A practical reference on NADH: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
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 the oxidized form of nicotinamide adenine dinucleotide, a coenzyme built from two nucleotides joined by a phosphate linkage. One nucleotide carries adenine, and the other carries nicotinamide; the plus sign denotes a formal positive charge on the nicotinamide ring, not a free proton. In cells, NAD+ and its reduced partner NADH form a reversible redox pair. That pair participates in electron transfer reactions throughout metabolism. The abbreviation NAD+ is common in biochemistry, while NAD(H) sometimes denotes the combined pool.
The molecule was first described in the early twentieth century as a factor that promoted fermentation in yeast extracts. Later work linked it to hydrogen transfer and to the oxidation of nutrients in living tissues. Its structure was resolved as a dinucleotide, which explained why it could accept and donate electrons at specific enzyme sites. Today, NAD+ is recognized as a central substrate and signaling precursor, not merely a metabolic cofactor. Whether all observed NAD+ changes reflect causal signaling remains an open question.
Related compounds include NADH, the reduced form, and NADP+, which carries an additional phosphate group. NADP+ and NADPH often serve in biosynthetic and antioxidant reactions, while NAD+ and NADH are more associated with energy-yielding catabolism. Nicotinamide, nicotinic acid, and nicotinamide riboside are precursors that can enter salvage pathways. The exact contribution of dietary precursors to tissue NAD+ pools is an area of active investigation. Some studies measure labeled precursors to trace those routes.
| Property | Value | Notes |
|---|---|---|
| Common name | Nicotinamide adenine dinucleotide (oxidized) | Often shortened to NAD+ |
| Chemical class | Dinucleotide | Contains nicotinamide and adenine moieties |
| Molecular formula | C21H27N7O14P2 | Free acid form; charge depends on pH |
| Molar mass | About 663.43 g/mol | Calculated for C21H27N7O14P2 |
| CAS number | 53-84-9 | Common identifier for beta-NAD+ |
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.
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.
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.
In order to avoid continuous activation of receptors on the post-synaptic or target cell, neurotransmitters must be removed from the synaptic cleft. Neurotransmitters are removed through one of three mechanisms:
== History == The areas later known as the Sudetenland never formed a single historical region, which makes it difficult to distinguish the history of the Sudetenland separately from that of Bohemia until the advent of nationalism in the 19th century.
=== Safety === Tests of common teas have detected residues of banned toxic pesticides. Additionally, tests have indicated contamination of heavy metals and toxic elements in some brewed teas, some having a proportional relationship between the concentration of contaminants and steeping time. Another study indicated that heavy metals in commercial teas are tightly bound to tea leaves, with a minor amount leeching off into the water while brewing.
Sources: en.wikipedia.org
== See also == Category:Cutaneous conditions Dermatology List of conditions associated with café au lait macules List of contact allergens List of cutaneous conditions associated with increased risk of nonmelanoma skin cancer List of cutaneous conditions associated with internal malignancy List of cutaneous conditions caused by mutations in keratins List of cutaneous neoplasms associated with systemic syndromes List of cutaneous conditions caused by problems with junctional proteins List of dental abnormalities associated with cutaneous conditions List of genes mutated in cutaneous conditions List of genes mutated in pigmented cutaneous lesions List of histologic stains that aid in diagnosis of cutaneous conditions List of human leukocyte antigen alleles associated with cutaneous conditions List of immunofluorescence findings for autoimmune bullous conditions List of inclusion bodies that aid in diagnosis of cutaneous conditions List of keratins expressed in the human integumentary system List of migrating cutaneous conditions List of mites associated with cutaneous reactions List of radiographic findings associated with cutaneous conditions List of specialized glands within the human integumentary system List of spiders associated with cutaneous reactions List of target antigens in pemphigoid List of target antigens in pemphigus List of verrucous carcinoma subtypes List of xanthoma variants associated with hyperlipoproteinemia subtypes
=== Effects === In general, MDMA users report feeling the onset of subjective effects within 30 to 60 minutes of oral consumption and reaching peak effect at 75 to 120 minutes, which then plateaus for about 3.5 hours. The desired short-term psychoactive effects of MDMA have been reported to include:
Sozusagen Paris, Munich 2016: Hanser. Einbruch der Wirklichkeit: Auf dem Flüchtlingstreck durch Europa, Munich 2016: C. H. Beck. Entlang den Gräben: Eine Reise durch das östliche Europa bis nach Isfahan, Munich 2018: C. H. Beck. Morgen ist da: Reden, Munich 2019: C. H. Beck. Jeder soll von da, wo er ist, einen Schritt näher kommen: Fragen nach Gott, Munich 2022: Hanser. Was jetzt möglich ist: 33 politische Situationen, Munich 2022: C.H. Beck. ISBN 978-3-406-79023-2. Das Alphabet bis S. Roman, Munich 2023: Hanser. ISBN 978-3-446-27745-8. In die andere Richtung jetzt. Eine Reise durch Ostafrika, Munich 2024: C.H. Beck, ISBN 978-3-406-81969-8. with Mehrdad Zaeri (illustration): Zu Hause ist es am schönsten, sagte die linke Hand und hielt sich an der Heizung fest, Berlin 2025: Hanser, ISBN 978-3-446-28260-5. Wenn sich unsere Herzen gleich öffnen. Über Politik und Liebe, Munich 2025: C.H. Beck, ISBN 978-3-406-83887-3. Sommer 24. Roman. Hanser, Berlin 2026, ISBN 978-3-446-28576-7. Köln. E Jeföhl. C.H. Beck, München 2026, ISBN 978-3-406-85095-0.
Sources: en.wikipedia.org
Fifty years after the introduction of fluoxetine and other SSRIs, these drugs remain widely used and effective for depression. Concerns about over prescription, under-treatment of depression through other modalities, and role in the over-medicalization of normal life remain debated.
== January 9, 1982 (Saturday) == A frigid blast of Arctic air began in the U.S. Midwest and South, setting records for cold in numerous cities, including a record low in Chicago of 26° below zero F (-32 °C) on the morning of January 10 and a wind chill factor of -100 °F (-73 °C). By January 17, there were 261 deaths attributed to hypothermia form the cold weather. The first World Cup series of cross-country skiing was started by the International Ski Federation, beginning with a meet in West Germany at Reit im Winkl for men and Klingenthal for women. Born: Catherine, Princess of Wales, wife since 2011 of William, Prince of Wales, heir apparent to the British throne; as Catherine Middleton in Reading, Berkshire Anusha Dandekar, Sudanese-born and Australian-raised Indian supermodel, veejay on MTV India, as well as a film actress, known for Juna Furniture (2024) and Baap Manus (2022); in Khartoum
=== Cancer diagnosis and departure === In the serial's first episodes of 2022, Ari takes the blame for Matthew's murder in order to protect Mia and Chloe. Ari is held on remand ahead of his sentencing hearing. Kipa-Williams explained that none of the Parata family can accept that Ari is going to prison. But he cannot accept seeing Chloe or Mia go there either, and he cannot work out a way where it would end well for them. Kipa-Williams continued, "He decides to take the fall because he knows he can handle it." Tane steps up as head of the family in Ari's absence, while Nikau pleads with his uncle to tell the police the truth. Kipa-Williams believed that his character's one regret was not marrying Mia. The storyline marked the beginning of Ari's exit from Home and Away, as he is later rushed to hospital with stabbing pains. Logan Bennett (Harley Bonner) initially thinks he may have appendicitis, but he later informs Ari that he has cancer of the appendix, which has spread to his abdomen. Logan also tells Ari that he could undergo a large, lengthy surgery to remove the tumours, but it would need to be repeated every few months. Ari decides not to go through with surgery as he wants to die on his terms. Daniel Kilkelly of Digital Spy reported that rumours of Kipa-Williams' exit from the serial had been circulating for months. Mia makes a "moving" proposal that she and Ari get married at the hospital, which he accepts. Ari insists that the day is about "celebration, not commiseration", and he and Mia marry in front of Tane, Nikau, and Chloe.
No visible clubbing – Fluctuation (increased ballotability) and softening of the nail bed only. No visible changes in nails. Mild clubbing – Loss of the normal <165° angle (Lovibond angle) between the nailbed and the fold (cuticula). Schamroth's window (see image) is obliterated. Clubbing is not obvious at a glance. Moderate clubbing – Increased convexity of the nail fold. Clubbing is apparent at a glance. Gross clubbing – Thickening of the whole distal (end part of the) finger (resembling a drumstick) Hypertrophic osteoarthropathy – Shiny aspect and striation of the nail and skin Schamroth's sign or Schamroth's window test (originally demonstrated by South African cardiologist Leo Schamroth on himself) is a popular test for clubbing. When the distal phalanges (bones nearest the fingertips) of corresponding fingers of opposite hands are directly opposed (place fingernails of the same finger on opposite hands against each other, nail to nail), a small diamond-shaped "window" is normally apparent between the nailbeds. If this window is obliterated, the test is positive, and clubbing is present.
Sources: en.wikipedia.org
The plus sign indicates the oxidized form of nicotinamide adenine dinucleotide, which can accept electrons. When it accepts electrons, it becomes NADH. The two forms together support redox reactions in cells.
No. NAD+ is the oxidized form and NADH is the reduced form. They differ by two electrons and a proton equivalent, and cells interconvert them during metabolism.
Yes. NAD+ is present in all living cells and is required for fundamental metabolic reactions. Its concentration varies by tissue, compartment, and time.
It indicates a formal positive charge on the nicotinamide ring. The molecule is not simply a protonated acid, and the charge is part of its redox chemistry.