This is a working overview of NAD+, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-05-19 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| IUPAC name | Nicotinamide adenine dinucleotide | Oxidized dinucleotide form |
| CAS Registry Number | 53-84-9 | Common entry for beta-NAD+ |
| Molecular formula | C21H27N7O14P2 | Free acid form |
| Molar mass | 663.43 g/mol | Calculated for free acid |
| Water solubility | Freely soluble | Charged dinucleotide; less soluble in organic solvents |
In cells, NAD+ functions primarily as an electron carrier. Dehydrogenase enzymes in glycolysis and the citric acid cycle transfer hydride from substrates to NAD+, producing NADH. NADH then delivers electrons to the mitochondrial respiratory chain, supporting ATP synthesis. In fermentation, NADH is reoxidized to NAD+ so that glycolysis can continue. The balance between NAD+ and NADH helps set metabolic flux. Beyond redox, NAD+ serves as a substrate for enzymes that cleave it, including sirtuins, poly(ADP-ribose) polymerases, and CD38. These reactions consume NAD+ and release nicotinamide and ADP-ribose products.
Biosynthesis occurs through salvage, Preiss-Handler, and de novo pathways. In mammals, the salvage pathway from nicotinamide predominates, and NAMPT is often described as rate-limiting. Nicotinamide riboside and nicotinic acid enter related routes that converge on NAD+ production. Tissue NAD+ concentrations vary widely and are maintained by a balance of synthesis and consumption. Some studies report age-related declines in certain tissues, but whether these changes cause disease or can be reversed to improve human health remains an open question.
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 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 aqueous solution, NAD+ is most stable under mildly acidic to neutral conditions and degrades faster at high pH or elevated temperature. The molecule can hydrolyze at the pyrophosphate bond or undergo nonenzymatic cyclization. Buffers, chelating agents, and cold temperatures slow these losses during analysis. Repeated freeze-thaw cycles are generally avoided because they can promote degradation and concentration changes. Light exposure is also controlled, though NAD+ is less photolabile than some related nucleotides.
Commercial NAD+ is supplied as a solid, often as the free acid or a salt, and purity is verified by chromatographic methods. Laboratories typically store it desiccated at minus 20 degrees Celsius or below. Working solutions are prepared fresh because even sterile aqueous solutions can lose activity over hours to days depending on pH and temperature. Documentation may include a certificate of analysis, an assay value, and a recommended retest date. Researchers should verify identity and purity when results depend on precise cofactor concentrations.
NAD+ is commonly measured by high-performance liquid chromatography with ultraviolet detection, often at 254 or 260 nm. Enzymatic cycling assays provide higher sensitivity by coupling NAD+ to a reporter reaction. Mass spectrometry can distinguish NAD+ from close analogues and confirm isotope labeling. Sample preparation usually involves rapid quenching of metabolism to prevent interconversion with NADH. Because NAD+ and NADH differ by one hydride, extraction conditions strongly affect the measured ratio.
=== Cell death === A cancer cell can die in three ways: apoptosis, necrosis, and autophagy. Excessive ROS can induce apoptosis through both the extrinsic and intrinsic pathways. In the extrinsic pathway of apoptosis, ROS are generated by Fas ligand as an upstream event for Fas activation via phosphorylation, which is necessary for subsequent recruitment of Fas-associated protein with death domain and caspase 8 as well as apoptosis induction. In the intrinsic pathway, ROS function to facilitate cytochrome c release by activating pore-stabilizing proteins (Bcl-2 and Bcl-xL) as well as inhibiting pore-destabilizing proteins (Bcl-2-associated X protein, Bcl-2 homologous antagonist/killer). The intrinsic pathway is also known as the caspase cascade and is induced through mitochondrial damage which triggers the release of cytochrome c. DNA damage, oxidative stress, and loss of mitochondrial membrane potential lead to the release of the pro-apoptotic proteins mentioned above stimulating apoptosis. Mitochondrial damage is closely linked to apoptosis and since mitochondria are easily targeted there is potential for cancer therapy. The cytotoxic nature of ROS is a driving force behind apoptosis, but in even higher amounts, ROS can result in both apoptosis and necrosis, a form of uncontrolled cell death, in cancer cells. Numerous studies have shown the pathways and associations between ROS levels and apoptosis, but a newer line of study has connected ROS levels and autophagy.
==== Other countries ==== In Canada, France, the Netherlands, and Germany, mescaline in raw form and dried mescaline-containing cacti are considered illegal drugs. However, anyone may grow and use peyote (Lophophora williamsii) as well as Echinopsis pachanoi and Echinopsis peruviana (San Pedro cactus) without restriction, as they are specifically exempt from legislation. In Canada, mescaline is classified as a schedule III drug under the Controlled Drugs and Substances Act, whereas peyote is exempt. In Russia, mescaline, its derivatives, and mescaline-containing plants are banned as narcotic drugs (Schedule I).
Interferon type I All type I IFNs bind to a specific cell surface receptor complex known as the IFN-α/β receptor (IFNAR) that consists of IFNAR1 and IFNAR2 chains. The type I interferons present in humans are IFN-α, IFN-β, IFN-ε, IFN-κ and IFN-ω. Interferon beta (IFN-β) can be produced by all nucleated cells when they recognize that a virus has invaded them. The most prolific producers of IFN-α and IFN-β are plasmacytoid dendritic cells circulating in the blood. Monocytes and macrophages can also produce large amounts of type I interferons when stimulated by viral molecular patterns. The production of type I IFN-α is inhibited by another cytokine known as Interleukin-10. Once released, type I interferons bind to the IFN-α/β receptor on target cells, which leads to expression of proteins that will prevent the virus from producing and replicating its RNA and DNA. Overall, IFN-α can be used to treat hepatitis B and C infections, while IFN-β can be used to treat multiple sclerosis. Interferon type II IFN type II binds to the interferon-gamma receptor (IFNGR), which consists of IFNGR1 and IFNGR2 chains. This group is also known as immune interferon and is activated by Interleukin-12. In most tetrapods (including humans), the only group is IFN-γ. Type II interferons are also released by cytotoxic T cells and Th1 cells. However, they block the proliferation of Th2 cells. The previous results in an inhibition of Th2 cells immune response and a further induction of Th1 immune response.
Plasma concentrations of methadone in recovering addicts can reach 4 μM during therapy, so the actions of methadone at both the hERG potassium channel and the Nav1.5 sodium channel are possibly clinically relevant in producing cardiac side effects. This also suggests that levomethadone is not completely free of cardiac toxicity.
Larger living areas on the Skylab space station (1973–1974) allowed for an on-board refrigerator and freezer. This allowed perishable and frozen items to be stored, making microgravity the primary obstacle of future missions. When Skylab's solar panels were damaged during its launch and the station had to rely on minimal power from the Apollo Telescope Mount until Skylab 2 crewmembers performed repairs, the refrigerator and freezer were among the systems that Mission Control kept operational. The Orbital Work Shop (OWS) module had a specially designed wardroom dedicated for food preparation and dining (see image on the right). A dining table was also available, and was designed to avoid hierarchical positions through its triangular layout and to support social cohesion. The table and chairs were fastened to the floor and fitted with foot and thigh restraints, allowing for a more normal eating experience. The trays used could warm the food, and had magnets to hold eating utensils and scissors used for opening food containers. It could accommodate all three crew members at the same time using a variety of microgravity restraints. As a result of the improved eating arrangement, astronauts aboard Skylab maintained some of the best nutritional intake recorded.
Sources: en.wikipedia.org
== Antagonists == Becampanel CNQX Dasolampanel DNQX Fanapanel (MPQX) Kaitocephalin Kynurenic acid – endogenous ligand L-theanine NBQX 3,5-Dibromo-L-phenylalanine, a naturally occurring halogenated derivative of L-phenylalanine Perampanel Selurampanel Tezampanel Zonampanel
The Padua botanical garden in 1545 is usually considered to be the first that is still in its original location. These gardens continued the practical value of earlier "physic gardens", often associated with monasteries, in which plants were cultivated for suspected medicinal uses. They supported the growth of botany as an academic subject. Lectures were given about the plants grown in the gardens. Botanical gardens came much later to northern Europe; the first in England was the University of Oxford Botanic Garden in 1621. German physician Leonhart Fuchs (1501–1566) was one of "the three German fathers of botany", along with theologian Otto Brunfels (1489–1534) and physician Hieronymus Bock (1498–1554) (also called Hieronymus Bock). Fuchs and Brunfels broke away from the tradition of copying earlier works to make original observations of their own. Bock created his own system of plant classification. Physician Valerius Cordus (1515–1544) authored a botanically and pharmacologically important herbal Historia Plantarum in 1544 and a pharmacopoeia of lasting importance, the Dispensatorium in 1546. Naturalist Conrad von Gesner (1516–1565) and herbalist John Gerard (1545 – c. 1611) published herbals covering the supposed medicinal uses of plants. Naturalist Ulisse Aldrovandi (1522–1605) was considered the father of natural history, which included the study of plants. In 1665, using an early microscope, Polymath Robert Hooke discovered cells (a term he coined) in cork, and a short time later in living plant tissue.
== Biological activity == Cortisone is a corticosteroid, functioning as both a glucocorticoid and mineralocorticoid. Cortisone itself is inactive and instead acts as a prodrug or prohormone of cortisol (hydrocortisone), which is responsible for its biological activity. It is metabolized into cortisol via the actions of 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1). Cortisol can also be metabolized back into cortisone by the actions of 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2). Through conversion into cortisol, cortisone acts indirectly as an agonist of the corticosteroid receptors, including the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR). In addition, through cortisol, it acts indirectly as an agonist of membrane corticosteroid receptors, including membrane glucocorticoid receptors (mGRs) and membrane mineralocorticoid receptors (mMRs). Cortisone has about 80% of the oral potency of hydrocortisone as both a glucocorticoid and mineralocorticoid when used clinically in humans. Relatedly, a dose of 25 mg cortisone is equivalent to about 20 mg hydrocortisone. In addition to its corticosteroid activity, cortisone has been reported to be a highly potent negative allosteric modulator of the GABAA receptor (1 pM–10 nM). This was demonstrated specifically in guinea pig ileum tissue.
== Adverse effects == Neonatal circumcision is generally a safe, low-risk procedure when done by an experienced practitioner. The most common acute complications are excessive bleeding, infection and the removal of either too much or too little foreskin. These complications occur in approximately 0.13% of procedures, with bleeding being the most common acute complication in the United States. Minor complications are reported to occur in approximately 3.8%. Severe complications are rare. A specific complication rate is difficult to determine due to inconsistencies in classification. Complication rates are greater when the procedure is performed by an inexperienced operator, in unsterile conditions, and older patient age. In patients circumcised after the neonatal period and into adolescence, minor complication rates rise from approximately 1.5% in neonates to about 6% in adolescents. This increase is believed to be a result of increased foreskin vascularity. Significant acute complications happen rarely, occurring in about 1 in 500 newborn procedures in the United States. Severe to catastrophic complications, including death, are so rare that they are reported only as individual case reports. Where a Plastibell device is used, the most common complication is the retention of the device occurring in around 3.5% of procedures. Other possible complications include buried penis, chordee, phimosis, skin bridges, urethral fistulas, and meatal stenosis. These complications may be partly avoided with proper technique, and are often treatable without requiring surgical revision.
Sources: en.wikipedia.org
With Robert J. Flaherty's Nanook of the North in 1922, documentary film embraced romanticism. Flaherty filmed a number of heavily staged romantic documentary films during this time period, often showing how his subjects would have lived 100 years earlier and not how they lived right then. For instance, in Nanook of the North, Flaherty did not allow his subjects to shoot a walrus with a nearby shotgun, but had them use a harpoon instead. Some of Flaherty's staging, such as building a roofless igloo for interior shots, was done to accommodate the filming technology of the time. Paramount Pictures tried to repeat the success of Flaherty's Nanook and Moana with two romanticized documentaries, Grass (1925) and Chang (1927), both directed by Merian C. Cooper and Ernest Schoedsack.
== Channel mix == In practice, many organizations use a mix of different channels; a direct sales force may call on larger customers. This may be complemented with other agents to cover smaller customers and prospects. When a single organization uses a variety of different channels to reach its markets, this is known as a multi-channel distribution network. In addition, online retailing or e-commerce is leading to disintermediation, the removal of intermediaries from a supply chain. Retailing via smartphone or m-commerce is also a growth area.
UR-AK49 is a drug used in scientific research which acts as a potent antagonist for the Neuropeptide Y / Pancreatic polypeptide receptor Y4, and also as a partial agonist at the histamine receptors H1 and H2. UR-AK49 is a pure antagonist at Y4 with no partial agonist effects, and although it is only slightly selective for Y4 over the related Y1 and Y5 receptors, as the first non-peptide Y4 antagonist developed UR-AK49 is expected to be useful in the study of this receptor and its role in the body.
Sources: en.wikipedia.org
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.
NAD+ is a small organic cofactor, not a protein or enzyme. It binds temporarily to enzymes such as dehydrogenases to assist electron transfer.
Intact NAD+ is generally not taken up efficiently by most cells because it is charged and water-soluble. Cells often rely on precursors such as nicotinamide or nicotinamide riboside to produce NAD+ internally.
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.