A practical reference on Research chemical: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-10-09 and is reviewed periodically as new material appears.
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.
Peptide bonds are vulnerable to protease attack, and Selank is no exception. Measured half-life in serum is short, on the order of minutes in several reports, which explains why intranasal administration is the common route described in the literature. Absorption across the nasal mucosa partially bypasses first-pass hepatic metabolism. Quantitative data on human bioavailability remain limited and are difficult to compare across studies.
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.
| 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 |
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.
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.
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.
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.
99Mo → 99mTc + e− + νe The molybdenum isotope has a half-life of approximately 66 hours (2.75 days), so the generator has a useful life of about two weeks. Most commercial 99mTc generators use column chromatography, in which 99Mo in the form of molybdate, MoO42− is adsorbed onto acid alumina (Al2O3). When the 99Mo decays it forms pertechnetate TcO4−, which because of its single charge is less tightly bound to the alumina. Pulling normal saline solution through the column of immobilized 99Mo elutes the soluble 99mTc, resulting in a saline solution containing the 99mTc as the dissolved sodium salt of the pertechnetate. The pertechnetate is treated with a reducing agent such as Sn2+ and a ligand. Different ligands form coordination complexes which give the technetium enhanced affinity for particular sites in the human body. 99mTc decays by gamma emission, with a half-life: 6.01 hours. The short half-life ensures that the body-concentration of the radioisotope falls effectively to zero in a few days.
The activated receptor must first interact with other proteins inside the cell before the ultimate physiological effect of the ligand on the cell's behavior is produced. Often, the behavior of a chain of several interacting cell proteins is altered following receptor activation. The entire set of cell changes induced by receptor activation is called a signal transduction mechanism or pathway.
=== Singles === "Since You Broke My Heart" / "We Know" — Reprise 0324 — released November 1964 "I'm A Fool" / "So Many Ways" — Reprise 0367 – May 1965 (No. 17 U.S., No. 23 CAN) "I'm A Fool" / "So Many Ways" / "Since You Broke My Heart" / "We Know" — Reprise 60072 ep (France) – May 1965 "Not The Lovin' Kind" / "Chimes of Freedom" — Reprise 0401 – September 1965 (No. 25 U.S., No. 15 Canada) "Please Don't Fight It" / "The Rebel Kind" — Reprise 0426 – November 1965 (No. 25 Canada) "Superman" / "I Can't Get Her Off My Mind" — Reprise 0444 – February 1966 (No. 94 U.S., No. 15 Canada) "Tie Me Down" / "It's Just The Way You Are" — Reprise 0462 – April 1966 "Look Out Girls (Here We Come)" / "She's So Far Out She's In" — Reprise 0469 – July 1966 "I Hope She's There Tonight" / "Josephine" — Reprise 0529 – November 1966 "If You're Thinkin' What I'm Thinkin'" / "Pretty Flamingo" — Reprise 0544 – January 1967 (No. 128 U.S., No. 2 CAN) "Two in the Afternoon" / "Good Luck, Best Wishes to You" — Reprise 0579 – April 1967 (No. 99 U.S., No. 5 CAN) "Kitty Doyle" / "Without Hurtin' Some" — Reprise 0619 – August 1967 (No. 108 U.S.) "My What a Shame" / "The Inside Outside Caspar Milquetoast Eskimo Flash" — Reprise 0653 – January 1968 "Tell Someone You Love Them" / "General Outline" — Reprise 0698 – June 1968 (No. 92 U.S., No. 67 Canada) "Thru Spray Colored Glasses" / "Someday" — Uni 55127 – April 1969 "Hawley" / "Let's Talk it Over" — Columbia 4-44975 – August 1969 "Lady Love" / "A Certain Sound" — Reprise 0965 – November 1970
== Formal oxidation states for pyrite, marcasite, molybdenite and arsenopyrite == From the perspective of classical inorganic chemistry, which assigns formal oxidation states to each atom, pyrite and marcasite are probably best described as Fe2+[S2]2−. This formalism recognizes that the sulfur atoms in pyrite occur in pairs with clear S−S bonds. These persulfide [−S−S−] units can be viewed as derived from hydrogen disulfide, H2S2. Thus pyrite would be more descriptively called iron persulfide, not iron disulfide. In contrast, molybdenite, MoS2, features isolated sulfide S2− centers and the oxidation state of molybdenum is Mo4+. The mineral arsenopyrite has the formula FeAsS. Whereas pyrite has [S2]2− units, arsenopyrite has [AsS]3− units, formally derived from deprotonation of arsenothiol (H2AsSH). Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe3+[AsS]3−.
Audience tastes were fairly eclectic during the 20th century, but several trends did emerge. During the silent era, films with war themes were popular with audiences, with The Birth of a Nation (American Civil War), The Four Horsemen of the Apocalypse, The Big Parade and Wings (all World War I) becoming the most successful films in their respective years of release, with the trend coming to an end with All Quiet on the Western Front in 1930. With the advent of sound in 1927, the musical—the genre best placed to showcase the new technology—took over as the most popular type of film with audiences, with 1928 and 1929 both being topped by musical films. The genre continued to perform strongly in the 1930s, but the outbreak of World War II saw war-themed films dominate again during this period, starting with Gone with the Wind (American Civil War) in 1939, and finishing with The Best Years of Our Lives (World War II) in 1946. Samson and Delilah (1949) saw the beginning of a trend of increasingly expensive historical dramas set during Ancient Rome/biblical times throughout the 1950s as cinema competed with television for audiences, with Quo Vadis, The Robe, The Ten Commandments, Ben-Hur and Spartacus all becoming the highest-grossing film of the year during initial release, before the genre started to wane after several high-profile failures. The success of White Christmas and South Pacific in the 1950s foreshadowed the comeback of the musical in the 1960s with West Side Story, Mary Poppins, My Fair Lady, The Sound of Music and Funny Girl all among the top films of the decade.
Sources: en.wikipedia.org
=== 2-D gel electrophoresis and western blotting === Two-dimensional gel electrophoresis (2-D gel) techniques in culmination with western blotting has been used for many years in the identification of immune response magnitude. This can be accomplished by comparing various samples against molecular-weight size markers for qualitative analysis and against known amounts of protein standards for quantitative analysis.
==== Food Distribution and Food Insecurity ==== Organizations that are founded to target food insecurity have relied on food distribution to serve people in need of regular nutritious foods. Food banks are the proper term to call these kind of organizations where they use "government sector, private sector, and civil society" to distribute and recover food that will ultimately go to waste. In the United States, there are many organizations all over the country that have the same similar goal however, there is not much effective collaboration between all organizations because it is challenging to coordinate efficient communication within one another. There is one large organization that focuses on distributing food to people who need it in the United States, Feeding America has over 200 food banks and 60,000 food pantries. There are more organizations that focus on distributing food that work independently and are not as big as Feeding America that contribute to distributing food to help with the issue of food insecurity.
The 2012 Colombian peace process refers to the dialogue in Havana, Cuba between the Colombian government and the FARC-EP to find a political solution to the armed conflict. After almost four years of peace negotiations, the Colombian state and the FARC announced consenus on a 6-point plan towards peace and reconciliation. The government also began a process of assistance and reparation for victims of the conflict. Recently, U.P. supporters reconstituted the political party within the reconciliation process. Colombia's congress approved the revised peace accord. In February 2015, the Historical Commission on the Conflict and its Victims (Comisión Histórica del Conflicto Armado y sus Víctimas – CHCV) published a report entitled "Contribution to an Understanding of the Armed Conflict in Colombia." The document addresses the "multiple reasons for the conflict, the principle factors and circumstances that made it possible, and the most notable impacts on the population", and explains Colombia's armed conflict in terms of international law.
In order to remove the thin and well preserved skin slices and strips from the donor, surgeons use a special surgical instrument called a dermatome. This usually produces a split-thickness skin graft, which contains the epidermis with only a portion of the dermis. The dermis left behind at the donor site contains hair follicles and sebaceous glands, both of which contain epidermal cells which gradually proliferate out to form a new layer of epidermis. The donor site may be extremely painful and vulnerable to infection. There are several ways to treat donor site pain. These include subcutaneous anesthetic agents, topical anesthetic agents, and certain types of wound dressings.
Sources: en.wikipedia.org
Protein tags are peptide sequences genetically grafted onto a recombinant protein. Tags are attached to proteins for various purposes. They can be added to either end of the target protein, so they are either C-terminus or N-terminus specific or are both C-terminus and N-terminus specific. Some tags are also inserted at sites within the protein of interest; they are known as internal tags. Affinity tags are appended to proteins so that they can be purified from their crude biological source using an affinity technique. Affinity tags include chitin binding protein (CBP), maltose binding protein (MBP), Strep-tag and glutathione-S-transferase (GST). The poly(His) tag is a widely used protein tag, which binds to matrices bearing immobilized metal ions. Solubilization tags are used, especially for recombinant proteins expressed in species such as E. coli, to assist in the proper folding in proteins and keep them from aggregating in inclusion bodies. These tags include thioredoxin (TRX) and poly(NANP). Some affinity tags have a dual role as a solubilization agent, such as MBP and GST. Chromatography tags are used to alter chromatographic properties of the protein to afford different resolution across a particular separation technique. Often, these consist of polyanionic amino acids, such as FLAG-tag or polyglutamate tag. Epitope tags are short peptide sequences which are chosen because high-affinity antibodies can be reliably produced in many different species. These are usually derived from viral genes, which explain their high immunoreactivity.
The first fullerene molecule to be discovered, and the family's namesake, buckminsterfullerene (C60), was prepared in 1985 by Richard Smalley, Robert Curl, James Heath, Sean O'Brien, and Harold Kroto at Rice University. The name was a homage to Buckminster Fuller, whose geodesic domes it resembles. Fullerenes have since been found to occur in nature. More recently, fullerenes have been detected in outer space. For the past decade, the chemical and physical properties of fullerenes have been a hot topic in the field of research and development, and are likely to continue to be for a long time. In April 2003, fullerenes were under study for potential medicinal use: binding specific antibiotics to the structure of resistant bacteria and even target certain types of cancer cells such as melanoma. The October 2005 issue of Chemistry and Biology contains an article describing the use of fullerenes as light-activated antimicrobial agents. In the field of nanotechnology, heat resistance and superconductivity are among the properties attracting intense research. A common method used to produce fullerenes is to send a large current between two nearby graphite electrodes in an inert atmosphere. The resulting carbon plasma arc between the electrodes cools into sooty residue from which many fullerenes can be isolated. There are many calculations that have been done using ab-initio Quantum Methods applied to fullerenes. By DFT and TDDFT methods one can obtain IR, Raman, and UV spectra. Results of such calculations can be compared with experimental results.
=== Digital === The library's first digitization project, American Memory, was launched in 1990, and was initially planned to choose 160 million objects from its collection to make digitally available on LaserDiscs and CDs, which were distributed to schools and libraries. After realizing that this plan would be too expensive and inefficient, and with the rise of the Internet, the library decided to instead make digitized material available over the Internet. This project was made official in the National Digital Library Program (NDLP), created in October 1994. By 1999, the NDLP had succeeded in digitizing over 5 million objects and had a budget of $12 million. As of 2022, the library's website contains 914 million unique digital objects, comprising over 21 petabytes of data. American Memory is a source for public domain image resources, as well as audio, video, and archived Web content. Nearly all of the lists of holdings, the catalogs of the library, can be consulted directly on its website. Librarians all over the world consult these catalogs, through the Web or through other media better suited to their needs, when they need to catalog for their collection a book published in the United States. They use the Library of Congress Control Number to make sure of the exact identity of the book. Digital images are also available at Snapshots of the Past, which provides archival prints. The library has a budget of $6–8 million each year for digitization, meaning that not all works can be digitized.
=== Dietary recommendations === The US Institute of Medicine (IOM) updated Estimated Average Requirements (EARs) and Recommended Dietary Allowances (RDAs) for selenium in 2000. If there is not sufficient information to establish EARs and RDAs, an estimate designated Adequate Intake (AI) is used instead. The current EAR for selenium for people ages 14 and up is 45 μg/day. The RDA is 55 μg/day. RDAs are higher than EARs so as to identify amounts that will cover people with higher-than-average requirements. RDA for pregnancy is 60 μg/day. RDA for lactation is 70 μg/day. For children ages 1–13 years, the RDA increases with age from 20 to 40 μg/day. As for safety, the IOM sets Tolerable upper intake levels (ULs) for vitamins and minerals when evidence is sufficient. In the case of selenium, the UL is 400 μg/day. Collectively the EARs, RDAs, AIs and ULs are referred to as Dietary Reference Intakes (DRIs). The European Food Safety Authority (EFSA) refers to the collective set of information as Dietary Reference Values, with Population Reference Intake (PRI) instead of RDA, and Average Requirement instead of EAR. AI and UL are defined the same as in the United States. For women and men ages 15 and older, the AI is set at 70 μg/day. AI for pregnancy is 70 μg/day; for lactation, 85 μg/day. For children ages 1–14 years, the AIs increase with age from 15 to 55 μg/day. These AIs are higher than the U.S. RDAs. The European Food Safety Authority reviewed the same safety question and set its UL at 300 μg/day, which is lower than the U.S. value.
=== Tumor lysis syndrome === In particularly large tumors and cancers with high white cell counts, such as lymphomas, teratomas, and some leukemias, some people develop tumor lysis syndrome. The rapid breakdown of cancer cells causes the release of chemicals from the inside of the cells. Following this, high levels of uric acid, potassium and phosphate are found in the blood. High levels of phosphate induce secondary hypoparathyroidism, resulting in low levels of calcium in the blood. This causes kidney damage and the high levels of potassium can cause cardiac arrhythmia. Although prophylaxis is available and is often initiated in people with large tumors, this is a dangerous side-effect that can lead to death if left untreated.
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.
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.