The short version of electrospray ionization fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-07-31 and is reviewed periodically as new material appears.
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.
Published clinical evidence is limited. Most controlled trials were conducted in Russia, enrolled modest numbers of participants, and appeared in Russian-language journals, which restricts independent verification. Reported outcomes include lower anxiety scores, improved attention and memory measures, and changes in fatigue ratings. Reviews written in English note methodological limitations such as small samples and inconsistent endpoints. Whether the compound produces clinically meaningful benefit relative to established anxiolytics is therefore an open question rather than an established finding.
Lyophilized Selank, the dry powder form, is generally stored frozen at minus 20 degrees Celsius or colder for long-term keeping. The solid is hygroscopic and should stay sealed, dry, and protected from light. Once dissolved, the peptide is less stable and is usually held refrigerated at 2 to 8 degrees Celsius for short periods. Repeated freezing and thawing is avoided because it can promote aggregation and loss of activity. Buffers and pH choice also affect how long a solution remains usable.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C33H57N11O9 | Free peptide form |
| Molecular mass | About 751.9 Da | Calculated average mass |
| Amino acid sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Single-letter form TKPRPGP |
| Structural basis | Tuftsin analogue | Extended version of a natural tetrapeptide |
| Development origin | Russian Academy of Sciences | Work carried out from the 1980s onward |
Published work on this peptide almost always uses intranasal delivery, with drops or a spray applied to the nasal mucosa. Some animal experiments have used subcutaneous or intraperitoneal injection, and a smaller number have compared routes directly. Oral administration is not a focus of the literature, because short peptides of this size are broken down by digestive enzymes and cross intestinal barriers poorly. How much of an intranasal dose reaches the bloodstream intact in humans remains an open question.
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.
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.
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.
Among other things, the parathyroid hormone causes calcium and phosphate to be released from the bones, which ultimately leads to renal bone disorders and calcification of the kidneys, skin, heart and blood vessels. In the kidneys, this calcification contributes to further destruction of the kidney tissue. The reduced responsiveness of the parathyroid cells to calcium disrupts the negative feedback of parathyroid hormone secretion, so that parathyroid hormone continues to be secreted despite the increase in calcium levels. As less phosphate reaches the renal tubules due to the reduced filtration rate, the inhibitory effect of parathyroid hormone on reabsorption in the main body has only a minor effect on the blood phosphate level. The loss of nephrons and the associated decrease in the number of sodium ion channels leads to a decrease in the concentration gradient in the kidney. However, this is the driving force for water reabsorption in the mid-piece and—in the presence of ADH—also in the collecting ducts. The result is a loss of water via the urine and thus drying out of the body, which is exacerbated by the loss of fluid during vomiting. One consequence of the kidneys' reduced ability to excrete hydrogen ions, phosphate and sulphate and the excessive loss of bicarbonate is the metabolic acidification of the blood (metabolic acidosis). Metabolic acidosis occurs in 80% of cats with chronic kidney disease.
Cave 14, a small and nearly square room with a vaulted ceiling (2.17x2.17 meters; 7 x 7 feet), is considered as later than the "Cave of the Musicians", and dated to the late 4th century CE to early 5th century CE, circa 400 CE, by Rhie. The cave has many designs showing Central Asian traders encountering various dangers on their way, such as being lost in the dark, and being saved by the Dragon-King Mabi. Cave 14 is considered as an important historical marker for the dress styles or the armour types worn by some of the figures.
Astatine is the rarest naturally occurring element. The total amount of astatine in the Earth's crust (quoted mass 2.36 × 1025 grams) is estimated by some to be less than one gram at any given time. Other sources estimate the amount of ephemeral astatine, present on earth at any given moment, to be up to one ounce (about 28 grams). Any astatine present at the formation of the Earth has long since disappeared; the four naturally occurring isotopes (astatine-215, -217, -218 and -219) are instead continuously produced as a result of the decay of radioactive thorium and uranium ores, and trace quantities of neptunium-237. The landmass of North and South America combined, to a depth of 16 kilometers (10 miles), contains only about one trillion astatine-215 atoms at any given time (around 3.5 × 10−10 grams). Astatine-217 is produced via the radioactive decay of neptunium-237. Primordial remnants of the latter isotope—due to its relatively short half-life of 2.14 million years—are no longer present on Earth. However, trace amounts occur naturally as a product of transmutation reactions in uranium ores. Astatine-218 was the first astatine isotope discovered in nature. Astatine-219, with a half-life of 56 seconds, is the longest lived of the naturally occurring isotopes. Isotopes of astatine are sometimes not listed as naturally occurring because of misconceptions that there are no such isotopes, or discrepancies in the literature. Astatine-216 has been counted as a naturally occurring isotope but reports of its observation (which were described as doubtful) have not been confirmed.
With its help, they have been able to predict the structure of virtually all the 200 million proteins that researchers have identified. Since their breakthrough, AlphaFold2 has been used by more than two million people from 190 countries. Among a myriad of scientific applications, researchers can now better understand antibiotic resistance and create images of enzymes that can decompose plastic.
Sources: en.wikipedia.org
==== Metal ions ==== Several metal cations have high affinities for imidazole, the functional group of the His-tag. Divalent cation M2+ (M = Mn, Fe, Co, Ni, Cu, Zn etc) transition metal imidazole complexes are most frequently used for this purpose. The choice of cation is generally a compromise between binding capacity and purity. Nickel is often used as it offers a good balance between these factors, while cobalt can be used when it is desired to increase the purity of purification as it has less affinity for endogenous proteins; binding capacity however is lower compared with nickel.
Majority (about 70% to 80%) is converted to bicarbonate ions (HCO3–) by the enzyme carbonic anhydrase in the red blood cells, by the reaction: CO2 + H2O → H2CO3 → H+ + HCO3– 5–10% is dissolved in blood plasma 5–10% is bound to hemoglobin as carbamino compounds Hemoglobin, the main oxygen-carrying molecule in red blood cells, carries both oxygen and carbon dioxide. However, the CO2 bound to hemoglobin does not bind to the same site as oxygen. Instead, it combines with the N-terminal groups on the four globin chains. However, because of allosteric effects on the hemoglobin molecule, the binding of CO2 decreases the amount of oxygen that is bound for a given partial pressure of oxygen. This is known as the Haldane Effect, and is important in the transport of carbon dioxide from the tissues to the lungs. Conversely, a rise in the partial pressure of CO2 or a lower pH will cause offloading of oxygen from hemoglobin, which is known as the Bohr effect.
=== Without insulin === When carbohydrate counting is used without insulin, it can be used as a tool to manage blood sugar levels. A certain number of carbohydrate grams or carbohydrate units is consumed with each meal and with each snack. In keeping the carbohydrate at a certain level, the blood sugar is able to remain within a normal level. The American Diabetes Association recommends starting at around 45–60 carbohydrate grams (3–4 carb units) at each meal, with potential to increase or decrease that amount.
Sources: en.wikipedia.org
=== P. s. pv. actinidiae === Mesarich et al. 2017 provides several libraries for transposon insertion sequencing of mutants of P. s. a. The kiwifruit industry in New Zealand has suffered catastrophic losses since their first known outbreak in 2007 from P. syringae pv. actinidiae. New Zealand is second to Italy in the total volume of kiwifruit exports making an annual revenue of $NZ 1 billion, making it the most economically valuable export in the country. In 2014 the loss of exports alone was as high as NZ$930 million. Growers had to pay for treatments, and removal of infected vines along with suffering the loss of capital value in their orchards. For some, the orchard values went from NZ$450,000/ha to $70,000/ha after the outbreak, which is the price of bare land. The total loss of equity for the country of New Zealand was as high as NZ$2 billion. Between 2010 and 2012 over 2,000 hectares (4,900 acres) of Italian kiwifruit orchards either were killed by P. syringae pv. actinidiae or were killed to contain the disease. The financial consequences for growers and their suppliers were severe, as were the economic consequences more widely.
=== Abuse potential === Pregabalin has potential for recreational use and abuse. It possesses a relatively wide therapeutic index and margin of safety compared to other central nervous system (CNS) depressants, and its effects may include euphoria, anxiolysis, and sedation. Although generally considered to have low abuse potential, reports describe pregabalin inducing sensations of euphoria, calmness, excitement, and a "high" comparable to that of cannabis. These effects may contribute to the development of substance dependence, and withdrawal symptoms can occur if the medication is stopped abruptly. While pregabalin and cannabis share certain effects, such as CNS depressant and orexigenic (appetite-stimulating) properties, they differ significantly in their pharmacodynamics. Cannabis is primarily an anxiogenic substance with mild psychedelic effects, whereas pregabalin is an anxiolytic agent associated with mild euphoria that is prone to rapid tolerance.
The administration of a nucleoside-modified messenger RNA sequence can cause a cell to make a protein, which in turn could directly treat a disease or could function as a vaccine; more indirectly the protein could drive an endogenous stem cell to differentiate in a desired way. The primary challenges of RNA therapy center on delivering the RNA to the appropriate cells. Challenges include the fact that naked RNA sequences naturally degrade after preparation; they may trigger the body's immune system to attack them as an invader; and they are impermeable to the cell membrane. Once within the cell, they must then leave the cell's transport mechanism to take action within the cytoplasm, which houses the necessary ribosomes. Overcoming these challenges, mRNA as a therapeutic was first put forward in 1989 "after the development of a broadly applicable in vitro transfection technique." In the 1990s, mRNA vaccines for personalized cancer were developed, typically using unmodified mRNA. mRNA based therapies continue to be investigated as a method of treatment or therapy for both cancer as well as auto-immune, metabolic, and respiratory inflammatory diseases. Gene editing therapies such as CRISPR may also benefit from using mRNA to induce cells to make the desired Cas protein. Since the 2010s, RNA vaccines and other RNA therapeutics have been considered to be "a new class of drugs". The first mRNA-based vaccines received restricted authorization and were rolled out across the world during the COVID-19 pandemic by Pfizer–BioNTech COVID-19 vaccine and Moderna, for example.
Sources: en.wikipedia.org
It is a seven-amino-acid peptide, Thr-Lys-Pro-Arg-Pro-Gly-Pro, produced by chemical synthesis rather than extracted from biological tissue. Its design is based on tuftsin, a natural immunomodulatory tetrapeptide. The C-terminal Pro-Gly-Pro segment is a common stabilising motif in short regulatory peptides.
The core four residues correspond to tuftsin, which occurs naturally as part of immunoglobulin G. The full seven-residue sequence, however, is not a known endogenous peptide. It is a laboratory-designed analogue intended to combine tuftsin-like activity with greater resistance to breakdown.
No single receptor has been confirmed as the primary target. Reports describe involvement of the GABAergic system, interference with enkephalin degradation, and shifts in neurotrophic factor expression. Because these observations come from different models and assays, they have not yet been integrated into one accepted mechanism.
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.