If you have been reading about mass spectrometry and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-04-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
Laboratory handling centers on minimizing exposure to water, heat and oxygen before use. Working solutions are typically prepared in sterile water or a mild buffer, and any residual particulate matter is removed by filtration. When the powder dissolves slowly, a small proportion of acetonitrile or dilute acetic acid is sometimes added as a co-solvent. Containers are kept sealed and desiccated between uses. Records of lot number, reconstitution date and storage conditions support later comparison of results across experiments.
Identity and purity are established with reversed phase high performance liquid chromatography coupled to mass spectrometry. The chromatographic step separates the target peptide from truncated sequences and deletion products, while the mass measurement confirms the expected molecular weight to within a fraction of a dalton. Because the two common variants differ by the presence of the linker, mass alone can distinguish them in the unconjugated state. Amino acid analysis and peptide mapping are used when sequence level confirmation is required.
Two related peptides circulate under the CJC-1295 label, and they differ mainly in how long they persist in circulation. The version carrying a drug affinity complex includes a maleimidopropionic acid linker that forms a covalent bond with serum albumin. The other version, usually written as modified GRF(1-29) or tetrasubstituted GRF(1-29), lacks that linker and is cleared quickly. Mixing the two produces inconsistent readings of published half-life values, because the linker rather than the receptor-facing sequence drives most of the difference.
The core sequence keeps the receptor-binding region of GHRH while replacing four positions that are vulnerable to dipeptidyl peptidase-4 and other proteases. Substitutions at positions 2, 8, 15, and 27 raise metabolic stability relative to the natural hormone. The N-terminal residues remain essential for activity, so changes there generally lower potency. Molecular weight sits near 3368 daltons for the tetrasubstituted analog without the linker, while the albumin-binding form is heavier because of the added maleimide group.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off white powder | Typical lyophilized form |
| Water solubility | Soluble | May need a small organic co-solvent |
| Purity assessment | Chromatographic peak area | Most certificates report a percentage figure |
| Storage temperature | Minus 20 C or lower | Dry, dark, sealed container |
| Identity check | Electrospray mass spectrometry | Compared against theoretical mass |
Exenatide (also Exendin-4, marketed as Byetta) is the first GLP-1 agonist approved for the treatment of type 2 diabetes. Exenatide is not an analogue of GLP but rather a GLP agonist. Exenatide has only 53% homology with GLP, which increases its resistance to degradation by DPP-4 and extends its half-life. A 2011 Cochrane review showed a HbA1c reduction of 0.20% more with Exenatide 2 mg compared to insulin glargine, exenatide 10 μg twice daily, sitagliptin and pioglitazone. Exenatide, together with liraglutide, led to greater weight loss than glucagon-like peptide analogues. Liraglutide, a once-daily human analogue (97% homology), has been developed by Novo Nordisk under the brand name Victoza. The product was approved by the European Medicines Agency (EMEA) on July 3, 2009, and by the U.S. Food and Drug Administration (FDA) on January 25, 2010. A 2011 Cochrane review showed a HbA1c reduction of 0.24% more with liraglutide 1.8 mg compared to insulin glargine, 0.33% more than exenatide 10 μg twice daily, sitagliptin and rosiglitazone. Liraglutide, together with exenatide, led to greater weight loss than glucagon-like peptide analogues. Taspoglutide is presently in Phase III clinical trials with Hoffman-La Roche. Lixisenatide (Lyxumia) Sanofi Aventis Semaglutide (Ozempic) (oral version is Rybelsus) Dulaglutide (Trulicity) - once weekly Albiglutide (Tanzeum) - once weekly Tirzepatide - once weekly (dual GLP-1 and GIP agonist; manufactured by Eli Lilly, and approved in 2022.
During the 13th century, Ghanaians developed their art of adinkra printing. Hand-printed and hand-embroidered adinkra clothes were made and used exclusively by royalty for devotional ceremonies. Each of the motifs that make up the corpus of adinkra symbolism has a name and meaning derived from a proverb, a historical event, human attitude, ethology, plant life-form, or shapes of inanimate and man-made objects. The meanings of the motifs may be categorised into aesthetics, ethics, human relations, and concepts. The Adinkra symbols have a decorative function as tattoos and also represent objects that encapsulate evocative messages that convey traditional wisdom, aspects of life, or the environment. There are symbols with meanings, with some linked with proverbs. In the words of Anthony Appiah, they were one of the means in a pre-literate society for "supporting the transmission of a complex and nuanced body of practice and belief". Kente cloth, the traditional or national cloth of Ghana, is worn by most southern Ghanaian ethnic groups, especially, the Akan Along with the adinkra cloth, Ghanaians use cloth fabrics for their traditional attire. The different ethnic groups have their own individual cloth. The most well known is the Kente cloth. Kente is a national costume and clothing, and these clothes are used to make traditional and modern Kente attire. Different symbols and colours mean different things. Kente is a ceremonial cloth hand-woven on a horizontal treadle loom and strips measuring about 4 inches wide are sewn together into larger pieces of cloths.
== Controlled == Certain surgeries for cerebral aneurysms or aortic arch defects require that blood circulation be stopped while repairs are performed. This deliberate temporary induction of clinical death is called circulatory arrest. It is typically performed by lowering body temperature to between 18 °C and 20 °C (64 and 68 °F) and stopping the heart and lungs. This state is called deep hypothermic circulatory arrest. At such low temperatures most patients can tolerate the clinically dead state for up to 30 minutes without incurring significant brain injury. Longer durations are possible at lower temperatures, but the usefulness of longer procedures has not been established yet. Controlled clinical death has also been proposed as a treatment for exsanguinating trauma to create time for surgical repair.
=== Synthetic dipeptides === Dipeptides are produced by coupling amino acids. The amino group on one amino acid is rendered non-nucleophilic (P in eq) and the carboxylic acid group in the second amino acid is deactivated as its methyl ester. The two modified amino acids are then combined in the presence of a coupling agent, which facilitates formation of the amide bond:
Sources: en.wikipedia.org
19 December – With the UK government signalling its willingness to delay local elections due in May 2026 for a year, the Electoral Commission raises concerns about further delays to elections, describing the process as one that is "damaging public confidence". 21 December – The Electoral Commission finds no "credible evidence of potential offences of electoral law" over Nigel Farage's election expenses. Scottish Labour MSP Pam Duncan-Glancy confirms she will not seek re-election to the Scottish Parliament at the 2026 election because she does not want her friendship with a convicted sex offender to "become a distraction". 22 December – Liberal Democrat leader Sir Ed Davey writes to the Equalities and Human Rights Commission to ask it to investigate government plans to delay local elections, which could affect as many as 10 million voters. The leader of Plymouth City Council confirms that local elections there will go ahead in May, but local elections in Exeter are still uncertain. 23 December – The UK government announces it is watering down its plans for inheritance tax on farmers, and will raise the threshold from £1m to £2.5m. Local Government Secretary Steve Reed writes to councils in England warning them not to adopt a four-day working week. Scotland's Justice Secretary, Angela Constance, is to face an investigation over comments she made about a grooming gang expert to determine whether she broke the ministerial code.
=== Optic nerve blood supply === The optic nerve head, or prelaminar disc, primarily receives blood from the peripapillary choroidal arterioles, which stem from the elliptical anastomotic annulus connected to the circle of Zinn-Haller. The circle of Zinn-Haller is formed by branches of the lateral and posterior ciliary arteries. Beyond this region, different segments of the optic nerve are supplied by various networks of arteries and capillaries originating from the ophthalmic artery and the central retinal artery. The Zinn-Haller circle also provides blood to the thin, sieve-like section of the eye's outer layer and the optic nerve fibers within it through small, inward-facing arteries. The area just behind this layer in the optic nerve is vascularized by small returning arteries and minute blood vessels that arise from the eye's surrounding circulation and the main ophthalmic artery, interweaving through the nerve's supporting fibers. The parts of the optic nerve located within the eye socket and the canal it traverses receive blood from small arteries branching off the primary network surrounding the eye, as well as from the central retinal artery. Fluorescein angiographic studies have demonstrated that during the acute phase of NAION, there is a delay in blood flow to the optic disc, suggesting a potential impairment in the arteries directly supplying it. Other research indicates that a drop in blood pressure within specific critical areas of the optic disc's blood supply network may increase its susceptibility to damage.
=== Biosynthesis === Biosynthesis takes place in bacteria, fungi and plants, but not animals. The biosynthetic precursors to riboflavin are ribulose 5-phosphate and guanosine triphosphate. The former is converted to L-3,4-dihydroxy-2-butanone-4-phosphate. Guanosine is degraded to 4-hydroxy-2,4,5-triaminopyrimidine, which is transformed into 5-amino-6-(D-ribitylamino)uracil. These two compounds are then the substrates for the penultimate step in the pathway, catalysed by the enzyme lumazine synthase in reaction EC 2.5.1.78.
Sources: en.wikipedia.org
The mass difference from the linker is large enough for routine detection by mass spectrometry. The unconjugated form gives a single sharp signal at its expected weight. Material that has already reacted with albumin shows a much higher mass and a broadened chromatographic peak.
Yes. Degradation proceeds faster once the powder is dissolved, especially at room temperature or after multiple freeze and thaw cycles. Working solutions are often aliquoted to avoid repeated handling. Lyophilized powder held cold and dry retains its properties far longer.
Truncated sequences, oxidized residues and aggregated forms can all elute near the main peak. Reversed phase chromatography resolves many of these species, so the number of peaks is a useful indicator of synthesis quality. A single peak does not by itself prove correct sequence, which is why mass confirmation is paired with it.
Natural GHRH is degraded quickly by dipeptidyl peptidase-4 and related enzymes, giving it a half-life measured in minutes. CJC-1295 carries substitutions that slow that breakdown, so it stays intact longer. Both act at the same pituitary receptor and produce the same class of signal.