If you have been reading about NADH 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 2025-12-05. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical name | Nicotinamide adenine dinucleotide | Oxidized form abbreviated NAD+ |
| Molecular formula | C21H27N7O14P2 | Free acid form |
| Molar mass | 663.43 g/mol | Calculated for free acid |
| CAS Registry Number | 53-84-9 | Common entry for beta-NAD+ |
| Appearance | White to off-white powder | Hygroscopic solid |
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.
Cells produce NAD+ through several biosynthetic routes. The salvage pathway recycles nicotinamide, while the Preiss-Handler pathway uses nicotinic acid, and a de novo route can start from tryptophan in some organisms. In mammals, the salvage pathway is generally considered the main source under ordinary conditions. Tissue concentrations vary widely by cell type and compartment, and measured declines with age have been reported in some studies. Whether such changes drive aging or mainly accompany it remains an open question.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a coenzyme present in all living cells. The molecule consists of two nucleotides linked by phosphate groups, with adenine and a nicotinamide ring as its principal features. In its oxidized form, the nicotinamide ring can accept a hydride ion, becoming NADH. This reversible conversion places NAD+ at the center of many electron-transfer reactions. Its role as a redox carrier is well established across bacteria, plants, fungi, and animals.
Beyond redox chemistry, NAD+ acts as a substrate for several enzyme families. ADP-ribosyltransferases, sirtuins, and CD38 ectoenzymes cleave the molecule into nicotinamide and ADP-ribose or related products. These reactions connect NAD+ availability to processes such as DNA repair, chromatin modification, and calcium signaling. Because the coenzyme is used in both electron transfer and signaling, cells maintain separate pools in compartments including the cytosol, mitochondria, and nucleus. The relative sizes and regulation of those pools remain active areas of study.
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.
Research on NAD+ spans biochemistry, aging biology, and metabolism. Studies often examine how NAD+ levels change with age, diet, exercise, or disease states, and whether precursor supplementation alters those levels. Findings in animal models do not automatically translate to humans, and measurement methods vary across studies. Questions about tissue-specific effects, long-term consequences, and causal relationships remain open. NAD+ itself is not established as a single therapeutic agent with a broad clinical role.
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.
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.
Describes the legal use of a prescription drug to treat a disease or condition for which the drug has not been approved by the U.S. Food and Drug Administration. (NCI) A drug prescribed for conditions other than those approved by the FDA. (NLM) Open label study
=== June 2006 === According to the Iraqi Defense Ministry, Private First Class Thomas Tucker and Private First Class Kristian Menchaca were reportedly "killed in a barbaric way," "slaughtered," and tortured to death, and their bodies were so mutilated that DNA tests are being performed to help identify their remains. The alleged group has said it was a revenge for the rape and murder of an Iraqi girl who was dishonoured by soldiers of the same brigade. Video of the killing of four Russian diplomats kidnapped in Iraq appear on the Internet. A group called the Mujahideen Shura Council released the hostage video.
=== Screenwriting === For her screenplay Look for Water, which she co-wrote with Dominic Mah, she was invited to the Sundance Screenwriters' Lab in June 2008. The screenplay has also received the Tribeca Film Festival L'Oreal Woman of Worth Vision Award, a Sundance CineReach grant, and a Sundance Institute Annenberg Feature Film Fellowship Grant.
=== Natural sciences === Chemical reactions: The rates of certain types of chemical reactions depend on the concentration of one or another reactant. Reactions whose rate depends only on the concentration of one reactant (known as first-order reactions) consequently follow exponential decay. For instance, many enzyme-catalyzed reactions behave this way. Electrostatics: In a RC circuit, the electric charge (or, equivalently, the potential) contained in a capacitor (capacitance C) discharges through a constant external load (resistance R) with exponential decay and similarly charges with the mirror image of exponential decay (when the capacitor is charged from a constant voltage source though a constant resistance). The exponential time-constant for the process is
=== Organ rejection === Immune responses to both organ rejection and severe bacterial infection can lead to similar symptoms such as swelling and fever that can make initial diagnosis difficult. To differentiate between acute rejection of an organ transplant and bacterial infections, plasma procalcitonin levels have been proposed as a potential diagnostic tool. Typically the levels of procalcitonin in the blood remain below 0.5 ng/mL in cases of acute organ rejection, which has been stated previously to be well below the 1 μg/mL typically seen in bacterial infection.
Sources: en.wikipedia.org
Having personally experienced a confused night action off Guadalcanal, Lee was not enthusiastic about a night engagement with Japanese surface forces, believing that his crews were not adequately trained for it. Shortly after learning Lee's opinion, Mitscher requested permission from Spruance to move TF 58 west during the night, to reach a launch position at dawn that would allow for a maximum aerial assault on the enemy force. Spruance considered for an hour, then refused Mitscher's request. Mitscher's staff was disappointed with Spruance's decision. Burke later commented: "We knew we were going to have hell slugged out of us in the morning. We knew we couldn't reach them. We knew they could reach us." Spruance's decision was influenced by his orders from Nimitz, who had made it clear that the protection of the invasion fleet was the primary mission of TF 58. Spruance had concerns that the Japanese would attempt to draw his main fleet away from the Marianas with a diversionary force while slipping an attack force in to destroy the landing fleet. Locating and destroying the Japanese fleet was not his primary objective, and he was unwilling to allow the main strike force of the Pacific Fleet to be drawn westward, away from the amphibious forces. Mitscher accepted the decision without comment. Spruance's decision in this matter, although subsequently criticized, was certainly justified; by this point in the war, it was well known that Japanese operational plans frequently relied on the use of decoys and diversionary forces.
== Career and writing == After leaving Oxford, Halliwell briefly lectured at the Portsmouth Polytechnic (1973–74). He took up a position as lecturer at King's College London in 1974, remaining there until 2000, rising to the position of Professor of Medical Biochemistry in the Division of Pharmacology. He also simultaneously held a visiting professorship at the University of California, Davis, United States (1995–99). After a 1998 sabbatical at the National University of Singapore (NUS), he moved there in 2000 as chair of the biochemistry department. As of 2018 he is a professor in the department of biochemistry at the NUS Yong Loo Lin School of Medicine. Halliwell is currently the Senior Advisor, Academic Appointments and Research Excellence, Office of the Provost, at the National University of Singapore (NUS). He is also Chairman of the Biomedical Research Advisory Council (BMAC), Agency for Science, Technology & Research (A*STAR). Halliwell served as the NUS's first Deputy President (Research and Technology) in 2006–15, founding the Graduate School for Integrative Sciences and Engineering, and overseeing a more than doubling in the university's research grants and the creation at NUS of Singapore's first Research Centre of Excellence (RCEs). He was subsequently appointed Senior Advisor to the NUS President. His textbook, Free Radicals in Biology and Medicine, co-written with John M. C. Gutteridge, is considered "an authoritative text in the field".
Anhydrous carboxylic acids form dimers by hydrogen bonding of the acidic hydrogen and the carbonyl oxygen. For example, acetic acid forms a dimer in the gas phase, where the monomer units are held together by hydrogen bonds. Many OH-containing molecules form dimers, e.g. the water dimer. Dimers that form based on weak electrostatic interaction and/or van der Waals interactions have a short lifetime, but can be stabilized through special laboratory setups such as matrix-isolation. A prominent example is the carbon dioxide dimer, which is likely to be relevant to Venus atmosphere. Excimers and exciplexes are excited structures with a short lifetime. For example, noble gases do not form stable dimers, but they do form the excimers Ar2*, Kr2* and Xe2* under high pressure and electrical stimulation. A notable example of a non-covalent, hydrogen-bonded homodimer is the cyclic hydroxylamine dimer (NH2OH)2 . Although pure hydroxylamine crystallizes in a monomeric form, its isolated cyclic dimeric structure was first trapped and experimentally observed in 2026 within a macrocyclic crown-ether solvate framework.
== Philanthropy == The Dunkin' Joy in Childhood Foundation is an independent 501(c)3 charitable organization founded in 2006 to provide the simple joys of childhood to kids battling hunger or illness. The Foundation partners with food banks, children's hospitals, and nonprofit organizations to fund joyful environments and experiences for children across the country. Since its founding, the Foundation has granted more than $70 million to hundreds of national and local charities. Kari Bornhorst McHugh served as Executive Director from March 2017 to August 2021. In December 2018, McHugh launched the Dogs for Joy program, the first initiative of its scale to place full-time specially trained facility dogs in children's hospitals nationwide, backed by more than $2 million in initial grants. As part of the launch, McHugh brought in Cooper Dunkin', a Black Lab/Golden Retriever mix trained by Canine Assistants, who served as the Foundation's Chief Joy Officer and program ambassador, visiting children's hospitals across the country. In 2020, the Foundation launched Joyful Spaces, a program funding the creation and renovation of playgrounds, healing gardens, and play spaces at children's hospitals. Also during the COVID-19 pandemic, the Foundation introduced Hero Recharge, created in partnership with outdoor adventure nonprofit First Descents to support healthcare workers, which received an honorable mention in the Corporate Social Responsibility category of Fast Company's 2021 World Changing Ideas Awards.
Flag Fen, east of Peterborough, England, is a Bronze Age site which was constructed about 3,500 years ago and consists of more than 60,000 timbers arranged in five very long rows, creating a wooden causeway (around 1 km or 0.6 mi long) across the wet fenland. Part-way across the structure a small island was formed. Items associated with it have led scholars to conclude that the island was of religious significance. Archaeological work began in 1982 at the site, which is located 800 m (0.5 mi) east of Fengate. Flag Fen is now part of the Greater Fens Museum Partnership. A visitor centre has been constructed on site and some areas have been reconstructed, including a typical Iron Age roundhouse dwelling. A section of the original causeway is preserved in wet conditions in the Preservation Hall.
Sources: en.wikipedia.org
NAD+ is the oxidized form, while NADH is the reduced form carrying an additional hydride equivalent. The pair participates in reversible electron transfer reactions. Their ratio helps indicate the redox state of a compartment.
NAD+ itself is not classified as a vitamin, but its precursor niacin is an essential nutrient in humans. Cells synthesize NAD+ from niacin, nicotinamide, nicotinamide riboside, or tryptophan. The intact dinucleotide is not obtained directly from typical diets in meaningful amounts.
Age-related studies often examine whether NAD+ levels decline in tissues and whether that decline affects mitochondrial function or DNA repair. Interventions using precursor molecules raise open questions about cause and effect. Current evidence does not establish that changing NAD+ levels slows human aging.
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.