If you have been reading about Sample quenching and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-06-10. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Beyond electron transfer, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer ADP-ribose units. Sirtuins, poly(ADP-ribose) polymerases, and CD38 consume NAD+ in regulatory reactions. These activities link NAD+ availability to DNA repair, chromatin modification, calcium signaling, and metabolic stress responses. Because consumption can exceed biosynthesis under some conditions, cellular NAD+ levels are dynamic rather than fixed. Enzyme affinity and local synthesis also influence how much NAD+ is available for signaling.
| Property | Value | Notes |
|---|---|---|
| Solubility | Freely soluble in water | Forms acidic solution; salt form may alter solubility |
| Typical storage temperature | -20 °C or lower | Desiccated and protected from light |
| Common analytical method | LC-MS | Used for biological quantification |
| UV absorbance maximum | 260 nm | Aqueous solution; pH dependent |
| Common synonym | Diphosphopyridine nucleotide | Older name abbreviated DPN |
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.
Quality control for NAD+ relies on identity, purity, and functional tests. A certificate of analysis may report high-performance liquid chromatography purity, ultraviolet spectrum, water content, and residual solvents. Because NAD+ is hygroscopic, gravimetric values can shift as material absorbs water, so purity should be interpreted alongside storage history. Mass spectrometry confirms molecular identity, while enzymatic assays show whether the material supports dehydrogenase activity. Commercial material is available as the free acid and as salts, and the counterion affects molecular weight, solubility, and how concentrations are calculated.
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.
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.
NAD+ is the oxidized form of nicotinamide adenine dinucleotide, a coenzyme built from two nucleotides joined by a phosphate linkage. One nucleotide carries adenine, and the other carries nicotinamide; the plus sign denotes a formal positive charge on the nicotinamide ring, not a free proton. In cells, NAD+ and its reduced partner NADH form a reversible redox pair. That pair participates in electron transfer reactions throughout metabolism. The abbreviation NAD+ is common in biochemistry, while NAD(H) sometimes denotes the combined pool.
The molecule was first described in the early twentieth century as a factor that promoted fermentation in yeast extracts. Later work linked it to hydrogen transfer and to the oxidation of nutrients in living tissues. Its structure was resolved as a dinucleotide, which explained why it could accept and donate electrons at specific enzyme sites. Today, NAD+ is recognized as a central substrate and signaling precursor, not merely a metabolic cofactor. Whether all observed NAD+ changes reflect causal signaling remains an open question.
Related compounds include NADH, the reduced form, and NADP+, which carries an additional phosphate group. NADP+ and NADPH often serve in biosynthetic and antioxidant reactions, while NAD+ and NADH are more associated with energy-yielding catabolism. Nicotinamide, nicotinic acid, and nicotinamide riboside are precursors that can enter salvage pathways. The exact contribution of dietary precursors to tissue NAD+ pools is an area of active investigation. Some studies measure labeled precursors to trace those routes.
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.
Biosynthesis occurs through salvage, Preiss-Handler, and de novo pathways. In mammals, the salvage pathway from nicotinamide predominates, and NAMPT is often described as rate-limiting. Nicotinamide riboside and nicotinic acid enter related routes that converge on NAD+ production. Tissue NAD+ concentrations vary widely and are maintained by a balance of synthesis and consumption. Some studies report age-related declines in certain tissues, but whether these changes cause disease or can be reversed to improve human health remains an open question.
==== Effects ==== RO5073012 by itself has no effect on locomotor activity in normal mice. It dose-dependently suppresses cocaine-induced hyperlocomotion (a psychostimulant-like effect) in rats, with near-complete suppression of cocaine-induced locomotor stimulation at the highest dose of RO5073012. Other TAAR1 agonists, including both partial agonists and full agonists, likewise suppress psychostimulant-induced hyperlocomotion. Conversely however, and in contrast to other TAAR1 partial agonists, RO5073012 non-significantly reduced the locomotor activity induced by amphetamine in normal mice. The reasons for this difference from other TAAR1 partial agonists are unclear, though RO5073012 has notably lower TAAR1 efficacy than other TAAR1 partial agonists. RO5073012 reduces basal locomotor activity in transgenic mice with TAAR1 overexpression. Amphetamine produces only weak locomotor stimulation in mice with TAAR1 overexpression, and RO5073012, by antagonizing the TAAR1, has been found to restore dextroamphetamine-induced hyperlocomotion in this context.
== Quasi-enantiomers == Quasi-enantiomers are molecular species that are not strictly enantiomers, but behave as if they were. In quasi-enantiomers, the majority of the molecule is reflected; however, an atom or group within the molecule is changed to a similar atom or group. Quasi-enantiomers can also be defined as molecules that have the potential to become enantiomers if an atom or group in the molecule were replaced. An example of quasi-enantiomers is (S)-bromobutane and (R)-iodobutane. Under normal conditions, the enantiomers for (S)-bromobutane and (R)-iodobutane are (R)-bromobutane and (S)-iodobutane respectively. Quasi-enantiomers also produce quasi-racemates, which are similar to normal racemates (see racemic mixture) in that they form an equal mixture of quasi-enantiomers. Quasi-enantiomers have applications in parallel kinetic resolution.
=== Available forms === Bicalutamide is available for the treatment of prostate cancer in most developed countries, including over 80 countries worldwide. It is available in 50 mg, 80 mg (in Japan), and 150 mg tablets for oral administration. The drug is registered for use as a 150 mg/day monotherapy for the treatment of LAPC in at least 55 countries, with the U.S. being a notable exception where it is registered only for use at a dosage of 50 mg/day in combination with castration. No other formulations or routes of administration are available or used. All formulations of bicalutamide are specifically indicated for the treatment of prostate cancer alone or in combination with surgical or medication castration. Due to the low water solubility of bicalutamide, bicalutamide in oral bicalutamide tablets is micronized to ensure small and consistent particle sizes and optimize oral bioavailability. A combined formulation of bicalutamide and the GnRH agonist goserelin in which goserelin is provided as a subcutaneous implant for injection and bicalutamide is included as 50 mg tablets for oral ingestion is marketed in Australia and New Zealand under the brand name ZolaCos CP (Zoladex–Cosudex Combination Pack).
Sources: en.wikipedia.org
=== Function and production === Human Chorionic Gonadotropin (hCG) is produced from the placenta after the implantation of a fertilized egg in the uterus. Fused villous syncytiotrophoblast cells and extravillous invasive cytotrophoblast cells make hCG. hCG promotes the production of corpus luteal progesterone which helps to maintain the corpus luteum for producing progesterone. hCG also stimulates the production of estrogen and testosterone in the ovaries.
=== Human intervention === Humans have semi-domesticated several species of honey bee by taking advantage of their swarming stage. Swarming is the means by which new colonies are established when there is no longer space for expansion in the colony's present hive. The old queen lays eggs that will develop into new queens and then leads as many as half the colony to a site for a new hive. Bees generally swarm before a suitable location for another hive has been discovered by scouts sent out for this purpose. Until such a location is found the swarm will simply conglomerate near the former hive, often from tree branches. These swarms are unusually docile and amenable to transport by humans. When provided with a suitable nesting site, such as a commercial Langstroth hive, the swarm will readily form a new colony in artificial surroundings. These semi-domesticated colonies are then looked after by humans practicing apiculture or meliponiculture. Captured bees are encouraged to forage, often in agricultural settings such as orchards, where pollinators are highly valued. The honey, pollen, wax and resins the bees produce are all harvested by humans for a variety of uses. The term "semi-domesticated" is preferred because all bee colonies, even those in very large agricultural apiculture operations, readily leave the protection of humans in swarms that can establish successful wild colonies. Much of the effort in commercial beekeeping is dedicated to persuading a hive that is ready to swarm to produce more honeycomb in its present location.
A revolution in nuclear strategic thought occurred with the introduction of the intercontinental ballistic missile (ICBM), which the Soviet Union first successfully tested in August 1957. In order to deliver a warhead to a target, a missile was much faster and more cost-effective than a bomber, and enjoyed a higher survivability due to the enormous difficulty of interception of the ICBMs (due to their high altitude and extreme speed). The Soviet Union could now afford to achieve nuclear parity with the United States in raw numbers, although for a time, they appeared to have chosen not to. Photos of Soviet missile sites set off a wave of panic in the U.S. military, something the launch of Sputnik would do for the American public a few months later. Politicians, notably then-U.S. Senator John F. Kennedy suggested that a "missile gap" existed between the Soviet Union and the United States. The US military gave missile development programs the highest national priority, and several spy aircraft and reconnaissance satellites were designed and deployed to observe Soviet progress. Early ICBMs and bombers were relatively inaccurate, which led to the concept of countervalue strikes — attacks directly on the enemy population, which would theoretically lead to a collapse of the enemy's will to fight. During the Cold War, the Soviet Union invested in extensive protected civilian infrastructure, such as large "nuclear-proof" bunkers and non-perishable food stores.
== Awards == 1999 - March of Dimes Basil O’Connor Award 1999 - Frederick J. Terman Junior Faculty Award 1999 - Rita Allen Foundation Scholar 1999 - American Heart Association New Investigator Award 2000 - Cancer Research Institute New Investigator Award 2001 - Pew Scholar 2002 - Keck Distinguished Medical Scholar 2004 - Established Investigator of the American Heart Association 2012 - Elected to National Academy of Sciences 2013 - NIHMERIT award 2015 - Member of Mathematical Sciences Jury for the Infosys Prize 2016 - Elected to National Academy of Medicine 2024 - Passano Award
Sources: en.wikipedia.org
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.
Liquid chromatography-mass spectrometry provides sensitive and specific quantification in cells and tissues. Enzymatic cycling assays are also widely used for plate-based measurement. Both methods need rapid sample processing to prevent post-collection changes.
Purity refers to the proportion of the intended dinucleotide relative to related nucleotides, salts, and water. A high-purity grade supports reproducible enzymatic assays. Researchers often check purity by chromatographic and spectroscopic methods before use.
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.