The short version of Dinucleotide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
| 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. |
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.
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.
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.
== Pharmaceutical manufacture == Calcitonin was extracted from the ultimobranchial glands (thyroid-like glands) of fish, particularly salmon. Salmon calcitonin resembles human calcitonin, but is more active. At present, it is produced either by recombinant DNA technology or by chemical peptide synthesis. The pharmacological properties of the synthetic and recombinant peptides have been demonstrated to be qualitatively and quantitatively equivalent.
=== Guest appearances === Snobs (13 January 2000) – 1 episode Loose Women (16 September 2011, 1 March 2012, 26 April 2013, 3 October 2013, 24 February 2014, 4 February 2016, 4 March 2016, 3 March 2017, 6 April 2017, 7 September 2017, 2 March 2018, 27 June 2018, 11 February 2019, 20 February 2019, 19 March 2019, 6 August 2020) – 16 episodes I'm a Celebrity...Get Me Out of Here! NOW! (23–25 November 2011, 16 November 2015) – 4 episodes Peter Andre: My Life (14 December 2011) – 1 episode That Sunday Night Show (8 January 2012) – 1 episode Celebrity Juice (15 March 2012, 9 May 2013, 11 April 2019, 24 October 2019, 12 November 2020) – 5 episodes This Morning (30 March 2012, 2 April 2012, 4 April 2012, 31 August 2012, 19 September 2012, 18 January 2013, 5 April 2013, 19 April 2013, 24 April 2013, 28 November 2014, 3 December 2014, 4 December 2014, 13 May 2015, 5 February 2016, 4 July 2016, 2 August 2016, 30 April 2018, 1 October 2018, 7 January 2019, 23 January 2019, 4 February 2019, 11 February 2019, 14 August 2019, 18 December 2019, 28 June 2024) – 25 episodes The Big Quiz (15 April 2012) – 1 episode 8 Out of 10 Cats (15 June 2012, 25 January 2013, 28 January 2020) – 3 episodes Big Brother's Bit on the Side (4 July 2012, 28 July 2013, 13 May 2015, 16 June 2017) – 4 episodes Let's Do Lunch with Gino & Mel (29 August 2012) – 1 episode Celebrity Big Brother's Bit on the Side (6 September 2012, 9 January 2013, 1 September 2013, 19 August 2014, 29 January 2015, 2 February 2016, 4–5 February 2016, 1 August 2017) – 9 episodes Fake Reaction (3 January 2013) – 1 episode 8 Out of 10 Cats Does Deal or No Deal (4 January 2013) – 1 episode Food Glorious Food (24 April 2013) – 1 episode Sunday Side Up (29 December 2013) – 1 episode Who's Doing the Dishes? (3 October 2014) – 1 episode Phillip's Live 24-Hour TV Marathon (1 December 2014) – 1 episode Mel & Sue (14 January 2015) – 1 episode If Katie Hopkins Ruled the World (6 August 2015) – 1 episode Kendra on Top (21 August 2015) – 1 episode Keep It in the Family (22 August 2015) – 1 episode Safeword (27 August 2015) – 1 episode Tina Malone: My New Body (1 October 2015) – 1 episode Tricked (27 October 2015) – 1 episode The Wright Stuff (4 February 2016) – 1 episode Virtually Famous (8 March 2016) – 1 episode In Therapy (5 July 2016) – 1 episode It's Not Me, It's You (29 July 2016) – 1 episode Sky News (25 October 2016, 6 September 2024) – 2 episodes Alan Carr's Specstacular (31 December 2016) – 1 episode Through the Keyhole (4 February 2017) – 1 episode BBC Radio 1 Teen Awards (22 October 2017, 21 October 2018) Celebrity 100% Hotter (25 January 2018) – 1 episode The Generation Game (1 April 2018) – 1 episode Livin' with Lucy (10 September 2018) – 1 episode ReFreshers Week Presented By Strongbow (1 October 2018) – 1 episode Your Face or Mine? (3 October 2018) – 1 episode Good Morning Britain (30 October 2018, 19 December 2018, 4 February 2019, 1 April 2019, 24 June 2019, 7 August 2019, 13 November 2019, 25 November 2019, 8 December 2020) – 9 episodes I'll Get This (4 December 2018) – 1 episode Lorraine (4 January 2019, 18 January 2019, 23 January 2019, 8 March 2019, 9 September 2019, 30 September 2019, 15 November 2019, 11 December 2023) – 8 episodes The Jonathan Ross Show (9 March 2019) – 1 episode The Real Housewives of Cheshire (22 April 2019, 11 November 2019) – 2 episodes The Crystal Maze (21 June 2019) – 1 episode Celebrity Catchphrase (31 August 2019) – 1 episode MTV Cribs UK (16 September 2019, 7 December 2020) – 2 episodes Dancing on Ice at Christmas (22 December 2019) – 1 episode The Big Narstie Show (7 February 2020) – 1 episode Inside Missguided: Made in Manchester (12 August 2020) – 1 episode Rolling In It (15 August 2020) – 1 episode Shopping with Keith Lemon (25 October 2020) – 1 episode Celebrity Supply Teacher (17 November 2020) – 1 episode The Wheel (19 December 2020, 18 December 2021) – 2 episodes Dancing on Ice (24 January 2021) – 1 episode Piers Morgan's Life Stories (11 February 2021) – 1 episode RuPaul's Drag Race UK (18 February 2021) – 1 episode Mel Giedroyc: Unforgivable (23 February 2021) – 1 episode Sophie Ellis-Bextor's Kitchen Disco Danceathon (16 November 2021) – 1 episode Angela Scanlon's Ask Me Anything (27 November 2021) – 1 episode The Weakest Link (23 December 2021) – 1 episode Celebrity MasterChef: Christmas Cook-Off (23 December 2021) – 1 episode The Travel Show (4 February 2022) – 1 episode Springwatch (8 June 2022) – 1 episode The Big Breakfast (20 August 2022, 27 August 2022, 3 September 2022) – 3 episodes The Great Scott TreadMills Challenge (16 November 2022) – 1 episode The Greatest Snowman (26 December 2022) – 1 episode Mwy Na Daffs a Taffs (2 March 2023) – 1 episode Would I Lie to You? (24 March 2023) – 1 episode The Great Stand Up to Cancer Bake Off (26 March 2023) – 1 episode Late Night Lycett (14 April 2023) – 1 episode Steph's Packed Lunch (16 May 2023) – 1 episode The Comedy Roast for SU2C (3 November 2023) – 1 episode Celebrity Antiques Road Trip (28 November 2023) – 1 episode Blankety Blank (23 December 2023) – 1 episode The Underdog: Josh Must Win (3 April 2024) – 1 episode Drama Queens (1 May 2024) – 1 episode Who Do You Think You Are? (26 September 2024) – 1 episode Katy Perry: Night of a Lifetime (21 December 2024) – 1 episode Pointless Celebrities (25 January 2025) – 1 episode ITV Racing: Cheltenham Festival Live (13 March 2025, 12 March 2026) – 2 episodes I'm a Celebrity: Unpacked (17 April 2026, 20 April 2026) – 2 episodes
=== Smear layer and its role in bonding === Smear layer refers to a layer of debris on the inorganic surface of substrate which comprises residual inorganic and organic components. This layer is produced whenever the tooth structure undergoes a preparation with a bur.
Sources: en.wikipedia.org
(2026) study the anatomy of ulna and femur or Sahelanthropus tchadensis, interpreted as indicative of presence of adaptations to bipedalism in spite of similarities in size and geometric morphometric shape to bones of chimpanzees. De Jager et al. (2026) study the frequency, position, and variability of cortical sulcal imprints in endocasts of extant chimpanzees and bonobos, providing a comparative resource for the studies of the brain evolution based on hominin fossils. Dunbar (2026) reevaluates data from the study of Deaner & Nunn (1999), finds evidence of changes in brain size following increases in body size in the evolution of primates but in a more complicated way that suggested by the original brain lag hypothesis, with an increase in body size followed by a progressively greater increase in brain size, and finds evidence of such evolution of brain and body size in hominins.
In the 1700s, a Swiss gynecologist, Peyer, published a description of a cystocele. He was able to describe and document both cystoceles and uterine prolapse. In 1730, Halder associated cystocele with childbirth. During this same time, efforts began to standardize the terminology that is still familiar today. In the 1800s, the surgical advancements of anesthesia, suturing, suturing materials, and acceptance of Joseph Lister's theories of antisepsis improved outcomes for women with cystocele. The first surgical techniques were practiced on female cadavers. In 1823, Geradin proposed that an incision and resection may provide treatment. In 1830, the first dissection of the vagina was performed by Dieffenbach on a living woman. In 1834, Mendé proposed that dissecting and repairing the edges of the tissues could be done. In 1859, Huguier proposed that the amputation of the cervix was going to solve the problem of elongation. In 1866, a method of correcting a cystocele was proposed that resembled current procedures. Sim subsequently developed another procedure that did not require the full-thickness dissection of the vaginal wall. In 1888, another method of treating anterior vaginal wall Manchester combined an anterior vaginal wall repair with an amputation of the cervix and a perineorrhaphy. In 1909, White noted the high rate of recurrence of cystocele repair. At this time it was proposed that reattaching the vagina to support structures was more successful and resulted in less recurrence.
== Prediction == Because viscosity depends continuously on temperature and pressure, it cannot be fully characterized by a finite number of experimental measurements. Predictive formulas become necessary if experimental values are not available at the temperatures and pressures of interest. This capability is important for thermophysical simulations, in which the temperature and pressure of a fluid can vary continuously with space and time. A similar situation is encountered for mixtures of pure fluids, where the viscosity depends continuously on the concentration ratios of the constituent fluids For the simplest fluids, such as dilute monatomic gases and their mixtures, ab initio quantum mechanical computations can accurately predict viscosity in terms of fundamental atomic constants, i.e., without reference to existing viscosity measurements. For the special case of dilute helium, uncertainties in the ab initio calculated viscosity are two order of magnitudes smaller than uncertainties in experimental values. For slightly more complex fluids and mixtures at moderate densities (i.e. sub-critical densities) Revised Enskog Theory can be used to predict viscosities with some accuracy. Revised Enskog Theory is predictive in the sense that predictions for viscosity can be obtained using parameters fitted to other, pure-fluid thermodynamic properties or transport properties, thus requiring no a priori experimental viscosity measurements. For most fluids, high-accuracy, first-principles computations are not feasible.
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.
Aqueous NAD+ solutions are best kept frozen in aliquots and protected from light. Repeated freezing and thawing is avoided because it can accelerate breakdown. Dry powder stored desiccated at -20 °C or lower typically remains stable for longer periods.