ADP-ribosylation 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 2026-02-21. Numbers and descriptions here follow the published literature rather than marketing material.
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.
NAD+ stands for nicotinamide adenine dinucleotide, the oxidized form of a coenzyme found in all living cells. The molecule consists of two nucleotides, adenine and nicotinamide ribose, joined through phosphate groups. Its chemical formula is C21H27N7O14P2, and the free acid has a molar mass near 663.43 grams per mole. In redox reactions, NAD+ accepts a hydride ion and becomes NADH. The pair NAD+ and NADH participates in hundreds of metabolic reactions, including steps in glycolysis, the citric acid cycle, and oxidative phosphorylation.
In cells, NAD+ functions primarily as an electron carrier. Dehydrogenase enzymes in glycolysis and the citric acid cycle transfer hydride from substrates to NAD+, producing NADH. NADH then delivers electrons to the mitochondrial respiratory chain, supporting ATP synthesis. In fermentation, NADH is reoxidized to NAD+ so that glycolysis can continue. The balance between NAD+ and NADH helps set metabolic flux. Beyond redox, NAD+ serves as a substrate for enzymes that cleave it, including sirtuins, poly(ADP-ribose) polymerases, and CD38. These reactions consume NAD+ and release nicotinamide and ADP-ribose products.
| Property | Value | Notes |
|---|---|---|
| Chemical name | Nicotinamide adenine dinucleotide | Oxidized form abbreviated NAD+ |
| Molecular formula | C21H27N7O14P2 | Free acid form |
| Molar mass | 663.43 g/mol | Calculated for free acid |
| CAS Registry Number | 53-84-9 | Common entry for beta-NAD+ |
| Appearance | White to off-white powder | Hygroscopic solid |
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.
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.
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.
Simulating the systemic environment in tectonic fault zones within the Earth's crust, pressure cycling forms vesicles periodically, as well as random peptide chains which are selected for ability to integrate into the vesicle membrane. Further selection of vesicles for stability could lead to functional peptide structures, increasing vesicle survival rate.
Olanzapine/fluoxetine (trade name Symbyax, created by Eli Lilly and Company) is a fixed-dose combination medication containing olanzapine (Zyprexa), an atypical antipsychotic, and fluoxetine (Prozac), a selective serotonin reuptake inhibitor (SSRI). Olanzapine/fluoxetine is primarily used to treat the depressive episodes of bipolar I disorder as well as treatment-resistant depression.
6 May – Terence Etherton, Baron Etherton, 73, British judge and politician, Master of the Rolls (2016–2021), chancellor of the High Court (2013–2016), and member of the House of Lords (since 2021). 20 May – Patrick O'Flynn, 59, British journalist (Daily Express) and politician, MEP (2014–2019), cancer. (death announced on this date) 13 June – Seán Neeson, 79, Northern Irish politician, MLA (1982–1986, 1998–2011). 1 July – David Lipsey, Baron Lipsey, 77, British journalist and life peer (since 1999). 7 July – Norman Tebbit, Baron Tebbit, 94, British politician, secretary of state for employment (1981–1983), chancellor of the Duchy of Lancaster (1985–1987), and MP (1970–1992). 9 July – Ian Blair, Baron Blair of Boughton, 72, British police officer and life peer, Commissioner of Police of the Metropolis (2005–2008), member of the House of Lords (since 2010). 13 July – Mark Schreiber, Baron Marlesford, 93, British politician, member of the House of Lords (since 1991). 17 July – Tommy Gallagher, 82, Northern Irish politician, MLA (1998–2011). (death announced on this date) 18 July – David Alliance, Baron Alliance, 93, Iranian-born British businessman, member of the House of Lords (2004–2025). 22 July – Sir Jamie McGrigor, 6th Baronet, 75, Scottish politician, MSP (1999–2016). (death announced on this date) 29 July – Meghnad Desai, Baron Desai, 85, Indian-born British economist and politician, member of the House of Lords (since 1991). 3 August – Stella Rimington, 90, British author and Director General of MI5 (1992–1996).
Sources: en.wikipedia.org
The definition of the topical route of administration sometimes states that both the application location and the pharmacodynamic effect thereof is local. In other cases, topical is defined as applied to a localized area of the body or to the surface of a body part regardless of the location of the effect. By this definition, topical administration also includes transdermal application, where the substance is administered onto the skin but is absorbed into the body to attain systemic distribution. If defined strictly as having local effect, the topical route of administration can also include enteral administration of medications that are poorly absorbable by the gastrointestinal tract. One such medication is the antibiotic vancomycin, which cannot be absorbed in the gastrointestinal tract and is used orally only as a treatment for Clostridioides difficile colitis.
Lysine malonylation (Kmal, maK), protein malonylation or malonylation, is a reversible post-translational modification (PTM) in eukaryotic and prokaryotic cells, in which a malonyl group (–CO–CH2–COOH) is added to a lysine (K) residue of a protein. It was first identified in 2011 by Peng et al. as an evolutionarily conserved modification and belongs to the acidic acyl modifications such as succinylation and glutarylation. As a dynamically regulated modification, it responds to conditions such as stress responses, metabolic processes, and mutations, thereby influencing the charge, structure, and function of proteins. This involves, among other things, the metabolic pathways of glucose and fatty acids as well as histone-mediated gene regulation, and is increasingly associated with immune regulation, angiogenesis, osteoarthritis, cancer and metabolic diseases such as obesity and type 2 diabetes. Its biological significance is increasingly recognized, but many aspects of its regulation and function remain unresolved, so that its therapeutic potential is still unexplored.
Gillnets may be used in fish maw fishing. However, gillnets can have high rates of bycatch. In the Gulf of California, gillnets set by poachers to catch totoaba also inadvertently catch vaquita, a critically endangered porpoise. The population of vaquita dropped 92% from 1997 to 2015, in large part from totoaba poaching. The 2019 documentary Sea of Shadows documented and condemned totoaba poaching and its negative effect on the vaquita population. In the Kikori River Delta of Papua New Guinea, gillnet fishermen trying to target the scaly croaker Nibea squamosa regularly trap elasmobranchs and dolphins as bycatch: targeted fish make up less than a quarter of the total catch.
In anatomy, fibrous joints are joints connected by fibrous tissue, consisting mainly of collagen. These are fixed joints where bones are united by a layer of white fibrous tissue of varying thickness. In the skull, the joints between the bones are called sutures. Such immovable joints are also referred to as synarthroses.
Sources: en.wikipedia.org
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.
NAD+ itself is not classified as a vitamin, but its precursor niacin is an essential nutrient in humans. Cells synthesize NAD+ from niacin, nicotinamide, nicotinamide riboside, or tryptophan. The intact dinucleotide is not obtained directly from typical diets in meaningful amounts.
Age-related studies often examine whether NAD+ levels decline in tissues and whether that decline affects mitochondrial function or DNA repair. Interventions using precursor molecules raise open questions about cause and effect. Current evidence does not establish that changing NAD+ levels slows human aging.
Nicotinamide adenine dinucleotide, with the plus sign indicating the oxidized form. It is a coenzyme present in all living cells. The reduced form is NADH.