Everything below concerns Redox cofactor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-12-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Quantification of NAD+ in biological samples usually relies on separation techniques coupled to sensitive detection. High-performance liquid chromatography with ultraviolet detection can measure the oxidized form by its absorbance near 260 nm, while mass spectrometry provides greater specificity and can distinguish NAD+ from close analogs. Enzymatic cycling assays use coupled dehydrogenase reactions to amplify signal and estimate NAD+ concentrations in cell or tissue extracts. Because NAD+ and NADH interconvert rapidly, sample preparation must quench metabolism quickly and preserve the redox state before analysis.
The stability of NAD+ depends on pH, temperature, light exposure, and the presence of degradative enzymes. Aqueous solutions are generally more stable under mildly acidic to neutral conditions and degrade faster under alkaline conditions or prolonged heat. The solid is hygroscopic and should be stored desiccated, often frozen, and protected from repeated freeze-thaw cycles. In laboratory handling, aliquots reduce repeated temperature changes, and chelating agents may limit metal-catalyzed hydrolysis in some buffers. These practices matter because even small amounts of NADH or hydrolysis products can interfere with quantitative assays.
Quality control for NAD+ materials typically combines identity, purity, and water content checks. Identity may be confirmed by ultraviolet spectrum, retention time in chromatography, or mass accuracy, while purity is assessed by HPLC peak area or quantitative nuclear magnetic resonance. Residual water and solvents can affect molar calculations and enzyme assays, so Karl Fischer titration or thermogravimetric analysis may be used. Commercial materials vary in grade and counterion form, and published methods should specify the exact salt or hydrate when reporting concentrations. Regulatory status depends on intended use, with research reagents, dietary ingredients, and clinical products treated under different frameworks.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | β-NAD+, coenzyme I, DPN | DPN stands for diphosphopyridine nucleotide; older literature uses this term. |
| CAS Registry Number | 53-84-9 | Free acid form of β-nicotinamide adenine dinucleotide. |
| Molecular formula | C21H27N7O14P2 | Anhydrous free acid; molar mass 663.43 g/mol. |
| Appearance | White to off-white powder | Crystalline solid; may absorb moisture from air. |
| Solubility | Freely soluble in water | Insoluble in most nonpolar organic solvents. |
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 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.
Chief of the Defence Force – overall senior command officer Chief of the Army Chief of the Air Force Chief of the Navy Chief of the Medical Service (Surgeon General) Staff Divisions under the Chief of Defence Staff included:
All of the alkali metals except lithium and caesium have at least one naturally occurring radioisotope: sodium-22 and sodium-24 are trace radioisotopes produced cosmogenically, potassium-40 and rubidium-87 have very long half-lives and thus occur naturally, and all isotopes of francium are radioactive. Caesium was also thought to be radioactive in the early 20th century, although it has no naturally occurring radioisotopes. (Francium had not been discovered yet at that time.) The natural long-lived radioisotope of potassium, potassium-40, makes up about 0.012% of natural potassium, and thus natural potassium is weakly radioactive. This natural radioactivity became a basis for a mistaken claim of the discovery for element 87 (the next alkali metal after caesium) in 1925. Natural rubidium is similarly slightly radioactive, with 27.83% being the long-lived radioisotope rubidium-87. Caesium-137, with a half-life of 30.17 years, is one of the two principal medium-lived fission products, along with strontium-90, which are responsible for most of the radioactivity of spent nuclear fuel after several years of cooling, up to several hundred years after use. It constitutes most of the radioactivity still left from the Chernobyl accident. Caesium-137 undergoes high-energy beta decay and eventually becomes stable barium-137. It is a strong emitter of gamma radiation. Caesium-137 has a very low rate of neutron capture and cannot be feasibly disposed of in this way, but must be allowed to decay.
== Further reading == Dimachkie, Mazen M.; Barohn, Richard J. (7 April 2013). "Chronic Inflammatory Demyelinating Polyneuropathy". Current Treatment Options in Neurology. 15 (3): 350–366. doi:10.1007/s11940-013-0229-6. ISSN 1092-8480. PMC 3987657. PMID 23564314. Katirji, Bashar; Kaminski, Henry J.; Ruff, Robert L. (2013-10-11). Neuromuscular Disorders in Clinical Practice. Springer Science & Business Media. ISBN 9781461465676. Retrieved 26 August 2016. Said, Professor Gérard (2014). Peripheral Neuropathy & Neuropathic Pain: Into The Light. tfm Publishing Limited. p. 17. ISBN 9781910079027. Retrieved 3 August 2016.
Sources: en.wikipedia.org
=== Prenatal tests === A prenatal test can be considered when the mother is a known or suspected carrier. Before invasive testing, determination of the fetal sex is important; while males are sometimes affected by this X-linked disease, female Duchenne muscular dystrophy is extremely rare. This can be achieved by ultrasound scan at 16 weeks or more recently by free fetal DNA (cffDNA) testing. Chorion villus sampling (CVS) can be done at 11–14 weeks and has a 1% risk of miscarriage. Amniocentesis can be done after 15 weeks and has a 0.5% risk of miscarriage. Non invasive prenatal testing can be done around 10–12 weeks. Another option in the case of unclear genetic test results is fetal muscle biopsy.
In Omega Spielhallen GmbH v Bonn a "laserdrome" business was banned by the Bonn council. It bought fake laser gun services from a UK firm called Pulsar Ltd, but residents had protested against "playing at killing" entertainment. The Court of Justice held that the German constitutional value of human dignity, which underpinned the ban, did count as a justified restriction on freedom to provide services. In Liga Portuguesa de Futebol v Santa Casa da Misericórdia de Lisboa the Court of Justice also held that the state monopoly on gambling, and a penalty for a Gibraltar firm that had sold internet gambling services, was justified to prevent fraud and gambling where people's views were highly divergent. The ban was proportionate as this was an appropriate and necessary way to tackle the serious problems of fraud that arise over the internet. In the Services Directive a group of justifications were codified in article 16, which the case law has developed.
== Mentions in culture == In the 2009 film inspired by Edgar Allan Poe's "The Tell-Tale Heart", Tell-Tale, Eastlack is mentioned and referred to as Harry Erlich. The mention occurs in a scene where characters are in a museum, and a skeleton is referred to. The scene provides some genuine facts, such as how Eastlack's skeleton does not require any wiring or glue to be held together in the museum because the fused bones hold it all in one piece.
== See also == Benign acute childhood myositis Inflammatory myopathies Myopathy (muscle disease) Myalgia (muscle pain) Masticatory muscle myositis (a disease in dogs) Perimyositis Sarcoidosis § Bones, joints, and muscles
Sources: en.wikipedia.org
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.
NAD+ is the oxidized form and can accept a hydride equivalent. NADH is the reduced form and donates electrons to the electron transport chain. The two forms cycle between each other during cellular respiration.
In mammals, NAD+ is synthesized mainly through salvage pathways using nicotinamide, nicotinamide riboside, or nicotinic acid. Tryptophan can also contribute through a de novo route. The salvage pathway is often considered the primary source in many tissues.
Common methods include LC-MS, HPLC with UV detection, and enzymatic cycling assays. Rapid quenching is needed because NAD+ and NADH interconvert. The chosen method should be validated for the sample matrix.