A practical reference on Nicotinamide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-03. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical formula | C21H27N7O14P2 | Free acid form; salt and hydrate forms differ in mass. |
| Molar mass | 663.43 g/mol | Anhydrous free acid; counterions and water change the value. |
| Appearance | White to off-white powder | Typical solid reagent; exact color varies by purity and form. |
| Solubility class | Highly water-soluble | Aqueous solutions are acidic; organic solubility is generally limited. |
| Common synonyms | DPN, coenzyme I, NAD | Older literature often uses diphosphopyridine nucleotide or DPN. |
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.
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 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.
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.
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.
Gerald W. Hart, a founding figure of the field of glycobiology, discovered and performed much of the pioneering work on intracellular O-GlcNAcylation beginning in the 1980s at Johns Hopkins School of Medicine. Hart and colleagues were probing for terminal GlcNAc residues on the surfaces of thymocytes and lymphocytes. Bovine milk β-1,4-galactosyltransferase, which reacts with terminal GlcNAc residues, was used to perform radiolabeling with UDP-[3H]galactose. Loss of signal from the labeled galactose following β-elimination of serine and threonine residues demonstrated that most of it was attached to proteins O-glycosidically; chromatography revealed that the major β-elimination product was Galβ1-4GlcNAcitol. Insensitivity to peptide N-glycosidase treatment provided additional evidence for O-linked GlcNAc. Permeabilizing cells with detergent prior to radiolabeling greatly increased the amount of [3H]galactose incorporated into Galβ1-4GlcNAcitol, leading the authors to conclude that most of the O-linked GlcNAc monosaccharide residues were intracellular. This was in stark contrast to the prevailing understanding that protein glycosylation was nearly or entirely exclusive to the secretory pathway, as the topic was dominated by research of highly abundant extracellular mucin-type O-glycans.
Mammals reproduce by internal fertilization and are solely gonochoric (having either male or female sex organs). Male mammals ejaculate semen during copulation through a penis, which may be contained in a prepuce when not erect. Male placentals also urinate through a penis, and some placentals also have a penis bone (baculum). Marsupials typically have forked penises, while echidnas have four-headed penises with two functioning heads. Depending on the species, penile erection is driven either by blood flow into vascular, spongy tissue or by muscular action. The testicles of most mammals descend into the scrotum which is typically posterior to the penis but is often anterior in marsupials. Female mammals generally have an external vulva and clitoris and labia, two internal paired oviducts, one or two uteri, one or two cervices and a vagina. Marsupials have two lateral vaginas and a medial vagina. The "vagina" of monotremes is better understood as a "urogenital sinus". The uterine systems of placentals can be duplex, with two uteri and cervices which open into the vagina, or bipartite, with two uterine horns with a single cervix connected to the vagina, or bicornuate, with two uterine horns connected distally but separated medially in a Y-shape, or simplex, with a single uterus.
=== Brand names === Gabapentin was originally sold under the brand name Neurontin. Since it became generic, it has been sold worldwide using over 300 different brand names. An extended-release formulation of gabapentin for once-daily administration was introduced in 2011 for postherpetic neuralgia under the brand name Gralise. In the US, Neurontin is sold by Viatris after Upjohn was spun off from Pfizer.
==== Meals ==== Food or beverage provided to employees on certain fishing vessels or certain fish processing facilities for the employer's convenience is 100% tax deductible to the employer, up from 50% previously.
Sources: en.wikipedia.org
There are several activated forms of macrophages. In spite of a spectrum of ways to activate macrophages, there are two main groups designated M1 and M2. M1 macrophages: as mentioned earlier (previously referred to as classically activated macrophages), M1 "killer" macrophages are activated by LPS and IFN-gamma, and secrete high levels of IL-12 and low levels of IL-10. M1 macrophages have pro-inflammatory, bactericidal, and phagocytic functions. In contrast, the M2 "repair" designation (also referred to as alternatively activated macrophages) broadly refers to macrophages that function in constructive processes like wound healing and tissue repair, and those that turn off damaging immune system activation by producing anti-inflammatory cytokines like IL-10. M2 is the phenotype of resident tissue macrophages, and can be further elevated by IL-4. M2 macrophages produce high levels of IL-10, TGF-beta and low levels of IL-12. Tumor-associated macrophages are mainly of the M2 phenotype, and seem to actively promote tumor growth. Macrophages exist in a variety of phenotypes which are determined by the role they play in wound maturation. Phenotypes can be predominantly separated into two major categories; M1 and M2. M1 macrophages are the dominating phenotype observed in the early stages of inflammation and are activated by four key mediators: interferon-γ (IFN-γ), tumor necrosis factor (TNF), and damage associated molecular patterns (DAMPs). These mediator molecules create a pro-inflammatory response that in return produce pro-inflammatory cytokines like Interleukin-6 and TNF.
Ptaquiloside can pass into the milk produced by bracken-fed cows and sheep. In 1996, Alonso-Amelot, Smith and co-workers found that ptaquiloside was excreted in milk at a concentration of 8.6 ± 1.2% of the amount ingested by a cow from bracken, and was linearly dose-dependent. On the basis of their experiments and the assumption that a person drinks 0.5 litres of milk daily, they estimated that this person might ingest about 10 mg of ptaquiloside per day, although only some of that amount will be absorbed. Ptaquiloside can also leach from the bracken leaves into water and soil. Numerous studies have reported the presence of ptaquiloside in the underground/surface water, and soil near bracken vegetation. The degradation speed of ptaquiloside in the soil is affected by the acidity, clay content, carbon content, temperature and presumably microbioactivity. Acidic condition (pH<4) and high temperature (at least 25 °C) facilitate ptaquiloside degradation, while the half-life of ptaquiloside in less acidic sandy soil is reported to be between 150 and 180 hours.
=== Asparagine === The biosynthesis of asparagine originates with aspartate using a transaminase enzyme. The enzyme asparagine synthetase produces asparagine, AMP, glutamate, and pyrophosphate from aspartate, glutamine, and ATP. In the asparagine synthetase reaction, ATP is used to activate aspartate, forming β-aspartyl-AMP. Glutamine donates an ammonium group, which reacts with β-aspartyl-AMP to form asparagine and free AMP.
where I is the identity tensor. The displacement of a body may be expressed in the form x = F(X), where X is the reference position of material points of the body; displacement has units of length and does not distinguish between rigid body motions (translations and rotations) and deformations (changes in shape and size) of the body. The spatial derivative of a uniform translation is zero, thus strains measure how much a given displacement differs locally from a rigid-body motion. A strain is in general a tensor quantity. Physical insight into strains can be gained by observing that a given strain can be decomposed into normal and shear components. The amount of stretch or compression along material line elements or fibers is the normal strain, and the amount of distortion associated with the sliding of plane layers over each other is the shear strain, within a deforming body. This could be applied by elongation, shortening, or volume changes, or angular distortion. The state of strain at a material point of a continuum body is defined as the totality of all the changes in length of material lines or fibers, the normal strain, which pass through that point and also the totality of all the changes in the angle between pairs of lines initially perpendicular to each other, the shear strain, radiating from this point. However, it is sufficient to know the normal and shear components of strain on a set of three mutually perpendicular directions.
== Taxonomy and naming == The fish was first described as Cobitis macracanthus by Pieter Bleeker in 1852. In 1989, its scientific name was changed to Botia macracanthus. In 2004, Dr. Maurice Kottelat divided the genus Botia, containing 47 different species, into seven separate genera, resulting in the clown loach being placed in a genus of its own, Chromobotia. Its scientific name roughly translates to "Large-thorned colourful warrior".
Sources: en.wikipedia.org
NAD+ is a coenzyme found in all living cells. It carries electrons in metabolic reactions and also serves as a substrate for enzymes involved in signaling and DNA repair. Its oxidized and reduced forms are central to energy metabolism.
NAD+ is the oxidized form and NADH is the reduced form. The pair accepts and donates electrons in redox reactions. Their ratio helps indicate the metabolic state of a cell or compartment.
No. Nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR) are precursors that cells can convert into NAD+. They are distinct molecules with different absorption and metabolism profiles.
Aqueous NAD+ solutions are best kept frozen in aliquots and protected from light. Repeated freezing and thawing is avoided because it can accelerate breakdown. Dry powder stored desiccated at -20 °C or lower typically remains stable for longer periods.