If you have been reading about LC-MS 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 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide built from adenine, nicotinamide, two ribose sugars, and two phosphate groups. The oxidized form carries a positive charge on the nicotinamide ring, while the reduced form, NADH, is neutral. This pair acts as a reversible electron carrier in cells. NAD+ is present in bacteria, plants, animals, and fungi. Its structure allows it to accept and donate electrons without being consumed in the reactions it supports.
In redox reactions, NAD+ accepts a hydride ion, which consists of two electrons and one proton. The hydride adds to the nicotinamide ring at a specific carbon, converting NAD+ into NADH. Dehydrogenase enzymes use this step in glycolysis, the citric acid cycle, and fatty acid oxidation. NADH later donates electrons to the mitochondrial electron transport chain, helping to drive ATP synthesis. The balance between NAD+ and NADH reflects the metabolic state of a cell, and shifts in that balance can alter how pathways operate.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave it and attach its ADP-ribose portion to other molecules. This group includes poly(ADP-ribose) polymerases, CD38, and sirtuins. Such reactions consume NAD+ and can influence its availability for metabolism. Cells replenish NAD+ through a salvage pathway that recycles nicotinamide and through routes starting from tryptophan or vitamin B3 forms. How these synthesis and consumption routes are coordinated across tissues remains an active area of study, and compartment-specific concentrations are difficult to measure directly.
Beyond redox catalysis, NAD+ is a substrate for enzymes that transfer ADP-ribose or remove acetyl groups from proteins. Sirtuins and poly(ADP-ribose) polymerases consume NAD+ and release nicotinamide as a byproduct. These reactions connect cellular energy status to gene regulation, DNA repair, and stress responses. Because NAD+ is used rather than merely recycled in such signaling, its concentration reflects both biosynthesis and consumption. The balance between salvage and de novo synthesis pathways determines available pools in different tissues.
Biosynthesis of NAD+ starts from nicotinamide, nicotinic acid, or nicotinamide riboside through salvage pathways. A rate-limiting enzyme, nicotinamide phosphoribosyltransferase, converts nicotinamide to nicotinamide mononucleotide. Further coupling with ATP yields NAD+. In mammals, the liver and muscle can synthesize NAD+ from dietary precursors, but tissue levels vary widely. Researchers study these pathways to understand age-related changes, metabolic disorders, and neurodegeneration. Direct causal links between NAD+ decline and disease remain an active area of investigation.
NAD+ is a dinucleotide composed of adenine, ribose, and nicotinamide groups joined by phosphate linkages. It serves as a coenzyme in oxidoreductase reactions, cycling between oxidized NAD+ and reduced NADH. The molecule is water-soluble and occurs in all living cells. Its nicotinamide ring accepts hydride ions during catabolic reactions, linking substrate oxidation to electron transport. This redox couple supports ATP production and helps maintain cytosolic and mitochondrial redox balance in many cell types.
| Property | Value | Notes |
|---|---|---|
| Molar mass | 663.43 g/mol | For the free acid form; salts have higher mass. |
| Appearance | White to off-white powder | Often hygroscopic; may clump on exposure to air. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture; avoid repeated freeze-thaw. |
| Common synonyms | beta-NAD, DPN | DPN stands for diphosphopyridine nucleotide, an older name. |
Laboratory handling of NAD+ follows standard practices for hygroscopic fine chemicals. Personnel typically avoid inhalation and skin contact, use gloves and eye protection, and work in a ventilated area. Quality control may include ultraviolet absorbance at the nicotinamide maximum, chromatographic purity, water content, and identity confirmation by mass spectrometry. Because commercial preparations can contain counterions, residual solvents, or related nucleotides, a certificate of analysis helps verify the material. Researchers should confirm that the form supplied matches the intended assay.
Measuring NAD+ in biological samples requires care because the molecule is chemically reactive and present at low concentrations in some tissues. Common approaches include enzymatic cycling assays, high-performance liquid chromatography, and liquid chromatography coupled to mass spectrometry. Each method has different sensitivity and specificity, and sample preparation can affect results. Acidic or alkaline extraction steps are used in some protocols, but the choice depends on the analyte and matrix. No single method is universally optimal for every tissue or fluid.
Solid NAD+ is relatively stable when kept dry, cold, and protected from light. Aqueous solutions are more vulnerable to hydrolysis and can lose activity during repeated freeze-thaw cycles or prolonged storage at ambient temperature. Stability depends on pH, ionic strength, and the presence of degrading enzymes or metal ions. For many laboratory uses, aliquots are stored frozen and thawed only once. Exact degradation rates vary by matrix, so stability should be checked for each application rather than assumed.
Quality control for NAD+ materials typically combines identity, purity, and water content checks. Identity may be confirmed by ultraviolet spectrum, retention time in chromatography, or mass accuracy, while purity is assessed by HPLC peak area or quantitative nuclear magnetic resonance. Residual water and solvents can affect molar calculations and enzyme assays, so Karl Fischer titration or thermogravimetric analysis may be used. Commercial materials vary in grade and counterion form, and published methods should specify the exact salt or hydrate when reporting concentrations. Regulatory status depends on intended use, with research reagents, dietary ingredients, and clinical products treated under different frameworks.
Quantification of NAD+ in biological samples usually relies on separation techniques coupled to sensitive detection. High-performance liquid chromatography with ultraviolet detection can measure the oxidized form by its absorbance near 260 nm, while mass spectrometry provides greater specificity and can distinguish NAD+ from close analogs. Enzymatic cycling assays use coupled dehydrogenase reactions to amplify signal and estimate NAD+ concentrations in cell or tissue extracts. Because NAD+ and NADH interconvert rapidly, sample preparation must quench metabolism quickly and preserve the redox state before analysis.
The Battle of Marengo, which largely ended the War of the Second Coalition, was fought with fewer than 60,000 men on both sides. The Battle of Austerlitz which ended the War of the Third Coalition involved fewer than 160,000 men. The Battle of Friedland which led to peace with Russia in 1807 involved about 150,000 men. After these defeats, the continental powers developed various forms of mass conscription to allow them to face France on even terms, and the size of field armies increased rapidly. The Battle of Wagram of 1809 involved 300,000 men, and 500,000 fought at Leipzig in 1813, of whom 150,000 were killed or wounded. About a million French soldiers became casualties (wounded, invalided or killed), a higher proportion than in the First World War. The European total may have reached 5,000,000 military deaths, including disease. France had the second-largest population in Europe by the end of the 18th century (28 million, as compared to Britain's 12 million and Russia's 35 to 40 million). It was well poised to take advantage of the levée en masse. Before Napoleon's efforts, Lazare Carnot played a large part in the reorganization of the French Revolutionary Army from 1793 to 1794—a time which saw previous French misfortunes reversed, with Republican armies advancing on all fronts.
== C == c-Abl Calpactin (Annexin) CHO1 Cortactin CamKinase II Calponin Chondramide Cortexillin CAP Caltropin CH-ILKBP CPb3 Cap100 Calvasculin Ciboulot Coactosin CAP23 CARMIL Acan125 Cingulin Cytovillin (Ezrin) CapZ/Capping Protein a-Catenin Cofilin CR16 Caldesmon CCT Comitin Calicin Centuarin Coronin
=== United States === According to the US Food and Drug Administration (FDA), an orphan drug is defined as one "intended for the treatment, prevention or diagnosis of a rare disease or condition, which is one that affects less than 200,000 persons in the US" (which equates to approximately 6 cases per 10,000 population) "or meets cost recovery provisions of the act".
=== Unit name === In 1993, the IUPAC proposed the shorter name "dalton" (with symbol "Da") for the unified atomic mass unit. As with other unit names such as watt and newton, "dalton" is not capitalized in English, but its symbol, "Da", is capitalized. The name was endorsed by the International Union of Pure and Applied Physics (IUPAP) in 2005. In 2003 the name was recommended to the BIPM by the Consultative Committee for Units, part of the CIPM, as it "is shorter and works better with [SI] prefixes". In 2006, the BIPM included the dalton in its 8th edition of the SI brochure of formal definitions as a non-SI unit accepted for use with the SI. The name was also listed as an alternative to "unified atomic mass unit" by the International Organization for Standardization in 2009. It is now recommended by several scientific publishers, and some of them consider "atomic mass unit" and "amu" deprecated. In 2019, the BIPM retained the dalton in its 9th edition of the SI brochure, while dropping the unified atomic mass unit from its table of non-SI units accepted for use with the SI, but secondarily notes that the dalton (Da) and the unified atomic mass unit (u) are alternative names (and symbols) for the same unit.
Sources: en.wikipedia.org
=== Preservation in a resin pour === A resin pour preservation allows for flowers like roses to be preserved in a clear transparent mould, making this method a great choice for ornamental preservation of flowers. Two separate resin elements are mixed in equal proportions and poured into a silicone mould, often in an ice cube shape, with the flower inserted. With each pour, a heat gun is used to remove air bubbles that form at the surface of the pour. Those attempting a resin pour preservation are recommended to wear a respirator and gloves as a resin pour can give off fumes and also a considerable amount of heat. The preservation of real dried flowers can also be done within a bezel-based structure poured with resin.
=== Medically-induced coma === In addition to anesthesia induction, sodium thiopental was historically used to induce medical comas. It has now been superseded by drugs such as propofol because their effects wear off more quickly than thiopental. Patients with brain swelling, causing elevation of intracranial pressure, either secondary to trauma or following surgery, may benefit from this drug. Sodium thiopental, and the barbiturate class of drugs, decrease neuronal activity thereby decreasing cerebral metabolic rate of oxygen consumption (CMRO2), thus decreasing the cerebrovascular response to carbon dioxide, which in turn decreases intracranial pressure. Patients with refractory elevated intracranial pressure (RICH) due to traumatic brain injury (TBI) may have improved long term outcome when barbiturate coma is added to their neurointensive care treatment. Reportedly, thiopental has been shown to be superior to pentobarbital in reducing intracranial pressure. This phenomenon is also called an inverse steal or Robin Hood effect as cerebral perfusion to all parts of the brain is reduced (due to the decreased cerebrovascular response to carbon dioxide) allowing optimal perfusion to ischaemic areas of the brain which have higher metabolic demands, since vessels supplying ischaemic areas of the brain would already be maximally dilated because of the metabolic demand.
=== Earth and agricultural sciences === In soil science, hydrology and agricultural sciences, water content has an important role for groundwater recharge, agriculture, and soil chemistry. Many recent scientific research efforts have aimed toward a predictive-understanding of water content over space and time. Observations have revealed generally that spatial variance in water content tends to increase as overall wetness increases in semiarid regions, to decrease as overall wetness increases in humid regions, and to peak under intermediate wetness conditions in temperate regions . There are four standard water contents that are routinely measured and used, which are described in the following table:
=== Executive authority and actions === Overall, Newsom has vetoed legislation at a rate comparable to that of his predecessors. From 2019 to 2021, he vetoed 12.7% of the bills the legislature passed on average. The rate declined over the course of the three legislative sessions. Newsom's vetoes have included bills to allow ranked-choice voting, require an ethnic studies class as a high school graduation requirement, regulate AI, and reduce penalties for jaywalking. Newsom used a larger than normal number of executive orders during the 2020 legislative session.
It has been argued that happiness at work is one of the driving forces behind positive outcomes at work, rather than just being a resultant product. Despite a large body of positive psychological research into the relationship between happiness and productivity, happiness at work has traditionally been seen as a potential by-product of positive outcomes at work, rather than a pathway to success in business. However a growing number of scholars, including Boehm and Lyubomirsky, argue that it should be viewed as one of the major sources of positive outcomes in the workplace.
Sources: en.wikipedia.org
It indicates the oxidized form, which has a positive charge on the nicotinamide nitrogen. The reduced partner NADH lacks that charge and carries added electrons. The plus sign is part of the standard abbreviation, not a separate ion.
No. It also serves as a substrate for signaling and DNA-repair enzymes such as sirtuins and PARPs. Those reactions consume NAD+ and connect its availability to cellular regulation. Energy transfer remains its most abundant known role.
NAD+ is the oxidized electron acceptor, while NADH is the reduced electron carrier. They form a reversible redox pair and differ by a hydride ion. Cells maintain different ratios of the two depending on conditions and compartment.
NAD+ is the oxidized form and NADH is the reduced form of the same coenzyme. NAD+ accepts electrons during oxidation reactions, becoming NADH, which can donate electrons in other reactions. The ratio between them helps describe a cell's redox state.