This is a working overview of NAD+, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-18. Anything still debated is marked as such rather than presented as settled.
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.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide built from adenine, nicotinamide, two ribose sugars, and two phosphate groups. The oxidized form carries a positive charge on the nicotinamide ring, while the reduced form, NADH, is neutral. This pair acts as a reversible electron carrier in cells. NAD+ is present in bacteria, plants, animals, and fungi. Its structure allows it to accept and donate electrons without being consumed in the reactions it supports.
In redox reactions, NAD+ accepts a hydride ion, which consists of two electrons and one proton. The hydride adds to the nicotinamide ring at a specific carbon, converting NAD+ into NADH. Dehydrogenase enzymes use this step in glycolysis, the citric acid cycle, and fatty acid oxidation. NADH later donates electrons to the mitochondrial electron transport chain, helping to drive ATP synthesis. The balance between NAD+ and NADH reflects the metabolic state of a cell, and shifts in that balance can alter how pathways operate.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave it and attach its ADP-ribose portion to other molecules. This group includes poly(ADP-ribose) polymerases, CD38, and sirtuins. Such reactions consume NAD+ and can influence its availability for metabolism. Cells replenish NAD+ through a salvage pathway that recycles nicotinamide and through routes starting from tryptophan or vitamin B3 forms. How these synthesis and consumption routes are coordinated across tissues remains an active area of study, and compartment-specific concentrations are difficult to measure directly.
| 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 |
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.
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.
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.
The molecule was first described in the early twentieth century as a factor that promoted fermentation in yeast extracts. Later work linked it to hydrogen transfer and to the oxidation of nutrients in living tissues. Its structure was resolved as a dinucleotide, which explained why it could accept and donate electrons at specific enzyme sites. Today, NAD+ is recognized as a central substrate and signaling precursor, not merely a metabolic cofactor. Whether all observed NAD+ changes reflect causal signaling remains an open question.
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.
=== Initial effects on health assistance === On February 6, 2025, reports indicated that the total number of employees to be retained was 294, out of a total of more than 10,000. Trump declared that agency leaders were "radical left lunatics", while the State Department ordered them to halt virtually all their projects, even if that meant ceasing programs that helped to eradicate smallpox and prevented millions of HIV cases. The freeze in HIV relief programs, including PEPFAR, is estimated to jeopardize treatment access for 20 million people, including 500,000 children. This drastic action led to sudden pauses in over 30 clinical trials for ailments such as HIV, malaria, cholera, cervical cancer, and tuberculosis, leaving participants with medical devices in their bodies and cut off from researchers, likely going against the principles of the Declaration of Helsinki.
==== Automation ==== An added benefit of using magnetic beads is that automated immunoprecipitation devices are becoming more readily available. These devices not only reduce the amount of work and time to perform an IP, but they can also be used for high-throughput applications.
=== Viewership === The Runner debuted at No. 2 on the worldwide Prime Video movie chart and in the top 10 in several European countries and Canada. It reached No. 1 in the United Kingdom and the United States, surpassing films including Project Hail Mary, Masters of the Universe, and Icefall. Streaming analytics firm FlixPatrol, which monitors daily updated VOD charts and streaming ratings worldwide, reported that the film ranked first in 38 countries by September 4, two days after its release, and continued to appear among the top-ranked titles in more than 50 territories. During the week of September 7–13, it ranked No. 2 on Prime Video's list of the most-watched English-language films, behind Drawn Together. On September 18, the film also ranked No. 2 on Prime Video's charts in the United States and worldwide. Nielsen Media Research, which records streaming viewership on certain U.S. television screens, announced that The Runner was the fourth most-streamed film between August 31 and September 6, garnering 368 million minutes viewed. The following week, from September 7–13, the film recorded 201 million minutes of watch time, ranking tenth.
Sources: en.wikipedia.org
=== Career === Since 2003, Paulsen has been based in Switzerland, where Ferring subsequently established its global headquarters in Saint-Prex. His business interests focus mainly on the Ferring Pharmaceuticals Group where he has worked since 1976 in senior executive positions. In addition, he has interests in real estate and viticulture. Frederik Paulsen also holds several board memberships. Until 2023, he was for instance a member of the board of directors of the tobacco company Philip Morris International. Since 2009 until 2022, Paulsen also held the position of Honorary Consul of the Russian Federation, in Lausanne, Switzerland. He was appointed Honorary Consul General in 2015. In 2020, he was appointed a Knight of the Order of St. John by Queen Elizabeth II.
=== Muscular origin === Myopathic origin BSS can be secondary to various muscular disorders or occur as a primary idiopathy. These etiologies are termed secondary and primary BSS respectively. Idiopathic primary BSS is a late-onset myopathy with progressive muscular weakness that is detected on the spinal extensor muscles in elderly patients and is more predominant in females. The pathogenesis of primary BSS is typically related to fibrosis and fatty infiltration of muscular tissues and to mitochondrial changes due to the aging process. Specifically, weakening occurs in the paravertebral muscles of patients. These paravertebral muscles have a great influence over the walking stance and gait of a patient, so fatty infiltration and degradation of these muscle lead to the characteristics that easily define BSS, such as the anterior flexion of the back combined with an ability to keep upright with any kind of support (e.g., holding onto a table). Secondary BSS can have a multitude of causes, making it hard to pinpoint to a specific muscular disorder. Some examples of diseases that have secondary BSS as a symptom are myopathies caused by muscular dystrophies, neuromuscular disorders, and inflammatory muscle diseases; metabolic or endocrine disorders; and mitochondrial myopathies.
==== 2900–2999 ==== Farm and Conservation Grant (Amendment) Regulations 1993 (S.I. 1993/2900) Farm and Conservation Grant (Variation) Scheme 1993 (S.I. 1993/2901) Medicines (Pharmacies) (Applications for Registration and Fees) Amendment Regulations 1993 (S.I. 1993/2902) Motor Vehicles (Type Approval and Approval Marks) (Fees) (Amendment) Regulations 1993 (S.I. 1993/2903) Occupational Pensions (Revaluation) Order 1993 (S.I. 1993/2904) Family Provision (Intestate Succession) Order 1993 (S.I. 1993/2906) Western Isles Islands Council (Brevig) Harbour Empowerment Order 1993 (S.I. 1993/2908) Transport Act 1985 (Modifications in Schedule 4 to the Transport Act 1968) (Further Modification) (Amendment) Order 1993 (S.I. 1993/2909) Education (Mandatory Awards) (No. 2) Regulations 1993 (S.I. 1993/2914) Education (Student Loans) (No.2) Regulations 1993 (S.I. 1993/2915) Forth Ports Authority (Dissolution) Order 1993 (S.I. 1993/2916) A43 Trunk Road (Weldon Bypass) Order 1993 (S.I. 1993/2917) A43 Trunk Road (Stamford Road, Northamptonshire) (Detrunking) Order 1993 (S.I. 1993/2918) Firearms (Amendment) Act 1988 (Firearms Consultative Committee) Order 1993 (S.I. 1993/2919) Bovine Embryo Collection and Transfer (Fees) Regulations 1993 (S.I. 1993/2920) Bovine Embryo Collection and Transfer Regulations 1993 (S.I. 1993/2921) Consumer Credit (Exempt Agreements) (Amendment) (No. 2) Order 1993 (S.I. 1993/2922) Imitation Dummies (Safety) Regulations 1993 (S.I. 1993/2923) Hill Livestock (Compensatory Allowances) (Amendment) (No. 2) Regulations 1993 (S.I.
The reduction and subsequent reoxidation of vitamin K coupled with carboxylation of Glu is called the vitamin K cycle. Humans are rarely deficient in vitamin K because, in part, vitamin K2 is continuously recycled in cells. Warfarin and other 4-hydroxycoumarins block the action of VKOR. This results in decreased concentrations of vitamin K and vitamin K hydroquinone in tissues, such that the carboxylation reaction catalyzed by the glutamyl carboxylase is inefficient. This results in the production of clotting factors with inadequate Gla. Without Gla on the amino termini of these factors, they no longer bind stably to the blood vessel endothelium and cannot activate clotting to allow formation of a clot during tissue injury. As it is impossible to predict what dose of warfarin will give the desired degree of clotting suppression, warfarin treatment must be carefully monitored to avoid underdose and overdose.
Sources: en.wikipedia.org
In 1974, a military coup overthrew the Estado Novo regime, and started the Carnation Revolution. This initiated the transition to democracy and the dissolution of Portugal's colonial empire, from the independence of the African colonies to the Handover of Macau in 1999. This period was marked by social, military, and political turmoil that culminated in street politics and violence and led Portugal to near civil war. The 1975 coup cleared the way for the approval of a new constitution and the holding of elections, beginning to subside tensions. After the revolution, in the late 1970s and throughout the 1980s, under the influence of new economic insights, Portugal set about dismantling socialist policies from that period and moving towards neoliberalism. In 1986, Portugal joined the European Economic Community (EEC), which introduced structural reforms. This led in the 1990s to considerable economic growth driven by credit-fuelled consumer spending and a sharp rise in private indebtedness. Together with the growth of the financial and non-tradable sectors, this contributed to macroeconomic imbalances and paved the way for economic stagnation after the 2000s. It ultimately led to the 2010–2014 Portuguese financial crisis resulted in an international bailout and intense austerity policies, causing lasting impacts such as young adults' employment insecurity.
=== Pests and predators === Liliaceae are subject to a wide variety of diseases and pests, including insects, such as thrips, aphids, beetles and flies. Also fungi, viruses and vertebrate animals such as mice and deer. An important horticultural and garden pest is the scarlet lily beetle (Japanese red lily beetle, Lilioceris lilii) and other Lilioceris species which attack Fritillaria and Lilium. Lilium species may be food plants for the Cosmia trapezina moth. A major pest of Tulips is the fungus, Botrytis tulipae. Both Lilium and Tulipa are susceptible to a group of five viruses of the family Potyviridae, specifically the potyvirus (named for potato virus Y) group, which includes the tulip-breaking virus (TBV) and the lily streak virus (lily mottle virus, LMoV) resulting in 'breaking' of the color of the flowers. The viruses are transmitted by aphids. This breaking effect was of economic importance during the tulip mania of the seventeenth century, because it appeared to be producing new varieties. In modern times tulip breeders have produced varieties that mimic the effect of the virus, without being infected. One of these varieties is known as 'Rembrandt', after the Dutch artist of that name. Contemporary tulip owners commonly had Rembrandt and other artists paint their flowers to preserve them for posterity, hence the 'broken' tulips were known as Rembrandt tulips at that time. Another modern variety is 'Princess Irene'. One of the tulip breaking viruses is also named the Rembrandt tulip-breaking virus (ReTBV).
Gene Expression Omnibus (GEO) A database of high-throughput functional genomics and gene expression data derived from experimental assays and next-generation sequencing and managed by the National Center for Biotechnology Information.
The aligned region is referred to as a homeomorphic domain, and this region may comprise several smaller homology domains that are shared with other families. Families may be further subdivided into subfamilies or grouped into superfamilies based on respective higher or lower levels of sequence similarity. The SCOP database reports 1296 families and the CATH database (version 1.7 beta), reports 1846 families. When the sequences of proteins with the same function are examined in greater detail, some are found to share high sequence similarity. They are obviously members of the same family by the above criteria. However, others are found that have very little, or even insignificant, sequence similarity with other family members. In such cases, the family relationship between two distant family members A and C can often be demonstrated by finding an additional family member B that shares significant similarity with both A and C. Thus, B provides a connecting link between A and C. Another approach is to examine distant alignments for highly conserved matches. At a level of identity of 50%, proteins are likely to have the same three-dimensional structure, and the identical atoms in the sequence alignment will also superimpose within approximately 1 Å in the structural model. Thus, if the structure of one member of a family is known, a reliable prediction may be made for a second member of the family, and the higher the identity level, the more reliable the prediction.
In 2008, Russia began a cyber attack on the Georgian government website, which was carried out along with Georgian military operations in South Ossetia. In 2008, Chinese "nationalist hackers" attacked CNN as it reported on Chinese repression on Tibet. Hackers from Armenia and Azerbaijan have actively participated in cyberwarfare as part of the Nagorno-Karabakh conflict, with Azerbaijani hackers targeting Armenian websites and posting Ilham Aliyev's statements. Jobs in cyberwarfare have become increasingly popular in the military. All four branches of the United States military actively recruit for cyber warfare positions. In a 2024 study on the use of military cyber operations during the Russo-Ukrainian War, Frederik A. H. Pedersen and Jeppe T. Jacobsen concluded that cyber operations in warfare may only be impactful on the tactical and operational levels in a war's beginning, when cyber and non-cyber operations can be aligned and complex cyber weapons can be prepared before war breaks out, as well as cumulatively on a strategic level.
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.
It indicates the oxidized form, which has a positive charge on the nicotinamide nitrogen. The reduced partner NADH lacks that charge and carries added electrons. The plus sign is part of the standard abbreviation, not a separate ion.