redox coenzyme comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-08-21. 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.
Laboratory measurement of NAD+ often begins with rapid quenching of cell or tissue samples to prevent enzymatic conversion. Acidic or alkaline extraction can precipitate proteins, but the chosen method affects recovery of oxidized and reduced forms. Enzymatic cycling assays provide high sensitivity by amplifying a NAD+-dependent reaction. High-performance liquid chromatography and mass spectrometry offer separation and structural confirmation. Each method has trade-offs in throughput, specificity, and the ability to distinguish NAD+ from close analogues.
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.
| 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+ |
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.
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.
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.
In order to avoid continuous activation of receptors on the post-synaptic or target cell, neurotransmitters must be removed from the synaptic cleft. Neurotransmitters are removed through one of three mechanisms:
Currently the railway has been under-grounded: the avenue will be enlarged and have same architecture style of southern Corso Inghilterra in downtown, becoming one of the major avenues of Turin. The northern part of the district was part of the former industrial district of Turin, recently reconverted to a park called Parco Dora. Mainly, in San Donato the portion reconverted was the one occupied by the plant of Michelin (west of Via Livorno) and Fiat ironwork plants (on the East). Differently for other portions of Parco Dora, this part has been totally reconverted to park without letting any evidence of the industrial area except for the cooling tower which stands along Corso Umbria and became a symbol of the park. Works are completed in the western area, where Corso Mortara has been closed to traffic and moved just a bit northern and covered by an artificial tunnel. It is possible to access the southern shore of the River Dora. South of the park, an interesting architecture of different levels is hosting a new shopping mall called Centro Commerciale Parco Dora. East of Via Livorno, works are still partially in progress, with the River Dora still to be uncovered by a big slab, on which the Fiat plants used to stand). West of Via Livorno, the Environment Park is a research centre for renewable energy.
=== 30 November === Ursula von der Leyen, president of the European Commission, suggested the creation of a UN court to investigate war crimes committed by Russia. Russia does not recognize the International Criminal Court, so the European Commission proposed two possible alternative ways to hold Russia accountable: either to create a court that would be set up by international treaties, or to create an international court with a number of judges from several countries. She estimated the war damage to Ukraine is about 600 billion Euros. She proposed a financial plan to help pay for this. She pointed out that the EU had frozen 300 billion Euros worth of Russian central bank reserves and 20 billion Euros worth of money belonging to Russian oligarchs, which she suggested should be invested. The investments could be given to Ukraine when sanctions are lifted. The original statement by Ursula von der Leyen included a claim that 100,000 Ukrainian soldiers and 20,000 Ukrainian civilians have been killed so far in the war. This angered Ukrainian military officials, who said that the death toll was classified information. In response, the European Commission edited the video of von der Leyen's speech to remove this information. Official publications of the text of the speech were also edited to omit the numbers.
Sources: en.wikipedia.org
Gorgonzola blue cheese takes its name from the village of Gorgonzola in Italy where it was first made. Belonging to the family of Stracchino cheeses, Gorgonzola is a whole milk, white, and "uncooked" cheese. This blue cheese is inoculated with Penicillium glaucum which, during ripening, produces the characteristic of blue-green veins. There are two variants with different odor: natural and creamy Gorgonzola. 63 components in natural Gorgonzola cheese and 52 components in creamy Gorgonzola cheese contribute to odor with 2-nonanone, 1-octen-3-ol, 2-heptanol, ethyl hexanoate, methylanisole and 2-heptanone being the prominent compounds for odor in both cheeses.
=== Moorosi's Revolt === The Cape government immediately began to undermine the traditional power structures of the Basuto. Under the terms of the Mercantile Law of 1871, trade was restricted to those in possession of a government license. In 1872, it implemented the responsible government system, under which the governor's legislative powers were transferred to the Cape Parliament. The Basuto were neither consulted nor formally informed. They were also barred from participating in the parliament unless they accepted to completely abandon their traditional laws and customs, a condition they deemed unacceptable. From that point on, Letsie I and the Governor's Agent in Basutoland, Colonel Griffith, became embroiled in a power struggle. The Cape-appointed magistrates were given autonomy in enforcing colonial legislation as they saw fit. The magistrates interfered with land disputes, when the Basuto previously held exclusive rights on land allocation. Authority over marriage disputes and disputes between the Basuto and white residents were likewise transferred to magistrates' courts. Basuto prophetesses claimed to have communicated in their dreams with the spirit of Moshoeshoe, who had become increasingly angry with the white man's interference in Basuto affairs. The southern corner of Basutoland was settled by the Baphuthi people. Their chief Moorosi was once a tributary ruler of Moshoeshoe who had reluctantly merged his territory with British Basutoland in 1869.
selectable marker A gene or other genetic material whose expression in cultured cells confers a selective advantage in the culture environment, causing cells expressing the gene to have one or more traits suitable for artificial selection. Selectable markers are widely used in the laboratory as a type of reporter, usually to indicate the success of a procedure meant to introduce exogenous DNA into a host cell such as transfection or transformation. A common example is an antibiotic resistance gene which is transformed into competent bacterial cells cultured on a medium containing the particular antibiotic, such that only those cells which have successfully taken up and expressed the gene are able to survive and grow into colonies.
Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus. This strength results from the covalent sp2 bonds formed between the individual carbon atoms. In 2000, a multiwalled carbon nanotube was tested to have a tensile strength of 63 GPa (9,100,000 psi). (For illustration, this translates into the ability to endure tension of a weight equivalent to 6,422 kilograms-force (62,980 N; 14,160 lbf) on a cable with cross-section of 1 mm2 (0.0016 sq in)). Further studies, such as one conducted in 2008, revealed that individual CNT shells have strengths of up to ≈100 GPa (15,000,000 psi), which is in agreement with quantum/atomistic models. Because carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm3, its specific strength of up to 48,000 kN·m/kg is the best of known materials, compared to high-carbon steel's 154 kN·m/kg. Although the strength of individual CNT shells is extremely high, weak shear interactions between adjacent shells and tubes lead to significant reduction in the effective strength of multiwalled carbon nanotubes and carbon nanotube bundles down to only a few GPa. This limitation has been recently addressed by applying high-energy electron irradiation, which crosslinks inner shells and tubes, and effectively increases the strength of these materials to ≈60 GPa for multiwalled carbon nanotubes and ≈17 GPa for double-walled carbon nanotube bundles. CNTs are not nearly as strong under compression.
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.
Many enzymes consume or produce NAD+ within seconds after a sample is collected. Quenching stops those reactions and helps preserve the ratio between oxidized and reduced forms. The exact quenching method depends on the tissue or cell type and the analytes of interest.