The short version of mass spectrometry fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-11-16. Anything still debated is marked as such rather than presented as settled.
Once dissolved, the peptide is considerably less stable than the solid. Aqueous solutions are usually prepared at neutral to slightly acidic pH, filtered, and divided into single-use aliquots before freezing. Repeated freeze-thaw cycles are a common cause of avoidable loss and are best prevented by never refreezing a thawed aliquot. Adsorption to plastic and glass surfaces can lower the measured concentration of dilute solutions, particularly below roughly 0.1 mg/mL. Buffer choice, salt content, and container material all influence how much peptide remains detectable after storage.
Identity and purity are established with standard peptide methods. Reversed-phase HPLC with ultraviolet detection near 214 nm resolves the parent peak from deletion and truncation byproducts, and reports typically quote a main-peak percentage. Mass spectrometry by electrospray or MALDI-TOF confirms the expected molecular mass, while amino acid analysis or peptide mapping can verify composition when the sequence itself is in question. A certificate of analysis that pairs a chromatogram with a mass spectrum is more informative than a purity figure alone. Counter-ion content and residual solvents are separate specifications and are frequently omitted.
Identity and purity of semax are established with reversed-phase high-performance liquid chromatography coupled to ultraviolet detection, usually at 214 nanometres. Mass spectrometry, most often electrospray ionisation in positive mode, confirms the molecular mass and reveals truncated sequences. Amino acid analysis and peptide mapping after enzymatic digestion provide additional structural confirmation. Laboratories typically report purity as the percentage area of the main peak, a figure that does not capture isomeric or oxidised variants unless the method resolves them.
The peptide is prone to several degradation pathways. Oxidation of the methionine residue produces a sulfoxide that elutes close to the parent peak in many chromatographic systems. Hydrolysis of peptide bonds and deamidation of susceptible residues in related sequences also reduce purity over time. Lyophilised material kept dry at minus twenty degrees Celsius and shielded from light is the most stable form commonly described in laboratory practice.
Material sold for laboratory use varies widely in stated purity and documentation. A certificate of analysis should list the analytical method, the column and detector used, and the observed purity value. Independent verification by an outside laboratory is the practical way to confirm identity when documentation is absent or internally inconsistent. Regulatory status differs by country, and a product legal in one jurisdiction may be unapproved or controlled in another.
| Property | Value | Notes |
|---|---|---|
| Solid storage temperature | -20 °C or below | Desiccated and protected from light |
| Solution storage temperature | -80 °C as single-use aliquots | Avoid repeated freeze-thaw cycles |
| Purity assessment method | RP-HPLC, around 214 nm | Reported as main-peak area percent |
| Identity confirmation method | ESI-MS or MALDI-TOF | Measured mass compared with calculated mass |
| Common synonyms | ACTH(4-10) analog; Met-Glu-His-Phe-Pro-Gly-Pro | Also written as Semaxum in some sources |
In 2016, she co-starred in the thriller American Romance, and had a supporting role in the psychological horror film Jack Goes Home. Also in 2016, she provided the English voice of Kiwako Seto in the video game Let It Die. American Romance, Jack Goes Home and Let It Die served as her final acting credits.
Chemical measures of water quality include dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total dissolved solids (TDS), pH, nutrients (nitrates and phosphorus), heavy metals, soil chemicals (including copper, zinc, cadmium, lead and mercury), and pesticides.
He headed the School of Pharmacy at Manchester on two occasions, 1988-1991 and 1998-2001, periods involving the move to clinical pharmacy and moving Pharmacy from the Faculty of Science and Engineering to the Faculty of Medicine, in recognition of the changing professional role of pharmacists from fabricator to health care advisor on medicines. Rowland has trained 90 Ph.D. students and scientists from a variety of disciplines. He also established ongoing annual postgraduate workshops in basic pharmacokinetics with Tomas Tozer (1977), and in advanced methods in pharmacokinetics and pharmacodynamics with Lewis Sheiner (1981). Rowland was president of EUFEPS (European Federation for Pharmaceutical Sciences, 1996-1999), and a Vice-President of FIP (International Pharmaceutical Federation, 2001-2009).
Sources: en.wikipedia.org
The UK government have agreed an unprecedented deal to work with Iraq to address the problem of people smuggling. Figures show an increase in the number of applications for Pension Credit following cuts to Winter Fuel Payments announced by the Chancellor in the 2024 Spending Review. Shadow Home Secretary Chris Philp suggests that automation and robots could be used instead of hiring low-paid migrant workers, and calls for UK businesses to invest more in these technologies. 29 November MPs vote 330 to 275 in favour of allowing assisted dying in England and Wales. The bill passes the first stage in the Commons but will be followed by months of parliamentary activity before it becomes a law. Louise Haigh resigns as Secretary of State for Transport after a past fraud offence comes to light. She is replaced by Heidi Alexander. The UK government announces that the cost of a TV licence will increase by £5 from April 2025 to £174.50. A British man, subsequently named as Tony Kerry, is killed in an incident involving a lift shaft while on holiday in the Turkish coastal resort of Antalya.
The leaves of the coca plant contain alkaloids that—when extracted chemically—are the source for cocaine base. The amount of coca alkaloid in the raw leaves is small, however. A cup of coca tea prepared from one gram of coca leaves (the typical contents of a tea bag) contains approximately 4.2 mg of organic coca alkaloid. (In comparison, a typical dose (a "line") of cocaine contains between 20 and 30 milligrams.) Owing to the presence of these alkaloids, coca tea is a mild stimulant; its consumption may be compared to consumption of a moderately strong cup of coffee or tea. The coca alkaloid content of coca tea is such that the consumption of one cup of coca tea can cause a positive result on a drug test for cocaine, however. Similar to decaffeination in coffee, coca tea can be decocainized. Just as decaffeinated coffee retains a small quantity of caffeine, decocainized coca tea will still contain a small quantity of organic coca alkaloids. There is little information on the pharmacological and toxicological effects of consuming coca tea. A chemical analysis by solid-phase extraction and gas chromatography–mass spectrometry (SPE-GC/MS) of Peruvian and Bolivian tea bags indicated the presence of significant amounts of cocaine, the metabolite benzoylecgonine, ecgonine methyl ester and trans-cinnamoylcocaine in coca tea bags and coca tea. Urine specimens were also analyzed from an individual who consumed one cup of coca tea and it was determined that enough cocaine and cocaine-related metabolites were present to produce a positive drug test.
== hCG preparations == Human chorionic gonadotropin (hCG) can be recovered from the urine of pregnant women or be produced from recombinant DNA. It acts similarly to LH, but the larger supply makes it less costly; it also has a longer half-life. In veterinary medicine, equine chorionic gonadotropin (eCG) extracted from pregnant mare serum is used instead on a variety of mammals, sometimes eliciting an immune response in non-horse species. In Women: Used to induce final maturation of follicle and subsequent ovulation. Also used for luteal phase support. In men: Used to treat select cases of Hypogonadotropic Hypogonadism in adult males. In off-label use, some urologists prescribe hCG in low doses in combination with testosterone replacement to preserve fertility. In male children: Also used to treat prepubertal cryptorchidism not due to anatomical obstruction. Therapy is usually administered between ages 4 and 9.
Hox genes A subset of highly conserved homeobox-containing genes whose protein products function as transcription factors essential for the proper organization of the body plan in developing animal embryos, ensuring that the correct structures are formed in the correct places. Hox genes are usually arranged on a chromosome in tandem arrays and are expressed sequentially during development, with the sequence of gene activation corresponding to their physical arrangement within the genome and/or the physical layout of the tissues in which they are expressed along the organism's anterior–posterior axis.
Sources: en.wikipedia.org
Each freeze-thaw cycle can degrade a fraction of the peptide and promote aggregation. Dividing a stock solution into single-use volumes removes repeated cycling as a variable. It also limits the time a thawed solution spends at room temperature.
A high main-peak percentage says little about identity, counter-ion content, or residual solvents. It also does not distinguish an isomer or a closely eluting analog. Mass confirmation and the accompanying documentation cover those gaps.
Salt form changes mass, solubility, and hygroscopicity, and acetate and trifluoroacetate salts behave differently in solution. Storage guidance still centers on -20 °C for powder and lower temperatures for solutions. The certificate should state which salt is present.
Reversed-phase high-performance liquid chromatography is the standard method, with detection in the ultraviolet range. Peak area percentage yields a purity figure for the main component. Mass spectrometry is normally run alongside to confirm molecular identity.