Redox cofactor is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-04-01. Numbers and descriptions here follow the published literature rather than marketing material.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a dinucleotide coenzyme built from an adenine nucleotide and a nicotinamide nucleotide joined by a pyrophosphate linkage. Its oxidized form carries a positive charge on the nicotinamide ring, while the reduced form, NADH, carries a hydride equivalent. The molecule participates in hundreds of oxidoreductase reactions, where it accepts or donates electrons and protons. Because it can cycle between oxidized and reduced states without net consumption, NAD+ functions as a reusable electron carrier rather than a fuel molecule.
In glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation, NAD+ is reduced to NADH at specific dehydrogenase steps. NADH then delivers electrons to the mitochondrial electron transport chain, mainly at complex I, supporting oxidative phosphorylation and ATP production. The balance between NAD+ and NADH, often expressed as a ratio, influences metabolic flux and redox homeostasis in different cellular compartments. Cytosolic and mitochondrial pools are connected but not identical, and their ratios can differ substantially because of compartment-specific enzymes and transport systems.
Beyond redox chemistry, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer its ADP-ribose moiety or remove acetyl groups. Sirtuins consume NAD+ during deacetylation, poly(ADP-ribose) polymerases use it in DNA damage responses, and CD38 enzymes hydrolyze it to signaling metabolites. These consumption pathways mean that NAD+ availability can influence gene regulation, DNA repair, and calcium signaling. Cellular NAD+ concentrations decline in some tissues with age in animal models, but whether this decline is a cause or consequence of aging in humans remains an active open question.
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 stability of NAD+ depends on pH, temperature, light exposure, and the presence of degradative enzymes. Aqueous solutions are generally more stable under mildly acidic to neutral conditions and degrade faster under alkaline conditions or prolonged heat. The solid is hygroscopic and should be stored desiccated, often frozen, and protected from repeated freeze-thaw cycles. In laboratory handling, aliquots reduce repeated temperature changes, and chelating agents may limit metal-catalyzed hydrolysis in some buffers. These practices matter because even small amounts of NADH or hydrolysis products can interfere with quantitative assays.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | β-NAD+, coenzyme I, DPN | DPN stands for diphosphopyridine nucleotide; older literature uses this term. |
| CAS Registry Number | 53-84-9 | Free acid form of β-nicotinamide adenine dinucleotide. |
| Molecular formula | C21H27N7O14P2 | Anhydrous free acid; molar mass 663.43 g/mol. |
| Appearance | White to off-white powder | Crystalline solid; may absorb moisture from air. |
| Solubility | Freely soluble in water | Insoluble in most nonpolar organic solvents. |
The nicotinamide ring undergoes reversible reduction at the para position, converting NAD+ to NADH. This reaction transfers a hydride equivalent, not a free hydrogen atom or electron alone. Because the redox pair has a defined reduction potential, it links oxidation of fuels to respiratory chain activity. Many dehydrogenases use NAD+ as a co-substrate and produce NADH. The ratio of NAD+ to NADH reflects metabolic state and influences flux through several pathways.
NAD+ also serves as a substrate for enzymes that cleave it, including sirtuins, PARPs, and CD38. These enzymes consume NAD+ and release nicotinamide and ADP-ribose or related products. The dual roles as redox cofactor and signaling substrate connect NAD+ to DNA repair, circadian regulation, and calcium signaling. Cellular NAD+ concentrations vary by tissue, time of day, and stress exposure. How these consumption pathways interact with redox balance remains an active area of research.
Commercial NAD+ is supplied as a solid, often as the free acid or a salt, and purity is verified by chromatographic methods. Laboratories typically store it desiccated at minus 20 degrees Celsius or below. Working solutions are prepared fresh because even sterile aqueous solutions can lose activity over hours to days depending on pH and temperature. Documentation may include a certificate of analysis, an assay value, and a recommended retest date. Researchers should verify identity and purity when results depend on precise cofactor concentrations.
NAD+ is commonly measured by high-performance liquid chromatography with ultraviolet detection, often at 254 or 260 nm. Enzymatic cycling assays provide higher sensitivity by coupling NAD+ to a reporter reaction. Mass spectrometry can distinguish NAD+ from close analogues and confirm isotope labeling. Sample preparation usually involves rapid quenching of metabolism to prevent interconversion with NADH. Because NAD+ and NADH differ by one hydride, extraction conditions strongly affect the measured ratio.
In aqueous solution, NAD+ is most stable under mildly acidic to neutral conditions and degrades faster at high pH or elevated temperature. The molecule can hydrolyze at the pyrophosphate bond or undergo nonenzymatic cyclization. Buffers, chelating agents, and cold temperatures slow these losses during analysis. Repeated freeze-thaw cycles are generally avoided because they can promote degradation and concentration changes. Light exposure is also controlled, though NAD+ is less photolabile than some related nucleotides.
== Applications == Pyrolysis gas chromatography is useful for the identification of involatile compounds. These materials include polymeric materials, such as acrylics or alkyds. The way in which the polymer fragments, before it is separated in the GC, can help in identification. Pyrolysis gas chromatography is also used for environmental samples, including fossil analysis and microplastic detection. Pyrolysis GC is used in forensic laboratories to analyze evidence found in crime scenes such as paints, adhesives, plastics, synthetic fibres and soil extracts.
By the middle of 1982, the Soviet Union alone maintained major mycological herbaria across 25 research institutions or museums and 11 universities, academies, and institutes, together preserving more than one million fungal specimens, including over 5,000 type specimens. The transition from morphology-based systematics to phylogenetics in the 1980s and 1990s further changed the role of historical collections, as scientists began extracting DNA from specimens collected more than a century earlier. Historical plant herbaria as well as dedicated mycological collections have also yielded valuable fungal and oomycete records when older specimens were re-examined for disease symptoms that were not the original focus of collection.
Since 1971, SI defined the "amount of substance" as a separate dimension of measurement. Until 2019, the mole was defined as the amount of substance that has as many constituent particles as there are atoms in 12 grams of carbon-12, with the dalton defined as +1/12 of the mass of a carbon-12 atom. Thus, during that period, the numerical value of the molar mass of a substance expressed in g/mol was exactly equal to the numerical value of the average mass of an entity (atom, molecule, formula unit) of the substance expressed in daltons. Since 2019, the mole has been redefined in the SI as the amount of any substance containing exactly 6.02214076×1023 entities, fixing the numerical value of the Avogadro constant NA when expressed in the unit mol−1, but because the dalton is still defined in terms of the experimentally determined mass of a carbon-12 atom, the numerical equivalence between the molar mass of a substance and the average mass of an entity of the substance is now only approximate, but equality may still be assumed with high accuracy—(the relative discrepancy is only of order 10–9, i.e. within a part per billion).
Sources: en.wikipedia.org
Chair, Financial Reporting Advisory Board. For Public Service. Diana Marjorie Parkes. Co-Founder and Patron, The Joanna Simpson Foundation. For services to Vulnerable Children Suffering from Domestic Abuse and Domestic Homicide. William James Pease-Watkin (Bill Watkin). Chief Executive, Sixth Form Colleges Association. For services to Further Education. Professor Andrew David Mark Pettegree, FBA. Historian and Author. For services to Literature. Andrew Kerry Pike, OBE. Lately Director, GREAT Britain and Northern Ireland Campaign, Cabinet Office. For Public Service. Erin Pizzey. Campaigner and Activist. For services to the Victims of Domestic Abuse. Professor Ann Prentice, OBE. Honorary Senior Visiting Fellow, MRC Epidemiology Unit, University of Cambridge. For services to British and Global Public Health Nutrition. Jessica Mary Pulay. Co-Head of Policy and Markets, UK Debt Management Office. For services to Public Finances. Professor Margaret Mary Rae. Lately President, UK Faculty of Public Health. For services to Public Health and to Public Health Standards. Dr. Mala Rao, OBE. Senior Clinical Fellow, Imperial College London. For services to Public Health, the NHS, and to Equality and Diversity. Mark Julian Read. Chief Executive Officer, WPP. For services to the Creative Industries. Simon Trevor Regis. Deputy Director, Department for Culture, Media and Sport Legal Advisers, Government Legal Department. For services to Legislation. Professor Elizabeth Jane Robertson. Professor of Developmental Biology, University of Oxford. For services to Medical Sciences.
BIOCEV (Biotechnology and Biomedicine Centre of the Academy of Sciences and Charles University) is a joint research institute located in Vestec, Czech Republic. Established in 2015, it is operated by six institutes of the Czech Academy of Sciences (CAS) and two faculties of Charles University (Faculty of Science, Charles University and First Faculty of Medicine, Charles University). The center maintains collaborative ties with other institutions in the STAR cluster.
=== Pharmacokinetics === Posaconazole is absorbed within three to five hours. It is predominantly eliminated through the liver, and has a half-life of about 35 hours. Oral administration of posaconazole taken with a high-fat meal exceeds 90% bioavailability and increases the concentration by four times compared to fasting state.
Mōri Motonari issued each soldier a bag of rice, fried rice, and mochi, the latter of which was chosen due to its portability, long shelf life, ability to provide high energy in small amounts, and Motonari's personal preference for it. Uesugi Kenshin would prepare massive feasts for his army before battles, known as kachidoki-meshi ("victory cry meals"), featuring delicacies such as "a mountain of rice ... black-boiled abalone, vinegar-washed fish and jellyfish sashimi, soups with seasonal vegetables and dried fish, walnut-roasted duck, simmered sand borer, and more", though Kenshin himself was noted to eat very little. During battles, Kenshin assembled supply convoys called konidatai staffed by peasants, who would deliver supplies and rations to troops. Toyotomi Hideyoshi is said to have regularly distributed food rations out to his officers and soldiers, and kept them well-fed. In one instance, while traveling from Ogaki to Nagahama (a 52 kilometer distance) in 1583, Hideyoshi sent scouts ahead to each village to ask that they prepare rice for Hideyoshi's army; the villages set out rice balls for the soldiers, allowing them to remain fed for the entire trip. In general, Japanese soldiers would bring uchigaibukuro, pouches used to store rice and medicine, into battle with them. They would also eat miso, dried taro stalk, and okayu as part of a soup prepared in a soldier's jingasa.
Sources: en.wikipedia.org
Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the practical lower limit for incandescent lamps is 1.5 volts. Very long filaments for high voltages are fragile, and lamp bases become more difficult to insulate, so lamps for illumination are not made with rated voltages over 300 volts. Some infrared heating elements are made for higher voltages, but these use tubular bulbs with widely separated terminals.
Lastly, beta-hydroxyacyl-CoA is oxidized to beta-ketoacyl-CoA while NAD+ is reduced to NADH, which follows the same process as the oxidation of malate to oxaloacetate. In the liver, the carboxylation of cytosolic pyruvate into intra-mitochondrial oxaloacetate is an early step in the gluconeogenic pathway which converts lactate and de-aminated alanine into glucose, under the influence of high levels of glucagon and/or epinephrine in the blood. Here the addition of oxaloacetate to the mitochondrion does not have a net anaplerotic effect, as another citric acid cycle intermediate (malate) is immediately removed from the mitochondrion to be converted into cytosolic oxaloacetate, which is ultimately converted into glucose, in a process that is almost the reverse of glycolysis. In protein catabolism, proteins are broken down by proteases into their constituent amino acids. Their carbon skeletons (i.e. the de-aminated amino acids) may either enter the citric acid cycle as intermediates (e.g. alpha-ketoglutarate derived from glutamate or glutamine), having an anaplerotic effect on the cycle, or, in the case of leucine, isoleucine, lysine, phenylalanine, tryptophan, and tyrosine, they are converted into acetyl-CoA which can be burned to CO2 and water, or used to form ketone bodies, which too can only be burned in tissues other than the liver where they are formed, or excreted via the urine or breath.
, the surface behaves elastically during contact. In both the Greenwood-Williamson and Mikic models the load is assumed to be proportional to the deformed area. Hence, whether the system behaves plastically or elastically is independent of the applied normal force.
== Historical use == Spirulina was a food source for the Aztecs and other Mesoamericans until the 16th century; the harvest from Lake Texcoco in Mexico and subsequent sale as cakes were described by one of Cortés' soldiers. The Aztecs called it tecuitlatl. Spirulina was found in abundance at Lake Texcoco by French researchers in the 1960s, but no reference to its use by the Aztecs as a daily food source was made after the 16th century, probably because of the draining of the surrounding lakes for agriculture and urban development. The topic of tecuitlatl, which was discovered in 1520, was not mentioned again until 1940, when the Belgian phycologist Pierre Dangeard mentioned a cake called dihe consumed by the Kanembu people, who harvest it from Lake Chad in the African nation of Chad. Dangeard studied the dihe samples and found it to be a dried purée of the spring form of the blue-green algae from the lake. The dihe is used to make broths for meals, and also sold in markets. The spirulina is harvested from small lakes and ponds around Lake Chad. During 1964 and 1965, the botanist Jean Leonard confirmed that dihe is made up of spirulina, and later studied a bloom of algae in a sodium hydroxide production facility. As a result, the first systematic and detailed study of the growth requirements and physiology of spirulina was performed as a basis for establishing large-scale production in the 1970s.
Tegafur is a chemotherapeutic prodrug of 5-fluorouracil (5-FU) used in the treatment of cancers. It is a component of the combination drug tegafur/uracil. When metabolised, it becomes 5-FU. It was patented in 1967 and approved for medical use in 1972.
Sources: en.wikipedia.org
NAD+ is an oxidized dinucleotide coenzyme that carries electrons in metabolic reactions. It is also consumed by signaling enzymes, including sirtuins and PARPs. Its reduced form is NADH.
NAD+ is the oxidized form and can accept a hydride equivalent. NADH is the reduced form and donates electrons to the electron transport chain. The two forms cycle between each other during cellular respiration.
In mammals, NAD+ is synthesized mainly through salvage pathways using nicotinamide, nicotinamide riboside, or nicotinic acid. Tryptophan can also contribute through a de novo route. The salvage pathway is often considered the primary source in many tissues.
Common methods include LC-MS, HPLC with UV detection, and enzymatic cycling assays. Rapid quenching is needed because NAD+ and NADH interconvert. The chosen method should be validated for the sample matrix.