This is a working overview of lyophilization, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-12-31 and is reviewed periodically as new material appears.
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.
Reported activity for Selank centers on anxiolytic and nootropic effects. Russian clinical reports describe use in anxiety and in cognitive or attention-related complaints. Most of this evidence comes from studies conducted by the same research groups that developed the peptide. Independent replication in other countries remains limited, and no major Western regulatory agency has approved the compound for any indication. The gap between local reports and external verification is a recurring point in discussions of the peptide.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic heptapeptide | Analog of the tetrapeptide tuftsin |
| Sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Reported consistently across pharmacopoeial descriptions |
| Appearance | White to off-white lyophilized powder | Typical form of research-grade material |
| Solubility | Freely soluble in water | Aqueous buffers; poor in nonpolar solvents |
| Typical storage temperature | -20 degrees Celsius | Lyophilized powder; protect from moisture |
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.
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.
Enzymatic stability motivates the extra three residues at the carboxyl end. Native tuftsin is cleaved quickly by circulating aminopeptidases and carboxypeptidases, which limits its duration of action and its usefulness as a tool compound. Extending the chain with proline-rich segments is a common design tactic because proline constrains the backbone and slows proteolysis. The same Pro-Gly-Pro motif appears in other Russian-developed peptides of the era. Whether the full seven-residue chain is required for activity, or whether it acts mainly as a prodrug releasing tuftsin, remains unresolved.
Selank is a synthetic heptapeptide with the sequence Thr-Lys-Pro-Arg-Pro-Gly-Pro. Its four N-terminal residues reproduce tuftsin, a tetrapeptide fragment of the immunoglobulin heavy chain, while the C-terminal Pro-Gly-Pro extension is a synthetic addition. The peptide has a molecular mass near 752 daltons and carries a net positive charge at physiological pH because of the arginine and lysine side chains. Published indexes list it under the name Selank and the sequence abbreviation TKPRPGP. Solid-phase peptide synthesis is the standard production route for research quantities.
Lyophilized material is generally stable for extended periods when kept dry at or below minus twenty degrees Celsius. Working solutions are less stable, and common practice is to aliquot and freeze them so that repeated freeze-thaw cycles are avoided. Aqueous solutions are sensitive to pH extremes and to microbial growth, so short-term storage at refrigerator temperature is typical. Oxidation and hydrolysis are the principal degradation routes. Reconstitution with sterile water or a mild buffer is standard, and solutions should be protected from light.
Regulatory treatment varies by jurisdiction. In Russia the compound is a registered prescription product, while in the European Union and the United States it is generally handled as a research chemical without a marketing authorization. Suppliers therefore operate outside pharmaceutical oversight, and buyers rely on supplier documentation for purity and identity claims. Chain of custody and third-party testing are the main verification tools. Analysts note that the absence of a pharmacopoeial monograph for research-grade material limits standardization across vendors.
== External links == Media related to Chocolate at Wikimedia Commons Quotations related to Chocolate at Wikiquote The dictionary definition of chocolate at Wiktionary Cookbook:Chocolate at Wikibooks Works related to Portal:Chocolate at Wikisource Chocolate travel guide from Wikivoyage
=== Other performance aspects === The evaluation of the performance cannot be considered complete without considering the limit of detection, the range of linear response and the signal reproducibility. EI is known as a low-efficiency ionization technique. Because less than 1/10 000 of the gas-phase sample molecules are ionized, impressive detection limits cannot be expected. However, the efficient interfacing mechanism of this interface allows picogram-level detection limit in selected ion monitoring (SIM) for most substances. On the other hand, soft ionization techniques such as ESI are, in some cases, far more efficient but generate fewer fragment ions. The cost of this attitude is paid in terms of structural information so that a second analyzer to generate MS/MS spectra is an obligation. A typical EI spectrum, in general, has extensive structural information, and a cheaper, single-stage mass spectrometer might be sufficient for analyte characterization or identification. As a rule of the thumb, nanogram-level sensitivity is obtained in full-scan mode for most substances. Linearity and reproducibility are two point of strength of the interface. Up to four orders of magnitude linearity with RSD lower than 10% are common values in many applications.
On radiographs, the differences in the mineralization of different parts of the tooth and surrounding periodontium can be noted; enamel appears lighter than dentin or pulp since it is denser than both and more radiopaque. Enamel does not contain collagen, as found in other hard tissues such as dentin and bone, but it does contain two unique classes of proteins: amelogenins and enamelins. While the role of these proteins is not fully understood, it is believed that they aid in the development of enamel by serving as a framework for minerals to form on, among other functions. Once it is mature, enamel is almost totally without the softer organic matter. Enamel is avascular and has no nerve supply within it and is not renewed, however, it is not a static tissue as it can undergo mineralization changes.
Boron neutron capture therapeutics are pharmaceuticals intended for use to deliver boron-10 to cancerous cells as part of boron neutron capture therapy (BNCT). Boron-10 atoms strongly absorb neutrons to form a metastable state of boron-11, which undergoes α-decay. By accumulating boron-10 in cancerous cells and subjecting the tumor to neutron radiation, high-energy α particles are selectively delivered only to the target cells. This neutron bombardment results in the selective destruction of the tumor cells that the boron-10 was absorbed into. As of 2023, the technology is available in Japan only, and even there few implementations have been reported.
Sources: en.wikipedia.org
There is no high-quality evidence showing that tea consumption has health effects, other than possibly increasing alertness caused by caffeine in the leaves. There is insufficient evidence that tea polyphenols have any effect on health or lowering disease risk. Black and green teas contain no essential nutrients in significant amounts, with the exception of the dietary mineral manganese, at 0.5 mg per cup or 26% of the Reference Daily Intake. Fluoride is sometimes present in tea; certain types of "brick tea", made from old leaves and stems, have the highest levels, enough to pose a health risk if too much tea is drunk, which has been attributed to high levels of fluoride in soils, acidic soils, and long brewing.
A black smoker or deep-sea vent is a type of hydrothermal vent found on the seabed, typically in the bathyal zone (with largest frequency in depths from 2,500 to 3,000 m (8,200 to 9,800 ft)), but also in lesser depths as well as deeper in the abyssal zone. They appear as black, chimney-like structures that emit a cloud of black material. Black smokers typically emit particles with high levels of sulfur-bearing minerals, or sulfides. Black smokers are formed in fields hundreds of meters wide when superheated water from below Earth's crust comes through the ocean floor (water may attain temperatures above 400 °C (752 °F)). This water is rich in dissolved minerals from the crust, most notably sulfides. When it comes in contact with cold ocean water, many minerals precipitate, forming a black, chimney-like structure around each vent. Chimneys thicken due to heat conduction encouraging crystallization. The deposited metal sulfides can become massive sulfide ore deposits in time. Some black smokers along the Azores segment of the Mid-Atlantic Ridge are exceptionally metal-rich; for instance, hydrothermal fluids from the Rainbow Vent Field contain up to 24,000 μM of dissolved iron. Black smokers were first discovered in 1979 on the East Pacific Rise by scientists from Scripps Institution of Oceanography during the RISE Project. They were observed using the deep submergence vehicle ALVIN from the Woods Hole Oceanographic Institution. Now, black smokers are known to exist in the Atlantic and Pacific Oceans, at an average depth of 2,100 m (6,900 ft).
=== Performing arts === The Coastal Credit Union Music Park at Walnut Creek hosts major international touring acts. In 2011, the Downtown Raleigh Amphitheater opened (now sponsored as the Red Hat Amphitheater), which hosts numerous concerts primarily in the summer months. An additional amphitheater sits on the grounds of the North Carolina Museum of Art, which hosts a summer concert series and outdoor movies. Nearby Cary is home to the Koka Booth Amphitheatre which hosts additional summer concerts and outdoor movies, and serves as the venue for regularly scheduled outdoor concerts by the North Carolina Symphony based in Raleigh. During the North Carolina State Fair, Dorton Arena hosts headline acts. The private Lincoln Theatre is one of several clubs in downtown Raleigh that schedules many concerts throughout the year in multiple formats (rock, pop, country). The Duke Energy Center for the Performing Arts complex houses the Raleigh Memorial Auditorium, the Fletcher Opera Theater, the Kennedy Theatre, and the Meymandi Concert Hall. In 2008, a new theatre space, the Meymandi Theatre at the Murphey School, was opened in the restored auditorium of the historic Murphey School. Theater performances are also offered at the Raleigh Little Theatre, Long View Center, Ira David Wood III Pullen Park Theatre, and Stewart and Thompson Theaters at North Carolina State University.
==== Antibodies ==== Two monoclonal antibodies have been approved to target amyloid beta – donanemab and lecanemab – but as of 2025, their role in treatment is uncertain because of side effects, questions about efficacy, and cost. Lecanemab is approved in the US, including a boxed warning about amyloid-related imaging abnormalities. A 2026 meta-analysis found that anti-amyloid antibodies have no effect in the treatment of Alzheimer's disease. A 2026 Cochrane review found no effect or at best small effect. Anti-amyloid antibodies may cause harmful adverse effects and have been shown to slow disease progression only in individuals with "early and mild AD, and cognitive benefits were often marginal."
==== Due to use of medication ==== Urine tests can be falsely positive in those that are taking the medications: chlorpromazine, promethazine, phenothiazines, methadone, aspirin, carbamazepine and drugs that cause high urinary pH.
Sources: en.wikipedia.org
2019 Ford EcoBoost 400 – in the final race of the 2019 Monster Energy NASCAR Cup Series, three teams – Premium Motorsports, Spire Motorsports and Rick Ware Racing – were found to have manipulated the race finish by parking their cars in order to allow the No. 27 team to score more points, passing the Gaunt Brothers Racing No. 96 in the standings to obtain an end of season cash bonus.
=== Liver === In July 2013, the US Food and Drug Administration (FDA) issued a warning that taking ketoconazole by mouth can cause severe liver injuries and adrenal gland problems: adrenal insufficiency and worsening of other diseases related to the gland conditions. It recommends oral tablets should not be a first-line treatment for any fungal infection. It should be used for the treatment of certain fungal infections, known as endemic mycoses, only when alternative antifungal therapies are not available or not tolerated. As contraindication it should not be used in people with acute or chronic liver disease.
The capacity of this molecule to act as a two-electron carrier (moving between the quinone and quinol form) and a one-electron carrier (moving between the semiquinone and one of these other forms) is central to its role in the electron transport chain due to the iron–sulfur clusters that can only accept one electron at a time and as a free radical–scavenging antioxidant.
== Spectroradiometers == Spectroradiometers, which operate almost like the visible region spectrophotometers, are designed to measure the spectral density of illuminants. Applications may include evaluation and categorization of lighting for sales by the manufacturer, or for the customers to confirm the lamp they decided to purchase is within their specifications. Components:
Sources: en.wikipedia.org
Selank is a synthetic seven-amino-acid peptide modeled on tuftsin, a fragment of the immunoglobulin G heavy chain. It was designed in Russia to combine anxiolytic and immunomodulatory properties in one molecule.
The first four residues of Selank reproduce the tuftsin sequence Thr-Lys-Pro-Arg. A Pro-Gly-Pro extension at the C-terminus was added to slow enzymatic breakdown and extend residence time.
It holds marketing authorization in Russia, where nasal drop formulations are sold. No equivalent approval exists in the European Union, the United States, or most other countries.
Selank is a synthetic peptide made of seven amino acids. It is modeled on tuftsin, a natural tetrapeptide, with an added three-residue tail. It is not a small-molecule drug.