This is a working overview of mass spectrometry, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-11-13 and is reviewed periodically as new material appears.
Identity and purity are usually assessed by reverse-phase high-performance liquid chromatography coupled to mass spectrometry. Retention time and observed mass are compared against a reference standard run under identical conditions. Impurity profiles reveal deamidation products, oxidized methionine variants, and truncated fragments that arise during synthesis or storage. Peptide mapping through enzymatic digestion confirms the primary sequence, while amino acid analysis offers an independent check on overall composition.
Stability studies examine how temperature, pH, and moisture influence degradation rates over time. In aqueous solution, hydrolysis and deamidation accelerate as pH moves away from mildly acidic conditions. Light exposure and residual metal ions can also trigger oxidation of susceptible residues. Accelerated aging at elevated temperature is used to estimate shelf life, though extrapolation to room temperature carries uncertainty because individual degradation pathways do not always scale predictably.
Certificate of analysis documents from suppliers typically report purity by chromatographic area, water content, and counter-ion identity. Independent verification is advisable because reported values can be generated under differing conditions. Impurity profiles matter for research use, where aggregates, deamidation products, and residual solvents may influence experimental results. Container, lot, and chain-of-custody records support traceability. Analytical results are method-dependent, so comparisons between laboratories require the same procedure and reference standards.
Lyophilized peptide material is typically stored at or below -20 °C, with -80 °C used for longer-term archives. Vials should remain sealed and desiccated because moisture promotes aggregation and hydrolysis. Repeated freeze-thaw cycles are avoided since they can alter peptide conformation and reduce recovery. Once reconstituted, solutions are generally kept at 2-8 °C and used within a defined window. Stability beyond those windows depends on buffer composition and concentration, and exact limits are product-specific rather than universal.
Identity and purity are assessed with reversed-phase high-performance liquid chromatography, which separates the peptide from related impurities by hydrophobicity. Mass spectrometry confirms molecular weight and detects truncation or modification products. Peptide mapping after enzymatic digestion verifies the amino acid sequence. Quantitation is often performed by LC-MS/MS or by immunoassay, and the two approaches can give different values because they measure different things. Method validation parameters such as accuracy, precision, and limit of quantitation are reported alongside results.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white lyophilized powder | Batch-to-batch variation is normal |
| Solubility class | Soluble in water, buffer, and dimethyl sulfoxide | Aqueous solubility is moderate |
| Typical storage temperature | Minus 20 degrees Celsius dry, 2 to 8 degrees Celsius reconstituted | Avoid repeated freeze-thaw |
| Common analytical method | Reverse-phase HPLC with electrospray mass detection | Used for purity and mass confirmation |
| Common synonyms | GLP-1 analog, semaglutide peptide | Wording varies across suppliers |
==== Mechanisms ==== Heme iron (or "haem iron”) in red meat has been associated with increased colorectal cancer risk. The American Institute for Cancer Research and World Cancer Research Fund have commented that "haem iron, which is present at high levels in red meat, has been shown to promote colorectal tumorigenesis by stimulating the endogenous formation of carcinogenic N-nitroso compound." N-Glycolylneuraminic acid (Neu5Gc) has also been suggested as a mechanism.
== Awards == Prix scientifique de la Fondation de France, with André Langaney, 1978 Prix de la Société française de physique, 1985 Le Relictocarabus meurguesianus, and insect discovered in Morocco, was named in her honour.
Nuclear batteries use small amounts (milligrams and microcuries) of radioisotopes with high energy densities. In one betavoltaic device design, radioactive material sits atop a device with adjacent layers of P-type and N-type silicon. Ionizing radiation directly penetrates the junction and creates electron–hole pairs. Nuclear isomers could replace other isotopes, and with further development, it may be possible to turn them on and off by triggering decay as needed. Current candidates for such use include 108Ag, 166Ho, 177Lu, and 242Am. As of 2004, the only successfully triggered isomer was 180mTa, which required more photon energy to trigger than was released. An isotope such as 177Lu releases gamma rays by decay through a series of internal energy levels within the nucleus, and it is thought that by learning the triggering cross sections with sufficient accuracy, it may be possible to create energy stores that are 106 times more concentrated than high explosive or other traditional chemical energy storage.
in the above equation modulo ln(2)) of the parent and daughter, respectively, and BR is the branching ratio. In transient equilibrium, the Bateman equation cannot be simplified by assuming the daughter's half-life is negligible compared to the parent's half-life. The ratio of daughter-to-parent activity is given by:
== Structure and membership == Article 10.(b) of the Draft Constitutional Declaration defines the Sovereignty Council to consist of five civilians chosen by the FFC, five military chosen by the TMC, and a civilian "selected by agreement" between the FFC and TMC. Under Article 10.(c) of the Draft Constitutional Declaration, for the first 21 months of the 39-month transitional period defined by the document, the chair of the Sovereignty Council was to be chosen by the five military members of the council. For the following 18 months, the chair was to be chosen by the five civilian members selected by the FFC. The military membership of the Sovereignty Council included General Abdel Fattah al-Burhan, General Hemedti, Lieutenant-General Yasser al-Atta, General Shams al-Din Khabbashi and Major-General Ibrahim Jabir Karim. Hemedti has been the deputy chairman of the Sovereignty Council in the past. The five civilians chosen by the FFC are Aisha Musa el-Said of the National Gathering Initiative; Siddiq Tawer, a prominent member of the Arab Socialist Ba'ath Party – Region of Sudan (and thereby a member of the National Consensus Forces) from the Nuba Mountains in South Kordofan; Mohamed al-Faki Suleiman of the Unionist Gathering from Northern Sudan; Hassan Sheikh Idris (or Hassan Mohamed Idris), a prominent member of the National Umma Party (and thereby a member of Sudan Call) from Kassala; and Mohammed Hassan Osman al-Ta'ishi of the Sudanese Professionals Association.
Sources: en.wikipedia.org
== Other uses == Gautampura Road railway station, Ujjain, Madhya Pradesh, India GP Strategies Corporation, an American consulting firm (NYSE ticker:GPX) GPX Tire Corporation, an American company producing tires Grand Prix (disambiguation), French for "Grand Prize", used in several sports
It is quite clear that the structure of the enzyme, to be specific the active site, is very important in understanding the mechanism of reaction. For this reason, Rees and colleagues studied the enzyme-ligand complex to get a clear answer for the role of the zinc ion. These studies found that, in free enzyme, the zinc coordination number is five; the metal center is coordinated with two imidazole Nδ1 nitrogens, the two carboxylate oxygens of glutamate-72, and a water molecule to form a distorted tetrahedral. However, once ligand binds at the active site of carboxypeptidase A, this coordination number can vary from five to six. When bound to dipeptide glycyl-L-tyrosine, the amino nitrogen of the dipeptide and the carbonyl oxygen replaced the water ligand. This would yield a coordination number of six for the zinc in the carboxypeptidase A- dipeptide glycyl-L-tyrosine complex. Electron density maps gave evidence that the amino nitrogen occupies a second position near glutamate-270. The closeness of these two residues would result in a steric hindrance preventing the water ligand from coordinating with zinc. This would result in a coordination number of five. Data for both are substantial, indicating that both situations occur naturally. There are two proposed mechanisms for the catalytic function of carboxypeptidase A. The first is a nucleophilic pathway involving a covalent acyl enzyme intermediate containing active site base Glu-270. Evidence for this anhydride intermediate is mixed; Suh and colleagues isolated what is assumed to by the acyl intermediate.
=== Autosamplers === The autosampler provides the means to introduce a sample automatically into the inlets. Manual insertion of the sample is possible but is no longer common. Automatic insertion provides better reproducibility and time-optimization.Different kinds of autosamplers exist. Autosamplers can be classified in relation to sample capacity (auto-injectors vs. autosamplers, where auto-injectors can work a small number of samples), to robotic technologies (XYZ robot vs. rotating robot – the most common), or to analysis: Liquid Static head-space by syringe technology Dynamic head-space by transfer-line technology Solid phase microextraction (SPME)
Kwäday Dän Ts'ìnchi ("Long ago person found" in the Southern Tutchone language of the Champagne and Aishihik First Nations), was found in August 1999 by three First Nations hunters at the edge of a glacier in Tatshenshini-Alsek Provincial Park, British Columbia, Canada. According to the Kwäday Dän Ts'ìnchi Project, the remains are the oldest well preserved mummy discovered in North America. (The Spirit Cave mummy although not well preserved, is much older.) Initial radiocarbon tests date the mummy to around 550 years-old.
A descriptor which is applied to any substance or process which is being investigated for clinical use but either has not commenced, or has not completed, clinical trials. Examples: candidate vaccine, candidate formulation. Case report
Sources: en.wikipedia.org
== SM == sm – (s) Samoan language (ISO 639-1 code) Sm – (s) Samarium SM (i) Sado-Masochism (s) San Marino (ISO 3166 and FIPS 10-4 country code digram) (i) Soldier's Manual (s) Submarine Minelayer (US Navy hull classification) SMA – (i) Scan Mirror Assembly SMART - many different meanings SMASS – (a) Small Main-Belt Asteroid Spectroscopic Survey SMB – (i) Super Mario Bros. SMCT – (i) Soldier's Manual of Common Tasks SMD – (i) Surface Mount Device SMDR – (i) Station Message Detail Recording sme – (s) Northern Sami language (ISO 639-2 code) SME (i) Scan Mirror Electronics Subject Matter Expert SMG (i) Sequential Motorsport Gearbox SubMachine Gun SMH – (a) Shaking My Head SMil – (a) Sadomasochisterne i landet (Danish SM organisation) SMIL – (a) Synchronized Multimedia Integration Language smo – (s) Samoan language (ISO 639-2 code) SMP – (i) Standard Military Pattern SM&R – (i) Source, Maintenance, and Recoverability SMR – (s) San Marino (ISO 3166 trigram) SMS – many, including: Short message service; see entry SMTP – (i) Simple Mail Transfer Protocol SMU – (i) Southern Methodist University SMV – (i) Symbolic model verification SMX many, including: (i) Server Macro Expansion (p) Solaris MINIX (p) Spatial multiplexing (p) Sulfamethoxazole; see entry SMZ many, including: (i) Silver Mt. Zion (p) Sulfamethazine (p) Sulfamethoxazole; see entry
Frederic Durán-Jordà fled to Britain in 1938 and worked with Dr Janet Vaughan at the Royal Postgraduate Medical School at Hammersmith Hospital to establish a system of national blood banks in London. With the outbreak of war appearing imminent in 1938, the War Office created the Army Blood Supply Depot (ABSD) in Bristol, headed by Lionel Whitby and in control of four large blood-depots around the country. British policy through the war was to supply military personnel with blood from centralized depots, in contrast to the approach taken by the Americans and Germans where troops at the front were bled to provide required blood. The British method proved more successful in adequately meeting all requirements, and over 700,000 donors were bled over the course of the war. This system evolved into the National Blood Transfusion Service established in 1946, the first national service to be implemented.
α-Ketoglutaric acid (AKG) is an organic compound with the formula HO2CCO(CH2)2CO2H. A white, nontoxic solid, it is a common dicarboxylic acid. Relevant to its biological roles, it exists in water as its conjugate base α-ketoglutarate. It is also classified as a 2-ketocarboxylic acid. β-Ketoglutaric acid is an isomer. "Ketoglutaric acid" and "ketoglutarate", when not qualified as α or β, almost always refers respectively to α-ketoglutaric acid or α-ketoglutarate. α-Ketoglutarate is an intermediate in the citric acid cycle, a set of cyclic reactions that supplies energy to cells. It is also an intermediate in or product of several other metabolic pathways. These include its being a component of metabolic pathways that: make amino acids and in the process regulate the cellular levels of carbon, nitrogen, and ammonia; reduce the cellular levels of potentially toxic reactive oxygen species; and synthesize the neurotransmitter γ-aminobutyric acid (GABA). A large body of preclinical (i.e., conducted in animal models of disease or on animal or human tissues) research has been conducted on the role of endogenous (generated within the body) α-ketoglutarate. A small amount of preclinical research has been done to determine the effects of providing additional exogenous α-ketoglutarate to biological systems. There is currently no randomized controlled trials showing α-ketoglutarate to have any pharmacological (drug-like) effects on humans. The Food and Drug Administration classifies α-ketoglutaric acid as "503A Category 3: Bulk Drug Substances Nominated Without Adequate Support".
=== Thermal cycling model === A stepwise model for the emergence of chemiosmosis, a key element in the origin of life on earth, proposes that primordial organisms used thermal cycling as an energy source (thermosynthesis), functioning essentially as a heat engine:
Sources: en.wikipedia.org
Manufacturers commonly state multi-year stability when the powder is kept dry and frozen. Actual shelf life depends on residual moisture, vial sealing, and storage temperature. A re-test by chromatography is the only way to confirm remaining purity.
Deamidated and oxidized forms are the most frequently reported impurities. Truncated peptide fragments from incomplete synthesis also appear at low levels. Their relative abundance grows with time, heat exposure, and unfavorable pH.
Retention time matching on a validated column provides strong circumstantial evidence. It does not distinguish compounds with similar hydrophobicity. Mass measurement or peptide mapping is needed for unambiguous identification.
The lyophilized powder is dissolved in a suitable solvent, often sterile water or a buffered diluent, with gentle mixing rather than vigorous shaking. Foaming and shear should be avoided because they can promote aggregation. The resulting solution is then stored cold and protected from light.