The short version of coenzyme fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Forms acidic solution; salt form may alter solubility |
| Typical storage temperature | -20 °C or lower | Desiccated and protected from light |
| Common analytical method | LC-MS | Used for biological quantification |
| UV absorbance maximum | 260 nm | Aqueous solution; pH dependent |
| Common synonym | Diphosphopyridine nucleotide | Older name abbreviated DPN |
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.
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.
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.
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.
=== Environmental chemistry === An important goal of environmental chemistry is tracing the source and degradation of pollutants. Various methods have been used for fingerprinting pools of environmental pollutants such as the bulk chemical composition of a spill, isotope ratios of the bulk chemical mixture, or isotope ratios of individual constituent compounds. Stable isotopes of carbon and hydrogen can be used as complementary fingerprinting techniques for natural gas. The DHR of hydrocarbons from the Deepwater Horizon oil spill was used to verify that they were likely from the Macondo well. HICs have also been used as a measure of the relative amount of biodegradation that has occurred in oil reservoirs in China, and studies on pure cultures of n-alkane degrading organisms have shown a chain-length dependence on the amount of hydrogen isotope fractionation during degradation. Additional studies have also shown hydrogen isotope effects in the degradation of methyl tert-butyl ether and toluene that have been suggested to be useful in the evaluation of the level of degradation of these polluting compounds in the environment. In both cases the residual unreacted compounds became 2H-enriched to a few tens of ‰, with variations exhibited between different organisms and degree of reaction completeness. These observations of heavy residual compounds have been applied to field observations of biodegradation reactions such as removal of benzene and ethylbenzene, which imparted a D/H fractionation of 27 and 50 ‰, respectively.
The wide-spread interest in the very remarkable specimen of the giant squid, now lying on the beach a few miles below the city, is mainly due to its enormous size. It is believed to be the largest specimen ever found. Its great size and immense weight have thus far prevented its being moved for a more careful examination. A dozen men with blocks and tackle not being able even to turn it over. Another effort will be made with more extensive apparatus by which it is hoped to drag it from the pit in which it now lies and placing it higher up on the beach so that a careful and thorough examination in the interest of science can be made and the exact species determined. Professor Verrill of Yale and Profs. True and Dale [Dall] of the Smithsonian are in constant correspondence with Dr. DeWitt Webb, President of the St. Augustine Scientific, Literary and Historical Society, in regard to it. Several photographs have been taken of it, but owing to its position, these have not been satisfactory. Mrs. John L. Wilson believes it to belong to an extinct species. Its hide is three and a half inches thick and its head is covered by a hood that prevents examination. Apparently it is a mass of cartilage and may have been dead in the water many days before it washed ashore on Anastasia Island. In the February issue of the American Journal of Science, Verrill even gave the animal a scientific name, Octopus giganteus (Verrill, 1897). He also added:
The Boer War saw the first war crimes prosecutions in British history. They centered around the Bushveldt Carbineers (BVC), a British Army irregular regiment of mounted rifles active in the Northern Transvaal. Originally raised in February 1901, the BVC was composed of British and Commonwealth servicemen with an admixture of defectors from the Boer Commandos. On 4 October 1901, a letter signed by 15 members of the Bushveldt Carbineers (BVC) garrison at Fort Edward was secretly dispatched to Col. F.H. Hall, the British Army Officer Commanding at Pietersburg. Written by BVC Trooper Robert Mitchell Cochrane, a former justice of the peace from Western Australia, the letter accused members of the Fort Edward garrison of six "disgraceful incidents":
The disorder prediction category is a part of biannual CASP experiment that is designed to test methods according accuracy in finding regions with missing 3D structure (marked in PDB files as REMARK465, missing electron densities in X-ray structures). Disorder prediction can be more complicated for de novo-emerged and orphan proteins, which often lack detectable homologs and are generally shorter than "classical" proteins, reducing the reliability of predictors trained largely on conserved, globular proteins. Comparative benchmarks further show that structure/disorder predictors behave differently on de novo and random proteins than on conserved proteins, including different relationships between predicted disorder and confidence scores of 3D structure predictors, such as AlphaFold and ESMfold.
Decreased TOR activity has been found to increase life span in S. cerevisiae, C. elegans, and D. melanogaster. The mTOR inhibitor rapamycin has been confirmed to increase lifespan in mice. It is hypothesized that some dietary regimes, like caloric restriction and methionine restriction, cause lifespan extension by decreasing mTOR activity. Some studies have suggested that mTOR signaling may increase during aging, at least in specific tissues like adipose tissue, and rapamycin may act in part by blocking this increase. An alternative theory is mTOR signaling is an example of antagonistic pleiotropy, and while high mTOR signaling is good during early life, it is maintained at an inappropriately high level in old age. Calorie restriction and methionine restriction may act in part by limiting levels of essential amino acids including leucine and methionine, which are potent activators of mTOR. The administration of leucine into the rat brain has been shown to decrease food intake and body weight via activation of the mTOR pathway in the hypothalamus. According to the free radical theory of aging, reactive oxygen species cause damage to mitochondrial proteins and decrease ATP production. Subsequently, via ATP sensitive AMPK, the mTOR pathway is inhibited and ATP-consuming protein synthesis is downregulated, since mTORC1 initiates a phosphorylation cascade activating the ribosome. Hence, the proportion of damaged proteins is enhanced. Moreover, disruption of mTORC1 directly inhibits mitochondrial respiration.
Sources: en.wikipedia.org
==== Plurality vs. unity of substantial form ==== Many medieval theologians and philosophers followed Aristotle in seeing a living being's soul as that being's form—specifically, its substantial form. However, they disagreed about whether X's soul is X's only substantial form. Some medieval thinkers argued that X's soul is X's only substantial form animating the entire body of X. In contrast, other medieval thinkers argued that a living being contains at least two substantial forms—(1) the shape and structure of its body, and (2) its soul, which makes its body alive.
=== Predators === The species Hydra oligactis is preyed upon by the flatworm Microstomum lineare. Some Coleps sp. have also been observed to attack Hydra polyps in groups, with them attacking Hydras' tentacles first before consuming the entire polyps. Some other common predators include carnivorous or omnivorous fishes such as guppies, bettas, and gouramis.
==== Spill control ==== A written policy needs to be in place in case of a spill of antineoplastic products. The policy should address the possibility of various sizes of spills as well as the procedure and personal protective equipment required for each size. A trained worker should handle a large spill and always dispose of all cleanup materials in the chemical waste container according to EPA regulations, not in a yellow chemotherapy waste container.
== Theoretical Analysis of an Ideal Penning Trap == The motion of a single charged particle in an ideal Penning trap (with perfect alignment of its magnetic field to the quadrupole potential) is an exactly solvable system in both classical and quantum mechanics. The particle's motion along the trap's axis is simple harmonic motion, and the motion in the trap's xy-plane is a perturbation of cyclotron motion that reduces to cyclotron motion exactly in the zero-electric-field limit.
Sources: en.wikipedia.org
=== Debate over origins === Murdijati Gardjito, a food historian at Gadjah Mada University, argued that tempeh was made by native Javanese people and that its preparation predates the introduction of Chinese-style tofu products. Some ancient texts mention tempe dhele, old Javanese for 'native soybean tempeh'; dhele was used to refer to the native soybean variety. White soybeans that are used to make most tempe dhele today used to be called dhele putih ('white soybeans'), and were only available in Java centuries later. Mary Astuti, a food historian at Gadjah Mada University specializing in tempeh, argued that the native variety of soybean had been grown before the Chinese arrived in the region. Sri Tandjung noted that Javanese had been eating cooked (native black) soybeans since the 12th century. By the 16th or the 19th century, depending on which period of time the writer of Serat Centhini referred to, Javanese people had mastered the art of cooking with tempeh, when it was not only eaten as is, but converted into different types of dishes, showing a full understanding and mastery of the food product. Gardjito noted that Javanese noble families rarely wrote about tempeh in ancient texts because it had never been a part of royal cuisine, but rather a staple food of the lower classes. Indonesian historian Ong Hok Ham suggests that tempeh might have been produced as a byproduct of tahu, the Indonesian word for tofu.
Even after the Meiji era when hybrid cattle were encouraged, there were still a considerable number of pure Wagyu cattle remaining in the Taisho era (1912–1926). As a policy for the improvement of Wagyu, efforts were made to eliminate negative characteristics of hybrid cattle as much as possible. Specifically, the elimination of sudare (tiger stripes), nori-kuchi (grayish-white lips), unagi-sen (different fur color on the dorsal line), white spots, etc. On the other hand, efforts were made to improve the physique and weight of both pure and improved Wagyu cattle, and from around the 1920s, the term "improved Wagyu" came to refer to all Wagyu cattle, including not only improved Wagyu but also pure Wagyu. Around 1919, the examination and registration of Wagyu began mainly in western Japan, and pedigrees and body types began to be registered. Nine breeds were registered: Tajima, Bisaku, Hiroshima, Bocho, Shimane, Inhaku, Bungo, Kumamoto, and Kagoshima. However, the examination and registration process was carried out by each prefecture, and the criteria for examination varied. Around 1925, the results of the improvements became visible: the negative characteristics of crossbreeding had almost disappeared from Wagyu cattle, their size and weight had increased, and improvements in hindquarters were clearly visible.
== External links == "Erythropoietin". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on 7 April 2020. Overview of all the structural information available in the PDB for UniProt: P01588 (Erythropoietin) at the PDBe-KB.
Sources: en.wikipedia.org
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.
Liquid chromatography-mass spectrometry provides sensitive and specific quantification in cells and tissues. Enzymatic cycling assays are also widely used for plate-based measurement. Both methods need rapid sample processing to prevent post-collection changes.
Purity refers to the proportion of the intended dinucleotide relative to related nucleotides, salts, and water. A high-purity grade supports reproducible enzymatic assays. Researchers often check purity by chromatographic and spectroscopic methods before use.
It indicates the oxidized form, which has a positive charge on the nicotinamide nitrogen. The reduced partner NADH lacks that charge and carries added electrons. The plus sign is part of the standard abbreviation, not a separate ion.