc. They have three prominent functions in the body. Some varieties are, save for bone, the structural components of cells and so of the body. Other varieties are enzymes, which coordinate the chemical reactions which are required for life: metabolism, protein construction and degradation, reproduction, etc. A smaller third class of proteins are hormones. Insulin, central to diabetes mellitus, is a protein and is a very small one.
TNF is a cytokine produced mainly by activated macrophages, and is the major extrinsic mediator of apoptosis. Most cells in the human body have two receptors for TNF: TNFR1 and TNFR2. The binding of TNF to TNFR1 has been shown to initiate the pathway that leads to caspase activation via the intermediate membrane proteins TNF receptor-associated death domain (TRADD) and Fas-associated death domain protein (FADD). cIAP1/2 can inhibit TNF signaling by binding to TRAF2. FLIP inhibits the activation of caspase-8. Binding of this receptor can also indirectly lead to the activation of transcription factors involved in cell survival and inflammatory responses. However, signalling through TNFR1 might also induce apoptosis in a caspase-independent manner. The link between TNF and apoptosis shows why an abnormal production of TNF plays a fundamental role in several human diseases, especially in autoimmune diseases. The TNF receptor superfamily also includes death receptors (DRs), such as DR4 and DR5. These receptors bind to the protein TRAIL and mediate apoptosis. Apoptosis is known to be one of the primary mechanisms of targeted cancer therapy. Luminescent iridium complex-peptide hybrids (IPHs) have recently been designed, which mimic TRAIL and bind to death receptors on cancer cells, thereby inducing their apoptosis.
Thorium-232 (232Th) is the main naturally occurring isotope of thorium, with a relative abundance of approximately 99.98%. It has a half-life of 14.0 billion years, which makes it the longest-lived isotope of thorium. It decays by alpha decay to radium-228; its decay chain terminates at stable lead-208. Thorium-232 is a fertile material; it can capture a neutron to form thorium-233, which subsequently undergoes two successive beta decays to uranium-233, which is fissile. As such, it has been used in the thorium fuel cycle in nuclear reactors; various prototype thorium-fueled reactors have been designed. However, as of 2024, thorium fuel has not been widely adopted for commercial-scale nuclear power. In 2025, China reported thorium-to-uranium conversion in an experimental molten-salt reactor.
Specialty drugs, a recent classification of pharmaceuticals, are high-cost drugs that are often biologics. The European Medicines Agency uses the term advanced therapy medicinal products (ATMPs) for medicines for human use that are "based on genes, cells, or tissue engineering", including gene therapy medicines, somatic-cell therapy medicines, tissue-engineered medicines, and combinations thereof. Within EMA contexts, the term advanced therapies refers specifically to ATMPs, although that term is rather nonspecific outside those contexts. Gene-based and cellular biologics, for example, often are at the forefront of biomedicine and biomedical research, and may be used to treat a variety of medical conditions for which no other treatments are available. Building on the market approvals and sales of recombinant virus-based biopharmaceuticals for veterinary and human medicine, the use of engineered plant viruses has been proposed to enhance crop performance and promote sustainable production. In some jurisdictions, biologics are regulated via different pathways from other small molecule drugs and medical devices.
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Baeckeoffe, a potato stew from Alsace Beef bourguignon, a French dish of beef stewed in red burgundy wine Bigos, a traditional stew in Polish cuisine Birria, a traditional stew from Mexico Bo kho (Vietnamese: bò kho), a beef stew in rich seasonings, served with bread, noodle or plain rice from Vietnam Bollito misto, consisting of beef, veal, and pork simmered in an aromatic vegetable broth from Italy Booyah, an American meat stew Bosnian pot, a stew with beef or lamb which is a national dish in Bosnia and Herzegovina Bouillabaisse, a fish stew from Provence Brongkos, a spicy Javanese meat with beans stew from Indonesia, made of Pangium edule, coconut milk, and various spices Brunswick stew, from Virginia and the Carolinas Burgoo, a Kentuckian stew Brudet, fish stew from Dalmatia regions, known in Greece as bourdeto Caldeirada, a fish stew from Portugal Carbonade flamande (stoofvlees), a traditional Belgian beef and onion stew made with Belgian beer Cawl, a Welsh stew Chakapuli, a Georgian stew made with lamb chops, coriander and tarragon leaves, and white wine Chanakhi, a Georgian lamb stew with tomatoes, aubergines, potatoes, greens, and garlic Charquicán, a Chilean dish Chicken mull, whole chicken and seasonings Chicken paprikash, chicken stew with paprika Chili con carne, a meat and chili pepper stew originating in Texas Chilorio, a pork stew from Sinaloa, Mexico Cincinnati chili, developed by Macedonian immigrants from Greece immigrants in the Cincinnati area Cholent, a slow-cooked Jewish dish Chorba (also spelt "shorba"), a stew like soup dish found in various North African, Middle Eastern, Central Asian, South Asian, and European cuisines Cochinita pibil, an orange color pork stew from Yucatán Peninsula, Mexico Cocido, a traditional Spanish and Portuguese strew with many variants (madrileño, montañés, à portuguesa, etc.) Cotriade, a fish stew from Brittany Cream stew, a yōshoku Japanese white stew Crow stew, a sour cream-based stew made with crow meat, popular in the United States during the Great Depression Daal, the Indian legume stew that has many varieties, a staple food throughout Asia Dalma, a traditional dish of Odisha, India; contains pulses with vegetables Daube, a French stew made with cubed beef braised in wine, vegetables, garlic, and herbs Dinuguan, pork blood stew from the Philippines Eintopf, ('one pot') the German word for a stew: many different regional specialty recipes for Eintopf are known in Germany. For example, the Kassel area has a type called Lumben un Fleeh in the local dialect (Standard German: Lumpen und Flöhe – 'rags and fleas'), which is quite similar to Irish stew. There are thicker German stews such as Hasenpfeffer or Labskaus; these would not usually be considered an Eintopf, though the technical difference is minor (longer cooking times and fewer vegetables) Estofadong baboy, pork stew from the Philippines Ewedu, vegetable stew from Nigeria Fabada asturiana, an Asturian bean and meat stew Feijoada, Brazilian or Portuguese bean stew Fårikål, traditional Norwegian stew with lamb or mutton and white cabbage Főzelék, a thick Hungarian vegetable dish Gaisburger Marsch, a German dish of stewed beef served with Spätzle and potatoes Gheimeh, an Iranian stew with cubed lamb and yellow split peas Ghormeh sabzi, an Iranian stew with green herbs, dried limes, beans, and sheep meat Goulash, a Hungarian meat stew with paprika Gumbo, a Louisiana creole dish Hachee, a Dutch type of stew with wine or vinegar Haleem, an Indian-Pakistani lentil and beef stew Hasenpfeffer, a sour, marinated rabbit stew from Germany Hayashi rice, a Japanese dish of beef, onions and mushrooms in red wine and demi-glace sauce, served with rice Irish stew, made with lamb or mutton, potato, onion, and parsley Ishtu, a curry in Kerala, India made from chicken or mutton, potato, and coconut milk Istrian stew or yota, or jota, a dish popular in Croatian and Slovenian Istra and NE Italy I-tal stew, a Rastafarian vegan dish of mostly Caribbean root vegetables and spices Jjigae, a diverse range of Korean stews Kaldereta, a goat meat stew from the Philippines Kalops, a traditional Swedish beef stew, with onions and carrots, served with potatoes and pickled beets Kare-kare, stewed beef or oxtail and vegetables in peanut sauce from the Philippines Karelian hot pot, from the region of Karelia in eastern Finland Kharcho is a traditional Georgian soup containing beef, rice, cherry plum purée, and chopped walnuts Khash, a traditional Armenian/Azerbaijani dish of pig's or cow's feet Khoresht, a variety of Persian stews, often prepared with saffron Kokkinisto, Greek stew with red meat, in a tomato passata with shallots, cinnamon, and other spices Kuurdak, a type of stew from Central Asia Kuzhambu, (also called Pulusu or Saaru, depending on region) a range of stews from southern India based on tamarind broth and vegetables, meat or fish Lobscouse, a Norwegian stew with beef, potato, onion, and carrot Lancashire hotpot, an English stew Lecsó, a summertime favourite in Hungary, vegetable stew with bell pepper and tomato as main ingredients Linseneintopf ("lentil stew") Lobby, a stew from Staffordshire, England Locro, a stew (mainly in the Andes region) Machanka, a Belarus and Ukraine pork stew Matelote, a French fish stew made with freshwater fish, fish stock, and wine Mechado, a Philippine beef stew Moppelkotze Moqueca, a Brazilian stew with fish (or shrimp, crab, or other seafood) as its main ingredient Mućkalica, a Serbian stew Nihari, an Indian meat stew, usually made with goat, chicken, lamb and less commonly beef. It is made overnight and served for breakfast. Nikujaga, a Japanese beef and potato stew Oil down, national dish of Grenada, made of breadfruit, salted meat, chicken, dumplings, callaloo, coconut milk, and spices Olla podrida, a Spanish red bean stew Pašticada, a Croatian stew from the region of Dalmatia Peperonata, an Italian stew made with peppers Pepposo, a Tuscan beef stew Pescado blanco, a white fish stew from Pátzcuaro, Michoacán, Mexico Pichelsteiner a traditional German stew Pörkölt, a Hungarian meat stew resembling goulash, flavoured with paprika Potjiekos, a South African stew Pot-au-feu, a simple French beef stew Pozole, a Mexican stew or soup Puchero, a stew from Andalusia, Spain, also common in South America and the Philippines Ratatouille, a French vegetable stew Rendang, an Indonesian spicy beef stew Ragoût, a French stew Sāmbār, a lentil-based spiced vegetable stew, cooked with pigeon pea and tamarind broth in South Indian cuisine Sancocho, a stew from the Caribbean Scouse, a stew commonly eaten by sailors throughout Northern Europe, popular in seaports such as Liverpool Semur, a typical Indonesian stew with beef or chicken, potatoes, carrots, various spices, and kecap manis (sweet soy sauce) Stufato, an Italian stew Steckrübeneintopf (based on rutabaga) Slumgullion, a watery stew of meat and vegetables Tagine, a Moroccan stew, named after the conical pot in which it is traditionally cooked or served Tocană, a Romanian stew prepared with tomato, garlic, and sweet paprika Tharid, a traditional Arab stew of bread in broth Wat, an Ethiopian and Eritrean stew Waterzooi, a Belgian stew Yahni, a Greek (γιαχνί), Turkish, and Persian stew
== Structure == MOFs are composed of two main components: an inorganic metal cluster (often referred to as a secondary-building unit or SBU) and an organic molecule called a linker. For this reason, the materials are often referred to as hybrid organic-inorganic materials. The organic units are typically mono-, di-, tri-, or tetravalent ligands. The choice of metal and linker dictates the structure and hence properties of the MOF. For example, the metal's coordination preference influences the size and shape of pores by dictating how many ligands can bind to the metal, and in which orientation.
== Conjugated zwitterions == Strongly polarized conjugated compounds (conjugated zwitterions) are typically very reactive, share diradical character, activate strong bonds and small molecules, and serve as transient intermediates in catalysis. Donor-acceptor entities are of vast use in photochemistry (photoinduced electron transfer), organic electronics, switching and sensing.
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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.
A reported purity value reflects the share of the main peak in one chromatographic run and says nothing about identity. Confirming that the expected sequence is present requires a separate measurement such as mass spectrometry. Purity and identity are distinct questions.
A mass spectrum reports the molecular masses present in a sample and shows whether they match the value expected for selank, near 751.9 Da. It also flags common artifacts such as truncation or adduct formation. It does not establish correct stereochemistry or complete sequence order on its own.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.