NADH 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.
Last reviewed on 2026-05-24. Where a claim depends on a specific study, the study is described rather than over-claimed.
Measuring NAD+ in biological samples requires rapid processing because the compound can degrade or interconvert after collection. Common approaches include enzymatic cycling assays, high-performance liquid chromatography, and mass spectrometry. Each method has different sensitivity, specificity, and susceptibility to interference from related nucleotides. Sample type matters: cultured cells, animal tissues, and human blood present distinct challenges. Reported values can vary widely across laboratories because of differences in extraction, normalization, and analytical platform. Standardization remains an open issue in the field.
NAD+ is relatively unstable in aqueous solution, especially at neutral or alkaline pH and at elevated temperatures. It is typically stored dry, protected from light and moisture, and kept cold or frozen for long-term use. Solutions are often prepared fresh or buffered to mildly acidic pH to slow hydrolysis. Repeated freeze-thaw cycles can reduce integrity. Laboratories may verify concentration using ultraviolet absorbance at 259 nm or by enzymatic assay. These handling practices are general laboratory conventions rather than universal rules.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Typical solid form; varies with purity |
| Storage temperature | -20 °C or lower | Common for long-term dry storage |
| Solubility class | Water-soluble | Also dissolves in aqueous buffers |
| Typical analytical method | HPLC or LC-MS | Used for quantification in complex samples |
| UV absorbance maximum | About 259 nm | In neutral aqueous solution |
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.
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.
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.
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.
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.
In glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation, NAD+ is reduced to NADH at specific dehydrogenase steps. NADH then delivers electrons to the mitochondrial electron transport chain, mainly at complex I, supporting oxidative phosphorylation and ATP production. The balance between NAD+ and NADH, often expressed as a ratio, influences metabolic flux and redox homeostasis in different cellular compartments. Cytosolic and mitochondrial pools are connected but not identical, and their ratios can differ substantially because of compartment-specific enzymes and transport systems.
Beyond redox chemistry, NAD+ serves as a substrate for enzymes that cleave the molecule and transfer its ADP-ribose moiety or remove acetyl groups. Sirtuins consume NAD+ during deacetylation, poly(ADP-ribose) polymerases use it in DNA damage responses, and CD38 enzymes hydrolyze it to signaling metabolites. These consumption pathways mean that NAD+ availability can influence gene regulation, DNA repair, and calcium signaling. Cellular NAD+ concentrations decline in some tissues with age in animal models, but whether this decline is a cause or consequence of aging in humans remains an active open question.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a dinucleotide coenzyme built from an adenine nucleotide and a nicotinamide nucleotide joined by a pyrophosphate linkage. Its oxidized form carries a positive charge on the nicotinamide ring, while the reduced form, NADH, carries a hydride equivalent. The molecule participates in hundreds of oxidoreductase reactions, where it accepts or donates electrons and protons. Because it can cycle between oxidized and reduced states without net consumption, NAD+ functions as a reusable electron carrier rather than a fuel molecule.
== History == The British have had a system of heroin maintenance since the 1920s. For decades it supplied a few hundred addicts nationwide, most of whom were doctors themselves. It was de-emphasized considerably during the 1960s-1980s as a result of the U.S.-led war on drugs. In the 1980s and early 1990s, Dr John Marks ran heroin-prescribing clinics in Liverpool, Widnes and Warrington that were highly controversial. Because of the lack of large-scale trials, only anecdotal evidence existed as to the efficacy of the treatment. This changed in 1994 when Switzerland, faced with one of the largest open drug scenes in Europe at the time, started large-scale trials on the potential use of diamorphine as a maintenance drug. They proved diamorphine to be a viable maintenance drug which has shown equal or better rates of success than methadone in terms of assisting long-term users establish stable, crime-free lives. These results encouraged countries like Germany and the Netherlands to conduct their own trials and finally to include heroin-assisted treatment fully as a part of the national health system in 2009. In Switzerland, heroin has been made available under supervision to addicts since around 1994. Several studies have been conducted between 1994 and 1996.
== BP in Positron Emission Tomography == BP is a pivotal measure in the use of positron emission tomography (PET) to measure the density of "available" receptors, e.g. to assess the occupancy by drugs or to characterize neuropsychiatric diseases (yet, one should keep in mind that binding potential is a combined measure that depends on receptor density as well as on affinity). An overview of the related methodology is e.g. given in Laruelle et al. (2002). Estimating BP with PET usually requires that a reference tissue is available. A reference tissue has negligible receptor density and its distribution volume should be the same as the distribution volume in the target region if all receptors were blocked. Although the BP can be measured in a relatively unbiased way by measuring the whole time course of labelled ligand association and blood radioactivity, this is practically not always necessary. Two other common measures have been derived, which involve assumptions, but result in measures that should correlate with BP:
{\displaystyle {\begin{aligned}\log K_{{\text{assoc}},1}&=\mathrm {p} K_{{\text{dissoc}},3}\\\log K_{{\text{assoc}},2}&=\mathrm {p} K_{{\text{dissoc}},2}\\\log K_{{\text{assoc}},3}&=\mathrm {p} K_{{\text{dissoc}},1}\end{aligned}}}
=== Acute === Proprioception is occasionally impaired spontaneously, especially when one is tired. Similar effects can be felt during the hypnagogic state of consciousness, during the onset of sleep. One's body may feel too large or too small, or parts of the body may feel distorted in size. Similar effects can sometimes occur during epilepsy or migraine auras. These effects are presumed to arise from abnormal stimulation of the part of the parietal cortex of the brain involved with integrating information from different parts of the body. Proprioceptive illusions can also be induced, such as the "Pinocchio illusion", the illusion that one's nose is growing longer. Temporary impairment of proprioception has also been known to occur from an overdose of vitamin B6 (pyridoxine and pyridoxamine). This is due to a reversible neuropathy. Most of the impaired function returns to normal shortly after the amount of the vitamin in the body returns to a level that is closer to that of the physiological norm. Impairment can also be caused by cytotoxic factors such as chemotherapy. It has been proposed that even common tinnitus and the attendant hearing frequency-gaps masked by the perceived sounds may cause erroneous proprioceptive information to the balance and comprehension centers of the brain, precipitating mild confusion. Temporary loss or impairment of proprioception may happen periodically during growth, mostly during adolescence.
Sources: en.wikipedia.org
=== Grand Lodge of Colon vs. Provincial Mother Lodge of Havana === By 1870, only seven lodges were left in the entire island of Cuba. On May 26, 1870, the former GOCA Lodges around Havana, distancing themselves from the Colon Freemasonry of Santiago de Cuba, established the First Provincial Mother Lodge of Havana. They elected as Grand Master Severino Fernández Mora, who was a former Spanish Army physician in the Military Health Service of Spain that had been exiled from the country for revolutionary activities and ideas. Quickly, the Supreme Council recalled the warrant for the Mother Lodge. On April 11, 1873, the Grand Lodge of Colon resumed its work, despite the fear of reprisal. In 1875, they arranged with the Supreme Council to secure jurisdiction over Symbolic Masonry and the authority to charter new lodges. In 1873, the Supreme Council sent out a decree that all bodies in Cuba were to be directed by the Consistory. This included the Grand Lodge of Colon. The Supreme Council also decreed that members of the 31st through 33rd Degrees were granted honorary membership at any Lodge in Cuba. On May 23, 1875, the Second Provincial Mother Lodge of Havana was established. In 1875, the Supreme Council sent two delegates to the Congress of Supreme Councils in Lausanne, Switzerland. Freemasons in Cuba were surprised that they were accepted where Spain's delegation was refused attendance. The Cuban representatives, David Elías Pierre and Benjamín Odio, became signatories to the Pact of Confederation of the Supreme Councils which the Congress produced.
Testing laboratories as per ISO/IEC 17025 Calibration laboratories as per ISO/IEC 17025 Medical testing laboratories as per ISO 15189 Proficiency Testing Providers (PTP) as per ISO/IEC 17043 Reference Material Producers (RMP) as per ISO 17034 Biobanking as per ISO 20387
The receptors for enkephalin are the δ-opioid receptor (DOR) and μ-opioid receptor (MOR). Opioid receptors are a group of G-protein-coupled receptors, with other opioids as ligands as well. The other endogenous opioids are dynorphins (that bind to κ-opioid receptor), endorphins (MOR), endomorphins, and nociceptin-orphanin FQ. The opioid receptors are ~40% identical to somatostatin receptors (SSTRs).
Preservative food additives can be antimicrobial – which inhibit the growth of bacteria or fungi, including mold – or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food constituents. Common antimicrobial preservatives include nisin, sorbates, calcium propionate, sodium nitrate/nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc.), EDTA, hinokitiol, and ε-polylysine. Antioxidants include tocopherols (Vitamin E), butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Other preservatives include ethanol. There is also another approach of impregnating packaging materials (plastic films or other) with antioxidants and antimicrobials.
The other route uses glutathione (GSH) to conjugate with arsenic (III) to form an arsenic (GS) 3 complex. This complex can form a monomethylated arsenic (III) GS complex, using Cyt19 arsenic methyltransferase, and this monomethylated GS complex is in equilibrium with the monomethylated arsenic (III). Cyt19 arsenic methyltransferase can methylate the complex one more time, and this forms a dimethylated arsenic GS complex, which is in equilibrium with a dimethyl arsenic (III) complex. Both of the mono-methylated and di-methylated arsenic compounds can readily be excreted in urine. However, the monomethylated compound was shown to be more reactive and more toxic than the inorganic arsenic compounds to human hepatocytes (liver), keratinocytes in the skin, and bronchial epithelial cells (lungs). Studies in experimental animals and humans show that both inorganic arsenic and methylated metabolites cross the placenta to the fetus, however, there is evidence that methylation is increased during pregnancy and that it could be highly protective for the developing organism. Enzymatic methylation of arsenic is a detoxification process; it can be methylated to methylarsenite, dimethylarsenite or trimethylarsenite, all of which are trivalent. The methylation is catalyzed by arsenic methyltransferase (AS3MT) in mammals, which transfers a methyl group on the cofactor S-adenomethionine (SAM) to arsenic (III). An orthologue of AS3MT is found in bacteria and is called CmArsM. This enzyme was tested in three states (ligand free, arsenic (III) bound and SAM bound).
Sources: en.wikipedia.org
The so-called "border war" of the 1970s and 1980s was not actually a war at all by classic standards. At the same time it eludes exact definitions. The core of it was a protracted insurgency in South West Africa, later South-West Africa/Namibia and still later Namibia. At the same time it was characterised by the periodical involvement of the SADF in the long civil war taking place in neighbouring Angola, because the two conflicts could not be separated from one another. The South West African People's Organisation (SWAPO) has described the South African Border War as the Namibian War of National Liberation and the Namibian Liberation Struggle. In the Namibian context, it is also commonly referred to as the Namibian War of Independence. However, these terms have been criticised for ignoring the wider regional implications of the war and the fact that most of the fighting took place in countries other than Namibia.
== Discovery == Catch bonds were first proposed in 1988 in the Proceedings of the Royal Society by M. Dembo et al. while at Los Alamos National Laboratory. While developing molecular model to study the critical tension required to detach a membrane bound to a surface through adhesion molecules, it was found that it is theoretically possible for bond dissociation to be increased by force, decreased by force, and independent of force. The terms "slip bond", "catch bond", and "ideal bond" were coined by Dembo to describe these three types of bond behaviors. Slip bonds represent the ordinary behavior originally modeled by G. Bell, Dembo's former postdoctoral mentor at Los Alamos National Laboratory in 1978. Slip bonds were supported by flow chamber experiments where forces are applied on molecular bonds linking cells to chamber floor under shear flow. By comparison, no decisive evidence of catch bonds was found until 2003. This is due to experimental conditions that were unfavorable for detecting catch bonds, as well as the counterintuitive nature of the bonds themselves. For example, most early experiments were conducted in 96 well plates, an environment that does not provide any flow. Some experiments failed to produce shear stress that is now known to be critical to lengthen the lifetimes of catch bonds, while other experiments conducted under flow conditions too weak or too strong for optimal shear-induced strengthening of these bonds.
In a study published in 2010, researchers from Peking University studying ultrasound images of infants who fell ill in the 2008 contamination found while most children in a rural Chinese area recovered, 12 per cent still showed kidney abnormalities six months later. "The potential for long-term complications after exposure to melamine remains a serious concern", the report said. "Our results suggest a need for further follow-up of affected children to evaluate the possible long-term impact on health, including renal function."
Azilsartan, candesartan, eprosartan, irbesartan, olmesartan, telmisartan, valsartan ARBs are generally well-tolerated, in which they are less likely to cause cough or angioedema compared to ACEI. Common side effects include hypotension, renal insufficiency, and hyperkalemia. The contraindications of ARBs are similar to those of ACEI, including the contraindicated combinations with ACEI or direct renin inhibitors, "triple whammy" (the concurrent use of an ARB with diuretics and NSAIDs) and in patients with a history of angioedema and pregnancy. In addition, ARB should be used with caution in patients with renal impairment and renal failure risk in severe bilateral renal stenosis
Preservation of the Church's autonomy and rights, as accepted by the constitution. Defence against any attack on the independence of Church bodies, on the development of religious life and on the practice of Christian charity. Effectual implementation of parity for recognised denominations. Rejection of any attempt to de-Christianise marriage. Preservation or founding of denominational schools. There were also more general demands such as for a more federal, decentralised state, a limitation of state expenditure, a just distribution of taxes, the financial strengthening of the middle classes and the legal "removal of such evil states, that threaten the worker with moral or bodily ruin". With such a manifesto, the number of Catholic representatives in the Prussian Diet rose considerably. In December 1870, they formed a new "Centre" faction, also called the "Constitution Party" to emphasise its adherence to constitutional liberties. Three months later, early in 1871, the Catholic representatives to the new national parliament, the Reichstag, also formed a "Centre" faction. The party not only defended the Church's liberties, but also supported representative government and minority rights in general, in particular those of German Poles, Alsatians, and Hannoverians. The Centre's main leader was the Hannoverian advocate Ludwig Windthorst and other major figures included Karl Friedrich von Savigny, Hermann von Mallinckrodt, Burghard Freiherr von Schorlemer-Alst, the brothers August Reichensperger and Peter Reichensperger, Franz von Ballestrem and Georg Count Hertling.
Sources: en.wikipedia.org
Researchers often use enzymatic cycling assays, liquid chromatography, or mass spectrometry. The choice depends on sample size, sensitivity needs, and available equipment. Because NAD+ can degrade quickly, rapid extraction and careful handling are important.
Differences can arise from sample type, extraction method, normalization strategy, and analytical platform. Time of day, diet, and physiological state may also matter. These factors make direct comparisons across studies difficult.
NAD+ is generally more stable when stored dry and cold, and it can degrade in aqueous solutions over time. Heat, light, and alkaline conditions can accelerate loss. Laboratory protocols therefore often recommend frozen storage and protection from light.
NAD+ and NADH can interconvert quickly after a sample is collected, which can alter the measured ratio. Rapid quenching and cold handling limit enzymatic and chemical changes.