heptapeptide 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 2026-02-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Naming for this compound is not fully standardised in English sources. The spelling Selanc appears in some transliterations, and catalogue entries may instead list the peptide sequence itself as the identifier. Reference material sometimes groups it with other short synthetic peptides studied for behavioural effects, which can create confusion when citations are compared. Distinguishing the exact sequence from related tuftsin analogues is therefore a practical first step when reviewing any dataset or specification sheet.
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.
| 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 |
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.
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.
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.
== Biuret reagent == The biuret reagent is made of sodium hydroxide (NaOH) and hydrated copper(II) sulfate, together with potassium sodium tartrate, the latter of which is added to chelate and thus stabilize the cupric ions. The reaction of the cupric ions with the nitrogen atoms involved in peptide bonds leads to the displacement of the peptide hydrogen atoms under the alkaline conditions. A tri- or tetra-dentate chelation with the peptide nitrogen produces the characteristic color. This is found with dipeptides. The reagent is commonly used in the biuret protein assay, a colorimetric test used to determine protein concentration by UV/VIS spectroscopy at wavelength 540 nm.
Chloramphenicol was first isolated from Streptomyces venezuelae in 1947 and in 1949 a team of scientists at Parke-Davis including Mildred Rebstock published their identification of the chemical structure and their synthesis. In 1972, Senator Ted Kennedy combined the two examples of the Tuskegee Syphilis Study and the 1958 Los Angeles Infant Chloramphenicol experiments as initial subjects of a Senate Subcommittee investigation into dangerous medical experimentation on human subjects. In 2007, the accumulation of reports associating aplastic anemia and blood dyscrasia with chloramphenicol eye drops led to the classification of "probable human carcinogen" according to World Health Organization criteria, based on the known published case reports and the spontaneous reports submitted to the National Registry of Drug-Induced Ocular Side Effects.
Among others, the logs detail how US authorities failed to investigate hundreds of reports of abuse, torture, rape and even murder by Iraqi police and soldiers, whose conduct appears to be systematic and normally unpunished and that US troops abused prisoners for years even after the Abu Ghraib scandal. Both the UK and the US have condemned the unauthorised release of classified material, but did not question its accuracy. In July 2019, the Euro-Mediterranean Human Rights Monitor and the Iraqi Centre for the Documentation of War Crimes released a joint statement in which they revealed testimonies from the Taji Prison in the north of Bagdad. The testimonies documented the Iraqi security forces' policies of humiliation and persecution against detainees in Iraqi prisons, where they are kept in a large camp, suffering harsh conditions, beaten, exploited, and deprived of their basic human rights.
== Terminology == In the United Kingdom, the name or names of the fruit followed by juice can only legally be used to describe a product that is 100% fruit juice, as required by the Fruit Juices and Fruit Nectars (England) Regulations and the Fruit Juices and Fruit Nectars (Scotland) Regulations 2003. However, a juice made by reconstituting concentrate can be called juice. A product described as fruit "nectar" must contain at least 25% to 50% juice, depending on the fruit. A juice or nectar including concentrate must state that it does. The term "juice drink" is not defined in the Regulations and can be used to describe any drink that includes juice, whatever the amount. Comparable rules apply in all EU member states in their respective languages. In the US, fruit juice can only legally be used to describe a product that is 100% fruit juice. A blend of fruit juice(s) with other ingredients, such as high-fructose corn syrup, is called a juice cocktail or juice drink. According to the Food and Drug Administration (FDA), the term "nectar" is generally accepted in the US and in international trade for a diluted juice to denote a beverage that contains fruit juice or puree, water, and artificial sweeteners. "No added sugar" is commonly printed on the labels of juice containers, but the products may contain large amounts of naturally occurring sugars; however, sugar content is listed with other carbohydrates on labels in many countries.
== Television episodes == "Half-Life", Icons season 3, episode 17 (2004) "Half-Life", Odyssey 5 episode 17 (2002) "Half Life", La Femme Nikita season 2, episode 7 (1998) "Half Life", Logan's Run episode 6 (1977) "Half Life", Medical Investigation episode 17 (2005) "Half Life", New Tricks series 8, episode 9 (2011) "Half Life", Sea Patrol season 3, episode 7 (2009) "Half Life", SeaChange season 3, episode 13 (2000)
Sources: en.wikipedia.org
==== Marine algae ==== The factors affecting δD of algal lipids are: δD of water, algal species (up to 160%), lipid type (up to 170%), salinity (+0.9±0.2% per PSU), growth rate (0 ~ −30% per day) and temperature (−2 ~ −8% per °C). In a study by Zhang et al. (2009), the δDs of fatty acids in Thalassiosira pseudonana chemostat cultures were −197.3‰, −211.2‰ and −208.0‰ for C14, C16 and C18 fatty acids respectively. The δD of C16 fatty acid in the algae A. e. unicocca at 25°C, was determined using the empirical equation y = 0.890x − 91.730, where x is the δD of water at harvest. For another algal species, B. v. aureus, the equation was y = 0.869x − 74.651. The degree of D/H fractionation in most algal lipids increases with increasing temperature and decreases with increasing salinity. The growth rates have different impacts on the D/H fractionation depending on the species types.
Once approved, the political reform referendum was convened for December 15. The government did not give any opportunity to the opposition to present its position ─ abstention ─ in the media it controlled, especially in the most influential one, the television ─ nor even in the radio ─ and deployed a formidable campaign in favor of the YES, so the result of the referendum did not bring any surprise: there was a high turnout, except in the Basque Country, and the YES won with 94.2% of the votes, while the NO, defended by the búnker, only got 2.6%. The "political reform", and implicitly the monarchy and its government, were thus legitimized by the popular vote. From that moment on, the opposition's demand for the formation of a government of "broad democratic consensus" no longer made sense. It would be the Suárez government that would assume the task that the opposition had assigned to that government: to call general elections. During the last week of January 1977 the most delicate moment of the transition before the elections took place, as the Francoists in the búnker set out to stop the process of change by creating a climate of panic that would justify the intervention of the Army. The first provocation came in Madrid's Gran Vía, when a student, Arturo Ruiz, who was taking part in a pro-amnesty demonstration was killed by thugs of the extreme right-wing group Fuerza Nueva ─ in the demonstration protesting the crime a demonstrator, María Luz Nájera, was killed by a police smoke canister.
Leukemia: diagnosis/recurrence, Biopsy;; Clinical Immunology Laboratory, Tissue lab "Aberrant cell population(phenotype); taxon;Biopsy(spec.)"; Clinical Immunology Laboratory, Tissue lab rearrangement of TCR/IgH- is. Biopsy;"Biopsy-(TCR+Igh- )-Immune rearrangement; clonality(0 1) = ?"; Clinical Immunology Laboratory, Tissue lab "Hem. Marker study, ADULTS over 16 years;Biopsy";Hem. Marker study, ADULTS over 16 years, Tissue biopsies;Hematology Marker Laboratory "Hem. Marker study, ADULTS over 16 years;Biopsy";Hem. Marker Examination, ADULTS over 16 years, Biopsy from Corpus Vitreum;Hematology Marker Laboratory Histologic examination of testis biopsy; Laboratory for Growth and Reproduction Miscellaneous analysis;DNA(spec.)-MLPA ocular melanoma; depends Miscellaneous analysis;FISH malignant melanoma choroidea; depends Helicobacter pylori (culture);Helicobacter pylori (culture); Clinical Microbiology Laboratory Tropheryma whipplei DNA/RNA;;Unknown Culture and resistance;Biopsy/tissue/bone tissue culture and resistance; Clinical Microbiology Laboratory
== Erinacine C == Erinacine C has also been observed to activate the transcription factor Nrf2 and has been observed to play a role in neurogenesis and neuroplasticity. Stimulator of NGF synthesis in vitro((299.1 ± 59.6) pg/mL at 1.0 mmol/L)
Sources: en.wikipedia.org
== Definitions == Given the increasing public interest in the concept of food noise during the early 2020s, researchers began to formulate formal definitions that could facilitate measurement of and studies about the phenomenon. The earliest published definition described food noise as "heightened and/or persistent manifestations of food cue reactivity, often leading to food-related intrusive thoughts and maladaptive eating behaviors". A second definition, published in 2024 by a separate research group, described food noise as “persistent, intrusive thoughts about food that are disruptive to daily life and make healthy behaviors difficult.” In 2025, another research group offered a third definition: “persistent thoughts about food that are perceived by the individual as being unwanted and/or dysphoric and may cause harm to the individual, including social, mental, or physical problems.”
==== Beverage ==== In 1966, the company bought a 53% controlling stake in Miller Brewing for $36 million from Lorraine Mulberger, the granddaughter of Frederick Miller, who sold the stake for religious reasons. The company sold the Miller stake in 1969 to Philip Morris for $130 million, after first cancelling an agreed-upon sale to PepsiCo for $120 million. This resulted in a lawsuit.
Major cities and regional rivalry played an important role in the wars. The disappearance of a central, imperial authority—and in some cases of even a local, viceregal authority (as in the cases of New Granada and Río de la Plata)—initiated a prolonged period of balkanization in many regions of Spanish America. It was not clear which political units should replace the empire, and there were no new national identities to replace the traditional sense of being Spaniards. The original juntas of 1810 appealed first to a sense of being Spanish, which was counterposed to the French threat; second, to a general American identity, which was counterposed to the Peninsula lost to the French; and third, to a sense of belonging to the major cities or local province, the patria in Spanish. More often than not, juntas sought to maintain a province's independence from the capital of the former viceroyalty or captaincy general as much as from the Peninsula itself. Armed conflicts broke out between the provinces over the question of whether some cities or provinces were to be subordinate to others as they had been under the crown. This phenomenon was particularly evident in South America. This rivalry also led some regions to adopt the opposite political cause to that chosen by their rivals. Peru seems to have remained strongly royalist in large part because of its rivalry with Río de la Plata, to which it had lost control of Upper Peru when the latter was elevated to a viceroyalty in 1776.
These are isostructural to the respective halides except for lithium cyanide, indicating that the cyanide ions may rotate freely. Ternary alkali metal halide oxides, such as Na3ClO, K3BrO (yellow), Na4Br2O, Na4I2O, and K4Br2O, are also known. The polyhalides are rather unstable, although those of rubidium and caesium are greatly stabilised by the feeble polarising power of these extremely large cations.
== Physical exam findings == In a studied case of Bornholm disease the chest pain was unable to be reproduced on palpation and failed to improve with changes in position. The pain was made worse during deep inhalation. A pleural rub was present, however lung auscultation was clear and rashes were absent.
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.
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, commonly written as TKPRPGP. It shares the first four residues with tuftsin and carries three prolines in the chain. The proline-rich tail is the main structural feature that separates it from the parent tetrapeptide.