If you have been reading about Dinucleotide 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 2026-07-29. Where a claim depends on a specific study, the study is described rather than over-claimed.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide composed of two nucleotides joined by phosphate groups. One nucleotide contains adenine; the other contains nicotinamide. The molecule exists in oxidized (NAD+) and reduced (NADH) forms, and the reversible hydride transfer between them underlies many metabolic oxidation-reduction reactions. In cells, NAD+ serves as an electron acceptor in pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation. Its concentration and redox ratio vary by compartment, tissue, and metabolic state.
Beyond redox chemistry, NAD+ is consumed as a substrate by enzymes that transfer ADP-ribose or remove acetyl groups. Sirtuins use NAD+ in deacylation reactions, poly(ADP-ribose) polymerases use it in DNA damage responses, and CD38 hydrolases convert it to signaling metabolites. Because these enzymes compete for the same pool, changes in NAD+ availability can influence multiple cellular processes. The relative contribution of each consumption route differs by cell type and condition, and precise quantitative links remain an active area of study.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C21H27N7O14P2 | Free acid form; salt and hydrate forms differ in mass. |
| Molar mass | 663.43 g/mol | Anhydrous free acid; counterions and water change the value. |
| Appearance | White to off-white powder | Typical solid reagent; exact color varies by purity and form. |
| Solubility class | Highly water-soluble | Aqueous solutions are acidic; organic solubility is generally limited. |
| Common synonyms | DPN, coenzyme I, NAD | Older literature often uses diphosphopyridine nucleotide or DPN. |
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.
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.
Substantial cephalopelvic disproportion Unfavorable fetal position or presentation (e.g., transverse lies) undeliverable without conversion before delivery Obstetric emergencies where maternal or fetal risk-to-benefit ratio favors surgery Fetal distress when delivery is not imminent Umbilical cord prolapse Uterine activity fails to progress adequately Hyperactive or hypertonic uterus Vaginal delivery is contraindicated (e.g., invasive cervical carcinoma, active genital herpes infection, total placenta previa, vasa previa, cord presentation or prolapse) Uterine or cervical scarring from previous cesarean section or major cervical or uterine (e.g., transfundal) surgery Unengaged fetal head History of hypersensitivity to oxytocin or any ingredient in the formulation
=== Gene mutations === Several gene mutations have been identified in patients with camptocormia. These include the RYR1 gene in axial myopathy, the DMPK gene in myotonic dystrophy, and genes related to dysferlinopathy and Parkinson's disease. These genes could serve as targets for gene therapy to treat the condition in the years to come.
A major part of EU law, and most of the EU's budget, concerns public regulation of enterprise and public services. A basic norm of the Treaty on the Functioning of the EU, in article 345, is that the "Treaties shall in no way prejudice the rules in Member States governing the system of property ownership", meaning the EU remains neutral between private or public ownership, but that it can require common standards. In the cases of education and health, member states generally organise public services and the EU requires free movement. There is a unified European Central Bank that funds private banks, and adopts a common monetary policy for price stability, employment and sustainability. The EU's policies on energy, agriculture and forestry, transport and buildings are crucial to end climate damage and shift completely to clean energy that does not heat the planet. Among these, 33% of the entire EU budget is spent on agricultural subsidies to farm corporations and owners. The EU also has an increasing number of policies to raise standards for communications, the internet, data protection, and online media. It has limited involvement in the military and security, but a Common Foreign and Security Policy.
== Theca interna == Theca interna cells express receptors for luteinizing hormone (LH) to produce androstenedione (an androgen), which via a few steps, gives the granulosa cells the precursor for estrogen manufacturing. After rupture of the mature ovarian follicle, the theca interna cells differentiate into the theca lutein cells of the corpus luteum, which continue to secrete androgens.
Sources: en.wikipedia.org
The violence began on 11 July, after a Druze vegetable merchant was assaulted by members of Bedouin tribes after they set up an improvised roadblock. The Bedouin attackers subjected him to sectarian insults and repeated death threats during his detention. He was later released to a remote village while blindfolded and in critical condition. In response, local Druze armed groups detained several individuals from Bedouin tribes the next day in an effort to recover the stolen property. This initiated a cycle of retaliatory kidnappings between the two sides, which quickly escalated into open armed clashes. On 13 July, the Bedouin fighters responded by establishing a checkpoint in the al-Maqwas neighborhood in eastern Suwayda city, where they captured several members of the local Druze armed groups. Armed clashes soon erupted between the two sides in and around the area, the clashes spread to at-Tira, al-Mazraa, and as-Sawra al-Kabira. Bedouins from Daraa Governorate arrived to the area to assist the Bedouin fighters. On 14 July, video was released showing a General Security vehicle, including a person making sectarian statements, declaring his participation in the conflict.
==== STS-118 ==== Caldwell Dyson was assigned to STS-118 on May 17, 2006. It was announced that she would serve as mission specialist 1 on the first flight of Space Shuttle Endeavour after the Columbia disaster. On August 8, 2007, Caldwell Dyson lifted off for the first time on the 119th Space Shuttle flight, the 22nd flight to the station, and the 20th flight for Endeavour. During the mission, she successfully added another truss segment, a new gyroscope and external spare parts platform to the International Space Station. A new system that enables docked shuttles to draw electrical power from the station to extend visits to the outpost was activated successfully. A total of four spacewalks (EVAs) were performed by three crew members. Endeavour carried some 5,000 pounds of equipment and supplies to the station and returned to Earth with some 4,000 pounds of hardware and no-longer-needed equipment. Traveling 5.3 million miles in space, the STS-118 mission was completed in 12 days, 17 hours, 55 minutes and 34 seconds. On day 7 of the flight of STS-118, Caldwell-Dyson celebrated her 38th birthday.
== Etymology == The name Qingzhou, meaning "Light Boat", is derived from a famous poem by the Tang dynasty poet Li Bai: "The light boat has already passed ten thousand mountains" (轻舟已过万重山). According to the developers, the name symbolizes the spirit of overcoming difficulties and the determination to explore the stars.
== History == Blue cheese is believed to have been discovered by accident when cheeses were stored in caves with naturally controlled temperature and moisture levels which happened to be favorable environments for varieties of harmless mold. Analysis of paleofeces sampled in the salt mines of Hallstatt, Austria showed that miners of the Hallstatt Period (800 to 400 BC) already consumed blue cheese and beer.
=== Pittsburgh Pirates (1960–62) === Mizell's trade to the Pirates was one of the catalysts of Pittsburgh's championship run that season. Facing the Giants on June 16, 1960, he threw 166 pitches and stayed in the ballgame for three hours and two minutes, allowing two runs through eight innings before allowing three hits to start the ninth and getting charged with three more runs, though he still earned the win in the 10–7 victory. "Shucks, no. I wasn't tired," he quipped after the game. On the strength of two shutouts, he pitched 30 consecutive scoreless innings from July 22 to August 9, the longest such streak of his career. The first shutout may have been his best game of the season; he held the Cubs to two hits in a 4–0 victory on July 29. Six days later, he allowed five hits but no runs to the Giants, securing a 1–0 triumph. On September 18, he won another 1–0 game, limiting Cincinnati to three hits in nine innings. In the month of September, he had a 5–1 record and a 3.14 ERA as the Pirates clinched the NL pennant. Mizell went 13-5 for the Pirates that season (14–8 overall) and finished sixth in the NL in winning percentage (.636). Between St. Louis and Pittsburgh, he had a 3.50 ERA (3.12 with the Pirates), striking out 113 and walking 74 in 211 innings. Of the walks, 10 were intentional. Mizell started Game 3 of the 1960 World Series against the New York Yankees but was removed in the first inning, having given up three hits and a walk while only retiring one hitter. He was charged with the loss as the Yankees won 10–0.
Sources: en.wikipedia.org
==== Addiction ==== Arguably, some people pursue ineffective shortcuts to feeling good. These shortcuts create positive feelings, but are problematic, in part because of the lack of effort involved. Some examples of these shortcuts include shopping, drugs, chocolate, loveless sex, and TV. These are problematic pursuits because all of these examples have the ability to become addictive. When happiness comes to us so easily, it comes with a price we may not realize. This price comes when taking these shortcuts is the only way to become happy, otherwise viewed as an addiction. A review by Amy Krentzman on the Application of Positive Psychology to Substance Use, Addiction, and Recovery Research, identified, in the field of positive psychology, three domains that allow an individual to thrive and contribute to society. One of these, A Pleasant Life, involves good feelings about the past, present, and future. To tie this with addiction, they chose an example of alcoholism. Research on positive affect and alcohol showed a majority of the population associates drinking with pleasure. The pleasure one feels from alcohol is known as somatic pleasure, which is immediate but a short lived sensory delight. The researchers wanted to make clear pleasure alone does not amount to a life well lived; there is more to life than pleasure. Secondly, the Engaged Life is associated with positive traits such as strength of character.
Immune-mediated causes could include transient factors as in Mycoplasma pneumoniae infection (cold agglutinin disease) or permanent factors as in autoimmune diseases like autoimmune hemolytic anemia (itself more common in diseases such as systemic lupus erythematosus, rheumatoid arthritis, Hodgkin's lymphoma, and chronic lymphocytic leukemia). Spur cell hemolytic anemia Any of the causes of hypersplenism (increased activity of the spleen), such as portal hypertension. Acquired hemolytic anemia is also encountered in burns and as a result of certain infections (e.g. malaria). Lead poisoning or poisoning by arsine or stibine causes non-immune hemolytic anemia. Runners can develop hemolytic anemia due to "footstrike hemolysis", the destruction of red blood cells in feet at foot impact. Low-grade hemolytic anemia occurs in 70% of prosthetic heart valve recipients, and severe hemolytic anemia occurs in 3%.
Episode Two opens with Alyx and Gordon learning a superportal to the Combine dimension has formed in the Citadel's place, progressing to a stage where the Combine can send reinforcements. They also discover that Alyx's encrypted data from the Citadel can reverse the portal, and so traverse the countryside to deliver the packet to another resistance headquarters at White Forest. As they progress, Combine Advisors have escaped the Citadel's destruction, and remaining Combine forces are regrouping, albeit under attacks by Vortigaunts. Aware of the resistance's plans to close the superportal, the Combine attack White Forest in force, but are repelled. The Combine are again the primary antagonist in the prequel Half-Life: Alyx, taking place between Half-Life and Half-Life 2. The game focuses on the efforts of Alyx Vance, her father Eli, and fellow resistance member Russell, as they attempt to infiltrate a massive Combine vault, believing it possesses a weapon that they could use to weaken the Combine occupation on Earth. After navigating through various quarantine zones of City 17 and rescuing Eli, they discover that the Vault is constructed not to hold a weapon, but as a prison, which they deduce to be holding Gordon Freeman. Alyx infiltrates the Vault and learns that it does not imprison Freeman, but is instead harboring the mysterious G-Man, who shows Alyx a glimpse of Eli's death in the future and offers her a chance to prevent it, which she accepts, before placing her in stasis.
== Structure == Two identified transcript variants are expressed in several tissues and are evolutionarily conserved in fish and swine. One transcript, 1a, excises an intron and encodes the functional protein; this protein is the receptor for the ghrelin ligand and defines a neuroendocrine pathway for growth hormone release. The second transcript (1b) retains the intron and does not function as a receptor for ghrelin; however, it may function to attenuate activity of isoform 1a. GHS-R1a is a member of the G-protein-coupled receptor (GPCR) family. Previous studies have shown that GPCRs can form heterodimers, or functional receptor pairs with other types of G-protein coupled receptors (GPCRs). Various studies suggest that GHS-R1a specifically forms dimers with the following hormone and neurotransmitter receptors: somatostatin receptor 5, dopamine receptor type 2 (DRD2), melanocortin-3 receptor (MC3R), and serotonin receptor type 2C (5-HT2c receptor). See "Function" section below for details on the purported functions of these heterodimers.
Sources: en.wikipedia.org
NAD+ is a coenzyme found in all living cells. It carries electrons in metabolic reactions and also serves as a substrate for enzymes involved in signaling and DNA repair. Its oxidized and reduced forms are central to energy metabolism.
NAD+ is the oxidized form and NADH is the reduced form. The pair accepts and donates electrons in redox reactions. Their ratio helps indicate the metabolic state of a cell or compartment.
No. Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are precursors that cells can convert into NAD+. They are distinct molecules with different absorption and metabolism profiles.
Aqueous NAD+ solutions are best kept frozen in aliquots and protected from light. Repeated freezing and thawing is avoided because it can accelerate breakdown. Dry powder stored desiccated at -20 °C or lower typically remains stable for longer periods.