tuftsin raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-12-24 and is reviewed periodically as new material appears.
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.
Lyophilised material kept dry at minus 20 degrees Celsius or colder is the most stable form, and suppliers commonly state a shelf life of two years or more under those conditions. Once dissolved, degradation accelerates through hydrolysis and deamidation, particularly at alkaline pH or elevated temperature. Working solutions are usually divided into single-use aliquots to avoid repeated freeze-thaw cycles. The choice of reconstitution solvent affects both stability and the ionic strength of the final preparation.
Reverse-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres is the standard purity method. Mass spectrometry, typically electrospray ionisation, confirms identity through the expected mass-to-charge pattern. Amino acid analysis can verify composition independently. Chiral purity requires separate techniques such as derivatisation followed by chromatographic separation, and such data are rarely reported for research-grade material.
Quantification in biological matrices relies on liquid chromatography coupled to tandem mass spectrometry with stable-isotope internal standards. Low plasma concentrations and adsorption to container surfaces both complicate measurement. Solid-phase extraction is often needed to reduce matrix interference before injection. Reported limits of quantification differ widely between laboratories, which makes direct comparison of pharmacokinetic results difficult and limits meta-analysis.
| 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 |
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.
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 studied chiefly as an animal-model anxiolytic with proposed secondary effects on memory and immune signaling. Reported mechanisms include modulation of the GABA-A receptor complex, inhibition of enkephalin-degrading enzymes, and shifts in monoamine turnover within limbic structures. Some experiments describe increased expression of brain-derived neurotrophic factor in the hippocampus after repeated dosing. No single molecular target has been confirmed, and the peptide does not bind any receptor with the selectivity typical of a conventional small-molecule drug. Mechanism therefore remains a set of hypotheses rather than an established pathway.
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.
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.
==== Toxicity ==== While application of inorganic nanoparticles in bionanotechnology shows encouraging advancements from a materials science perspective, the use of such materials in vivo is limited by issues related with toxicity, biodistribution and bioaccumulation. Because metal inorganic nanoparticle systems degrade into their constituent metal atoms, challenges may arise from the interactions of these materials with biosystems, and a considerable amount of the particles may remain in the body after treatment, leading to a buildup of metal particles potentially resulting in toxicity. Recently, however, some studies have shown that certain nanoparticle environmental toxicity effects aren't apparent until nanoparticles undergo transformations to release free metal ions. Under aerobic and anaerobic conditions, it was found that copper, silver, and titanium nanoparticles released low or insignificant levels of metal ions. This is evidence that copper, silver, and titanium NP are slow to release metal ions, and may therefore appear at low levels in the environment. Additionally, nanoshell coatings significantly protect against degradation in the cellular environment and also reduce QDs toxicity by reducing metal ion leakage from the core.
== See also == Metal carbonyl cluster Metal carbon dioxide complex Metal phosphine complex – Chemical compounds containing phosphorus and metalsPages displaying short descriptions of redirect targets Alkaline earth octacarbonyl complex
== Technology == MA/MH technology is achieved by combining proprietary blends of polymers to obtain the desired MVTR and then manipulating the oxygen (O2) and carbon dioxide (CO2) transmission rates of the polymer by laser and/or mechanical microperforations. The result is a film which is tailored to provide the optimum modified atmosphere and modified humidity for the produce to be packaged. "Film composition and extent of microperforation are tailored in accordance with the respiratory activity and weight of the produce packaged, anticipated temperature fluctuations during storage and shipment, and expected physiological and pathological responses of the produce to CO2/O2 concentrations and humidity levels inside the package. ... [MA/MH] packaging allow[s] the formation of a desirable modified atmosphere, retarding ripening and senescence of the produce. Additional beneficial effects ... include reduction of decay, chilling injury, leaf elongation, leaf sprouting, tissue discoloration, peel blemishes, and formation of off-odors, and inhibition of bacterial growth on the produce surface."
=== 1970s === The scientific and medical markets have always been important for Edwards. The introduction of X-ray technology required the use of a vacuum. Vacuum technology also played an important role in the development of neuroimaging (brain scanners), like MRI, CT, and PET scanners. The first home computers were brought to the market in the 1970s and the development of computer technology has been unstoppable ever since. The mass production of CRT displays and integrated circuits necessitated electronic companies to scale up, with vacuum installations becoming bigger and demand for vacuum purity increasing. In the 1970s, Edwards Vacuum also collaborated with Seiko Seiki for the invention of magnetically suspended turbopumps. These molecular turbopumps use magnetically levitated bearings, which eliminate the risk of vacuum contamination, require less maintenance, and feature lower noise and vibration levels. This type of technology is particularly suitable for scientific applications and the harsh processes in semiconductor manufacturing. The newly emerged dry pumps and turbomolecular pumps supported innovation in the scientific instrument markets over the next couple of decades. The scientific instrument market is now the second biggest market for Edwards Vacuum, after the semiconductor and electronics industry.
Alkaloids are generated by various living organisms, especially by higher plants – about 10 to 25% of those contain alkaloids. Therefore, in the past the term "alkaloid" was associated with plants. The alkaloids content in plants is usually within a few percent and is inhomogeneous over the plant tissues. Depending on the type of plants, the maximum concentration is observed in the leaves (for example, black henbane), fruits or seeds (Strychnine tree), root (Rauvolfia serpentina) or bark (cinchona). Furthermore, different tissues of the same plants may contain different alkaloids. Beside plants, alkaloids are found in certain types of fungus, such as psilocybin in the fruiting bodies of the genus Psilocybe, and in animals, such as bufotenin in the skin of some toads and a number of insects, markedly ants. Some amines, such as adrenaline and serotonin, which play an important role in higher animals, are similar to alkaloids in their structure and biosynthesis and are sometimes called alkaloids.
Sources: en.wikipedia.org
In 1771, Samuel Engel mentions, in his Traité de la nature, de la culture, et de l'utilité des pommes de terre par un ami des hommes, that half of Europeans live on bread and the other half on potatoes, and also that bread is made by mixing a third or a quarter of potato with cereal flour, which gives a dish "preferred by taste, to bread of pure wheat". He refers to various authors, including François Mustel who wrote Mémoire sur les pommes de terre et sur le pain économique. Mustel invented, before 1766, a kind of inverted jointer plane to grate potatoes, peeled or not, into a fine mush that must be mixed with wheat flour: the proportion of one 1/3 flour to 2/3 potatoes gives an edible bread he says, 50% of each ingredient a good one, and at the rate of 2/3 to 1/3, it is difficult to notice that the bread is not pure wheat; the mixture must be kneaded with ordinary sourdough, but less water is used and less heat is applied, which produces an additional saving; this bread keeps fresher for longer, it remains edible for fifteen days, instead of six for traditional bread. This prolongation of freshness, which is very appreciable, encourages many Ardennes farmers to add to their bread, until the 1980s, some 10% of potatoes, the Gaumais going up to 50%. Research on the use of the tuber for bread making was numerous in France at the end of the 18th century, but this did not lead to the massive perpetuation of this practice.
The most common cause of ketoacidosis is a deficiency of insulin in type 1 diabetes or late-stage type 2 diabetes. This is called diabetic ketoacidosis and is characterized by hyperglycemia, dehydration and metabolic acidosis. Other electrolyte disturbances such as hyperkalemia and hyponatremia may also be present. A lack of insulin in the bloodstream allows unregulated fatty acid release from adipose tissue which increases fatty acid oxidation to acetyl CoA, some of which is diverted to ketogenesis. This raises ketone levels significantly above what is seen in normal physiology.
The homeostatic mechanism which controls the plasma sodium concentration is rather more complex than most of the other homeostatic mechanisms described on this page. The sensor is situated in the juxtaglomerular apparatus of kidneys, which senses the plasma sodium concentration in a surprisingly indirect manner. Instead of measuring it directly in the blood flowing past the juxtaglomerular cells, these cells respond to the sodium concentration in the renal tubular fluid after it has already undergone a certain amount of modification in the proximal convoluted tubule and loop of Henle. These cells also respond to rate of blood flow through the juxtaglomerular apparatus, which, under normal circumstances, is directly proportional to the arterial blood pressure, making this tissue an ancillary arterial blood pressure sensor. In response to a lowering of the plasma sodium concentration, or to a fall in the arterial blood pressure, the juxtaglomerular cells release renin into the blood. Renin is an enzyme which cleaves a decapeptide (a short protein chain, 10 amino acids long) from a plasma α-2-globulin called angiotensinogen. This decapeptide is known as angiotensin I. It has no known biological activity. However, when the blood circulates through the lungs a pulmonary capillary endothelial enzyme called angiotensin-converting enzyme (ACE) cleaves a further two amino acids from angiotensin I to form an octapeptide known as angiotensin II. Angiotensin II is a hormone which acts on the adrenal cortex, causing the release into the blood of the steroid hormone, aldosterone.
Between 2001 and 2003, Starbucks opened six (of 80 planned) locations in Israel and having struggled with fierce local competition, Starbucks, along with its partner Delek, however, in April 2003, after losing US$6 million Starbucks Israel closed all six of its locations in Israel, citing "on-going operational challenges" and a "difficult business environment". In January 2011, Starbucks and Tata Coffee, Asia's largest coffee plantation company, announced plans for a strategic alliance to bring Starbucks to India and also to source and roast coffee beans at Tata Coffee's Kodagu facility. In January 2011, Starbucks introduced its largest cup size, the Trenta, which can hold 31 US fluid ounces (920 ml). In October 2011, Starbucks opened another location in Beijing, China, at the Beijing Capital International Airport's Terminal 3, international departures hall; making the company's 500th store in China. The store is the seventh location at the airport. In January 2012, despite a false start in 2007, Starbucks created a 50:50 joint venture with Tata Global Beverages called Tata Starbucks. Tata Starbucks owned and operated Starbucks outlets in India as Starbucks Coffee "A Tata Alliance". Starbucks opened its first store in India in Mumbai on October 19, 2012. On February 1, 2013, Starbucks opened its first store in Ho Chi Minh City, Vietnam, and its first location in Hanoi in July 2014. As of January 2026, the brand has opened over 150 stores in the country.
Signs and Symptoms: 4 Phases: Premycotic Phase: Scale-like red rash on areas of the skin that are not exposed to the sun. Patch Phase: An itchy, thin rash Plaque Phase: Raised bumps or lesions present on the skin Tumor Phase: Tumors begin to form on the skin near or under the lesions. 4 Stages Diagnosis: Physical exam to check for lesions Peripheral blood smear Use a microscope to count the number of blood cells and look at their shape. Skin biopsy Checks for signs of cancer Immunophenotyping Flow cytometry T-cell receptor gene rearrangement test Liver Function Test HIV test X-ray, CT scan, and PET scan To determine if the lymphoma is metastatic Treatments: Chemotherapy Radiation Drug Therapy Photodynamic Therapy Biologic Therapy using Interferon Targeted Therapy UV Radiation Therapy Clinical Trials being pursued Stem cell transplant combined with chemoradiation Clinical trials being pursued
Sources: en.wikipedia.org
The Gibbs phase rule states that, under most thermodynamic conditions (fixed temperature, pressure, chemical potential, and other intensive thermodynamic properties), for each chemical species, only one phase is thermodynamically stable (i.e. have the lowest Gibbs free energy per volume), except on certain boundaries, such as the coexistence of ice and water right at the freezing point. In particular, since each crystal morph is a phase of matter, this implies that under normal circumstances, there exists only a single crystal morph at thermodynamic equilibrium. However, some phases may be kinetically stable, even if not energetically so. Disappearing polymorphs occur when there are two morphs of a substance, and one morph has lower Gibbs free energy, but is kinetically slower to form. Thus, when the crystal is first formed, the kinetically faster morph occurs first. Eventually, by accident or catalysis, the other morph occurs, which can then serve as seed crystal. More abstractly stated, disappearing polymorphs are morphs that are kinetically stable but not thermodynamically stable.
==== Formation of metastable species ==== As the gas (M) enters the ion source, an electric potential in the range of +1 to +5 kV is applied to generate a glow discharge. The glow discharge plasma contains short-lived energetic species including electrons, ions, and excimers. Ion/electron recombination leads to the formation of long-lived excited-state neutral atoms or molecules (metastable species, M*) in the flowing afterglow region. The DART gas can be heated from room temperature (RT) to 550 °C to facilitate desorption of analyte molecules. Heating is optional but may be necessary depending on the surface or chemical being analyzed. The heated stream of gaseous metastable species passes through a porous exit electrode that is biased to a positive or negative potential in the range 0 to 530V. When biased to a positive potential, the exit electrode acts to remove electrons and negative ions formed by Penning ionization from the gas stream to prevent ion/electron recombination and ion loss. If the exit electrode is biased to a negative potential, electrons can be generated directly from the electrode material by surface Penning ionization. An insulator cap at the terminal end of the ion source protects the operator from harm.
Unmodified mRNA inhibits immunogenicity by triggering the production of interferons that block the generation of T helper cells, which direct B cells to produce antibodies. CureVac attempted to evade immune detection by altering the RNA sequence in a way that does not affect the coded protein, but structural differences in the non-coding regions might have affected immunogenicity. Unmodified mRNA may have decreased tolerability, leading to the adoption of a lower dose, but studies of the Pfizer–BioNTech and Moderna vaccines found only modest gains at higher doses. A next-generation vaccine from CureVac in collaboration with GlaxoSmithKline, also using unmodified mRNA, is more stable inside cells and produces higher levels of neutralizing antibodies in animals.
Muslims, India's largest religious minority, have contributed significantly to a synthetic Indo-Islamic religious culture. Sufism, the heterodox mystical movement in Islam found receptiveness among adherents of the medieval regional Shaivite and Vaishnavite traditions of Bhakti. Sikh gurdwaras and Sufi dargahs often attract both visitors and worshippers from other religions. India has monastic traditions such as that of Jain ascetics some of whom practice an extreme form of nonviolence (ahimsa) and Buddhist communities that have preserved ancient styles of meditations. This religious diversity coexists with religious endogamy—people rarely marry outside their faith. There is also religious segregation in housing—religious groups cluster by choice or necessity. Thus, India's religious picture has both rich intermixing and clear divisions.
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.
Dry powder is best kept sealed, protected from light, and held at minus 20 degrees Celsius or below. Desiccant packaging helps limit moisture uptake because the material is hygroscopic. A sealed vial should be allowed to equilibrate to room temperature before opening to reduce condensation.