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.
Updated 2026-06-27. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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+ stands for nicotinamide adenine dinucleotide, the oxidized form of a coenzyme found in all living cells. The molecule consists of two nucleotides, adenine and nicotinamide ribose, joined through phosphate groups. Its chemical formula is C21H27N7O14P2, and the free acid has a molar mass near 663.43 grams per mole. In redox reactions, NAD+ accepts a hydride ion and becomes NADH. The pair NAD+ and NADH participates in hundreds of metabolic reactions, including steps in glycolysis, the citric acid cycle, and oxidative phosphorylation.
| Property | Value | Notes |
|---|---|---|
| Molar mass | 663.43 g/mol | For the free acid form; salts have higher mass. |
| Appearance | White to off-white powder | Often hygroscopic; may clump on exposure to air. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture; avoid repeated freeze-thaw. |
| Common synonyms | beta-NAD, DPN | DPN stands for diphosphopyridine nucleotide, an older name. |
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 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 humans, NAD+ can be synthesized from nicotinic acid, nicotinamide, nicotinamide riboside, and tryptophan through overlapping pathways. The salvage pathway recycles nicotinamide back to NAD+ and is often considered a major route in many tissues. Dietary precursors and intracellular recycling both contribute to the pool, but the quantitative importance of each source remains an active research question. NAD+ levels are not uniform across organs or cell compartments. Measurements in blood do not necessarily reflect concentrations inside tissues.
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.
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.
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.
Well-being is what is intrinsically good for a person. Also called welfare and quality of life, it is a measure of how well life is going for someone. In the broadest sense, it covers the balance of all positive and negative aspects of a person's life. More narrowly, it refers only to positive degrees and contrasts with ill-being, which denotes negative ones. In this sense, well-being is what egoists typically seek for themselves and altruists aim to enhance in others, serving as a central goal of many individual and societal endeavors. Researchers discuss different types of well-being by how they are measured, who they belong to, and which domain of life they affect. Subjective well-being refers to how a person feels about and evaluates their life. Objective well-being encompasses factors that can be assessed from an external perspective, such as health, income, and security. Individual well-being concerns the quality of life of a particular person, whereas community well-being measures how well a group of people functions and thrives. Forms of well-being belonging to specific domains of life include physical, psychological, emotional, social, and economic well-being. Theories of well-being aim to identify its essential features. Hedonism argues that well-being ultimately depends on the balance of pleasure over pain. Desire theories hold that the satisfaction of desires is the source of well-being. Objective list theories assert that a combination of diverse elements is responsible for well-being.
Insulin ( ; from Latin insula 'island') is a peptide hormone produced by beta cells of the pancreatic islets encoded in humans by the insulin (INS) gene. It is the main anabolic hormone of the body. It regulates the metabolism of carbohydrates, fats, and protein by promoting the absorption of glucose from the blood into cells of the liver, fat, and skeletal muscles. In these tissues the absorbed glucose is converted into either glycogen, via glycogenesis, or fats (triglycerides), via lipogenesis; in the liver, glucose is converted into both. Glucose production and secretion by the liver are strongly inhibited by high concentrations of insulin in the blood. Circulating insulin also affects the synthesis of proteins in a wide variety of tissues. It is thus an anabolic hormone, promoting the conversion of small molecules in the blood into large molecules in the cells. Low insulin in the blood has the opposite effect, promoting widespread catabolism, especially of reserve body fat. Beta cells are sensitive to blood sugar levels so that they secrete insulin into the blood in response to high level of glucose, and inhibit secretion of insulin when glucose levels are low. Insulin production is also regulated by glucose: high glucose promotes insulin production while low glucose levels lead to lower production. Insulin enhances glucose uptake and metabolism in the cells, thereby reducing blood sugar.
=== Economic considerations === The cost-effectiveness of circumcision has been studied to determine whether a policy of circumcising all newborns or a policy of promoting and providing inexpensive or free access to circumcision for all adult men who choose it would result in lower overall societal healthcare costs. As HIV/AIDS is an incurable disease that is expensive to manage, significant effort has been spent studying the cost-effectiveness of circumcision to reduce its spread in parts of Africa that have a relatively high infection rate and low circumcision prevalence. Several analyses have concluded that circumcision programs for adult men in Africa are cost-effective and in some cases cost-saving. In Rwanda, circumcision has been found to be cost-effective across a wide range of age groups from newborn to adult, with the greatest savings achieved when it is performed in the newborn period due to the lower cost per procedure and greater timeframe for HIV infection protection. Circumcision to prevent HIV transmission in adults has also been found to be cost-effective in South Africa, Kenya, and Uganda, with cost savings estimated in the billions of US dollars over 20 years. Hankins et al. (2011) estimated that a $1.5 billion investment in circumcision for adults in 13 high-priority African countries would yield $16.5 billion in savings.
==== Phycobilins ==== Phycobilins are a third group of pigments found in cyanobacteria, and glaucophyte, red algal, and cryptophyte chloroplasts. Phycobilins come in all colors, though phycoerytherin is one of the pigments that makes many red algae red. Phycobilins often organize into relatively large protein complexes about 40 nanometers across called phycobilisomes. Like photosystem I and ATP synthase, phycobilisomes jut into the stroma, preventing thylakoid stacking in red algal chloroplasts. Cryptophyte chloroplasts and some cyanobacteria don't have their phycobilin pigments organized into phycobilisomes, and keep them in their thylakoid space instead.
Sources: en.wikipedia.org
The persistence of American unipolar predominance in the international system since the end of the Cold War has caused a rupture in the American school of Realist … theory ... Yet the ongoing failure of potential rivals to the US, such as China, Russia, or the EU to develop military capabilities that come anywhere close to those of the US seems to have defied this prediction. Despite the apparently radical imbalance of the international political system, smaller states are not trying to build up their military power to match that of the US or forming formal alliance systems to oppose it… The absence of balancing against the US constitutes a serious anomaly for neorealist theory. Fareed Zakaria asks, "Why is no one ganging up against the United States?" And John Ikenberry and John M. Owen ask the same question. Prominent Historian of the Cold War, John Lewis Gaddis, poses a more general question and replies: Do the weak always unite against the strong? "In theory, yes, but in practice and in history, not necessarily." One of the issues the discipline of political science "has been wrestling with recently is why there is still no anti-American coalition despite the overwhelming dominance of the United States since the end of the Cold War." French or Chinese officials publicly denounce "hyperpower" and aspire for "multipolarity" but refrain from forming a counterbalancing coalition. "Rhetorically, leaders and public want the United States to be balanced" but "we find very little balancing." French academic Michel Winock said: "Before we could say we were on American side.
Although overall yields are comparatively low, Lower Saxony is also an important supplier of crude oil in the European Union. Mineral products still mined today include iron. Radioactive waste is frequently transported in the area to the city of Salzgitter, for the deep geological repository Schacht Konrad and between Schacht Asse II in the Wolfenbüttel district and Lindwedel and Höfer. Manufacturing is another large part of the regional economy. Despite decades of gradual downsizing and restructuring, the carmaker Volkswagen with its five production plants within the state's borders still remains the single biggest private-sector employer, its world headquarters in Wolfsburg. Due to the Volkswagen Law, which has recently been ruled illegal by the European Union's high court, the state of Lower Saxony is still the second-largest shareholder, owning 20.3% of the company. Thanks to the importance of car manufacturing in Lower Saxony, a thriving supply industry is centred around its regional focal points. Other mainstays of the Lower Saxon industrial sector include aviation (the region of Stade is called CFK-Valley), shipbuilding (such as Meyer Werft), biotechnology, and steel. Medicine plays a major role; Hanover and Göttingen have two large University Medical Schools and hospitals, and Otto Bock in Duderstadt is the largest producer of prosthetics and associated componentry in the world. The service sector has gained importance following the demise of manufacturing in the 1970s and 1980s.
== Research == Filorexant was studied for but was not found to be effective in the treatment of diabetic neuropathy, migraine, and major depressive disorder in phase 2 clinical trials. Seltorexant is under development for treatment of major depressive disorder however and is in phase 3 trials for this indication. Also, suvorexant is in a phase 4 trial for use as an adjunct to antidepressant therapy in people with major depressive disorder and residual insomnia.
=== Function === PNECs may play a role with chemoreceptors in hypoxia detection. This is best supported by the presence of an oxygen-sensitive potassium channel coupled to an oxygen sensory protein in the rabbit lumenal membrane. They are hypothetically involved in regulating localized epithelial cell growth and regeneration through a paracrine mechanism, whereby their signaling peptides are released into the environment. In addition, they contain neuroactive substances which are released from basal cytoplasm. These substances induce autonomic nerve terminals or vasculature in the deep lamina propria.
== Mechanism of action == When a tumor stimulates the growth of new vessels, it is said to have undergone an 'angiogenic switch'. The principal stimulus for this angiogenic switch appears to be oxygen deprivation, although other stimuli such as inflammation, oncogenic mutations and mechanical stress may also play a role. The angiogenic switch leads to tumor expression of pro-angiogenic factors and increased tumor vascularization. Specifically, tumor cells release various pro-angiogenic paracrine factors (including angiogenin, vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and transforming growth factor-β (TGF-β). These stimulate endothelial cell proliferation, migration and invasion resulting in new vascular structures sprouting from nearby blood vessels. Cell adhesion molecules, such as integrins, are critical to the attachment and migration of endothelial cells to the extracellular matrix.
Sources: en.wikipedia.org
=== Bismarck brown === Bismarck brown (also Bismarck brown Y or Manchester brown) imparts a yellow colour to acid mucins and an intense brown color to mast cells. One default of this stain is that it blots out any other structure surrounding it and makes the quality of the contrast low. It has to be paired with other stains in order to be useful. Some complementing stains used alongside Bismark brown are Hematoxylin and Toluidine blue which provide better contrast within the histology sample.
== Use == The first publication on vinylene carbonate described its Diels-Alder reaction using the example of its addition reaction with 2,3-dimethylbutadiene to a bicyclic carbonate and subsequent hydrolysis to cis-4,5-dihydroxy-1,2-cyclohexene:
Some non-α-amino acids exist in organisms. In these structures, the amine group is displaced further from the carboxylic acid end of the amino acid molecule. Thus a β-amino acid has the amine group bonded to the second carbon away, and a γ-amino acid has it on the third. Examples include β-alanine, GABA, and δ-aminolevulinic acid.
== Budget principles == The U.S. Constitution (Article I, section 9, clause 7) states that "No money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law; and a regular Statement and Account of Receipts and Expenditures of all public Money shall be published from time to time." Each year, the president of the United States submits a budget request to Congress for the following fiscal year as required by the Budget and Accounting Act of 1921. Current law (31 U.S.C. § 1105(a)) requires the president to submit a budget no earlier than the first Monday in January, and no later than the first Monday in February. Typically, presidents submit budgets on the first Monday in February. The budget submission has been delayed, however, in some new presidents' first year when the previous president belonged to a different party. The federal budget is calculated largely on a cash basis. That is, revenues and outlays are recognized when transactions are made. Therefore, the full long-term costs of programs such as Medicare, Social Security, and the federal portion of Medicaid are not reflected in the federal budget. By contrast, many businesses and some other national governments have adopted forms of accrual accounting, which recognizes obligations and revenues when they are incurred. The costs of some federal credit and loan programs, according to provisions of the Federal Credit Reform Act of 1990, are calculated on a net present value basis. Federal agencies cannot spend money unless funds are authorized and appropriated by law.
Sources: en.wikipedia.org
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.
No. It also serves as a substrate for signaling and DNA-repair enzymes such as sirtuins and PARPs. Those reactions consume NAD+ and connect its availability to cellular regulation. Energy transfer remains its most abundant known role.
NAD+ is the oxidized electron acceptor, while NADH is the reduced electron carrier. They form a reversible redox pair and differ by a hydride ion. Cells maintain different ratios of the two depending on conditions and compartment.
Nicotinamide adenine dinucleotide, with the plus sign indicating the oxidized form. It is a coenzyme present in all living cells. The reduced form is NADH.