A practical reference on LC-MS: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-07-30. Anything still debated is marked as such rather than presented as settled.
NAD+ is a dinucleotide composed of nicotinamide, ribose, and adenine linked by phosphate groups. Its full name is nicotinamide adenine dinucleotide, with "+" denoting the oxidized form. The molecule acts as a coenzyme in redox reactions, cycling between NAD+ and NADH. In cells, it participates in electron transfer during glycolysis, the citric acid cycle, and oxidative phosphorylation. It is distinct from NADP+, which carries an additional phosphate group and supports different biosynthetic reactions.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common name | Nicotinamide adenine dinucleotide (oxidized) | Often shortened to NAD+ |
| Chemical class | Dinucleotide | Contains nicotinamide and adenine moieties |
| Molecular formula | C21H27N7O14P2 | Free acid form; charge depends on pH |
| Molar mass | About 663.43 g/mol | Calculated for C21H27N7O14P2 |
| CAS number | 53-84-9 | Common identifier for beta-NAD+ |
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.
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.
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.
Research on NAD+ often examines changes with age, diet, exercise, and disease states, but causal relationships are difficult to establish. Some studies measure NAD+ levels, while others assess enzyme activity or downstream markers. In the literature, terms such as "NAD+ decline" and "NAD+ boosting" appear in both scientific and commercial contexts, sometimes without precise definitions. Whether changes in measured NAD+ directly produce health effects remains an open question. Results from cells, animals, and humans cannot be assumed to translate directly.
Nicotinamide adenine dinucleotide, commonly abbreviated NAD+, is a coenzyme present in all living cells. The molecule consists of two nucleotides linked by phosphate groups, with adenine and a nicotinamide ring as its principal features. In its oxidized form, the nicotinamide ring can accept a hydride ion, becoming NADH. This reversible conversion places NAD+ at the center of many electron-transfer reactions. Its role as a redox carrier is well established across bacteria, plants, fungi, and animals.
Beyond redox chemistry, NAD+ acts as a substrate for several enzyme families. ADP-ribosyltransferases, sirtuins, and CD38 ectoenzymes cleave the molecule into nicotinamide and ADP-ribose or related products. These reactions connect NAD+ availability to processes such as DNA repair, chromatin modification, and calcium signaling. Because the coenzyme is used in both electron transfer and signaling, cells maintain separate pools in compartments including the cytosol, mitochondria, and nucleus. The relative sizes and regulation of those pools remain active areas of study.
A semen analysis (plural: semen analyses), also called seminogram or spermiogram, evaluates certain characteristics of a male's semen and the sperm contained therein. It is done to help evaluate male fertility, whether for those seeking pregnancy or verifying the success of vasectomy. Depending on the measurement method, just a few characteristics may be evaluated (such as with a home kit) or many characteristics may be evaluated (generally by a diagnostic laboratory). Collection techniques and precise measurement method may influence results. The assay is also referred to as ejaculate analysis, human sperm assay (HSA), sperm function test, and sperm assay. Semen analysis is a complex test that should be performed in andrology laboratories by experienced technicians with quality control and validation of test systems. A routine semen analysis should include: physical characteristics of semen (color, odor, pH, viscosity and liquefaction), volume, concentration, morphology and sperm motility and progression. To provide a correct result it is necessary to perform at least two, preferably three, separate seminal analyses with an interval between them of seven days to three months. The techniques and criteria used to analyze semen samples are based on the WHO manual for the examination of human semen and sperm-cervical mucus interaction published in 2021.
== Reactivity == The high acidity of the imido N-H is the result of the pair of flanking electron-withdrawing carbonyl groups. Both sodium phthalimide and potassium phthalimide are well known. The latter can be made by reaction of phthalimide with potassium carbonate or potassium hydroxide.. The potassium salt is used in the Gabriel synthesis of primary amines.
=== Availability === Phenibut is approved in Russia, Ukraine, Belarus, Georgia and Latvia for medical use. It is not approved or available as a medication in other countries in the European Union, the United States, or Australia. In countries where phenibut is not a licensed pharmaceutical drug, it is sold online without a prescription as a "nutritional supplement". It is often used as a form of self-medication for social anxiety.
Sources: en.wikipedia.org
=== Marketing controversy === In 2001, Eli Lilly's chairman, president and CEO, Sidney Taurel, told shareholders: "No medicine better symbolizes our mission than Xigris," calling it "one of our industry's genuine breakthroughs." Xigris was designed to fight sepsis, a condition that kills more than 200,000 Americans annually. It was the only approved drug for sepsis, and it costs $8,000 to treat a single patient. Lilly hoped it would be a blockbuster, with sales of at least a billion dollars a year. But, after five years on the market, sales were only $200 million. Eli Lilly used the Belsito & Company PR firm in a marketing campaign to promote Xigris. A report accused the company of initiating false reports of a shortage of the drug to boost sales. Belsito and Company spread the word that the drug was being "rationed" and physicians were being 'systematically forced' to decide who would live and who would die. As part of this effort, Lilly provided a group of physicians and bioethicists with a $1.8 million grant to form the Values, Ethics, and Rationing in Critical Care (VERICC) Task Force, purportedly to address ethical issues raised by rationing in the intensive care unit. Finally, the Surviving Sepsis Campaign was established, in theory to raise awareness of severe sepsis and generate momentum toward the development of treatment guidelines. This marketing campaign was especially troublesome because Xigris has been linked to increased risk of serious bleeding in patients who used it as well as other concerns.
==== Illegal marketing of gabapentin for off-label uses settlement (2004) ==== In 1993, the Food and Drug Administration (FDA) approved gabapentin only for treatment of seizures. Warner–Lambert, which merged with Pfizer in 2000, used continuing medical education and medical research, sponsored articles about the drug for the medical literature, and alleged suppression of unfavorable study results, to promote gabapentin. Within five years, the drug was being widely used for off-label uses such as treatment of pain and psychiatric conditions. Warner–Lambert admitted to violating FDA regulations by promoting the drug for pain, psychiatric conditions, migraine, and other unapproved uses. In 2004, the company paid $430 million in one of the largest settlements to resolve criminal and civil health care liability charges. It was the first off-label promotion case successfully brought under the False Claims Act. A Cochrane review concluded that gabapentin is ineffective in migraine prophylaxis. The American Academy of Neurology rates it as having unproven efficacy, while the Canadian Headache Society and the European Federation of Neurological Societies rate its use as being supported by moderate and low-quality evidence.
During the period of the Rhodesian Bush War in the late 1960s and 1970s, the BSAP formed an important part of the white minority government's fight against Communist guerrillas. The force formed a riot unit; a tracker combat team (later renamed the Police Anti-Terrorist Unit or PATU); a police field force, Police Support Unit, (who were distinguished by wearing black boots), an Urban Emergency Unit, a Police Reserve Air Wing or PRAW, and a Marine Division. Many of its white personnel were national servicemen and conscripted reservists. At independence, the force had a strength of approximately 11,000 regulars (about 60% black) and almost 35,000 reservists, of whom the overwhelming majority were white. A former BSAP officer, Daniel Carney, wrote a book titled Whispering Death about the BSAP in anti-terrorist operations which was later made into the film Albino.
As they were cut off from all European funds, finances were more stretched than ever. At one stage, Zita was reduced to making salad and spinach dishes from dandelion leaves. However, all her sons were active in the war effort. Otto promoted the dynasty's role in a post-war Europe and met regularly with Franklin Roosevelt; Robert was the Habsburg representative in London; Carl Ludwig and Felix joined the United States Army, serving with several American-raised relatives of the Mauerer line; Rudolf smuggled himself into Austria in the final days of the war to help organise the resistance. In 1945 Empress Zita celebrated her birthday on the first day of peace, 9 May. She was to spend the next two years touring the United States and Canada to raise funds for war-ravaged Austria and Hungary.
Sources: en.wikipedia.org
== Primary indexes == In addition to the primary indices listed below, Russell publishes Value and Growth versions of each U.S. index. This divides each index roughly in half, separating companies classified as value stocks from those classified as growth stocks. Companies can appear in both the value and growth versions of an index, though the total number of shares between the value and growth versions will equal the number in the main index. The primary indices are:
=== Yolk sac vasculogenesis === Expressed in high levels in the extraembryonic membranes throughout development, HAND1 also plays a functional role in vascular development of the yolk sac. Though not strictly required for vasculogenesis, data has shown that HAND1 contributes to the fine-tuning of the vasculogenic response in the yolk sac, recruiting smooth muscle cells to the endothelial network in order to refine the primitive endothelial plexus to a functional vascular system. This relationship has been demonstrated in the HAND1-null mouse model, where embryos lacking the HAND1 gene had a yolk sac vasculature defect caused by lack of vasculature refinement leading to the accumulation of hematopoietic cells between the yolk sac and the amnion.
=== Pattern hair loss === Finasteride is also used to treat male pattern baldness (androgenic alopecia), a condition that develops in up to 80% of Caucasian men aged 70 and over. In the United States, finasteride and minoxidil are the only two FDA-approved drugs for the treatment of male pattern hair loss as of 2017. Treatment with finasteride slows further hair loss. Two meta-analyses found finasteride's efficacy caused about 15% hair regrowth. Specifically oral finasteride was observed to regrow about 18 hair follicles in a square centimeter area of scalp. In comparison a full head of hair usually has 120 hair follicles per square centimeter scalp. Taking finasteride leads to a reduction in scalp and serum DHT levels; by lowering scalp levels of DHT, finasteride can maintain or increase the amount of terminal hairs in the anagen phase by inhibiting and sometimes reversing miniaturization of the hair follicle. Finasteride is most effective on the crown but can reduce hair loss in all areas of the scalp. Finasteride has also been tested for pattern hair loss in women; however, the results were no better than placebo. Finasteride is less effective in the treatment of scalp hair loss than dutasteride.
Sources: en.wikipedia.org
The plus sign indicates the oxidized form of nicotinamide adenine dinucleotide, which can accept electrons. When it accepts electrons, it becomes NADH. The two forms together support redox reactions in cells.
No. NAD+ is the oxidized form and NADH is the reduced form. They differ by two electrons and a proton equivalent, and cells interconvert them during metabolism.
Yes. NAD+ is present in all living cells and is required for fundamental metabolic reactions. Its concentration varies by tissue, compartment, and time.
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.