The short version of HPLC fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-02-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
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 |
|---|---|---|
| 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 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.
In aqueous solution, NAD+ is most stable under mildly acidic to neutral conditions and degrades faster at high pH or elevated temperature. The molecule can hydrolyze at the pyrophosphate bond or undergo nonenzymatic cyclization. Buffers, chelating agents, and cold temperatures slow these losses during analysis. Repeated freeze-thaw cycles are generally avoided because they can promote degradation and concentration changes. Light exposure is also controlled, though NAD+ is less photolabile than some related nucleotides.
In cells, NAD+ functions primarily as an electron carrier. Dehydrogenase enzymes in glycolysis and the citric acid cycle transfer hydride from substrates to NAD+, producing NADH. NADH then delivers electrons to the mitochondrial respiratory chain, supporting ATP synthesis. In fermentation, NADH is reoxidized to NAD+ so that glycolysis can continue. The balance between NAD+ and NADH helps set metabolic flux. Beyond redox, NAD+ serves as a substrate for enzymes that cleave it, including sirtuins, poly(ADP-ribose) polymerases, and CD38. These reactions consume NAD+ and release nicotinamide and ADP-ribose products.
Biosynthesis occurs through salvage, Preiss-Handler, and de novo pathways. In mammals, the salvage pathway from nicotinamide predominates, and NAMPT is often described as rate-limiting. Nicotinamide riboside and nicotinic acid enter related routes that converge on NAD+ production. Tissue NAD+ concentrations vary widely and are maintained by a balance of synthesis and consumption. Some studies report age-related declines in certain tissues, but whether these changes cause disease or can be reversed to improve human health remains an open question.
NAD+ stands for nicotinamide adenine dinucleotide, the oxidized form of a coenzyme found in all living cells. The molecule consists of two nucleotides, adenine and nicotinamide ribose, joined through phosphate groups. Its chemical formula is C21H27N7O14P2, and the free acid has a molar mass near 663.43 grams per mole. In redox reactions, NAD+ accepts a hydride ion and becomes NADH. The pair NAD+ and NADH participates in hundreds of metabolic reactions, including steps in glycolysis, the citric acid cycle, and oxidative phosphorylation.
== Causes == Conditions that chronically increase the pressure within the abdomen can predispose people to uterine prolapse. This includes chronic obstructive pulmonary disease (COPD), obesity, chronic cough, straining due to chronic constipation, and repetitive heavy lifting. Tobacco smoking has been found to be correlated to pelvic organ prolapse both due to the risk of developing lung conditions that lead to chronic cough or COPD as well as the negative effects of tobacco chemicals on connective tissue.
Corynebacterium xerosis is a gram-positive, rod-shaped bacterium in the genus Corynebacterium. Although it is frequently a harmless commensal organism living on the skin and in the mucous membranes, C. xerosis is also a clinically relevant opportunistic pathogen that has been attributed to many different infections in animals and humans. However, its actual prominence in human medicine is up for debate due to early difficulties distinguishing it from other Corynebacterium species in clinical isolates.
== Biography == Woodroof was born in Dallas, Texas, on February 3, 1950, to Garland Odell Woodroof (March 17, 1917, in Texas – December 3, 1983, in Dallas) and Willie Mae Hughes (November 25, 1917, in Oklahoma – November 19, 1996, in Dallas). His first marriage was to Mary Etta Pybus on June 28, 1969, in Dallas; they had a daughter. They divorced on March 23, 1972. On May 6, 1972, he married a woman named Rory S. Flynn in Dallas. They divorced on May 21, 1973. He then married Brenda Shari Robin on October 4, 1982, in Lubbock. They divorced on March 4, 1986, after he was diagnosed with HIV. It was recorded that Woodroof had a mercurial personality. One reporter writes that "Woodroof took guns to his doctor’s office, prompting Steven Pounders to 'fire him as a patient.'" Woodroof later sent the doctor roses, and the doctor took him back. Woodroof was said to have lost all his friends after they found out he was HIV-positive. The movie Dallas Buyers Club depicts Woodroof as holding homophobic views prior to contracting HIV. Other people who knew Woodroof said that he did not harbor anti-gay beliefs and was openly bisexual. He was a member of the Dallas Gay Alliance.
== Further reading == Aziz, Nusrate; Asadullah, M Niaz (2017). "Military spending, armed conflict and economic growth in developing countries in the post–Cold War era" (PDF). Journal of Economic Studies. 44 (1): 47–68. doi:10.1108/JES-01-2015-0021. Bartel, Fritz (2022). The Triumph of Broken Promises: The End of the Cold War and the Rise of Neoliberalism. Harvard University Press. ISBN 9780674976788. Henriksen, Thomas H. (2017). Cycles in US Foreign Policy Since the Cold War. Palgrave Macmillan. Jones, Bruce D.; Stedman, Stephen John (2017). "Civil Wars & the Post–Cold War International Order". Dædalus. 146 (4): 33–44. Menon, Rajan; Rumer, Eugene B., eds. (2015). Conflict in Ukraine: The Unwinding of the Post–Cold War Order. MIT Press. Peterson, James W. (2017). Russian-American relations in the post–Cold War world. Oxford UP. Sakwa, Richard (2017). Russia against the Rest: The Post–Cold War Crisis of World Order. Cambridge UP. p. 362. Wood, Luke B. (2017). "The politics of identity and security in post–Cold War Western and Central Europe". European Politics and Society. 18 (4): 552–556. doi:10.1080/23745118.2017.1376444.
Sources: en.wikipedia.org
Naturally occurring ytterbium (70Yb) is composed of seven stable isotopes: 168Yb, 170Yb–174Yb, and 176Yb, with 174Yb being the most abundant (31.90% natural abundance). 30 radioisotopes have been characterized, with the most stable being 169Yb with a half-life of 32.014 days, 175Yb with a half-life of 4.185 days, and 166Yb with a half-life of 56.7 hours. All of the remaining radioactive isotopes have half-lives that are less than 2 hours, with the majority of them being less than 20 minutes. This element also has 18 meta states, with the most stable being 169mYb (half-life 46 seconds). The known isotopes of ytterbium range from 149Yb to 189Yb. The primary decay mode before the most abundant stable isotope, 174Yb is electron capture giving thulium isotopes; the primary mode after is beta emission giving lutetium isotopes. Of interest to modern quantum optics, the different ytterbium isotopes follow either Bose–Einstein statistics or Fermi–Dirac statistics, leading to different behavior in optical lattices.
=== Separation of powers === On 24 October, the Sudanese Professionals Association (SPA) claimed that civilian members of the Sovereignty Council violated the constitutional constraints on their power by appearing to coordinate with Rapid Support Forces (RSF) and override the Ministry of Health's role in managing vector control against the spread of dengue fever and chikungunya. The SPA stated, "the campaign appeared to be the scene of direct interaction of the [RSF] with the health situation in the concerned states, in the absence of health departments at the federal or state level. ... [The] whole issue of health is not the prerogative of the Sovereign Council." Sudan Tribune expressed concern that the RSF and its leader Hemedti were trying to improve the RSF's image, damaged by its carrying out of crimes against humanity in the War in Darfur and human rights violations during the 3 June 2019 Khartoum massacre.
Several small-scale studies involving 15 or fewer test subjects conducted in the 1950s and 1960s reported that adrenochrome triggered psychotic reactions such as thought disorder and derealization. In 1954, researchers Abram Hoffer and Humphry Osmond claimed that adrenochrome is a neurotoxic, psychotomimetic substance and may play a role in schizophrenia and other mental illnesses. In what Hoffer called the "adrenochrome hypothesis", he and Osmond in 1967 speculated that megadoses of vitamin C and niacin could cure schizophrenia by reducing brain adrenochrome. The treatment of schizophrenia with such potent anti-oxidants is controversial. In 1973, the American Psychiatric Association reported methodological flaws in Hoffer's work on niacin as a schizophrenia treatment and referred to follow-up studies that did not confirm any benefits of the treatment. Multiple additional studies in the United States, Canada, and Australia similarly failed to find benefits of megavitamin therapy to treat schizophrenia. The adrenochrome theory of schizophrenia waned, despite some evidence that it may be psychotomimetic, as adrenochrome was not detectable in people with schizophrenia. In the early 2000s, interest was renewed by the discovery that adrenochrome may be produced normally as an intermediate in the formation of neuromelanin. This finding may be significant because adrenochrome is detoxified at least partially by glutathione-S-transferase. Some studies have found genetic defects in the gene for this enzyme. Adrenochrome is also believed to have cardiotoxic properties.
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.
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.