Redox coenzyme 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 2025-12-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Nicotinamide adenine dinucleotide (oxidized) | Often shortened to NAD+ |
| Chemical class | Dinucleotide | Contains nicotinamide and adenine moieties |
| Molecular formula | C21H27N7O14P2 | Free acid form; charge depends on pH |
| Molar mass | About 663.43 g/mol | Calculated for C21H27N7O14P2 |
| CAS number | 53-84-9 | Common identifier for beta-NAD+ |
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.
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.
Cardona completed his PhD at the University of Barcelona (2000–2005), where he studied developmental biology. He then undertook postdoctoral research on Drosophila neuroanatomy at UCLA (2005–2008). Between 2008 and 2011, Cardona was a Group Leader at the Institute of Neuroinformatics, jointly run by the University of Zurich and ETH Zurich. During this period, he developed computational and image-processing methods for neural circuit reconstruction and co-founded two influential open-source platforms that have become widely adopted in the neuroscience community. Cardona joined the Howard Hughes Medical Institute (HHMI) Janelia Research Campus in 2012, serving as Group Leader until 2019. In 2019, he was appointed Programme Leader at the MRC Laboratory of Molecular Biology and Professor at the University of Cambridge, where he leads research on whole-brain connectomics, circuit development, and structure–function relationships in neural systems.
year is the laboratory's determination of the age of the sample, in radiocarbon years range is the laboratory's estimate of the error in the age, at 1σ confidence. 'BP' stands for "before present", referring to a reference date of 1950, so that "500 BP" means the year AD 1450. For example, the uncalibrated date "UtC-2020: 3510 ± 60 BP" indicates that the sample was tested by the Utrecht van der Graaff Laboratorium ("UtC"), where it has a sample number of "2020", and that the uncalibrated age is 3510 years before present, ± 60 years. Related forms are sometimes used: for example, "2.3 ka BP" means 2,300 radiocarbon years before present (i.e. 350 BC), and "14C yr BP" might be used to distinguish the uncalibrated date from a date derived from another dating method such as thermoluminescence. Calibrated 14C dates are frequently reported as "cal BP", "cal BC", or "cal AD", again with 'BP' referring to the year 1950 as the zero date. Radiocarbon gives two options for reporting calibrated dates. A common format is "cal date-range confidence", where:
=== Self discharge === Batteries gradually self-discharge even if not connected and delivering current. Li-ion rechargeable batteries have a self-discharge rate typically stated by manufacturers to be 1.5–2% per month. The rate increases with temperature and state of charge. A 2004 study found that for most cycling conditions self-discharge was primarily time-dependent; however, after several months of stand on open circuit or float charge, state-of-charge dependent losses became significant. The self-discharge rate did not increase monotonically with state-of-charge, but dropped somewhat at intermediate states of charge. Self-discharge rates may increase as batteries age. In 1999, self-discharge per month was measured at 8% at 21 °C, 15% at 40 °C, 31% at 60 °C. By 2007, monthly self-discharge rate was estimated at 2% to 3%, and 2–3% by 2016. By comparison, the self-discharge rate for NiMH batteries dropped, as of 2017, from up to 30% per month for previously common cells to about 0.08–0.33% per month for low self-discharge NiMH batteries, and is about 10% per month in NiCd batteries.
Sources: en.wikipedia.org
== Structure == Pseudopeptidoglycan is composed of two sugars, N-acetylglucosamine and N-acetyltalosaminuronic acid. These sugars are made of different amino acids, and the peptide cross-links within pseudopeptidoglycan are formed with different amino acids. The peptide bond is formed between the lysine of a N-acetyltalosaminuronic acid and a glutamine of a parallel N-acetyltalosaminuronic acid. Pseudopeptidoglycan, like peptidoglycan in bacteria, forms a mesh-like layer outside of the plasma membrane of the archaea.
On the campaign trail, Talarico often tells a story from when he was a middle school teacher about a student who was kicked out of fifth grade for bringing a knife to school and threatening his teacher. Talarico later had the boy as a student and said that his behavior improved before he got into a fight and was kicked out of school again. Talarico blamed the events on the Texas legislature cutting public school funding, which he said led to the school's therapist being laid off. Since Talarico won the nomination, his campaign has been noted for its record-breaking fundraising. In the first quarter of 2026, it raised over $27 million, more than any Senate campaign ever for that period, and more than double the totals raised by the two previous Democratic nominees' campaigns in Texas during the same period, with Colin Allred raising $9.5 million in the first quarter of 2024, and Beto O'Rourke raising $6.7 million in 2018.
In obese people, the relative proportion of Firmicutes (Gram-positive bacteria) in gut microbiota is increased resulting in greater conversion of the non-genotoxic primary bile acid, cholic acid, to carcinogenic deoxycholate. Exercise decreases deoxycholate in the colon. Humans whose level of physical activity placed them in the top third had a 17% decrease in fecal bile acid concentration compared to those whose level of physical activity placed them in the lowest third. Rats provided with an exercise wheel had a lower ratio of secondary bile acids to primary bile acids than sedentary rats in their feces. There is a positive association of exercise and physical activity with cancer prevention, tolerance to cancer-directed therapies (radiation and chemotherapy), reduction in recurrence, and improvement in survival.
Sources: en.wikipedia.org
is known as the Lamb vector. For the special case of an incompressible flow, the pressure constrains the flow so that the volume of fluid elements is constant: isochoric flow resulting in a solenoidal velocity field with
India: The Ministry of External Affairs asked Indian nationals to avoid non-essential travel to Venezuela after US action and asked that nationals already in Venezuela remain in contacts with the Indian embassy in Caracas. It urged those involved to resolve conflicts amicably through communication in order to maintain regional peace and stability. Indonesia: Yvonne Mewengkang, spokesperson for the Ministry of Foreign Affairs, called for "de-escalation and dialogue" while protecting citizens, emphasizing "the importance of respecting international law and the principles of the UN Charter." It was monitoring the situation for the safety of Indonesian nationals. It later issued a formal statement on 4 January 2026, calling on all relevant parties to promote a peaceful settlement through de-escalation measures and dialogue, while continuing to prioritize the protection of civilians and respecting political affairs, ways-of-life, and Venezuela's sovereignty. The ministry also asked Indonesian nationals in Venezuela, especially Caracas, to keep calm and remain in contact with the Indonesian Embassy in Caracas. On 5 January 2026, the First Commission of the House of Representatives formally requested the foreign ministry to prepare emergency evacuation procedures if the situation worsens. Iran: The Ministry of Foreign Affairs issued a statement strongly condemning the US attack on Venezuela, calling on the United Nations and other states to respond to what it described as a blatant violation of the country's national sovereignty and territorial integrity.
In Mexico, for example, the illicit trafficking of cannabis is thought to constitute the majority of many of the cartels' earnings, and the main way in which the cartels finance many other illegal activities; including the purchase of other illegal drugs for trafficking, and for acquiring weapons that are ultimately used to commit murders (causing a burgeoning in the homicide rates of many areas of the world, but particularly Latin America). Some studies show that the increased legalization of cannabis in the United States (beginning in 2012 with Washington Initiative 502 and Colorado Amendment 64) has led Mexican cartels to smuggle less cannabis in exchange for more heroin.
=== Long-overlap-based assembly === There have been a variety of long-overlap-based assembly methods developed in recent years. One of the most commonly used methods, the Gibson assembly method, was developed in 2009, and provides a one-pot DNA assembly method that does not require the use of restriction enzymes or integrases. Other similar overlap-based assembly methods include Circular Polymerase Extension Cloning (CPEC), Sequence and Ligase Independent Cloning (SLIC) and Seamless Ligation Cloning Extract (SLiCE). Despite the presence of many overlap assembly methods, the Gibson assembly method is still the most popular. Besides the methods listed above, other researchers have built on the concepts used in Gibson assembly and other assembly methods to develop new assembly strategies like the Modular Overlap-Directed Assembly with Linkers (MODAL) strategy, or the Biopart Assembly Standard for Idempotent Cloning (BASIC) method.
Sources: en.wikipedia.org
The plus sign indicates the oxidized form of nicotinamide adenine dinucleotide, which can accept electrons. When it accepts electrons, it becomes NADH. The two forms together support redox reactions in cells.
No. NAD+ is the oxidized form and NADH is the reduced form. They differ by two electrons and a proton equivalent, and cells interconvert them during metabolism.
Yes. NAD+ is present in all living cells and is required for fundamental metabolic reactions. Its concentration varies by tissue, compartment, and time.
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.