This is a working overview of mass spectrometry, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-03-20. Anything still debated is marked as such rather than presented as settled.
Clinical evidence comes mainly from small studies conducted in Russia, several of which were open-label or lacked robust blinding. Reported outcomes include lower anxiety scores, changes in attention measures, and effects on asthenic states following illness. Sample sizes are typically in the tens of participants, and independent replication outside the region is scarce. Reviews published in English generally note the limited methodological quality of the underlying trials. Whether the compound produces clinically meaningful effects under rigorous conditions remains unresolved.
Proposed mechanisms center on modulation of the GABA system, but no single molecular target has been confirmed. Rodent studies report changes in GABA-A receptor expression and in the turnover of serotonin, dopamine, and norepinephrine in several brain regions. Increases in brain-derived neurotrophic factor and its receptor have also been described after repeated administration. These findings come largely from animal models, and the degree to which they describe human neurochemistry remains an open question. The mechanism is best characterized as multi-system and not fully resolved.
Pharmacokinetic data are limited. Like most short peptides, Selank is vulnerable to plasma and tissue peptidases, and its measured half-life in circulation is short, on a minutes scale. The Pro-Gly-Pro tail slows this degradation but does not eliminate it. Intranasal administration is the route described in most reports, with absorption through the nasal mucosa and a hypothesized path into the central nervous system that avoids the blood-brain barrier. Direct measurements of human brain exposure are unavailable, so distribution claims rest on inference from animal work.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Route studied | Intranasal | Predominant route in published reports |
| Circulation stability | Short, minutes scale | Peptidases cleave it; the tail slows the process |
| Analytical method | RP-HPLC with mass spectrometry | Used for identity and purity assessment |
| Reported outcome domains | Anxiety and cognitive measures | Derived from small, mostly regional trials |
| Regulatory status | Marketed in Russia | Availability outside that market is limited |
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.
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.
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.
Characterization of Selank in a laboratory setting relies on standard peptide methods. Reverse-phase high-performance liquid chromatography separates the target from related impurities and provides a purity figure, commonly reported as 95 percent or higher. Mass spectrometry, typically electrospray ionization or matrix-assisted laser desorption, confirms the molecular mass and helps detect truncation or modification. Amino acid analysis can verify composition when a sequence-level check is needed. These techniques together establish identity and purity for a given lot.
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.
Based on scientific tests over five decades, government safety agencies have determined that polystyrene is safe for use in foodservice products. For example, polystyrene meets the stringent standards of the U.S. Food and Drug Administration and the European Commission/European Food Safety Authority for use in packaging to store and serve food. The Hong Kong Food and Environmental Hygiene Department reviewed the safety of serving various foods in polystyrene foodservice products and reached the same conclusion as the U.S. FDA. From 1999 to 2002, a comprehensive review of the potential health risks associated with exposure to styrene was conducted by a 12-member international expert panel selected by the Harvard Center for Risk Assessment. The scientists had expertise in toxicology, epidemiology, medicine, risk analysis, pharmacokinetics, and exposure assessment. The Harvard study reported that styrene is naturally present in trace quantities in foods such as strawberries, beef, and spices, and is naturally produced in the processing of foods such as wine and cheese. The study also reviewed all the published data on the quantity of styrene contributing to the diet due to migration of food packaging and disposable food contact articles, and concluded that risk to the general public from exposure to styrene from foods or food-contact applications (such as polystyrene packaging and foodservice containers) was at levels too low to produce adverse effects. Polystyrene is commonly used in containers for food and drinks.
== Drug testing == Detectable levels of propoxyphene/dextropropoxyphene may stay in a person's system for up to 9 days after last dose and can be tested for specifically in nonstandard urinalysis, but may remain in the body longer in minuscule amounts. Propoxyphene does not show up on standard opiate/opioid tests because it is not chemically related to opiates as part of the OPI or OPI 2000 panels, which detect morphine and related compounds. It is most closely related to methadone.
During the 1990s, Brazil saw a surge of critical and commercial success with films such as O Quatrilho (Fábio Barreto, 1995), O Que É Isso, Companheiro? (Bruno Barreto, 1997) and Central do Brasil (Walter Salles, 1998), all of which were nominated for the Academy Award for Best Foreign Language Film, the latter receiving a Best Actress nomination for Fernanda Montenegro. The 2002 crime film City of God, directed by Fernando Meirelles, was critically acclaimed, scoring 90% on Rotten Tomatoes, being placed in Roger Ebert's Best Films of the Decade list and receiving four Academy Award nominations in 2004, including Best Director. Notable film festivals in Brazil include the São Paulo and Rio de Janeiro International Film Festivals and the Gramado Festival. The film I'm Still Here, directed by Walter Salles, was nominated for Best Actress (Torres) and Best Picture at the 97th Academy Awards, and won Best International Feature Film, becoming the first-ever Brazilian produced film to win an Academy Award. The film The Secret Agent had its world premiere at the main competition of the 2025 Cannes Film Festival on 18 May 2025, where it won the Best Actor prize for Wagner Moura, the Best Director prize for Mendonça and the FIPRESCI Prize. It received further widespread critical acclaim.
Humans have more than the commonly cited five senses. The number of senses in various categorizations ranges from 5 to more than 20. In addition to sight, smell, taste, touch, and hearing, which were the senses identified by Aristotle, humans can sense balance and acceleration (equilibrioception), pain (nociception), body and limb position (proprioception or kinesthetic sense), and relative temperature (thermoception). Other senses sometimes identified are the sense of time, echolocation, itching, pressure, hunger, thirst, fullness of the stomach, need to urinate, need to defecate, blood carbon dioxide (CO2) levels, and electric field sensation. All different tastes can be detected on all parts of the tongue by taste buds, with slightly increased sensitivities in different locations depending on the person; the tongue map showing the contrary is fallacious. There are not four primary tastes, but five: in addition to bitter, sour, salty, and sweet, humans have taste receptors for umami, which is a "savory" or "meaty" taste. Fat does interact with specific receptors in taste bud cells, but whether it is a sixth primary taste remains inconclusive. The human sense of smell is not weak or underdeveloped. Humans have similar senses of smell to other mammals, and are more sensitive to some odors than rodents and dogs.
Sources: en.wikipedia.org
=== Properties === In terms of molecular structure, synephrine has a phenethylamine skeleton, with a phenolic hydroxy- group, an alcoholic hydroxy- group, and an N-methylated amino-group. Alternatively, synephrine might be described as a phenylethanolamine with an N-methyl and p-hydroxy substituent. The amino-group confers basic properties on the molecule, whereas the phenolic –OH group is weakly acidic: the apparent (see original article for discussion) pKas for protonated synephrine are 9.55 (phenolic H) and 9.79 (ammonium H). Common salts of racemic synephrine are its hydrochloride, C9H13NO2.HCl, m.p. 150–152°, the oxalate (C9H13NO2)2.C2H2O4, m.p. 221–222 °C, and the tartrate (Sympatol), (C9H13NO2)2.C4H6O6, m.p. 188–190 °C. The presence of the hydroxy-group on the benzylic C of the synephrine molecule creates a chiral center, so the compound exists in the form of two enantiomers, d- and l- synephrine, or as the racemic mixture, d,l- synephrine. The dextrorotatory d-isomer corresponds to the (S)-configuration, and the levorotatory l-isomer to the (R)-configuration. Racemic synephrine has been resolved using ammonium 3-bromo-camphor-8-sulfonate. The enantiomers were not characterized as their free bases, but converted to the hydrochloride salts, with the following properties: (S)-(+)-C9H13NO2.HCl: m.p. 178 °C; [α] = +42.0°, c 0.1 (H2O); (R)-(−)-C9H13NO2.HCl: m.p. 176 °C; [α] = −39.0°, c 0.2 (H2O) (−)-Synephrine, as the free base isolated from a Citrus source, has m.p. 162–164 °C (with decomposition). The X-ray structure for synephrine has been determined.
== Patterns of amino acid replacement == Evolution of proteins is slower than DNA since only nonsynonymous mutations in DNA can result in amino acid replacements. Most mutations are neutral to maintain protein function and structure. Therefore, the more similar amino acids are, the more probable that they will be replaced. Conservative replacements are more common than radical replacements, since they can result in less important phenotypic changes. On the other hand, beneficial mutations, enhancing protein functions are most likely to be radical replacements. Also, the physicochemical distances, which are based on amino acids properties, are negatively correlated with probability of amino acids substitutions. Smaller distance between amino acids indicates that they are more likely to undergo replacement.
==== Tax descriptions ==== The federal personal income tax is progressive, meaning a higher marginal tax rate is applied to higher ranges of income. For example, in 2010 the tax rate that applied to the first $17,000 in taxable income for a couple filing jointly was 10%, while the rate applied to income over $379,150 was 35%. The top marginal tax rate has declined considerably since 1980. For example, the top tax rate was lowered from 70% to 50% in 1980 and reached as low as 28% in 1988. The Bush tax cuts of 2001 and 2003, extended by President Obama in 2010, lowered the top rate from 39.6% to 35%. The American Taxpayer Relief Act of 2012 raised the income tax rates for individuals earning over $400,000 and couples over $450,000. There are numerous exemptions and deductions, that typically result in a range of 35–40% of U.S. households owing no federal income tax. The recession and tax cut stimulus measures increased this to 51% for 2009, versus 38% in 2007. In 2011 it was found that 46% of households paid no federal income tax, however the top 1% contributed about 25% of total taxes collected. In 2014, the top 1% paid approximately 46% of the federal income taxes, excluding payroll taxes. The federal payroll tax (FICA) partially funds Social Security and Medicare. For the Social Security portion, employers and employees each pay 6.2% of the workers gross pay, a total of 12.4%. The Social Security portion is capped at $118,500 for 2015, meaning income above this amount is not subject to the tax.
== History == 2C-EF was originally named by Alexander Shulgin in his 1991 book PiHKAL (Phenethylamines I Have Known and Loved). However, he only speculated about it and never actually synthesized or tested it himself. Subsequently, 2C-EF was synthesized and tested by others such as Daniel Trachsel.
Many mothers have to return to work a short time after their babies have been born. In the U.S., about 70% of mothers with children younger than three years old work full-time, with 1/3 of the mothers returning to work within 3 months and 2/3 returning within 6 months. Working outside of the home and full-time work are significantly associated with lower rates of breastfeeding and breastfeeding for a shorter duration of time. According to the Centers for Disease Control and Prevention, support for breastfeeding in the workplace includes several types of employee benefits and services, including writing corporate policies to support breastfeeding women; teaching employees about breastfeeding; providing designated private space for breastfeeding or expressing milk; allowing flextime to support milk expression during work; giving mothers options for returning to work, such as remote work, part-time jobs, and extended maternity leave; providing on-site or near-site child care; providing high-quality breast pumps; and offering professional lactation consultants. Programs to promote and assist nursing mothers have been found to help maintain breastfeeding. In the United States the CDC reports on a study that "examined the effect of corporate lactation programs on breastfeeding behavior among employed women in California [which] included prenatal classes, perinatal counseling, and lactation management after the return to work".
Sources: en.wikipedia.org
Reports describe effects on GABA-A receptor expression, monoamine turnover, and neurotrophic factor levels. These are proposed mechanisms drawn mainly from animal models. No single molecular target has been established.
Intranasal delivery is the route described in most published work. It is used because the peptide is degraded quickly once it reaches circulation. Direct evidence of brain penetration in humans is lacking.
Most trials are small, regionally concentrated, and often lack rigorous blinding or placebo control. Independent replication is limited. Reviews in English generally rate the evidence as preliminary.
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.