The short version of Redox cofactor fits in a sentence. The long version — which is the one that helps — is below.
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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.
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.
Laboratory measurement of NAD+ usually begins with rapid sample quenching because the molecule can change form after collection. Enzymatic cycling assays amplify signal through coupled reactions and are suited to small samples. High-performance liquid chromatography with ultraviolet detection separates NAD+ from related nucleotides. Liquid chromatography-mass spectrometry offers higher specificity and can distinguish NAD+ from close analogs. Each method has trade-offs in sensitivity, throughput, and equipment needs, so reported values depend heavily on extraction and detection choices.
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.
| Property | Value | Notes |
|---|---|---|
| IUPAC name | Nicotinamide adenine dinucleotide | Oxidized dinucleotide form |
| CAS Registry Number | 53-84-9 | Common entry for beta-NAD+ |
| Molecular formula | C21H27N7O14P2 | Free acid form |
| Molar mass | 663.43 g/mol | Calculated for free acid |
| Water solubility | Freely soluble | Charged dinucleotide; less soluble in organic solvents |
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.
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.
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.
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.
Besides economic and social costs to implement anti–money-laundering laws, improper attention to data protection practices may entail disproportionate costs to individual privacy rights. In June 2011, the data-protection advisory committee to the European Union issued a report on data protection issues related to the prevention of money laundering and terrorist financing, which identified numerous transgressions against the established legal framework on privacy and data protection. The report made recommendations on how to address money laundering and terrorist financing in ways that safeguard personal privacy rights and data protection laws. In the United States, groups such as the American Civil Liberties Union have expressed concern that money laundering rules require banks to report on their own customers, essentially conscripting private businesses "into agents of the surveillance state".
Manifold are thy shapings, Providence! / Many a hopeless matter gods arrange / What we expected never came to pass / What we did not expect the gods brought to bear / So have things gone, this whole experience through! This deliberate murder of her children by Medea appears to be Euripides' invention, although some scholars believe Neophron created this alternate tradition. Her filicide would go on to become the standard for later writers. Pausanias, writing in the late 2nd century AD, records five different versions of what happened to Medea's children after reporting that he has seen a monument for them while traveling in Corinth.
Israel started evacuating the settlements located close to the border with Lebanon in October 2023 with more than 60 thousand evacuated by April 2024. In the early afternoon of 21 October, several rockets were fired from Lebanon toward the Shebaa Farms; there were no injuries. The IDF conducted a drone strike on the team of militants that launched the rockets. A short while later, anti-tank guided missiles were fired from Lebanon toward Margaliot and Hanita; two foreign workers were injured. The IDF conducted airstrikes against the missile teams. In the evening, another anti-tank guided missile was fired from Lebanon toward Bar'am. One IDF soldier was seriously injured and two others suffered minor injuries. The IDF responded with several airstrikes in southern Lebanon, some of which targeted other missile teams preparing attacks. The IDF conducted airstrikes against two Syrian military positions on 24 October in southwestern Syria, marking the first time the IDF publicly targeted the Syrian military since the Israel–Gaza war began. Hezbollah attacked 19 IDF military sites with missiles and artillery shells and fired one-way attack drones at an IDF position for the first time since the conflict began.
Sources: en.wikipedia.org
Around 2010, large lithium-ion batteries were introduced in place of other chemistries to power systems on some aircraft; as of January 2014, there had been at least four serious lithium-ion battery fires, or smoke, on the Boeing 787 passenger aircraft, introduced in 2011, which did not cause crashes but had the potential to do so. UPS Airlines Flight 6 crashed in Dubai after its payload of lithium batteries spontaneously ignited during flight and severely damaged crucial systems of the aircraft. To reduce fire hazards, research projects are intended to develop non-flammable electrolytes.
==== Off-line ==== Off-line storage requires some direct action to provide access to the storage media: for example, inserting a tape into a tape drive or plugging in a cable. Because the data is not accessible via any computer except during limited periods in which they are written or read back, they are largely immune to on-line backup failure modes. Access time varies depending on whether the media are on-site or off-site.
. The carbon-carbon bond lengths of benzene are 140 picometers (pm) long, which are greater than a C=C double bond (135 pm) but shorter than a C-C single bond (147 pm). In terms of bonding, the molecular orbital (MO) description involves three bonding pi-MOs. A valence bond description involves a superposition of resonance structures. Its considerable stability and distinctive chemical properties are manifested in the phenomenon of aromaticity. To reflect the delocalized nature of the bonding, benzene is often depicted with a circle inside a hexagonal arrangement of carbon atoms.
Sources: en.wikipedia.org
== Moisture content == Water activity is related to water content in a non-linear relationship known as a moisture sorption isotherm curve. These isotherms are substance- and temperature-specific. Isotherms can be used to help predict product stability over time in different storage conditions.
To gain regulatory approval, the milbemycin oxime/lufenuron heartworm treatment was divested to Virbac. In March 2015, the company announced it would join Hanmi Pharmaceutical in developing and commercializing Hanmi's phase I Bruton's tyrosine kinase inhibitor HM71224 in a deal that could yield $690 million. A day later, however, the company announced another deal with China's Innovent Biologics to co-develop and commercialize at least three of Innovent's treatments over the next decade, in a deal which could generate up to $456 million; the collaboration was subsequently expanded in 2022, according to Innovent. As part of the deal, the company contributed its c-Met monoclonal antibody, and Innovent contributed a monoclonal antibody, which targets CD-20. The second compound from Innovent is a preclinical immunooncology molecule. The following week, the company announced it would restart its collaboration with Pfizer surrounding the Phase III trial of Tanezumab. Pfizer is expected to receive an upfront sum of $200 million from the company. In April 2015, Lilly engaged CBRE Group to sell its biomanufacturing facility in Vacaville, California, a 52 acres (0.21 km2) campus and facility that is one of the largest biopharmaceutical manufacturing centers in the US. In July 2016, Lechleiter retired and was succeeded by David Ricks. In January 2017, Elanco, at the time a subsidiary of Lilly, acquired Boehringer Ingelheim Vetmedica, a subsidiary of Boehringer Ingelheim's US feline, canine, and rabies vaccines portfolio, for $885 million.
Iced tea can be purchased, like soda, in canned or bottled form at vending machines and convenience stores; usually, this pre-made tea is sweetened with corn syrup, and sometimes some other flavoring, such as lemon or raspberry, is added. Also, like other soft drinks, it can be purchased as a fountain drink, though in some establishments it is pumped from a bag-in-box, and in others, it is simply poured from a separate container that contains freshly brewed tea. In restaurants, iced tea is usually served unsweetened except in the Southeastern United States where iced tea is much more common and is available both sweet and unsweetened and "iced tea" is often considered to be "sweet tea" unless otherwise specified. The reason for the pre-sweetening is that it may be difficult to dissolve sugar in iced tea, even with constant stirring. The result can be insufficiently sweetened tea or gritty, undissolved sugar crystals in the tea. In the Northern United States and the Western United States, "tea" generally means the hot beverage and iced tea is referred to by name. Iced tea's popularity in the United States has led to an addition to standard cutlery sets; the iced tea spoon is a standard flatware teaspoon, but with a long handle, suitable for stirring sugar into the taller glasses commonly used for iced tea.
=== Shop N Save === Dairy Farm Singapore acquired Shop N Save in 2003, 35 stores from QAF and Belgian retailer, Delhaize. It was a former discount supermarket chain in Singapore, operating 50 stores located across the island in HDB estates and suburban malls. It sells a range of cheap products and fresh food. In 2013, it was merged with Giant.
Sources: en.wikipedia.org
NAD+ is the oxidized form, while NADH is the reduced form carrying an added hydride. The two form a redox pair that cells use in many energy-yielding reactions.
NAD+ is a small organic cofactor, not a protein or enzyme. It binds temporarily to enzymes such as dehydrogenases to assist electron transfer.
Intact NAD+ is generally not taken up efficiently by most cells because it is charged and water-soluble. Cells often rely on precursors such as nicotinamide or nicotinamide riboside to produce NAD+ internally.
Common methods include enzymatic cycling assays, HPLC with UV detection, and LC-MS. The choice depends on sample size, specificity needs, and available equipment. Rapid quenching before analysis is important because NAD+ and NADH can interconvert.