redox coenzyme raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-03-31. Anything still debated is marked as such rather than presented as settled.
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.
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.
Laboratory measurement of NAD+ usually begins with rapid sample quenching because the molecule can change form after collection. Enzymatic cycling assays amplify signal through coupled reactions and are suited to small samples. High-performance liquid chromatography with ultraviolet detection separates NAD+ from related nucleotides. Liquid chromatography-mass spectrometry offers higher specificity and can distinguish NAD+ from close analogs. Each method has trade-offs in sensitivity, throughput, and equipment needs, so reported values depend heavily on extraction and detection choices.
| Property | Value | Notes |
|---|---|---|
| UV absorption maximum | 259–260 nm | Aqueous solution; pH-dependent |
| Common salt form | Disodium salt | Improves aqueous solubility |
| Typical storage temperature | -20 °C or lower | Desiccated and protected from light |
| Common analytical method | HPLC with UV detection | Often paired with mass spectrometry |
| Aqueous stability | pH and temperature dependent | Degrades faster at alkaline pH and high heat |
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.
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.
NAD+ also serves as a substrate for enzymes that cleave it, including sirtuins, PARPs, and CD38. These enzymes consume NAD+ and release nicotinamide and ADP-ribose or related products. The dual roles as redox cofactor and signaling substrate connect NAD+ to DNA repair, circadian regulation, and calcium signaling. Cellular NAD+ concentrations vary by tissue, time of day, and stress exposure. How these consumption pathways interact with redox balance remains an active area of research.
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.
compared four sterile wound-cleansing solutions (saline, Ringer's solution, Prontosan® and Octenisept®) using a wound coating model consisting of slides containing dried blood plasma or fibrin. The concentration of dissolved proteins was measured and the findings indicate that a surfactant containing solution (polyhexamethylene biguanide with betaine) (Prontosan®) was more effective than saline in removing the protein (adhered dried plasma or fibrin). The proteins in the antiseptic solution (Octenisept®) were denatured and became insoluble. The authors suggest this implies that the antiseptic solution is unsuitable as a 'general' wound cleanser and that its use should be restricted to infected wounds. In a double-blind, randomised, stratified, controlled, parallel-group study the influence of two antiseptics (octenidine, polyhexanide) versus a placebo of Ringer's solution on wound healing in a porcine model was conducted. Assessment of healing was recorded using planimetry and histopathology. At nine days post wounding, the octenidine-treated wounds demonstrated retarded contraction at significantly greater extent than placebo and polyhexanide. At days 18 and 28 the polyhexanide treated wounds supported contraction significantly more than placebo and octenidine. The polyhexanide treated wounds led to complete wound closure after 22.9 days, in comparison to the placebo octenidine treated wounds respectively, 24.1 days (p < 0.05) and 28.3 days (no statistical difference to placebo).
In 2013, between 128 and 232 million people used cannabis (2.7% to 4.9% of the global population between the ages of 15 and 65). Cannabis is by far the most widely used illicit substance, with the highest use among adults (as of 2018) in Zambia, the United States, Canada, and Nigeria.
=== Grhl2 === Grhl2 is involved in lower jaw formation of mammals, among other craniofacial developmental processes. It is also evolutionarily closest to Grhl1, compared to Grhl3, while still exhibiting the highly conserved functions that all Grhl genes share. It also appears that Grhl2 is involved in the fusion of the facial bones and that disruption to the regulation of Grhl2 can lead to cranioschisis/split face during embryonic development, often causing death. Continuing with the trend of incomplete fusion, the formation of the neural tube and abdominal wall is also regulated by Grhl2, evident by observation of incomplete closure of these structures, leading to spina bifida and thoracoabdominoschisis, following loss of Grhl2 function in mutant mice models for Grhl2. Additionally, over-expression of Grhl2 can also lead to mice developing spina bifida, showing the delicate balance in regulation required for Grhl2. Grhl2 is also related to breast cancer progression due to its ability to regulate epithelial cells and other processes such as epithelial-mesenchymal transition (EMT), although it is not known if EMT is promoted or inhibited by Grhl2. However, tumour progression is more associated with the epithelial tissue phenotype. Interestingly, within zebrafish there are two separate orthologues, grhl2a and grhl2b. Comparing the homology of these two orthologues to the human and mice equivalent, Grhl2, showed that grhl2b had 36 out of 47 amino acids identical (77% identical), meaning it was slightly more conserved than grhl2a, which had 34 out of 47 (72% identical).
=== Coup-proofing === In what is referred to as "coup-proofing", regimes create structures that make it hard for any small group to seize power. These coup-proofing strategies may include the strategic placing of family, ethnic, and religious groups in the military; creation of an armed force parallel to the regular military; and development of multiple internal security agencies with overlapping jurisdiction that constantly monitor one another. It may also involve frequent salary hikes and promotions for members of the military, and the deliberate use of diverse bureaucrats. Research shows that some coup-proofing strategies reduce the risk of coups occurring. However, coup-proofing reduces military effectiveness, and limits the rents that an incumbent can extract. One reason why authoritarian governments tend to have incompetent militaries is that authoritarian regimes fear that their military will stage a coup or allow a domestic uprising to proceed uninterrupted – as a consequence, authoritarian rulers have incentives to place incompetent loyalists in key positions in the military. A 2016 study shows that the implementation of succession rules reduce the occurrence of coup attempts. Succession rules are believed to hamper coordination efforts among coup plotters by assuaging elites who have more to gain by patience than by plotting. According to political scientists Curtis Bell and Jonathan Powell, coup attempts in neighbouring countries lead to greater coup-proofing and coup-related repression in a region.
Sources: en.wikipedia.org
== Early life and education == In 1974, Eaton graduated from Montana State University with a Bachelor of Science in Pre-Medical Sciences. Under the guidance of Curtis Klaassen and John Doull, he earned a Ph.D. in pharmacology and toxicology at the University of Kansas Medical Center in 1978. In 1979, he joined the faculty at the University of Washington after completing a postdoctoral fellowship in toxicology at the same institution after earning his Ph.D.
The author has attenuated Natrum muriaticum (common table-salt) until there was not a single saline property left ... and yet, with one drop of that attenuation in a goblet of water, and a teaspoonful of the water administered at intervals of three hours, she has cured a patient sinking in the last stage of typhoid fever. The highest attenuation of homœopathy and the most potent rises above matter into mind. This discovery leads to more light. From it may be learned that either human faith or the divine Mind is the healer and that there is no efficacy in a drug. She argued that even naming and reading about disease could turn thoughts into physical symptoms, and that the recording of ages might reduce the human lifespan. To explain how individuals could be harmed by poison without holding beliefs about it, she referred to the power of majority opinion. Eddy allowed exceptions from Christian Science prayer, including for dentistry, optometry and broken limbs; she said she had healed broken bones using "mental surgery," but that this skill would be the last to be learned. But for the most part (then and now), Christian Scientists believe that medicine and Christian Science are incompatible. Medicine asserts that something needs to be fixed, while Christian Science asserts that spiritual reality is perfect and beliefs to the contrary need to be corrected. In the 1890s Richard Cabot of Harvard Medical School studied the healing testimonies published by the Christian Science Journal, which Eddy founded in 1883, for his senior thesis.
==== Iatrogenic calcinosis cutis ==== Iatrogenic calcinosis cutis is characterized by firm nodules in the subcutis or dermis, which are caused by calcium salts precipitating quickly in the skin. This occurrence typically manifests as a warm, sensitive swelling at the site of venipuncture, and it most frequently happens following the extravasation of intravenous calcium chloride, calcium gluconate, or phosphate-containing solutions. Iatrogenic calcification, which manifests as soft yellow-white epidermal plaques, has also been linked to calcium salt exposure via electroencephalography or electromyographic electrode compounds.
Sources: en.wikipedia.org
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.
Purity is often checked by HPLC with UV detection, sometimes paired with mass spectrometry for identity. An assay against a standard can quantify the active cofactor content.
Solid NAD+ is usually kept dry, cold, and protected from light. Aqueous working solutions are best prepared fresh because degradation depends on pH, temperature, and time.
Common methods include enzymatic cycling assays, HPLC with UV detection, and LC-MS. The choice depends on sample size, specificity needs, and available equipment. Rapid quenching before analysis is important because NAD+ and NADH can interconvert.