Everything below concerns proteolysis. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-19. Numbers and descriptions here follow the published literature rather than marketing material.
Selank is not a naturally occurring peptide and has no known endogenous counterpart in human physiology. Russian-language sources frequently call it TP-7, while English-language sources use the name Selank almost exclusively. Database indexing is uneven, partly because early reports appeared in regional journals that are not widely cataloged. Some summaries describe the material as a tuftsin analog and others as a synthetic heptapeptide; the labels overlap rather than conflict. Citing the primary sequence resolves ambiguity more reliably than the research or trade name alone.
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.
Peptide stability depends strongly on temperature, moisture, and pH. Lyophilized Selank is generally most stable when stored cold and dry, with freezer temperatures commonly used for long-term storage. In solution, the compound is susceptible to hydrolysis and to microbial growth if it is not handled aseptically. The C-terminal proline-rich extension appears to slow enzymatic cleavage relative to tuftsin, though quantitative degradation rates vary with the matrix and the conditions tested. Published stability data specific to Selank remain sparse.
Quality assessment of Selank samples typically combines purity determination with identity confirmation and counter-ion analysis. Purity is usually reported as a percentage by chromatographic area, with values above 95 percent often quoted for research-grade material. Water content and residual solvents are checked in lyophilized batches because they affect both stability and accurate mass determination. A reported purity figure does not by itself establish that a sample is the intended sequence, so orthogonal methods are needed to rule out sequence isomers or truncation products.
| Property | Value | Notes |
|---|---|---|
| Peptide sequence | Thr-Lys-Pro-Arg-Pro-Gly-Pro | Seven residues; tuftsin plus a Pro-Gly-Pro tail |
| Molecular formula | C33H57N11O9 | Commonly reported value for the free peptide |
| Monoisotopic mass | Roughly 751.4 Da | Average molecular mass near 751.9 Da |
| Appearance | White to off-white powder | Typically supplied as a lyophilized solid |
| Solubility class | Freely soluble in water | Also dissolves in saline and other polar solvents |
Proposed mechanisms centre on the GABAergic system. Animal and tissue studies report changes in GABA-A receptor expression and reduced activity of GABA transaminase, the enzyme that degrades GABA. Effects on monoamine turnover, including serotonin and dopamine pathways, are also described, and a separate line of work links the peptide to increased expression of brain-derived neurotrophic factor in hippocampal tissue. Most of these findings come from rodent models and cell preparations. How the individual observations combine into a single coherent mode of action is not settled.
Pharmacokinetic data are sparse and largely derived from animal work. After intranasal administration the peptide appears in plasma within minutes, and reported half-lives are short, on the order of minutes to tens of minutes. Degradation proceeds through ordinary proteolytic cleavage into constituent amino acids and smaller fragments. Direct evidence that intact Selank reaches brain tissue in meaningful amounts is limited, and the extent of blood-brain barrier penetration is debated. Some authors argue that fragments, not the parent peptide, carry much of the observed activity.
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.
==== USP14/UBP6 ==== In contrast to Rpn11, USP14 and UCH37 are the DUBs that do not always associated with the proteasome and are not essential for ubiquitin dependent degradation. Instead, these DUBs are proposed to "edit" the ubiquitin code of a substrate that is already engaged with the proteasome. In cells, about 10-40% of the proteasomes were found to have USP14 associated. Ubp6/USP14 is a member of the Ubiquitin Specific Protease (USP) family, utilizing a catalytic cysteine to cleave ubiquitin. Along with the USP, Ubp6/USP14 contains a Ubiquitin-like protein (UBL) that binds the proteasome. Ubp6/USP14 is largely activated by the proteasome and exhibit a very low DUB activity alone. Once activated, USP14 was found to suppress proteasome function by its DUB activity and by inducing parallel pathways of proteasome conformational transitions, one of which turned out to directly prohibit substrate insertion into the AAA-ATPase, as first observed biochemically and later confirmed by time-resolved cryogenic electron microscopy. It appears that USP14 regulates proteasome function at multiple checkpoints by both catalytically competing with Rpn11 and allosterically reprogramming the AAA-ATPase states, which is rather unexpected for a DUB. These observations imply that the proteasome regulation may depend on its dynamic transitions of conformational states.
Trent Reznor of Nine Inch Nails said in the 2010 documentary Rush: Beyond the Lighted Stage that Rush is one of his favourite bands, and he has also cited the band's early 1980s period in particular as a major influence on him in regard to incorporating keyboards and synthesizers into hard rock. Rush had been eligible for nomination into the Rock and Roll Hall of Fame since 1998. The band was nominated for entry in 2012, and their induction was announced on December 11, 2012. A reason for their previous exclusion may have been their genre. USA Today writer Edna Gundersen criticized the Hall of Fame for excluding some genres, including progressive rock. Supporters cited the band's accomplishments, including longevity, proficiency, and influence, as well as commercial sales figures and RIAA certifications. In the years before induction, Lifeson expressed his indifference toward the perceived slight, saying, "I couldn't care less. Look who's up for induction; it's a joke". In his acceptance speech on the occasion of Rush's induction into the Roll Hall of Fame on April 18, 2013, Lifeson spontaneously recited his prepared text in "blah blah blah" speech, annoying his band fellows and confusing the audience. On April 24, 2010, the documentary Rush: Beyond the Lighted Stage, directed by Scot McFadyen and Sam Dunn, premiered at the Tribeca Film Festival. It received the Tribeca Film Festival Audience Award. The film was nominated for Best Long Form Music Video at the 53rd Grammy Awards, losing to When You're Strange, a documentary about The Doors.
=== Classic === Classic MSUD is the most common type of MSUD. It also has the earliest onset and is presented with the most severe symptoms. Symptoms can be seen from within 7–10 days of birth. The maple syrup odor to the earwax is apparent around 12 hours after birth. The sweet-smelling urine is presented around a week after birth when protein metabolism has accelerated. Some other signs that may be seen are poor feeding, vomiting, irritability, lethargy, apnea, seizures, acidosis, and encephalopathy. Infants with classic MSUD will display subtle symptoms within the first 24–48 hours. Subtle symptoms include poor feeding, either bottle or breast, lethargy, and irritability. The infant will then experience increased focal neurologic signs. These neurologic signs include athetosis, hypertonia, spasticity, and opisthotonus that lead to convulsions and coma. If MSUD is left untreated, central neurologic function and respiratory failure will occur and lead to death. Although MSUD can be stabilized, there are still threats of metabolic decompensation and loss of bone mass that can lead to osteoporosis, pancreatitis, and intracranial hypertension. Additional signs and symptoms that can be associated with classic MSUD include intellectual limitation and behavioral issues.
=== Safer sex programmes === Many schools now provide safer sex education to teen and pre-teen students, who may engage in sexual activity. Since some adolescents are going to have sex, a harm-reductionist approach supports a sexual education which emphasizes the use of protective devices like condoms and dental dams to protect against unwanted pregnancy and the transmission of STIs. This runs contrary to abstinence-only sex education, which teaches that educating children about sex can encourage them to engage in it. These programmes have been found to decrease risky sexual behaviour and prevent sexually transmitted infections. They also reduce rates of unwanted pregnancies. Abstinence-only programmes do not appear to affect HIV risks in developed countries with no evidence available for other areas.
Sources: en.wikipedia.org
isomeric genes Two or more genes that are equivalent and redundant in the sense that, despite coding for distinct gene products, they each result in the same phenotype when set within the same genetic background. If several isomeric genes are present in a single genotype they may be either cumulative or non-cumulative in their contributions to the phenotype.
Secondary structure prediction is a set of techniques in bioinformatics that aim to predict the local secondary structures of proteins based only on knowledge of their amino acid sequence. For proteins, a prediction consists of assigning regions of the amino acid sequence as likely alpha helices, beta strands (often termed extended conformations), or turns. The success of a prediction is determined by comparing it to the results of the DSSP algorithm (or similar e.g. STRIDE) applied to the crystal structure of the protein. Specialized algorithms have been developed for the detection of specific well-defined patterns such as transmembrane helices and coiled coils in proteins. The best modern methods of secondary structure prediction in proteins were claimed to reach 80% accuracy after using machine learning and sequence alignments; this high accuracy allows the use of the predictions as feature improving fold recognition and ab initio protein structure prediction, classification of structural motifs, and refinement of sequence alignments. The accuracy of current protein secondary structure prediction methods is assessed in weekly benchmarks such as LiveBench and EVA.
== Poiseuille's equation for an ideal isothermal gas == For a compressible fluid in a tube the volumetric flow rate Q(x) and the axial velocity are not constant along the tube; but the mass flow rate is constant along the tube length. The volumetric flow rate is usually expressed at the outlet pressure. As fluid is compressed or expanded, work is done and the fluid is heated or cooled. This means that the flow rate depends on the heat transfer to and from the fluid. For an ideal gas in the isothermal case, where the temperature of the fluid is permitted to equilibrate with its surroundings, an approximate relation for the pressure drop can be derived. Using ideal gas equation of state for constant temperature process (i.e.,
Sources: en.wikipedia.org
The sequence is Thr-Lys-Pro-Arg-Pro-Gly-Pro, written TKPRPGP in one-letter code. It combines the tetrapeptide tuftsin with a carboxyl-terminal Pro-Gly-Pro extension. This full sequence identifies the molecule more precisely than the research name.
No peptide with this exact sequence has been identified as an endogenous substance. It is a laboratory-designed analog of tuftsin, a naturally occurring immunomodulatory tetrapeptide. The Pro-Gly-Pro extension has no known natural source.
Proline introduces conformational constraints that make a peptide less accessible to common peptidases. This is a standard stabilization strategy in peptide design. The added residues also increase the distance between the active tuftsin portion and typical cleavage sites.
The most common approach combines reverse-phase liquid chromatography with mass spectrometry. Chromatography separates the components while mass spectrometry confirms the molecular mass. Peptide sequencing or tandem mass analysis can further verify the amino acid order.