NAD+ comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-11-22. Numbers and descriptions here follow the published literature rather than marketing material.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a coenzyme present in all living cells. The molecule consists of two nucleotides linked by phosphate groups, with adenine and a nicotinamide ring as its principal features. In its oxidized form, the nicotinamide ring can accept a hydride ion, becoming NADH. This reversible conversion places NAD+ at the center of many electron-transfer reactions. Its role as a redox carrier is well established across bacteria, plants, fungi, and animals.
Beyond redox chemistry, NAD+ acts as a substrate for several enzyme families. ADP-ribosyltransferases, sirtuins, and CD38 ectoenzymes cleave the molecule into nicotinamide and ADP-ribose or related products. These reactions connect NAD+ availability to processes such as DNA repair, chromatin modification, and calcium signaling. Because the coenzyme is used in both electron transfer and signaling, cells maintain separate pools in compartments including the cytosol, mitochondria, and nucleus. The relative sizes and regulation of those pools remain active areas of study.
Cells produce NAD+ through several biosynthetic routes. The salvage pathway recycles nicotinamide, while the Preiss-Handler pathway uses nicotinic acid, and a de novo route can start from tryptophan in some organisms. In mammals, the salvage pathway is generally considered the main source under ordinary conditions. Tissue concentrations vary widely by cell type and compartment, and measured declines with age have been reported in some studies. Whether such changes drive aging or mainly accompany it remains an open question.
Stability of NAD+ depends on form, temperature, pH, and water content. The solid is generally more stable than solutions, and it should be kept dry and cold. In solution, hydrolysis can cleave the dinucleotide, especially under alkaline conditions or at elevated temperature. Light exposure may also contribute to degradation. Buffers, chelating agents, and sterile handling can reduce losses, but no single condition preserves all preparations indefinitely. Researchers often prepare working solutions shortly before use and verify activity or purity after storage.
Quality control for NAD+ relies on identity, purity, and functional tests. A certificate of analysis may report high-performance liquid chromatography purity, ultraviolet spectrum, water content, and residual solvents. Because NAD+ is hygroscopic, gravimetric values can shift as material absorbs water, so purity should be interpreted alongside storage history. Mass spectrometry confirms molecular identity, while enzymatic assays show whether the material supports dehydrogenase activity. Commercial material is available as the free acid and as salts, and the counterion affects molecular weight, solubility, and how concentrations are calculated.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C21H27N7O14P2 | Oxidized free acid form; charge depends on pH. |
| Molar mass | 663.43 g/mol | Calculated for the free acid. |
| CAS Registry Number | 53-84-9 | For the anhydrous free acid; salts have different identifiers. |
| Appearance | White to off-white powder | Solid material; hygroscopic. |
| Solubility | Water-soluble | Dissolves in aqueous buffers; solubility varies with pH and salt. |
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.
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.
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.
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.
Stability studies show that NAD+ can hydrolyze under prolonged heat, extreme pH, or microbial contamination. Phosphate buffers near neutral pH are often used for short-term handling, though exact stability depends on concentration, temperature, and matrix. In biological samples, endogenous enzymes can rapidly degrade NAD+, making cold chain and fast processing important. Analytical reports should state extraction conditions, internal standards, and validation parameters. Without those details, comparisons across studies remain difficult and potentially misleading.
Laboratory measurement of NAD+ often begins with rapid quenching of cell or tissue samples to prevent enzymatic conversion. Acidic or alkaline extraction can precipitate proteins, but the chosen method affects recovery of oxidized and reduced forms. Enzymatic cycling assays provide high sensitivity by amplifying a NAD+-dependent reaction. High-performance liquid chromatography and mass spectrometry offer separation and structural confirmation. Each method has trade-offs in throughput, specificity, and the ability to distinguish NAD+ from close analogues.
Purified NAD+ is typically supplied as a white to off-white powder and stored desiccated at low temperature. Airtight containers limit moisture uptake, while protection from light reduces degradation of the nicotinamide ring. Aqueous stock solutions are less stable than solid material and are often aliquoted before freezing. Repeated freeze-thaw cycles can lower integrity, so working portions are kept separate. Purity is commonly checked by ultraviolet absorbance near 260 nm, high-performance liquid chromatography, or mass spectrometry.
== Evolution == Relaxin 1 and relaxin 2 arose from the duplication of a proto-RLN gene between 44.2 and 29.6 million years ago in the last common ancestor of catarrhine primates. The duplication that led to RLN1 and RLN2 is thought to have been a result of positive selection and convergent evolution at the nucleotide level between the relaxin gene in New World monkeys and the RLN1 gene in apes. As a result, Old World monkeys, a group that includes the subfamilies colobines and cercopithecines, have lost the RLN1 paralog, but apes have retained both the RLN1 and the RLN2 genes.
=== Music === Musician David Bowie described himself as Jungian in his relationship to dreams and the unconscious. Bowie sang of Jung on his album Aladdin Sane (a pun on "a lad insane") and attended the exhibition of The Red Book in New York with artist Tony Oursler, who described Bowie as "reading and speaking of the psychoanalyst with passion". Bowie's 1967 song "Shadow Man" encapsulates a key Jungian concept, while in 1987 Bowie described the Glass Spiders of Never Let Me Down as Jungian mother figures around which he not only anchored a worldwide tour but also created an enormous onstage effigy. British rock band the Police released an album titled Synchronicity in 1983. The American rock band Tool was influenced by Jungian concepts in its album Ænima, the title a play on the concepts of anima and animus. In the song "Forty Six & 2", the singer seeks to become a more evolved self by exploring and overcoming his Shadow. Jung's texts influenced Argentinian musician Luis Alberto Spinetta in his 1975 conceptual album Durazno sangrando, specifically the songs "Encadenado al ánima" and "En una lejana playa del ánimus", which deal with anima and animus. Jung appeared on the front cover of The Beatles' Sgt. Pepper's Lonely Hearts Club Band. He is referenced in The Streets song the "Irony of it All" from the album Original Pirate Material. The South Korean band BTS's 2019 album Map of the Soul: Persona is based on Jung's Map of the Soul, which gives the basic principles of Jung's analytical psychology.
==== Cargo handling ==== Dover Cargo Terminal West opened in December 2019, replacing berthing and handling facilities at the Eastern Docks. Two new berths can accommodate ships of 340 metres (1,120 ft) and 240 metres (790 ft) simultaneously with a minimum quay depth of 9.5 metres (31 ft). The new purpose-built cold chain and warehousing complex is capable of handling fresh produce, containers, project cargo, general cargo, breakbulk, grain and roll-on/roll-off.
Graphene was properly isolated and characterized in 2004 by Andre Geim and Konstantin Novoselov at the University of Manchester. They pulled graphene layers from graphite with a common adhesive tape in a process called micro-mechanical cleavage, colloquially referred to as the Scotch tape technique. The graphene flakes were then transferred onto a thin silicon dioxide layer on a silicon plate ("wafer"). The silica electrically isolated the graphene and weakly interacted with it, providing nearly charge-neutral graphene layers. The silicon beneath the SiO2 could be used as a "back gate" electrode to vary the charge density in the graphene over a wide range. This work resulted in the two winning the Nobel Prize in Physics in 2010 for their groundbreaking experiments with graphene. Their publication and the surprisingly easy preparation method that they described, sparked a "graphene gold rush". Research expanded and split off into many different subfields, exploring different exceptional properties of the material—quantum mechanical, electrical, chemical, mechanical, optical, magnetic, etc.
Sources: en.wikipedia.org
The coke-making or "coking" process consists of heating the material in "coking ovens" to very high temperatures (up to 900 °C or 1,700 °F) so that the molecules are broken down into lighter volatile substances, which leave the vessel, and a porous but hard residue that is mostly carbon and inorganic ash. The amount of volatiles varies with the source material, but is typically 25–30% of it by weight. High temperature pyrolysis is used on an industrial scale to convert coal into coke. This is useful in metallurgy, where the higher temperatures are necessary for many processes, such as steelmaking. Volatile by-products of this process are also often useful, including benzene and pyridine. Coke can also be produced from the solid residue left from petroleum refining. The original vascular structure of the wood and the pores created by escaping gases combine to produce a light and porous material. By starting with a dense wood-like material, such as nutshells or peach stones, one obtains a form of charcoal with particularly fine pores (and hence a much larger pore surface area), called activated carbon, which is used as an adsorbent for a wide range of chemical substances. Biochar is the residue of incomplete organic pyrolysis, e.g., from cooking fires. It is a key component of the terra preta soils associated with ancient indigenous communities of the Amazon basin. Terra preta is much sought by local farmers for its superior fertility and capacity to promote and retain an enhanced suite of beneficial microbiota, compared to the typical red soil of the region.
== Action mechanism, pharmacokinetics == Like other local anesthetics belonging in the amide group trimecaine decreases the cell membrane permeability, causes depolarization and shortens the action potential. Anesthetic effect starts within 15 minutes and remains 60–90 minutes. Its biological half-life is ca. 90 minutes. 10% of trimecaine is excreted unchanged (90% as its metabolites). It passes through the hematoencephalic and placental barriers.
The media claimed that it was taking advantage of the lack of a nationally recognised framework for safety and quality across online-only telehealth services by advertising prescription-only drugs on social media.
Sources: en.wikipedia.org
A honey bee that is away from the hive foraging for nectar or pollen will rarely sting, except when stepped on or roughly handled. Honey bees will actively seek out and sting when they perceive the hive to be threatened, often being alerted to this by the release of attack pheromones (below). Although it is widely believed that a worker honey bee can sting only once, this is only partially true: although the stinger is in fact barbed so that it lodges in the victim's skin, tearing loose from the bee's abdomen and leading to its death in minutes, this only happens if the skin of the victim is sufficiently thick, such as a mammal's. Honey bees are the only hymenoptera with a strongly barbed sting, though yellow jackets and some other wasps have small barbs. The venom of the honeybee contains histamine, mast cell degranulating peptide, melittin, phospholipase A2, hyaluronidase and acid phosphatase. The three proteins in honeybee venom that are important allergens are phospholipase A2, hyaluronidase and acid phosphatase. In addition, the polypeptide melittin is also antigenic. Bumblebee venom appears to be chemically and antigenically related to honeybee venom. Bees with barbed stingers can often sting other insects without harming themselves. Queen honeybees and bees of many other species, including bumblebees and many solitary bees, have smoother stingers with smaller barbs and can sting mammals repeatedly. The sting's injection of apitoxin into the victim is accompanied by the release of alarm pheromones, a process which is accelerated if the bee is fatally injured.
=== From free energy calculation === In practice, it can be difficult to obtain statistically converged and accurate protonation free energies from titration curves if ⟨x⟩ is close to a value of 1 or 0. In this case, one can use various free energy calculation methods to obtain the protonation free energy. To obtain the free energy, one starts with a collection of states generated by some type of simulation of the residue being protonated; this can be obtained via molecular dynamics or metropolis MC (including the biased metropolis MC and many other variants). A second algorithm then looks at these states to calculate the change in free energy before and after protonation. Methods for calculating the free energy change from an ensemble of states that have been applied to pKa calculation include:
=== COVID-19 misinformation === During the COVID-19 pandemic, Ayyadurai used social media to spread various conspiracy theories and misinformation about the pandemic. In January 2020, he claimed that COVID-19 was patented by the Pirbright Institute, but the patent he referenced relates to avian coronavirus, which infects birds, not SARS-CoV-2, the virus responsible for the pandemic. Ayyadurai defined COVID-19 as "an overactive dysfunctional immune system that overreacts and that's what causes damage to the body", and claimed that vitamin C could be used to treat it. He alleged that COVID-19 was spread by the "deep state" and accused Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, of being a "Deep State Plant". Ayyadurai called for Fauci to be fired and his supporters lobbied for Fauci to be replaced by Ayyadurai. In March 2020, Ayyadurai published an open letter to then-U.S. President Donald Trump, writing that a national lockdown was unnecessary and advocated that large doses of vitamins could prevent and cure COVID-19. In April 2020, Politico and Vanity Fair reported that QAnon supporter DeAnna Lorraine recommended that Ayyadurai be included in COVID-19 discussions at Donald Trump's White House.
== Forensic science and humanitarian work == The International Committee of the Red Cross (ICRC) uses forensic science for humanitarian purposes to clarify the fate of missing persons after armed conflict, disasters or migration, and is one of the services related to Restoring Family Links and Missing Persons. Knowing what has happened to a missing relative can often make it easier to proceed with the grieving process and move on with life for families of missing persons. Forensic science is used by various other organizations to clarify the fate and whereabouts of persons who have gone missing. Examples include the NGO Argentine Forensic Anthropology Team, working to clarify the fate of people who disappeared during the period of the 1976–1983 military dictatorship. The International Commission on Missing Persons (ICMP) used forensic science to find missing persons, for example after the conflicts in the Balkans. Recognising the role of forensic science for humanitarian purposes, as well as the importance of forensic investigations in fulfilling the state's responsibilities to investigate human rights violations, a group of experts in the late-1980s devised a UN Manual on the Prevention and Investigation of Extra-Legal, Arbitrary and Summary Executions, which became known as the Minnesota Protocol. This document was revised and re-published by the Office of the High Commissioner for Human Rights in 2016.
Sources: en.wikipedia.org
NAD+ is a coenzyme found in living cells and is the oxidized form of nicotinamide adenine dinucleotide. It accepts electrons in redox reactions and also serves as a substrate for certain signaling and repair enzymes.
NAD+ becomes NADH when it accepts a hydride ion during oxidation-reduction reactions. NADH then donates electrons to other molecules, after which the carrier can return to the NAD+ form.
No, nicotinamide is a smaller molecule and a component of NAD+. Cells can use nicotinamide to rebuild NAD+ through the salvage pathway.
Common methods include enzymatic cycling assays, HPLC with UV detection, and LC-MS. The choice depends on sample size, specificity needs, and available equipment. Rapid quenching before analysis is important because NAD+ and NADH can interconvert.