redox carrier is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-10-31. Numbers and descriptions here follow the published literature rather than marketing material.
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.
In glycolysis, NAD+ accepts electrons during the oxidation of glyceraldehyde-3-phosphate, forming NADH. The tricarboxylic acid cycle and fatty acid oxidation also generate NADH, which donates electrons to the mitochondrial electron transport chain. This flow supports ATP synthesis and helps maintain the redox balance of the cell. Other dehydrogenases use NAD+ as a cofactor for biosynthetic reductions and detoxification reactions. NADH is later reoxidized to sustain continued flux through these pathways.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer ADP-ribose units. Sirtuins, poly(ADP-ribose) polymerases, and CD38 consume NAD+ in regulatory reactions. These activities link NAD+ availability to DNA repair, chromatin modification, calcium signaling, and metabolic stress responses. Because consumption can exceed biosynthesis under some conditions, cellular NAD+ levels are dynamic rather than fixed. Enzyme affinity and local synthesis also influence how much NAD+ is available for signaling.
NAD+ is a dinucleotide composed of adenine, ribose, and nicotinamide moieties linked by phosphate groups. Its oxidized form carries a positive charge on the nicotinamide ring, which enables reversible hydride transfer. The molecule functions as a coenzyme in oxidoreductase reactions rather than as a dietary vitamin in its intact form. Cells maintain separate pools in cytoplasm, mitochondria, and nucleus. This compartmentalization allows distinct redox environments while preserving a shared chemical identity.
| Property | Value | Notes |
|---|---|---|
| Molar mass | 663.43 g/mol | For the free acid form; salts have higher mass. |
| Appearance | White to off-white powder | Often hygroscopic; may clump on exposure to air. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture; avoid repeated freeze-thaw. |
| Common synonyms | beta-NAD, DPN | DPN stands for diphosphopyridine nucleotide, an older name. |
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.
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 a dinucleotide composed of two nucleotides joined by a pyrophosphate linkage. One nucleotide contains adenine, and the other contains nicotinamide. The oxidized form carries a positive charge on the nicotinamide ring and is abbreviated NAD+. It functions as a cofactor in hydride-transfer reactions, accepting electrons in catabolic pathways. In cells, it interconverts with reduced NADH, forming a redox couple central to energy metabolism. The molecule is water-soluble and does not cross cell membranes freely without specific transport or precursor pathways.
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.
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.
Research on NAD+ spans biochemistry, aging biology, and metabolism. Studies often examine how NAD+ levels change with age, diet, exercise, or disease states, and whether precursor supplementation alters those levels. Findings in animal models do not automatically translate to humans, and measurement methods vary across studies. Questions about tissue-specific effects, long-term consequences, and causal relationships remain open. NAD+ itself is not established as a single therapeutic agent with a broad clinical role.
Lyon, Davor Solter and Azim Surani, for their pioneering work on epigenetic gene regulation in mammalian embryos 2005 Martin Chalfie and Roger Y. Tsien, for their pioneering development of powerful new tools that allow the direct visualization of molecules in living cells 2004 Andrew Z. Fire, Craig C. Mello, Victor Ambros and Gary Ruvkun, for their pioneering achievements in the discovery of gene silencing by double-stranded RNA 2003 Masakazu Konishi, Peter Marler and Fernando Nottebohm, for their pioneering achievements in the ethology and neurology of birdsong 2002 Ira Herskowitz, for his pioneering achievements in yeast genetics and cell biology 2001 Joan A. Steitz, for her work in establishing a sub-field of molecular biology concerning small nuclear ribonucleoproteins 2000 Peter B. Moore, Harry F. Noller, Jr. and Thomas A. Steitz, for their discovery that peptide bond formation on the ribosome is catalyzed exclusively by ribosomal RNA 1999 Roderick MacKinnon, for his research into the molecular foundations of electrical signal generation in neurons and other types of cells 1998 Elizabeth Blackburn and Carol Greider, for their outstanding work on the maintenance of telomeres 1997 H. Robert Horvitz and John E. Sulston, for their pioneering studies of cell lineage in the nematode worm 1996 Richard Axel, Linda B. Buck and A. James Hudspeth, for establishing the molecular basis of the senses of smell and hearing 1995 Thomas D. Pollard and James A. Spudich, for their fundamental contributions to our understanding of molecular motors 1994 Robert G.
== Discovery == The discovery of dye-ligand ability is from a blue dye called blue dextran. The blue dye is used as a void volume (V0) marker for a gel filtration column. It has shown that the dye has a property to bind to some certain proteins like pyruvate kinase and elute out with the void volume. Later on, it was found that "cibacron blue FG3-A", reactive dye link to dextran, is responsible for the interaction with the proteins.
=== Europe === Albania: Foreign Minister Elisa Spiropali expressed Albania's full support for the US. Among other things, she said: "As a steadfast U.S. ally and NATO member, Albania stands shoulder to shoulder with American leadership in the defense of democratic principles and global security." Andorra: Foreign Minister Imma Tor emphasised the Andorran government's opposition to "Maduro's oppressive regime" and "we trust that the political transition process will continue peacefully and in accordance with international law". Belarus: President Alexander Lukashenko "categorically condemned" the strikes and the Belarusian Ministry of Foreign Affairs said the US' "armed aggression" was a "direct threat" to international peace and security. Bosnia and Herzegovina: The Ministry of Foreign Affairs expressed Bosnia and Herzegovina's support for the "people of Venezuela and for stability in the country and the wider region", calling on "all actors to act rationally, responsibly and with restraint to prevent further escalation and suffering". The Ministry added that "Maduro is a dictator, the world would be a better place without a ruler like him." Czech Republic: Prime Minister Andrej Babiš stated that he hopes that "the citizens of Venezuela will have freedom and democracy, and that they will choose a democratic regime". Foreign Minister Petr Macinka stated the importance of calming the situation in Venezuela and to conduct diplomatic negotiations, including with the local opposition.
Costa declined to identify countries or banks that may have received any drug money, saying that would be inappropriate because his office is supposed to address the problem, not apportion blame. Though street-level drug sales are widely viewed as lucrative, a study by Sudhir Venkatesh suggested that many low-level employees receive low wages. In a study he made in the 1990s working closely with members of the Black Gangster Disciple Nation in Chicago, he found that one gang (essentially a franchise) consisted of a leader (a college graduate named J.T.), three senior officers, and 25 to 75 street level salesmen ('foot soldiers') depending on season. Selling crack cocaine, they took in approximately $32,000 per month over a six-year period. This was spent as follows: $5,000 to the board of twenty directors of the Black Gangster Disciple Nation, who oversaw 100 such gangs for approximately $500,000 in monthly income. Another $5,000 monthly was paid for cocaine, and $4,000 for other non-wage expenses. J.T. took $8,500 monthly for his own salary. The remaining $9,500 monthly went to pay the employees a $7 per hour wage for officers and a $3.30 per hour wage for foot soldiers. Contrary to a popular image of drug sales as a lucrative profession, many of the employees were living with their mothers by necessity. Despite this, the gang had four times as many unpaid members who dreamed of becoming foot soldiers.
Sources: en.wikipedia.org
=== Competition === In an interview in Swedish business monthly Affärsvärlden in 2006, then Tetra Pak CEO Dennis Jönsson stated that Tetra Pak's main competitor was Swiss manufacturer SIG Combibloc, adding that Tetra Pak's main competition generally no longer comes from companies producing similar packaging but from industries and companies producing other types of packaging with a lower cost of production, like the PET bottle. Jönsson perceived the PET bottle as Tetra Pak's biggest threat in the European market at the time. The Norwegian company Elopak/Pure-Pak produces similar style carton packages and has historically been Tetra Pak's principal competitor. The Chinese packaging company Greatview has begun challenging Tetra Pak, both in the Chinese market and in Europe.
Their first son Prince Aegon was born in 120 AC, while their second son was born in 122 AC and named after Viserys. In 126 AC, Rhaenyra requested that Luke be recognized as the heir to Driftmark, which several members of House Velaryon protested under the accusation that he was not Laenor's son. As Viserys angrily ordered their tongues to be cut out, he slipped and cut his hand on the Iron Throne, a severe injury that gave him a fever from infection. Some maesters feared that he would die, but Viserys lived after two of his fingers were removed by Maester Gerardys, and he would never sit on the Iron Throne again. Gerardys was recommended by Rhaenyra as a replacement for the dead Grand Maester Mellos, while Alicent recommended Maester Alfador, her family's maester. Viserys decided to appoint neither man as Grand Maester and deferred to the Citadel to fill the office, who chose Maester Orwyle. As Viserys' health gradually weakened, Otto filled the small council with members loyal to the greens, including Lord Larys Strong, Ser Tyland Lannister, and Ser Jasper Wylde. Lord Commander of the Kingsguard Criston Cole was also an ardent supporter of Alicent, with Orwyle being politically neutral and Lord Lyman Beesbury opposing the greens. Viserys passed away in his sleep in 129 AC, having been discovered by a servant who informed Alicent of his status. In the interim, Alicent did not disclose Viserys' death to the public and summoned the small council to a secret meeting.
==== Historical funding ==== Over the last century, the responsibility to allocate funding has shifted from the OD and Advisory Committee to the individual ICs and Congress increasingly set apart funding for particular causes. In the 1970s, Congress began to earmark funds specifically for cancer research, and in the 1980s there was a significant amount allocated for AIDS/HIV research. Funding for the NIH has often been a source of contention in Congress, serving as a proxy for the political currents of the time. During the 1980s, President Reagan repeatedly tried to cut funding for research, only to see Congress partly restore funding. The political contention over NIH funding slowed the nation's response to the AIDS epidemic; while AIDS was reported in newspaper articles from 1981, no funding was provided for research on the disease. In 1984 National Cancer Institute scientists found implications that "variants of a human cancer virus called HTLV-III are the primary cause of acquired immunodeficiency syndrome (AIDS)," a new epidemic that gripped the nation. In 1992, the NIH encompassed nearly 1 percent of the federal government's operating budget and controlled more than 50 percent of all funding for health research and 85 percent of all funding for health studies in universities. From 1993 to 2001 the NIH budget doubled. For a time, funding essentially remained flat, and for seven years after the 2008 financial crisis, the NIH budget struggled to keep up with inflation. In 1999 Congress increased the NIH's budget by $2.3 billion to $17.2 billion in 2000.
Sources: en.wikipedia.org
==== Deoxygenated hemoglobin ==== Deoxygenated hemoglobin (deoxyhemoglobin) is the form of hemoglobin without the bound oxygen. The absorption spectra of oxyhemoglobin and deoxyhemoglobin differ. The oxyhemoglobin has significantly lower absorption of the 660 nm wavelength than deoxyhemoglobin, while at 940 nm its absorption is slightly higher. This difference is used for the measurement of the amount of oxygen in a patient's blood by an instrument called a pulse oximeter. This difference also accounts for the presentation of cyanosis, the blue to purplish color that tissues develop during hypoxia. Deoxygenated hemoglobin is paramagnetic; it is weakly attracted to magnetic fields. In contrast, oxygenated hemoglobin exhibits diamagnetism, a weak repulsion from a magnetic field.
The epiphyseal arteries and osteogenic cells invade the epiphysis, depositing osteoclasts and osteoblasts which erode the cartilage and build bone, respectively. This occurs at both ends of long bones but only one end of digits and ribs.
As a modified atmosphere, pure or mixed with carbon dioxide, to nitrogenate and preserve the freshness of packaged or bulk foods (by delaying rancidity and other forms of oxidative damage). Pure nitrogen as food additive is labelled in the European Union with the E number E941. In incandescent light bulbs as an inexpensive alternative to argon. In fire suppression systems for Information technology (IT) equipment. In the manufacture of stainless steel. In the case-hardening of steel by nitriding. In some aircraft fuel systems to reduce fire hazard (see inerting system). To inflate race car and aircraft tires, reducing the problems of inconsistent expansion and contraction caused by moisture and oxygen in natural air. Nitrogen is commonly used during sample preparation in chemical analysis. It is used to concentrate and reduce the volume of liquid samples. Directing a pressurised stream of nitrogen gas perpendicular to the surface of the liquid causes the solvent to evaporate while leaving the solute(s) and un-evaporated solvent behind. Nitrogen can be used as a replacement, or in combination with, carbon dioxide to pressurise kegs of some beers, particularly stouts and British ales, due to the smaller bubbles it produces, which makes the dispensed beer smoother and headier. A pressure-sensitive nitrogen capsule known commonly as a "widget" allows nitrogen-charged beers to be packaged in cans and bottles. Nitrogen tanks are also replacing carbon dioxide as the main power source for paintball guns.
==== Urquía Carreño resigns ==== On August 18, 2024, a special session of more than a hundred Freemasons was called by Urquía Carreño to gather at the theatre hall of the Grand Lodge of Cuba, on the 3rd floor of the building. One Cuban Freemason told reporters that: "...he had manipulated a circus to stay in office. He's shameless, they were lies after lies; all the brothers were standing asking him to hand over the keys to his office." The people in the theatre started chanting: "Hand over and leave!" After tensions had escalated, Urquía Carreño left the theatre to go back to his office. However, the Freemasons followed him up to the eleventh floor. Urquía Carreño agreed to meet with representatives of the delegation in his office, so three men were chosen to represent them. The three men sat with three of Urquía Carreño's men, and discussed terms of negotiation, while the rest of the delegation waited in the hallway. On August 18, 2024, after two hours of negotiation, Urquía Carreño finally relented and agreed to tender his resignation. In his resignation, he said that it was: "for the good of the institution." Mayker Filema Duarte assumed the role of Acting Grand Master until an election could be held, and immediately launched a financial audit of the entire Grand Lodge. At the beginning of September, Filema Duarte accused Urquía Carreño of the theft of yet another $MN2,116,555.33, stolen sometime between January and August 2024.
Sources: en.wikipedia.org
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.
No. It also serves as a substrate for signaling and DNA-repair enzymes such as sirtuins and PARPs. Those reactions consume NAD+ and connect its availability to cellular regulation. Energy transfer remains its most abundant known role.
NAD+ is the oxidized electron acceptor, while NADH is the reduced electron carrier. They form a reversible redox pair and differ by a hydride ion. Cells maintain different ratios of the two depending on conditions and compartment.
NAD+ is the oxidized form, while NADH is the reduced form carrying an additional hydride equivalent. The pair participates in reversible electron transfer reactions. Their ratio helps indicate the redox state of a compartment.