The short version of Redox cofactor fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-06-10 and is reviewed periodically as new material appears.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C21H27N7O14P2 | Applies to the free acid form of beta-NAD+ |
| Molar mass | 663.43 g/mol | Calculated from the free acid formula |
| Redox couple | NAD+/NADH | Standard reduction potential near -0.32 V at pH 7 |
| Primary role | Electron carrier | Participates in oxidoreductase reactions |
| Common synonym | Diphosphopyridine nucleotide | Historical abbreviation DPN |
Research on NAD+ often examines changes with age, diet, exercise, and disease states, but causal relationships are difficult to establish. Some studies measure NAD+ levels, while others assess enzyme activity or downstream markers. In the literature, terms such as "NAD+ decline" and "NAD+ boosting" appear in both scientific and commercial contexts, sometimes without precise definitions. Whether changes in measured NAD+ directly produce health effects remains an open question. Results from cells, animals, and humans cannot be assumed to translate directly.
Measuring NAD+ in biological samples requires rapid processing because the compound can degrade or interconvert after collection. Common approaches include enzymatic cycling assays, high-performance liquid chromatography, and mass spectrometry. Each method has different sensitivity, specificity, and susceptibility to interference from related nucleotides. Sample type matters: cultured cells, animal tissues, and human blood present distinct challenges. Reported values can vary widely across laboratories because of differences in extraction, normalization, and analytical platform. Standardization remains an open issue in the field.
NAD+ is relatively unstable in aqueous solution, especially at neutral or alkaline pH and at elevated temperatures. It is typically stored dry, protected from light and moisture, and kept cold or frozen for long-term use. Solutions are often prepared fresh or buffered to mildly acidic pH to slow hydrolysis. Repeated freeze-thaw cycles can reduce integrity. Laboratories may verify concentration using ultraviolet absorbance at 259 nm or by enzymatic assay. These handling practices are general laboratory conventions rather than universal rules.
Commercial NAD+ is available at research grade, often with purity specifications determined by high-performance liquid chromatography. Certificates of analysis may report water content, residual solvents, and counterion identity. Identity can be confirmed by ultraviolet absorbance near 260 nm, mass spectrometry, or enzymatic activity. Because different salt forms and hydration states exist, researchers should verify that the product matches the intended molecular form. Lot-to-lot variation in purity can affect quantitative assays and should be documented.
Solid NAD+ is usually supplied as a white to off-white powder or lyophilized preparation. It is hygroscopic and should be kept desiccated at low temperature, commonly -20 °C or below for long-term storage. Aqueous solutions are less stable than dry material and are often prepared fresh or stored frozen in aliquots. Light exposure and repeated freeze-thaw cycles can promote degradation, so amber containers and single-use aliquots are preferred. Buffered solutions near neutral pH are generally less stable than acidic or frozen preparations.
Quantification of NAD+ in biological samples typically uses liquid chromatography coupled to mass spectrometry. Enzymatic cycling assays offer higher throughput and rely on NAD+ dependent dehydrogenases to amplify signal. Both approaches require careful sample quenching because NAD+ can be rapidly consumed or converted after collection. Acidic extraction is common for NAD+, while alkaline conditions favor NADH in some protocols. Isotopically labeled internal standards help correct for losses during extraction and ionization.
Beyond redox chemistry, NAD+ serves as a substrate for enzymes that transfer ADP-ribose or remove acetyl groups. Sirtuins, PARPs, and CD38-family enzymes consume NAD+ and produce nicotinamide and ADP-ribose-related products. These reactions link NAD+ availability to DNA repair, chromatin modification, and cellular signaling. Because the molecule is central to energy metabolism and regulation, changes in its concentration are studied in aging, immunity, and metabolic research. The balance between synthesis and consumption varies by tissue, developmental stage, and physiological state.
In humans, NAD+ can be synthesized from nicotinic acid, nicotinamide, nicotinamide riboside, and tryptophan through overlapping pathways. The salvage pathway recycles nicotinamide back to NAD+ and is often considered a major route in many tissues. Dietary precursors and intracellular recycling both contribute to the pool, but the quantitative importance of each source remains an active research question. NAD+ levels are not uniform across organs or cell compartments. Measurements in blood do not necessarily reflect concentrations inside tissues.
NAD+ is a dinucleotide composed of nicotinamide, ribose, and adenine linked by phosphate groups. Its full name is nicotinamide adenine dinucleotide, with "+" denoting the oxidized form. The molecule acts as a coenzyme in redox reactions, cycling between NAD+ and NADH. In cells, it participates in electron transfer during glycolysis, the citric acid cycle, and oxidative phosphorylation. It is distinct from NADP+, which carries an additional phosphate group and supports different biosynthetic reactions.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer ADP-ribose units. Sirtuins, poly(ADP-ribose) polymerases, and CD38 consume NAD+ in regulatory reactions. These activities link NAD+ availability to DNA repair, chromatin modification, calcium signaling, and metabolic stress responses. Because consumption can exceed biosynthesis under some conditions, cellular NAD+ levels are dynamic rather than fixed. Enzyme affinity and local synthesis also influence how much NAD+ is available for signaling.
NAD+ is a dinucleotide composed of adenine, ribose, and nicotinamide moieties linked by phosphate groups. Its oxidized form carries a positive charge on the nicotinamide ring, which enables reversible hydride transfer. The molecule functions as a coenzyme in oxidoreductase reactions rather than as a dietary vitamin in its intact form. Cells maintain separate pools in cytoplasm, mitochondria, and nucleus. This compartmentalization allows distinct redox environments while preserving a shared chemical identity.
== Legal issues == On June 25, 2010, Bayer sued Teva for falsely claiming that Teva's Gianvi was stabilized by betadex as a clathrate, and could consequently be advertised as a generic of Yaz. The settlement resulted in Teva changing its product marketing to remove the claim that it used the same ingredients as Yaz. Bayer's method specifically prevents oxidative degradation of the estrogen, while Teva's does not. In January 2015, the Supreme Court of the United States decided for Teva on the Copaxone patent in Teva Pharmaceuticals USA, Inc. v. Sandoz, Inc. In December 2016, the attorneys general of 20 states filed a civil complaint accusing Teva of a coordinated scheme to artificially maintain high prices for a generic antibiotic and diabetes drug. The complaint alleged price collusion schemes between six pharmaceutical firms including informal gatherings, telephone calls, and text messages. In January 2019, the Supreme Court of the United States decided for Teva in Helsinn Healthcare S.A. v. Teva Pharmaceuticals USA Inc. On May 11, 2019, Teva Pharmaceuticals USA was one of 19 drug companies sued for price fixing in the United States by 44 states for inflating its prices, sometimes up to 1000%, in an illegal agreement among it and its competitors. In June 2021, Teva agreed to pay $925M to settle allegations it had engaged in price fixing in Mississippi. In January 2022, Teva agreed to pay $425M to settle allegations that it had concealed price fixing practices from shareholders. In May 2019, Teva Pharmaceuticals USA agreed to pay $85 million to the U.S.
== Safety == Avobenzone is not generally recognised as safe and effective (GRASE) by the FDA for lack of sufficient data to support this claim. However, it is still the only FDA approved UVA filter (up to 3% concentration). Avobenzone is also approved in all other jurisdictions, such as EU (up to 5%), Australia, and Japan. A 2017 study at Lomonosov Moscow State University found that chlorinated water and ultraviolet light can cause avobenzone to disintegrate into various other organic compounds, including; phenolic acids, aldehydes, phenols, and acetophenones which can cause adverse health effects.
Intracavernous injection, an injection into the base of the penis. Intradermal, (into the skin itself) is used for skin testing some allergens, and also for mantoux test for tuberculosis. Intralesional (into a skin lesion), is used for local skin lesions, e.g. acne medication. Intramuscular (into a muscle), e.g. many vaccines, antibiotics, and long-term psychoactive agents. Recreationally the colloquial term 'muscling' is used.
==== Clumped isotopes ==== Clumped isotopes present a distinct set of challenges for isotopic reference materials. By convention the clumped isotope composition of CO2 liberated from CaCO3 (Δ47) and CH4 (Δ18/Δ13CH3D/Δ12CH2D2) are reported relative to a stochastic distribution of isotopes. That is, the ratio of a given isotopologue of a molecule with multiple isotopic substitutions against a reference isotopologue is reported normalized to that same abundance ratio where all isotopes are distributed randomly. In practice the chosen reference frame is almost always the isotopologue with no isotopic substitutions. This is 12C16O2 for carbon dioxide and 12C1H4 for methane. Standard isotopic reference materials are still required in clumped isotope analysis for measuring the bulk δ values of a sample, which are used to calculate the expected stochastic distribution and subsequently to infer clumped isotope temperatures. However, the clumped isotope composition of most samples are altered in the mass spectrometer during ionization, meaning that post-measurement data correction requires having measured materials of known clumped isotope composition. At a given temperature equilibrium thermodynamics predicts the distribution of isotopes among possible isotopologues, and these predictions can be calibrated experimentally. To generate a standard of known clumped isotope composition, current practice is to internally equilibrate analyte gas at high temperatures in the presence of a metal catalyst and assume that it has the Δ value predicted by equilibrium calculations.
However, unlike special interest groups these committees have come under some oversight regulation and are required to make formal records available to the public. As of 2002, about 1,000 of these advisory committees were described in the FACA searchable database.
Sources: en.wikipedia.org
The types of entrees vary with the producer and the issued menu (of which there are usually 7 to 12), but the common set is based on a traditional Russian outdoorsmen fare, is largely formed out of the commercially available canned food, and usually includes 1 portion of stewed beef or pork, two meat-with-vegetables dishes, like various porridges, stews or canned fish, and one or two spreads, such as liver pâté, sausage stuffing or processed cheese. Desserts may include fruit jams, chocolate and/or walnut spreads, chocolate bars, sweetened condensed milk, etc., but baked goods are usually avoided out of concerns about their shelf life. Other variants may add canned speck and/or dried fish or exchange the hexamine tablets for the flameless heater.
== June 19, 1915 (Saturday) == A royal decree from Denmark allowed Iceland, still a Danish colony, to get its own flag. Born: Pat Buttram, American actor, best known for the role of Mr. Haney in the TV series Green Acres; as Maxwell Emmett Buttram, in Addison, Alabama, United States (d. 1994) Died: Benjamin F. Isherwood, 92, American naval officer, rear admiral and Engineer-in-Chief of the United States Navy, co-founder of the Bureau of Steam Engineering (b. 1822) Sergei Taneyev, Russian pianist and composer, best known for his opera Oresteia; died of a heart attack (b. 1856)
=== Kenny Kilbane === Kenny Kilbane (Conor MacNeill) is a VP on Pierpoint's FX desk, and Yasmin's line manager. Throughout the first season, Kenny subjects Yasmin to repeated bullying and verbal abuse in the workplace, which he often blames on his alcoholism. In one case, Yasmin brings Kenny to a client dinner she arranged with her family friend Maxim Alonso, but Kenny embarrasses her when he orders a stripper to perform a lap dance on Yasmin in front of her disgusted clients. On RIF day, however, Kenny's boss Hilary Wyndham advises that Yasmin not report his behavior during her interview, suggesting that being a "team player" would help her career prospects. In series 2, Kenny returns to work following a long stint in rehab during the COVID-19 pandemic, noticeably kinder to his colleagues and vocal about his commitment to self-improvement and repentance. Yasmin, though still uncomfortable around Kenny, invites him to another client dinner, which ends up going well after Kenny and the client bond over both attending AA. When Yasmin announces her departure from the FX desk for a role in private wealth management (PWM), Kenny takes her aside and offers a sincere, tearful apology for his past behavior. Later, however, new FX hire Venetia Berens reports to Kenny that CPS client Nicole Craig sexually assaulted her, and that Yasmin dismissed her concerns. Kenny confronts Yasmin about her response, but Yasmin berates him for his hypocrisy given his own history of abusive conduct towards her, and brands him a narcissist lording his sobriety over others.
=== DNA repair === Two classical DNA repair pathways, nucleotide excision repair and base excision repair, are present in hydra, and these repair pathways facilitate unhindered reproduction. The identification of these pathways in hydra is based, in part, on the presence in the hydra genome of genes homologous to genes in other genetically well studied species that have been demonstrated to play key roles in these DNA repair pathways.
== Literature == Half Life (Jackson novel), a 2006 novel by Shelley Jackson Half-Life (Krach novel), a 2004 novel by Aaron Krach Halflife (Michalowski novel), a 2004 novel by Mark Michalowski Rozpad połowiczny (Half-Life), a 1988 award-winning dystopia novel by Edmund Wnuk-Lipiński
Sources: en.wikipedia.org
TC/EA (or HTC, high temperature conversion; HTP, high temperature pyrolysis; HTCR, high temperature carbon reduction) is an "online" or "continuous flow" preparation method typically followed by IRMS detection. This is a "bulk" technique that measures all the hydrogen in a sample and provides the average isotope signal. The weighed sample is placed in a tin or silver capsule and dropped into a pyrolysis tube of TC/EA. The tube is made of glassy carbon with glassy carbon filling, so oxygen isotopes can be measured simultaneously without oxygen exchange with ceramic (Al2O3) surface. The molecules are then reduced into CO and H2 at high temperature (>1400°C) in the reactor. The gaseous products are separated through gas chromatography (GC) using helium as the carrier gas, followed by a split-flow interface, and finally detected by IRMS. TC/EA method can be problematic for organic compounds with halogen or nitrogen due to the competition between the pyrolysis byproducts (e.g. HCl and HCN) and H2 formation. In addition, it is susceptible to contamination with water, so samples must be scrupulously dried. An adaption of this method is to determine the non-exchangeable (C-H) and exchangeable hydrogen (bounds to other elements, e.g. O, S and N) in organic matter. The samples are equilibrated with water in sealed autosampler carousels at 115°C and then transferred into pyrolysis EA followed by IRMS measurement. TC/EA method is quick with fairly high precision (~1‰).
Chronometric dating is a process of archaeological and geological age determination. Often confused with Absolute dating, Chronometric dating measures time through consistent natural processes (such as the degradation of the C14 atom) and provides a date range, not an absolute date, to the dated event.
=== March === On March 1, Bob Power died at the age of 73. On March 26, the MOBO Awards 2026 were held. Olivia Dean won Song of the Year for "Man I Need", Album of the Year for The Art of Loving, and Best Female Act. Raye won Video of the Year for "Where Is My Husband!". Wizkid won Best African Music Act. Ayra Starr won Best International Act. Flo won Best R&B/Soul Act. On the same day, the 2026 iHeartRadio Music Awards were held. Kehlani won R&B Song of the Year for "Folded". Chris Brown won R&B Artist of the Year. Leon Thomas won R&B Album of the Year for Pholks and Best New R&B Artist. Moliy won World Artist of the Year.
=== Dwarf sports === Dwarfs have support and compete in sport by a number of organizations nationally and internationally. They are included in some events in the athletics at the Summer Paralympics. The Dwarf Athletic Association of America and the Dwarf Sports Association UK provide opportunities for dwarfs to compete nationally and internationally in the Americas and Europe, respectively. The World Dwarf Games (WDG) are a multi-sport event for athletes of short stature. The WDG have been held every four years since 1993 and are the world's largest sporting event exclusively for athletes with dwarfism. The Dwarf Sports Association UK organizes between 5 and 20 events per month for athletes with restricted growth conditions in the UK. For instance, swimming and bicycling are often recommended for people with skeletal dysplasias, since those activities put minimal pressure on the spine. Since its early days, professional wrestling has had the involvement of dwarf athletes. "Midget wrestling" had its heyday in the 1950s–'70s, when wrestlers such as Little Beaver, Lord Littlebrook, and Fuzzy Cupid toured North America, and Sky Low Low was the first holder of the National Wrestling Alliance's World Midget Championship. In the next couple of decades, more wrestlers became prominent in North America including foreign wrestlers like Japan's Little Tokyo. Although the term is seen by some as pejorative, many past and current midget wrestlers including Hornswoggle said they take pride in the term due to its history in the industry and its marketability.
Tyrosine hydroxylase catalyzes the reaction in which L-tyrosine is hydroxylated in the meta position to obtain L-3,4-dihydroxyphenylalanine (L-DOPA). The enzyme is an oxygenase which means it uses molecular oxygen to hydroxylate its substrates. One of the oxygen atoms in O2 is used to hydroxylate the tyrosine molecule to obtain L-DOPA and the other one is used to hydroxylate the cofactor. Like the other aromatic amino acid hydroxylases (AAAHs), tyrosine hydroxylase use the cofactor tetrahydrobiopterin (BH4) under normal conditions, although other similar molecules may also work as a cofactor for tyrosine hydroxylase. The AAAHs converts the cofactor 5,6,7,8-tetrahydrobiopterin (BH4) into tetrahydrobiopterin-4a-carbinolamine (4a-BH4). Under physiological conditions, 4a-BH4 is dehydrated to quinonoid-dihydrobiopterin (q-BH2) by the enzyme pterin-4a-carbinolamine dehydrase (PCD) and a water molecule is released in this reaction. Then, the NAD(P)H dependent enzyme dihydropteridine reductase (DHPR) converts q-BH2 back to BH4. Each of the four subunits in tyrosine hydroxylase is coordinated with an iron(II) atom presented in the active site. The oxidation state of this iron atom is important for the catalytic turnover in the enzymatic reaction. If the iron is oxidized to Fe(III), the enzyme is inactivated. The product of the enzymatic reaction, L-DOPA, can be transformed to dopamine by the enzyme DOPA decarboxylase.
Sources: en.wikipedia.org
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.
No; NAD+ and related dinucleotides occur across bacteria, archaea, plants, fungi, and animals. Its central role in electron transfer and enzyme catalysis is deeply conserved, though specific pathways for making and using it can differ among organisms.
NAD+ is a charged, water-soluble dinucleotide and generally does not diffuse freely across cell membranes. Cells rely on precursor molecules and dedicated transport or salvage pathways. This limited permeability shapes how researchers deliver or measure NAD+ in experimental systems.
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.