NAD+ comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-02-03. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
NAD+ is a dinucleotide composed of two nucleotides joined by a pyrophosphate linkage. One nucleotide contains adenine, and the other contains nicotinamide. The oxidized form carries a positive charge on the nicotinamide ring and is abbreviated NAD+. It functions as a cofactor in hydride-transfer reactions, accepting electrons in catabolic pathways. In cells, it interconverts with reduced NADH, forming a redox couple central to energy metabolism. The molecule is water-soluble and does not cross cell membranes freely without specific transport or precursor pathways.
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.
| 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 |
Related compounds include NADH, the reduced form, and NADP+, which carries an additional phosphate group. NADP+ and NADPH often serve in biosynthetic and antioxidant reactions, while NAD+ and NADH are more associated with energy-yielding catabolism. Nicotinamide, nicotinic acid, and nicotinamide riboside are precursors that can enter salvage pathways. The exact contribution of dietary precursors to tissue NAD+ pools is an area of active investigation. Some studies measure labeled precursors to trace those routes.
NAD+ is the oxidized form of nicotinamide adenine dinucleotide, a coenzyme built from two nucleotides joined by a phosphate linkage. One nucleotide carries adenine, and the other carries nicotinamide; the plus sign denotes a formal positive charge on the nicotinamide ring, not a free proton. In cells, NAD+ and its reduced partner NADH form a reversible redox pair. That pair participates in electron transfer reactions throughout metabolism. The abbreviation NAD+ is common in biochemistry, while NAD(H) sometimes denotes the combined pool.
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.
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.
In glycolysis, NAD+ accepts electrons during the oxidation of glyceraldehyde-3-phosphate, forming NADH. The tricarboxylic acid cycle and fatty acid oxidation also generate NADH, which donates electrons to the mitochondrial electron transport chain. This flow supports ATP synthesis and helps maintain the redox balance of the cell. Other dehydrogenases use NAD+ as a cofactor for biosynthetic reductions and detoxification reactions. NADH is later reoxidized to sustain continued flux through these pathways.
== Safety == DNCB induces a type IV hypersensitivity reaction in almost all people exposed to it, so it is used medically to assess the T cell activity in patients. This is a useful diagnostic test for immunocompromised patients. It can also be used to treat warts. DNCB can cause contact dermatitis.
At this time, Variety still had The Birth of a Nation ahead of The Big Parade ($6,400,000) on distributor rentals and—if its estimate is correct—Snow White and the Seven Dwarfs ($8,500,000) would not have earned enough on its first theatrical run to take the record; although it would have been the highest-grossing 'talkie', displacing The Singing Fool ($5,900,000). Although received wisdom holds that it is unlikely The Birth of a Nation was ever overtaken by a silent-era film, the record would fall to 1925's Ben-Hur ($9,386,000) if The Birth of a Nation earned significantly less than its estimated gross. In addition to its gross rental earnings through public exhibition, The Birth of a Nation played at a large number of private, club and organizational engagements which figures are unavailable for. It was hugely popular with the Ku Klux Klan who used it to drive recruitment, and at one point Variety estimated its total earnings to stand at around $50 million. Despite later retracting the claim, the sum has been widely reported even though it has never been substantiated. While it is generally accepted that Gone with the Wind took over the record of highest-grossing film on its initial release—which is true in terms of public exhibition—it is likely it did not overtake The Birth of a Nation in total revenue until a much later date, with it still being reported as the highest earner up until the 1960s.
=== Tang and Song Dynasties === Material from the Tang and Song dynastyies (C. 618–1279 A.D) has also been excavated and analysed using ceramic petrography, revealing a plethora of information on trade links, as well as stylistic elements. The Tang dynasty in Shanghai is well-known for its three-colour pottery and its bright colours. After analysing the remains of these artefacts, scientists have been able to trace trade over time, and can now see that maritime trade was only established later on in its history. Qinglong town, the heart of the dynasty was a prosperous maritime economy, with extensive links to adjacent islands. Indeed, through analyses of pottery from Qinglong and surrounding areas, archaeologists have discovered that the Tang and Song Dynasties had trade links with Persians, Arabs, Hindu Indians, Malays, Bengalis, Sinhalese, Khmers, Chams, Jews and Nestorian Christians of the Near East - a vast trade network that helps to explain the wide array of colours and materials in their ceramics.
Lamivudine/zidovudine, sold under the brand name Combivir among others, is a fixed-dose combination antiretroviral medication used to treat HIV/AIDS. It contains two antiretroviral medications, lamivudine and zidovudine. It is used together with other antiretrovirals. It is taken by mouth twice a day. Common side effects include headache, feeling tired, nausea, diarrhea, and fever. Severe side effects may include bone marrow suppression, muscle damage, worsening of hepatitis B if previously infected, high blood lactate and liver enlargement. It may be part of a recommended treatment during pregnancy. The medications are both of the nucleoside reverse transcriptase inhibitor (NRTI) class. They work by blocking the action of the enzyme, reverse transcriptase, that the virus requires to reproduce. Lamivudine/zidovudine was approved for medical use in the United States in 1997, and in the European Union in 1998. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication.
== Production == Cadmium is a common impurity in zinc ores, and it is most often isolated during the production of zinc. Some zinc ores concentrates from zinc sulfate ores contain up to 1.4% of cadmium. In the 1970s, the output of cadmium was 2.9 kilograms (6.5 lb) per ton of zinc. Zinc sulfide ores are roasted in the presence of oxygen, converting the zinc sulfide to the oxide. Zinc metal is produced either by smelting the oxide with carbon or by electrolysis in sulfuric acid. Cadmium is isolated from the zinc metal by vacuum distillation if the zinc is smelted, or cadmium sulfate is precipitated from the electrolysis solution. The British Geological Survey reports that in 2001, China was the top producer of cadmium with almost one-sixth of the world's production, closely followed by South Korea and Japan.
Sources: en.wikipedia.org
=== Mast cell activation disorders === Mast cell activation disorders (MCAD) are a spectrum of immune disorders that are unrelated to pathogenic infection and involve similar symptoms that arise from secreted mast cell intermediates, but differ slightly in their pathophysiology, treatment approach, and distinguishing symptoms. The classification of mast cell disorders is complex and has been repeatedly modified. The World Health Organization (WHO) classification of 2016 was updated in the WHO 5th Edition Classification of Haematolymphoid Tumours of 2022 and the International Consensus Classification (ICC) schema of 2022, which differ somewhat in their classification of subcategories of systemic mastocytosis. The incidence and prevalence of MCAD's subcategories of mastocytosis and MCAS have not yet been established through epidemiological studies.
Homocysteine is biosynthesized naturally via a multi-step process. First, methionine receives an adenosine group from ATP, a reaction catalyzed by S-adenosyl-methionine synthetase, to give S-adenosyl methionine (SAM). SAM is a widely used source of methyl radicals and a cofactor for radical SAM enzymes. Transfer of the methyl group to an acceptor molecule results in the formation of S-adenosyl-homocysteine. Hydrolysis of this thioether gives L-homocysteine. L-Homocysteine reacts with tetrahydrofolate (THF) to give L-methionine.
== History and development == A recipe for cream soda written by E. M. Sheldon and published in Michigan Farmer in 1852 called for water, cream of tartar (potassium bitartrate), Epsom salts, sugar, egg, and milk to be mixed, then heated, then mixed again once cooled with water and a quarter teaspoonful of baking soda to make an effervescent drink. It was suggested as a temperance drink preferable to those of "Uncle Bacchus" and in compliance with the recently introduced Maine law. An alternative recipe can be found combining a soda of choice as well as whipped cream. Alexander C. Howell of Vienna, New Jersey, was granted a patent for "cream soda-water" on June 27, 1865. Howell's cream soda-water was made with sodium bicarbonate, water, sugar, egg whites, wheat flour, and "any of the usual flavoring materials—such as oil of lemon, extracts of vanilla, pine-apple, to suit the taste". Before drinking, the cream soda-water was mixed with water and an acid, such as tartaric acid or citric acid. In Canada, James William Black of Berwick, Nova Scotia, was granted a U.S. patent on December 8, 1885, and a Canadian patent on July 5, 1886, for "ice-cream soda". Black's ice-cream soda, which contained whipped egg whites, sugar, lime juice, lemons, citric acid, flavoring, and bicarbonate of soda, was a concentrated syrup that could be reconstituted into an effervescent beverage by adding ordinary ice water. In the United States, Ugo H. Sodini helped to pioneer in the creation of vanilla cream soda.
Low genetic variation was found to occur between the three song characteristics in C. brunneus and C. jacobsi and no sex linkage was found. Peg numbers on the stridulatory file, while different between the two species, are surprisingly not dependent on song characteristics. Genetics cannot account for the difference in peg number. Instead additive effects explain the phenotypic variation in both song characteristics and peg number between C. brunneus, C. jacobsi, and their hybrids.
== 23S rRNA Helix 26a == The 23S ribosomal RNA is composed of six domains forming a complex network of molecular interactions. A central single-stranded region connects all of the domains through base-pairing of the two halves, forming Helix 26a. Some consider Helix 26a to be Domain 0 due to its action as a central core and compact folding unit. Comparison of 23S and 28S ribosomal RNA sequences across species demonstrate conservation of Helix 26a. Helices continue to provide the support as the backbone of domain architecture.
Sources: en.wikipedia.org
=== Rodents === The glans penis of the marsh rice rat is long and robust, averaging 7.3 mm (0.29 in) long and 4.6 mm (0.18 in) broad. Winkelmann's mouse can most readily be distinguished from its close relatives by its partially corrugated glans penis. In Thomasomys ucucha, the glans penis is rounded, short, and small and is superficially divided into left and right halves by a trough at the top and a ridge at the bottom. Most of the glans is covered with spines, except for an area near the tip. The glans penis of a male cape ground squirrel is large with a prominent baculum.
To make the proteins accessible to antibody detection, they are moved from within the gel onto a membrane, a solid support, which is an essential part of the process. There are two types of membrane: nitrocellulose (NC) or polyvinylidene difluoride (PVDF). NC membrane has high affinity for protein and its retention abilities. However, NC is brittle, and does not allow the blot to be used for re-probing, whereas PVDF membrane allows the blot to be re-probed. The most commonly used method for transferring the proteins is called electroblotting. Electroblotting uses an electric current to pull the negatively charged proteins from the gel towards the positively charged anode, and into the PVDF or NC membrane. The proteins move from within the gel onto the membrane while maintaining the organization they had within the gel. An older method of transfer involves placing a membrane on top of the gel, and a stack of filter papers on top of that. The entire stack is placed in a buffer solution which moves up the paper by capillary action, bringing the proteins with it. In practice this method is not commonly used due to the lengthy procedure time. As a result of either transfer process, the proteins are exposed on a thin membrane layer for detection. Both varieties of membrane are chosen for their non-specific protein binding properties (i.e. binds all proteins equally well). Protein binding is based upon hydrophobic interactions, as well as charged interactions between the membrane and protein.
Despite the limited clinical experience in these decades, that era is remarkable for the demonstration of the role technology has in neuromodulation, and there are some case reports of deep brain stimulation for a variety of problems, real or perceived. Delgado hinted at the power of neuromodulation with his implants in the bovine septal region and the ability of electrical stimulation to blunt or alter behavior. Further attempts at this "behavioral modification" in humans were difficult and seldom reliable, and contributed to the overall lack of progress in central nervous system neuromodulation from that era. Attempts at intractable pain syndromes were met with more success, but again hampered by the quality of technology. In particular, the so-called DBS "zero" electrode (consisting of a contact loop on its end) had an unacceptable failure rate, and revisions were fraught with more risk than benefit. Overall, attempts at using electrical stimulation for "behavioral modification" were difficult and seldom reliable, slowing development of DBS. Attempts at addressing intractable pain syndromes with DBS were met with more success, but again hampered by the quality of technology. A number of physicians who hoped to address hitherto intractable problems sought development of more specialized equipment; for instance, in the 1960s, Wall's colleague Bill Sweet recruited engineer Roger Avery to make an implantable peripheral nerve stimulator. Avery started the Avery Company, which made a number of implantable stimulators.
One of the claimants of the English throne opposing William the Conqueror, Edgar Atheling, eventually fled to Scotland. King Malcolm III of Scotland married Edgar's sister Margaret, and came into opposition to William who had already disputed Scotland's southern borders. William invaded Scotland in 1072, riding as far as Abernethy where he met up with his fleet of ships. Malcolm submitted, paid homage to William and surrendered his son Duncan as a hostage, beginning a series of arguments as to whether the Scottish Crown owed allegiance to the King of England. Normans went into Scotland, building castles and founding noble families that would provide some future kings, such as Robert the Bruce, as well as founding a considerable number of the Scottish clans. King David I of Scotland, whose elder brother Alexander I had married Sybilla of Normandy, was instrumental in introducing Normans and Norman culture to Scotland, part of the process some scholars call the "Davidian Revolution". Having spent time at the court of Henry I of England (married to David's sister Maud of Scotland), and needing them to wrestle the kingdom from his nephew Máel Coluim mac Alaxandair, David had to reward many with lands. The process was continued under David's successors, most intensely of all under William the Lion. The Norman-derived feudal system was applied in varying degrees to most of Scotland.
The heart evolved no less than 380 million years ago in fish. Fish have what is often described as a two-chambered heart, consisting of one atrium to receive blood and one ventricle to pump it. However, the fish heart has entry and exit compartments that may be called chambers, so it is also sometimes described as three-chambered or four-chambered, depending on what is counted as a chamber. The atrium and ventricle are sometimes considered "true chambers", while the others are considered "accessory chambers". Primitive fish have a four-chambered heart, but the chambers are arranged sequentially so that this primitive heart is quite unlike the four-chambered hearts of mammals and birds. The first chamber is the sinus venosus, which collects deoxygenated blood from the body through the hepatic and cardinal veins. From here, blood flows into the atrium and then to the powerful muscular ventricle where the main pumping action will take place. The fourth and final chamber is the conus arteriosus, which contains several valves and sends blood to the ventral aorta. The ventral aorta delivers blood to the gills where it is oxygenated and flows, through the dorsal aorta, into the rest of the body. (In tetrapods, the ventral aorta has divided in two; one half forms the ascending aorta, while the other forms the pulmonary artery). In the adult fish, the four chambers are not arranged in a straight row but instead form an S-shape, with the latter two chambers lying above the former two. This relatively simple pattern is found in cartilaginous fish and in the ray-finned fish.
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 the oxidized form, while NADH is the reduced form carrying an added hydride. The two form a redox pair that cells use in many energy-yielding reactions.