Everything below concerns NADH. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-03-04. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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 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.
| 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 |
Commercial NAD+ is available at research grade, often with purity specifications determined by high-performance liquid chromatography. Certificates of analysis may report water content, residual solvents, and counterion identity. Identity can be confirmed by ultraviolet absorbance near 260 nm, mass spectrometry, or enzymatic activity. Because different salt forms and hydration states exist, researchers should verify that the product matches the intended molecular form. Lot-to-lot variation in purity can affect quantitative assays and should be documented.
Solid NAD+ is usually supplied as a white to off-white powder or lyophilized preparation. It is hygroscopic and should be kept desiccated at low temperature, commonly -20 °C or below for long-term storage. Aqueous solutions are less stable than dry material and are often prepared fresh or stored frozen in aliquots. Light exposure and repeated freeze-thaw cycles can promote degradation, so amber containers and single-use aliquots are preferred. Buffered solutions near neutral pH are generally less stable than acidic or frozen preparations.
Quantification of NAD+ in biological samples typically uses liquid chromatography coupled to mass spectrometry. Enzymatic cycling assays offer higher throughput and rely on NAD+ dependent dehydrogenases to amplify signal. Both approaches require careful sample quenching because NAD+ can be rapidly consumed or converted after collection. Acidic extraction is common for NAD+, while alkaline conditions favor NADH in some protocols. Isotopically labeled internal standards help correct for losses during extraction and ionization.
Research on NAD+ spans biochemistry, aging biology, and metabolism. Studies often examine how NAD+ levels change with age, diet, exercise, or disease states, and whether precursor supplementation alters those levels. Findings in animal models do not automatically translate to humans, and measurement methods vary across studies. Questions about tissue-specific effects, long-term consequences, and causal relationships remain open. NAD+ itself is not established as a single therapeutic agent with a broad clinical role.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide composed of two nucleotides joined by phosphate groups. One nucleotide contains adenine; the other contains nicotinamide. The molecule exists in oxidized (NAD+) and reduced (NADH) forms, and the reversible hydride transfer between them underlies many metabolic oxidation-reduction reactions. In cells, NAD+ serves as an electron acceptor in pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation. Its concentration and redox ratio vary by compartment, tissue, and metabolic state.
Beyond redox chemistry, NAD+ is consumed as a substrate by enzymes that transfer ADP-ribose or remove acetyl groups. Sirtuins use NAD+ in deacylation reactions, poly(ADP-ribose) polymerases use it in DNA damage responses, and CD38 hydrolases convert it to signaling metabolites. Because these enzymes compete for the same pool, changes in NAD+ availability can influence multiple cellular processes. The relative contribution of each consumption route differs by cell type and condition, and precise quantitative links remain an active area of study.
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.
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.
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.
The calculations involve several steps and include an intermediate value called the "radiocarbon age", which is the age in "radiocarbon years" of the sample: an age quoted in radiocarbon years means that no calibration curve has been used − the calculations for radiocarbon years assume that the atmospheric 14C/12C ratio has not changed over time. Calculating radiocarbon ages also requires the value of the half-life for 14C. In Libby's 1949 paper he used a value of 5720 ± 47 years, based on research by Engelkemeir et al. This was remarkably close to the modern value, but shortly afterwards the accepted value was revised to 5568 ± 30 years, and this value was in use for more than a decade. It was revised again in the early 1960s to 5,730 ± 40 years, which meant that many calculated dates in papers published prior to this were incorrect (the error in the half-life is about 3%). For consistency with these early papers, it was agreed at the 1962 Radiocarbon Conference in Cambridge (UK) to use the "Libby half-life" of 5568 years. Radiocarbon ages are still calculated using this half-life, and are known as "Conventional Radiocarbon Age". Since the calibration curve (IntCal) also reports past atmospheric 14C concentration using this conventional age, any conventional ages calibrated against the IntCal curve will produce a correct calibrated age.
== Research == A relatively recent avenue of drug research in treating depression and drug addiction is through PPARα and PPARγ activation. Both TLR4-mediated and NF-κB-mediated signalling pathways have been implicated in the development of addiction to several drugs such as opioids and cocaine, and therefore are appealing targets for pharmacotherapy. Despite a breadth of preclinical research showing potential in animal models in the treatment of drug addictions including alcohol, nicotine, cocaine, opioids and methamphetamine, the human evidence is limited with the amount of trials looking at using PPAR agonists for humans still being low; and so far (as of 2020) not being particularly promising. There are several suggested hypotheses for the poor translation from animal to human research evidence such as the potency and selectivity of PPAR ligands, sex-related variability, and species differences in the distribution and signaling of PPAR.
==== Beginning of the conflict ==== The report claimed that open hostilities started "... with a large-scale Georgian military operation against the town of Tskhinvali and the surrounding areas, launched in the night of 7 to 8 August 2008", but "... any explanation of the origins of the conflict cannot focus solely on the artillery attack on Tskhinvali in the night of 7/8 August", since "... it was only the culminating point of a long period of increasing tensions, provocations and incidents", and there was "... no way to assign overall responsibility for the conflict to one side alone." The beginning of the armed conflict between Georgia and South Ossetia was dated by the commission to 7 August 2008 at 23.35; however, the commission acknowledged that "a violent conflict had already been going on before in South Ossetia", and "President Saakashvili's order on 7 August 2008 at 23.35 and the ensuing military attack on Tskhinvali [...] has to be seen as but one element in an on-going chain of events for military violence had also been reported before the outbreak of the open hostilities on 7 August 2008." It is believed that direct military confrontation between Russia and Georgia began on 8 August 2008.
The prognosis is worse in those with larger burns, those who are older, and females. The presence of a smoke inhalation injury, other significant injuries such as long bone fractures, and serious co-morbidities (e.g. heart disease, diabetes, psychiatric illness, and suicidal intent) also influence prognosis. On average, of those admitted to burn centers in the United States, 4% die, with the outcome for individuals dependent on the extent of the burn injury. For example, admittees with burn areas less than 10% TBSA had a mortality rate of less than 1%, while admittees with over 90% TBSA had a mortality rate of 85%. In Afghanistan, people with more than 60% TBSA burns rarely survive. The Baux score has historically been used to determine prognosis of major burns. However, with improved care, it is no longer very accurate. The score is determined by adding the size of the burn (% TBSA) to the age of the person and taking that to be more or less equal to the risk of death. Burns in 2013 resulted in 1.2 million years lived with disability and 12.3 million disability adjusted life years.
The more serious resistance in the départements was crushed by declaring a state of siege and by the "mixed commissions". The plebiscite of 20 December ratified by a huge majority the coup d'état in favour of the prince-president, who alone reaped the benefit of the excesses of the Republicans and the reactionary passions of the monarchists.
Sources: en.wikipedia.org
== Bibliography == Chapple, Christopher Key (1993), Nonviolence to Animals, Earth, and Self in Asian Traditions, State University of New York Press Crane, Eva, ed. (1975). Honey: A Comprehensive Survey. London: Heinemann. ISBN 9780434902705. Crane, Eva (1980). A Book of Honey. New York: Charles Scribner's Sons. ISBN 9780684166513. OCLC 7172738. Jaini, Padmanabh S. (1998) [1979], The Jain Path of Purification, Delhi: Motilal Banarsidass, ISBN 978-81-208-1578-0 Krell, R. (1996). Value-added products from beekeeping. Food and Agriculture Organization of the United Nations. p. 5. ISBN 978-92-5-103819-2. Retrieved 5 January 2016. Root, A. I.; Root, E. R. (2005) [1879]. The ABC and XYZ of Bee Culture. Kessinger Publishing. ISBN 978-1-4179-2427-1. Retrieved 5 January 2016.
=== Allergy === In rare circumstances, humans can develop an allergy to semen, called human seminal plasma sensitivity. It appears as a typical localized or systemic allergic response upon contact with seminal fluid. There is no one protein in semen responsible for the reaction. Symptoms can appear after first intercourse or after subsequent intercourse. A semen allergy can be distinguished from a latex allergy by determining if the symptoms disappear with use of a condom. Desensitization treatments are often very successful.
=== 3D-QSAR === The acronym 3D-QSAR or 3-D QSAR refers to the application of force field calculations requiring three-dimensional structures of a given set of small molecules with known activities (training set). The training set needs to be superimposed (aligned) by either experimental data (e.g. based on ligand-protein crystallography) or molecule superimposition software. It uses computed potentials, e.g. the Lennard-Jones potential, rather than experimental constants and is concerned with the overall molecule rather than a single substituent. The first 3-D QSAR was named Comparative Molecular Field Analysis (CoMFA) by Cramer et al. It examined the steric fields (shape of the molecule) and the electrostatic fields which were correlated by means of partial least squares regression (PLS). The created data space is then usually reduced by a following feature extraction (see also dimensionality reduction). The following learning method can be any of the already mentioned machine learning methods, e.g. support vector machines. An alternative approach uses multiple-instance learning by encoding molecules as sets of data instances, each of which represents a possible molecular conformation. A label or response is assigned to each set corresponding to the activity of the molecule, which is assumed to be determined by at least one instance in the set (i.e. some conformation of the molecule). On June 18, 2011 the Comparative Molecular Field Analysis (CoMFA) patent has dropped any restriction on the use of GRID and partial least-squares (PLS) technologies.
=== 24 January === At least 70 people were killed in an RSF drone strike on the maternity ward of the Saudi Hospital in El Fasher that also destroyed its emergency department. The SAF claimed to have broken the siege around the Signal Corp's base in Khartoum. The RSF denied the claims. The SAF also claimed to have broken the siege around its General Headquarters in Khartoum and retook the El-Jeili oil refinery. The SAF and allied militias repelled an RSF attack on El Fasher following the expiration of the latter's ultimatum for the SAF to withdraw. The JDF claimed it had killed more than 400 RSF militants, destroyed more than 25 vehicles and captured 30 others. Ayub Osman Nahar resigned as an advisor to Hemedti, saying that he refused to be part of the RSF's atrocities against civilians and accusing the group of burning villages and killing civilians in North Darfur and Gezira State.
=== Lesions === The majority of vocal fold lesions primarily arise in the cover of the folds. Since the basal lamina secures the epithelium to the superficial layer of the lamina propria with anchoring fibers, this is a common site for injury. If a person has a phonotrauma or habitual vocal hyperfunction, also known as pressed phonation, the proteins in the basal lamina can shear, causing vocal fold injury, usually seen as nodules or polyps, which increase the mass and thickness of the cover. The squamous cell epithelium of the anterior glottis are also a frequent site of laryngeal cancer caused by smoking.
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 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.