LC-MS raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-12-19 and is reviewed periodically as new material appears.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical name | Nicotinamide adenine dinucleotide (oxidized form) | NAD+ denotes the oxidized redox state |
| Common synonyms | Diphosphopyridine nucleotide; coenzyme I | Older names appear in historical literature |
| Molar mass | About 663.43 g/mol | Free acid value; salts and hydrates differ |
| Appearance | White to off-white powder | The purified solid is white; solutions are clear |
| Solubility | Highly soluble in water | Aqueous buffers are common laboratory solvents |
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.
Commercial NAD+ is available at research grade, often with purity specifications determined by high-performance liquid chromatography. Certificates of analysis may report water content, residual solvents, and counterion identity. Identity can be confirmed by ultraviolet absorbance near 260 nm, mass spectrometry, or enzymatic activity. Because different salt forms and hydration states exist, researchers should verify that the product matches the intended molecular form. Lot-to-lot variation in purity can affect quantitative assays and should be documented.
Quantification of NAD+ in biological samples usually relies on separation techniques coupled to sensitive detection. High-performance liquid chromatography with ultraviolet detection can measure the oxidized form by its absorbance near 260 nm, while mass spectrometry provides greater specificity and can distinguish NAD+ from close analogs. Enzymatic cycling assays use coupled dehydrogenase reactions to amplify signal and estimate NAD+ concentrations in cell or tissue extracts. Because NAD+ and NADH interconvert rapidly, sample preparation must quench metabolism quickly and preserve the redox state before analysis.
The stability of NAD+ depends on pH, temperature, light exposure, and the presence of degradative enzymes. Aqueous solutions are generally more stable under mildly acidic to neutral conditions and degrade faster under alkaline conditions or prolonged heat. The solid is hygroscopic and should be stored desiccated, often frozen, and protected from repeated freeze-thaw cycles. In laboratory handling, aliquots reduce repeated temperature changes, and chelating agents may limit metal-catalyzed hydrolysis in some buffers. These practices matter because even small amounts of NADH or hydrolysis products can interfere with quantitative assays.
Quality control for NAD+ materials typically combines identity, purity, and water content checks. Identity may be confirmed by ultraviolet spectrum, retention time in chromatography, or mass accuracy, while purity is assessed by HPLC peak area or quantitative nuclear magnetic resonance. Residual water and solvents can affect molar calculations and enzyme assays, so Karl Fischer titration or thermogravimetric analysis may be used. Commercial materials vary in grade and counterion form, and published methods should specify the exact salt or hydrate when reporting concentrations. Regulatory status depends on intended use, with research reagents, dietary ingredients, and clinical products treated under different frameworks.
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.
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.
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.
=== Bleeding === SSRIs directly increase the risk of abnormal bleeding by lowering platelet serotonin levels, which are essential to platelet-driven hemostasis. SSRIs interact with anticoagulants, like warfarin, and antiplatelet drugs, like aspirin. This includes an increased risk of GI bleeding, and post operative bleeding. The relative risk of intracranial bleeding is increased, but the absolute risk is low. SSRIs are known to cause platelet dysfunction. This risk is greater in those who are also on anticoagulants, antiplatelet agents and NSAIDs (nonsteroidal anti-inflammatory drugs), as well as with the co-existence of underlying diseases such as cirrhosis of the liver or liver failure.
== History == Pfizer brought the drug to market as Vfend. A generic version of the tablet form of voriconazole was introduced in the US in 2011 after Pfizer and Mylan settled litigation under the Hatch-Waxman Act; a generic version of the injectable form was introduced in 2012. In Europe, patent protection expired in 2011, and pediatric administrative exclusivity expired in 2016.
Food and Drug Administration (FDA), the United States Department of Agriculture (USDA), United Nations University (UNU) and the United States National Academy of Sciences when judging the quality of protein in the human is not PER or BV but the Protein Digestibility Corrected Amino Acid Score (PDCAAS), as it is viewed as accurately measuring the correct relative nutritional value of animal and vegetable sources of protein in the diet.
Sources: en.wikipedia.org
=== Dermis === The dermis lies next to the epidermis. It is a 1–2 mm layer mainly composed of fibroblasts and immune cells (e.g. dermal dendritic cells, macrophages, T cells, mast cells) in a collagen and elastic fiber extracellular matrix. These immune cells play important roles in parasitic infections, psoriasis induction, tumor progression, dermal inflammation, angiogenesis, wound healing, tissue remodeling, skin sensitization, and tolerance. Therefore, the regional accumulation of drugs in the dermis is necessary for the prevention and treatment of these local skin diseases. The hair follicle is an invagination of epidermis cells deep into the dermis. The follicular route is critical in the topical delivery of particle-based formulations and hydrophilic, high-molecular-weight drugs. The follicular route provides benefits such as deeper penetration, prolonged residence duration, faster entry into the skin, and site-specific targeting.
The tropylium ion or cycloheptatrienyl cation is an aromatic species with a formula of [C7H7]+. Its name derives from the molecule tropine from which cycloheptatriene (tropylidene) was first synthesized in 1881. Salts of the tropylium cation can be stable, even with nucleophiles of moderate strength e.g., tropylium tetrafluoroborate and tropylium bromide (see below). Its bromide and chloride salts can be made from cycloheptatriene and bromine or phosphorus pentachloride, respectively. It is a regular heptagonal, planar, cyclic ion. It has 6 π-electrons (4n + 2, where n = 1), which fulfills Hückel's rule of aromaticity. It can coordinate as a ligand to metal atoms. The structure shown is a composite of seven resonance contributors in which each carbon atom carries part of the positive charge.
With a chemical structure resembling amphetamines and other precursors, myristicin can also be used to synthesize psychoactive amphetamines. Under controlled conditions, myristicin isolated from nutmeg oil can be converted into MMDMA, a synthetic "designer drug" that is less potent than MDMA but produces comparable stimulant and hallucinogenic effects.
P.H., professor in the Department of Biostatistics in the UAB School of Public Health George Howard explains that "Asking someone how much they weigh is probably the second worst question behind how much money they make," "From past research, we know that women tend to under-report their weight, and men tend to over-report their height." Howard said as far as equivalency between the self-reported and measured data sets, the East South Central region showed the least misreporting. "This suggests that people from the South come closer to telling the truth than people from other regions, perhaps because there's not the social stigma of being obese in the South as there is in other regions." The area of the United States with the highest obesity rate is American Samoa (75% obese and 95% overweight).
Sources: en.wikipedia.org
=== The Ait Soussan organisation === The Ait Soussan organisation is a criminal organisation led by Houssine Ait Soussan. He is a major drug trafficker who also used to own the Dutch football-club ZVV 't Knooppunt. Houssine Ait Soussan is notably a prominent figure within the Moroccan mafia in the Netherlands and Belgium, and he was also allied with the Bouyakhrichan organisation. The Ait Soussan organisation is responsible for distributing tons of cocaine across all of Western Europe. Houssine Ait Soussan is also considered to be one of the original participating figures within the Mocro-War, which was sparked after a missing shipment of cocaine in the port of Antwerp. As a result of this, Houssine Ait Soussan is believed to be behind the kidnapping of Abdelkader "the Jew" Bouker, a major Belgian-Moroccan drug trafficker who worked closely together with the Israeli mafia, and went missing in 2016. He was also believed to be behind the kidnapping of Younes El Ballouti, the younger brother of Othman El Ballouti, who is considered to be one of the biggest drug lords in Belgium. Houssine Ait Soussan allegedly kidnapped him as revenge, because Colombian cartels preferred to work with the El Ballouti clan instead of his organisation. Houssine Ait Soussan was for many years wanted by the Dutch and Belgian authorities for his involvement in numerous of assassinations and kidnappings, which mostly took place in Antwerp and Brussels. He orchestrated his kidnappings and assassinations from Central America, to stay off the radar from the European police.
== Honours and awards == 2000 – Human Frontier Science Program Long-Term Postdoctoral Fellowship. 2004 – Career Development Award, Human Frontier Science Program 2007 – Starting Grant, European Research Council 2013 – Rector's Prize for Excellence in Research and Teaching, Hebrew University of Jerusalem 2015 – Sir Zelman Cowen Universities Fund Prize for Discovery in Medical Research 2018 – Michael Milken Prize for Excellence in Teaching.
=== Gelling agents === Gelling agents are food additives used to thicken and stabilize various foods, like jellies, desserts and candies. The agents provide the foods with texture through formation of a gel. Some stabilizers and thickening agents are gelling agents. Typical gelling agents are based on polysaccharides such as natural gums, starches, pectins and agar-agar or proteins such as gelatin. Examples are:
Sources: en.wikipedia.org
It indicates a formal positive charge on the nicotinamide ring. The molecule is not simply a protonated acid, and the charge is part of its redox chemistry.
NAD+ is the oxidized form, while NADH is the reduced form carrying two additional electrons and a proton. The two forms interconvert in many metabolic reactions.
No. NADP+ contains an extra phosphate group on the adenine ribose. NADP+ and NADPH tend to participate in different biosynthetic and antioxidant pathways.
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.