Everything below concerns salvage pathway. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-09-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| 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+ |
Laboratory handling of NAD+ follows standard practices for hygroscopic fine chemicals. Personnel typically avoid inhalation and skin contact, use gloves and eye protection, and work in a ventilated area. Quality control may include ultraviolet absorbance at the nicotinamide maximum, chromatographic purity, water content, and identity confirmation by mass spectrometry. Because commercial preparations can contain counterions, residual solvents, or related nucleotides, a certificate of analysis helps verify the material. Researchers should confirm that the form supplied matches the intended assay.
Measuring NAD+ in biological samples requires care because the molecule is chemically reactive and present at low concentrations in some tissues. Common approaches include enzymatic cycling assays, high-performance liquid chromatography, and liquid chromatography coupled to mass spectrometry. Each method has different sensitivity and specificity, and sample preparation can affect results. Acidic or alkaline extraction steps are used in some protocols, but the choice depends on the analyte and matrix. No single method is universally optimal for every tissue or fluid.
Solid NAD+ is relatively stable when kept dry, cold, and protected from light. Aqueous solutions are more vulnerable to hydrolysis and can lose activity during repeated freeze-thaw cycles or prolonged storage at ambient temperature. Stability depends on pH, ionic strength, and the presence of degrading enzymes or metal ions. For many laboratory uses, aliquots are stored frozen and thawed only once. Exact degradation rates vary by matrix, so stability should be checked for each application rather than assumed.
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.
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.
Commercial NAD+ is supplied as a solid, often as the free acid or a salt, and purity is verified by chromatographic methods. Laboratories typically store it desiccated at minus 20 degrees Celsius or below. Working solutions are prepared fresh because even sterile aqueous solutions can lose activity over hours to days depending on pH and temperature. Documentation may include a certificate of analysis, an assay value, and a recommended retest date. Researchers should verify identity and purity when results depend on precise cofactor concentrations.
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.
The female movement of the 1960s, combined with Title IX and the all around fitness revolution, gave birth to new alternative perspectives of feminine beauty that included an athletic physique of toned muscle. This athletic physique was found in various popular media outlets such as fashion magazines. Female bodybuilders changed the limits of traditional femininity as their bodies showed that muscles are not only just for men.
=== May 2009 === On 18 May 2009, the SENSEX surged up 2,110.79 points to close at 14,285.21, from its previous closing of 12,174.42, for its largest single day rally. Less than a month later, on 4 June 2009, the SENSEX would cross the 15,000 mark. However, the SENSEX remained volatile during the summer of 2009. The SENSEX plunged by 869.65 points on 6 July 2009, the day of Union Budget presentation in Parliament on concerns over high fiscal deficit. This was the biggest Budget-day loss for the index. On 17 August 2009, the SENSEX lost 626.71 points. Once again, the SENSEX would recover from the volatility. On 7 September 2009, the SENSEX crossed the 16,000 mark, closing at 16,016.32 points. The index would gain 3,000 points over the next 12 months, as the SENSEX crossed the 19,000 mark on 13 September 2010, closing at 19,208.33 points.
=== Oxygen carriers === Hemoglobin, which is the principal oxygen-carrier in humans, has four subunits in which the iron(II) ion is coordinated by the planar macrocyclic ligand protoporphyrin IX (PIX) and the imidazole nitrogen atom of a histidine residue. The sixth coordination site contains a water molecule or a dioxygen molecule. By contrast the protein myoglobin, found in muscle cells, has only one such unit. The active site is located in a hydrophobic pocket. This is important as without it the iron(II) would be irreversibly oxidized to iron(III). The equilibrium constant for the formation of HbO2 is such that oxygen is taken up or released depending on the partial pressure of oxygen in the lungs or in muscle. In hemoglobin the four subunits show a cooperativity effect that allows for easy oxygen transfer from hemoglobin to myoglobin. In both hemoglobin and myoglobin it is sometimes incorrectly stated that the oxygenated species contains iron(III). It is now known that the diamagnetic nature of these species is because the iron(II) atom is in the low-spin state. In oxyhemoglobin the iron atom is located in the plane of the porphyrin ring, but in the paramagnetic deoxyhemoglobin the iron atom lies above the plane of the ring. This change in spin state is a cooperative effect due to the higher crystal field splitting and smaller ionic radius of Fe2+ in the oxyhemoglobin moiety. Hemerythrin is another iron-containing oxygen carrier. The oxygen binding site is a binuclear iron center.
=== Human civilization: a model for extrapolation === Kardashev poses the following question: "Is it possible to describe the development of a civilization in general terms over large cosmological periods?" Now many of the fundamental parameters that characterize the development of civilization on Earth are growing exponentially. In the field of energy, astronomer Don Goldsmith estimated that the Earth receives about one billionth of the Sun's energy, and that humans use about one millionth of it. So we consume about one millionth of a billionth of the Sun's total energy. Since human expansion is exponential, we can determine how long it will take for humanity to go from Type II to Type III according to Michio Kaku. Thus, the rate of development of our own world remains the only criterion for extrapolating the state of civilizations older than humanity. The same is true for social values and basic needs according to Ashkenazi. Therefore, the time to double technical knowledge is about 10 years, and to double energy output, available reserves, and population is about 25 years. Two scenarios are then possible: spatial expansion or energy stagnation, the latter being possible only for 125 years, according to Kardashev, using the following relationship
Sources: en.wikipedia.org
=== Nuclear fission === Einsteinium has a high rate of nuclear fission that results in a low critical mass. This mass is 9.89 kilograms for a bare sphere of 254Es, and can be lowered to 2.9 kg by adding a 30-centimeter-thick steel neutron reflector, or even to 2.26 kg with a 20-cm-thick reflector made of water. However, even this small critical mass far exceeds the total amount of einsteinium isolated so far, especially of the rare 254Es.
== Charlie Hebdo Speech in Cologne (2015) == On January 14, 2015, Kermani delivered a speech at the Appellhofplatz in Cologne during the memorial rally “We Are Charlie – For Freedom and Diversity.” The rally was organized by the coalition Köln stellt sich quer [Cologne puts up resistance] in memory of the victims of the Islamist-motivated terrorist attack on the editorial office of the satirical magazine Charlie Hebdo in Paris. Garnering nationwide attention, Kermani’s speech was widely discussed. It directed itselfprimarily at Muslims and the frequently repeated argument that Islam has nothing to do with terror and violence. At the same time, Kermani advocated for assigning greater importance to compassion and, first and foremost, to remaining free.
By enabling three-dimensional movement within DMF, the technology can be used even more extensively in biological applications, as it could more accurately mimic 3-D microenvironments. A large benefit of employing this type of method is that it allows for two different environments to be accessible by the droplet, which can be taken advantage of by splitting the microfluidic tasks among the two surfaces. For example, while the lower plane can be used to move droplets, the upper plate can carry out the necessary chemical and/or biological processes. This advantage can be translated into practical experiment protocols in the biological community, such as coupling with DNA amplification. This also allows for the chip to be smaller, and to give researchers more freedom in designing platforms for microdroplet analysis.
BRD-6929, also widely known as "compound 60" (Cpd-60 or Cmpd60), is a histone deacetylase (HDAC) inhibitor which is used in scientific research. It has been described in the past as the prototypical selective HDAC1 and HDAC2 inhibitor. However, subsequent findings suggest that BRD-6929 may not actually be selective for HDAC1 and HDAC2 over HDAC3.
=== May === 1 May – Bob Brockie, biologist, cartoonist (National Business Review) and columnist (Dominion Post) (born 1932). 2 May – Sir Bob Jones, property magnate, writer, and politician, founder of the New Zealand Party (1983) (born 1939). 5 May Shane Richardson, motorcycle racer (born c. 1996). Shane Solomon, lawyer and Māori leader (Waikato Tainui) (born 1963). 6 May – Bill McCaw, rugby union player (Southland, national team), oldest living All Black (since 2023) (born 1927). 9 May – Fred Graham, rugby union player (New Zealand Māori), educator and sculptor, Te Tohu mō Te Arikinui Dame Te Atairangikaahu (2017), Arts Foundation of New Zealand Icon (since 2018) (born 1928). 13 May – Danny Lendich, businessman and midget car racing team owner, introduced Wendy's to New Zealand (1988) (born 1944). 14 May – Lionel Hill-Smith, Empire Games hurdler (1950) (born 1929). 15 May – Durham Havill, local politician and businessman, Mayor of Westland (1989–1998) (born 1944). 16 May – Tuppy Diack, rugby union player (Otago, Southland, national team) and administrator, president of the Otago Rugby Football Union (2005) (born 1930). 17 May – Clive Rennie, educator, principal of Rangitikei College (1986–1991), Mountainview High School (1997–2000) and Otago Boys' High School (2000–2014) (born 1944). 18 May – John Simpson, silversmith and fine arts academic (University of Canterbury) (born 1925). 21 May – Frank Gibson Jr., jazz drummer and drum tutor (born 1946). 23 May – Roger Bridge, businessman and political party official (National) (born 1958).
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 a coenzyme found in all living cells. It carries electrons in metabolic reactions and also serves as a substrate for enzymes involved in signaling and DNA repair. Its oxidized and reduced forms are central to energy metabolism.