A practical reference on NAD+: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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. |
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.
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.
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.
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.
Laboratory handling of NAD+ follows standard practices for hygroscopic fine chemicals. Personnel typically avoid inhalation and skin contact, use gloves and eye protection, and work in a ventilated area. Quality control may include ultraviolet absorbance at the nicotinamide maximum, chromatographic purity, water content, and identity confirmation by mass spectrometry. Because commercial preparations can contain counterions, residual solvents, or related nucleotides, a certificate of analysis helps verify the material. Researchers should confirm that the form supplied matches the intended assay.
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.
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.
== Epidemiology == The exact incidence of MELAS is unknown. It is one of the more common conditions in a group known as mitochondrial diseases. Nation-wide studies from Japan and Finland have suggested a prevalence of 1 in 500,000 people and 16 in 100,000 people, respectively. Together, mitochondrial diseases occur in about 1 in 4,000 people.
Cigarettes are taxed both to reduce use and to raise revenue. Higher prices for cigarettes discourage smoking. Every 10% increase in the price of cigarettes reduces youth smoking by about 7% and overall cigarette consumption by about 4%. The World Health Organization (WHO) recommends that globally cigarettes be taxed at a rate of at least 75% of their sale price as a way of deterring cancer, cardiovascular diseases and other negative health outcomes. Cigarette sales are a significant source of tax revenue in many countries. This fact has historically been an impediment for health groups seeking to discourage cigarette smoking, since governments seek to maximize tax revenues. Furthermore, some countries have made cigarettes a state monopoly, which has the same effect on the attitude of government officials outside the health field.
== Specific uses == Affinity chromatography can be used in a number of applications, including nucleic acid purification, protein purification from cell free extracts, and purification from blood. By using affinity chromatography, one can separate proteins that bind to a certain fragment from proteins that do not bind that specific fragment. Because this technique of purification relies on the biological properties of the protein needed, it is a useful technique and proteins can be purified many folds in one step.
Damon Fields – Also known as Demon Copperhead due to his "copper-wire hair and some version of attitude." (David Copperfield) "Mom" Fields – Demon's mother. Demon's birthfather (also named Damon) dies the summer before Demon is born. (Clara Copperfield) Murrell Stone – Also known as Stoner. Demon’s cruel stepfather. (Edward Murdstone) Nance Peggot – Neighbor of Demon and his mom. Nance and Mr. Peggot often watch out for Demon and provide some stability in his early years. (Clara Peggotty) Mr. Peggot – Nance Peggot's husband. Hammerhead Kelly – "Hammerhead Kelly, that was some form of Peggot-cousin add-on by marriage." (Ham Peggotty) Matt Peggot – Also known as Maggot. Grandson of Nance and Mr. Peggot, with whom he lives because his mother is in jail. June Peggot – Daughter of Nance and Mr. Peggot who has moved to Knoxville after receiving her nursing degree. (Daniel Peggotty) Emmy – Peggot niece who lives with her Aunt June in Knoxville. Demon and Emmy have a childhood affection. (Emily or Little Em'ly) Sterling Ford – Also known as Fast Forward. Demon's fellow orphan at the Creaky Farm and a star on the Lee High football team, the Generals. (James Steerforth) Tommy Waddell – Also known as Waddles. Demon's long-term friend and an orphan that he meets at Creaky Farm. Tommy doodles and draws skeletons, using his art to deal with stress; later, he works at a local newspaper where he and Demon create a newspaper comic strip. (Tommy Traddles) Sophie – Tommy's long-distance girlfriend (living in Pennsylvania) and later his wife.
Sources: en.wikipedia.org
== Adverse effects == Side effects that are most often seen with this medication include dizziness, hypotension, headache. A clinical trial done on over 7000 participants showed higher rates of nasopharyngitis in those taking valsartan/hydrochlorothiazide (2.4% versus 1.9% in placebo). A dose-related side effect seen is hypotension, occurring in 0.7% of participants on the highest dose of the medication. Risk of hypotension and hyperkalemia increases when valsartan/hydrochlorothiazide is used with ACE inhibitors or aliskiren. Less common side effects that occur less than 1% of the time include angina pectoris, rash, syncope, abdominal pain, and vertigo.
15 July – Six members of the environmental protest group, Climate Camp Scotland, are arrested after the group occupies the Ineos gas power station at Grangemouth oil refinery. 16 July – A pod of 55 pilot whales dies after becoming stranded at Traigh Mhor beach at North Tolsta on the Isle of Lewis. 19 July – Police launch an operation to remove climate change protestors from Grangemouth Refinery, making 11 arrests. 21 July – Police Scotland confirms that climate change protestors have ended their demonstrations at two oil refineries at Grangemouth and Clydebank. 22 July – Four climate change protestors are arrested at Grangemouth after chaining themselves to an old washing machine. 25 July Following a trial at the High Court in Glasgow, Connor Gibson, 20, is found guilty of the sexual assault and murder of his 16-year-old sister, Amber Gibson, in November 2021. Stephen Corrigan, unknown to the siblings, is convicted of concealing the body. The Scottish Government approves a £500m plan to expand Argyll's Hollow Mountain underground power station. 26 July – The Scottish COVID-19 Inquiry begins, with its opening hearing taking place in Dundee. 27 July – First Minister Humza Yousaf unveils a new Scottish Government paper on independence that includes plans for Scottish citizenship and passports. 28 July – Glasgow Life confirms it has cancelled the 2023 Bonfire Night event usually held on Glasgow Green and has no plans to hold any similar events in future.
=== Division of Animal Nutrition === In March 1927, due to the concerted efforts of Professor David Rivett, and following an agreement with the University of Adelaide that Robertson could continue his relationship with the university, Robertson became the head of the CSIR's first-ever division, the Division of Animal Nutrition. A red brick two-storey building, funded by the Commonwealth Government, and dedicated to animal nutrition research, was designed by the university's architect, Louis Laybourne-Smith. It contained a special laboratory designed by Robertson, and was erected by the CSIR on the university's campus "upon land very generously made available for this purpose by the University" (BR.65). The CSIR Building, known today as The Brailsford Robertson Building, was opened by the Prime Minister, Stanley Bruce, on 22 October 1928.
Sources: en.wikipedia.org
== History == While the use of PEDs has expanded in recent times, the practice of using substances to improve performance has been around since the Ancient Olympic Games. In the Olympic Games of 668 BC, Charmis had consumed a diet consisting of dried figs which was thought, at the time, to be a significant factor in winning the 200-yard stade race. Ancient Greek athletes at the time also incorporated substances such as wine and brandy into their training routines. Stimulants derived from plants (e.g., Cola nitida, Bufotenin, etc.) were used by the Roman gladiators to overcome injuries and fatigue. In the late 19th century as modern medicine and pharmacology were developing, PEDs saw an increase in use. Supplements were now exclusively being used to enhance muscular work capacity. The main substances being used included alcoholic drinks, caffeine, and mixtures created by the athletic trainers (e.g., strychnine tablets made of cocaine and brandy). In the 20th century, testosterone was isolated and characterized by scientists. In 1941, the first record of synthesized testosterone use occurred when a horse was given testosterone which successfully improved its race performance. Sports trainers soon after began advocating for testosterone use. Images of bodybuilders with massive muscles began circulating which further perpetuated a desire among athletes to use testosterone. In 1967, the first prohibited substance list and anti-doping measures were implemented at the 1968 Olympics. In the 1980s, the main PEDs were cortisone and anabolic steroids.
Helium is used as a shielding gas in arc welding processes on materials that are contaminated and weakened by air or nitrogen at welding temperatures. A number of inert shielding gases are used in gas tungsten arc welding, but helium is used instead of cheaper argon especially for welding materials that have higher heat conductivity, like aluminium or copper.
=== Other lymphoid tissue === Lymphoid tissue associated with the lymphatic system is concerned with immune functions in defending the body against infections and the spread of tumours. It consists of connective tissue formed of reticular fibers, with various types of leukocytes (white blood cells), mostly lymphocytes enmeshed in it, through which the lymph passes. Regions of the lymphoid tissue that are densely packed with lymphocytes are known as lymphoid follicles. Lymphoid tissue can either be structurally well organized as lymph nodes or may consist of loosely organized lymphoid follicles known as the mucosa-associated lymphoid tissue (MALT). The central nervous system also has lymphatic vessels. The search for T cell gateways into and out of the meninges uncovered functional meningeal lymphatic vessels lining the dural sinuses, anatomically integrated into the membrane surrounding the brain.
=== Sleepwalking and complex sleep behaviors === Zolpidem has drawn significant media attention due to reports of complex sleep behaviors (CSBs), including sleepwalking, sleep-driving, and other activities performed while not fully conscious. Notable incidents include media reports in the United States concerning events such as Congressman Patrick Kennedy's motor vehicle accident and in Australia following a fatal 20 metres (66 ft) fall from the Sydney Harbour Bridge involving an individual reportedly under the influence of zolpidem. In May 2018, actress Roseanne Barr attributed a controversial remark on Twitter to the effects of zolpidem. Barr's tweet compared Valerie Jarrett, a Black woman and former advisor to Barack Obama, to an ape. The comparison sparked widespread condemnation and led to the cancellation of Roseanne. The incident prompted Sanofi, the manufacturer of Ambien, to issue a public statement clarifying that "racism is not a known side effect" of the medication.
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.