Everything below concerns UV detection. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-22. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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 |
|---|---|---|
| Common synonyms | β-NAD+, coenzyme I, DPN | DPN stands for diphosphopyridine nucleotide; older literature uses this term. |
| CAS Registry Number | 53-84-9 | Free acid form of β-nicotinamide adenine dinucleotide. |
| Molecular formula | C21H27N7O14P2 | Anhydrous free acid; molar mass 663.43 g/mol. |
| Appearance | White to off-white powder | Crystalline solid; may absorb moisture from air. |
| Solubility | Freely soluble in water | Insoluble in most nonpolar organic solvents. |
Research on NAD+ spans biochemistry, aging biology, and metabolism. Studies often examine how NAD+ levels change with age, diet, exercise, or disease states, and whether precursor supplementation alters those levels. Findings in animal models do not automatically translate to humans, and measurement methods vary across studies. Questions about tissue-specific effects, long-term consequences, and causal relationships remain open. NAD+ itself is not established as a single therapeutic agent with a broad clinical role.
Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide composed of two nucleotides joined by phosphate groups. One nucleotide contains adenine; the other contains nicotinamide. The molecule exists in oxidized (NAD+) and reduced (NADH) forms, and the reversible hydride transfer between them underlies many metabolic oxidation-reduction reactions. In cells, NAD+ serves as an electron acceptor in pathways such as glycolysis, the citric acid cycle, and oxidative phosphorylation. Its concentration and redox ratio vary by compartment, tissue, and metabolic state.
Biosynthesis of NAD+ starts from nicotinamide, nicotinic acid, or nicotinamide riboside through salvage pathways. A rate-limiting enzyme, nicotinamide phosphoribosyltransferase, converts nicotinamide to nicotinamide mononucleotide. Further coupling with ATP yields NAD+. In mammals, the liver and muscle can synthesize NAD+ from dietary precursors, but tissue levels vary widely. Researchers study these pathways to understand age-related changes, metabolic disorders, and neurodegeneration. Direct causal links between NAD+ decline and disease remain an active area of investigation.
NAD+ is a dinucleotide composed of adenine, ribose, and nicotinamide groups joined by phosphate linkages. It serves as a coenzyme in oxidoreductase reactions, cycling between oxidized NAD+ and reduced NADH. The molecule is water-soluble and occurs in all living cells. Its nicotinamide ring accepts hydride ions during catabolic reactions, linking substrate oxidation to electron transport. This redox couple supports ATP production and helps maintain cytosolic and mitochondrial redox balance in many cell types.
Beyond redox catalysis, NAD+ is a substrate for enzymes that transfer ADP-ribose or remove acetyl groups from proteins. Sirtuins and poly(ADP-ribose) polymerases consume NAD+ and release nicotinamide as a byproduct. These reactions connect cellular energy status to gene regulation, DNA repair, and stress responses. Because NAD+ is used rather than merely recycled in such signaling, its concentration reflects both biosynthesis and consumption. The balance between salvage and de novo synthesis pathways determines available pools in different tissues.
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.
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.
== Terminology structure == Each NPU entry holds a structured definition of the 'result type' it identifies. The definitions are expressed using well established concepts and terms from the field of laboratory medicine. References to internationally acknowledged classifications, nomenclatures and terminologies are filed where possible. This ensures that the definitions are unambiguous, and that the meaning of each concept will remain stable and accessible over time. The definition structure is based on the scientific concept of 'examination' – an examination studies one or more properties of a system (a delimited part of the universe). In a clinical laboratory terminology such as the NPU terminology the system of interest is assumed to be (part of) the patient or the environment, and the NPU definition structure states:
== Adverse effects == Data from clinical trials submitted to regulatory authorities showed that rimonabant caused depressive disorders or mood alterations in up to 10% of subjects and suicidal ideation in around 1%, and in Europe it was contraindicated for people with any psychiatric disorder, including clinical depression. Data from a large, randomized, clinical trial (CRESCENDO) with > 9,000 patients receiving rimonabant treatment demonstrated a rate of psychiatric adverse events (anxiety, depression, depressed mood, or insomnia) of greater than 30%. Additionally, nausea and upper respiratory tract infections were very common adverse effects (occurring in more than 10% of people); common adverse effects (occurring in between 1% and 10% of people) included gastroenteritis, anxiety, irritability, insomnia and other sleep disorders, hot flushes, diarrhea, vomiting, dry or itchy skin, tendonitis, muscle cramps and spasms, fatigue, flu-like symptoms, and increased risk of falling. The FDA's advisory committee concurred with concerns raised by the review divisions. Based on human and on animal data, it appeared that the therapeutic window was narrow. EMA postmarketing surveillance data suggested that the risk of psychiatric disorders in people taking rimonabant was doubled.
N-Desethyletonitazene (NDE, Noretonitazene) is a benzimidazole derivative with potent opioid effects which has been sold as a designer drug. It is better known as an active metabolite of the related compound etonitazene, but has similar activity to the parent compound and has sometimes appeared as a drug of abuse in its own right, first being identified in New Zealand in 2024.
In the average person, the diaphragm should be intersected by the 5th to 7th anterior ribs at the mid-clavicular line, and 9 to 10 posterior ribs should be viewable on a normal PA inspiratory film. An increase in the number of viewable ribs implies hyperinflation, as can occur, for example, with obstructive lung disease or foreign body aspiration. A decrease implies hypoventilation, as can occur with restrictive lung disease, pleural effusions or atelectasis. Underexpansion can also cause interstitial markings due to parenchymal crowding, which can mimic the appearance of interstitial lung disease. Enlargement of the right descending pulmonary artery can indirectly reflect changes of pulmonary hypertension, with a size greater than 16 mm abnormal in men and 15 mm in women. Appropriate penetration of the film can be assessed by faint visualization of the thoracic spines and lung markings behind the heart. The right diaphragm is usually higher than the left, with the liver being situated beneath it in the abdomen. The minor fissure can sometimes be seen on the right as a thin horizontal line at the level of the fifth or sixth rib. Splaying of the carina can also suggest a tumor or process in the middle mediastinum or enlargement of the left atrium, with a normal angle of approximately 60 degrees. The right paratracheal stripe is also important to assess, as it can reflect a process in the posterior mediastinum, in particular the spine or paraspinal soft tissues; normally it should measure 3 mm or less.
A 2017 film adaptation of Wonder, starring Julia Roberts, Owen Wilson and Jacob Tremblay, was released in November 2017. A stage adaption premiered in 2025, with actor Garrett McNally, who has Treacher Collins syndrome himself, portraying the character in certain shows. Alison Midstokke, who appears in the drama film Happy Face (2018), is an actress and activist who has the condition.
Sources: en.wikipedia.org
The king cobra (Ophiophagus hannah) is the longest venomous snake in the world, and it can inject very high volumes of venom in a single bite. The venom LD50 is 1.80 mg/kg SC according to Broad et al. (1979). The mean value of subcutaneous LD50 of five wild-caught king cobras in Southeast Asia was determined to be 1.93 mg/kg. Between 350 and 500 mg (dry weight) of venom can be injected at once (Minton, 1974). In another study by Broad et al. (1979), the average venom quantity was 421 mg (dry weight of milked venom). The maximum venom yield is approximately 1000 mg (dry weight). The king cobra has a fearsome reputation. When annoyed, it spreads a narrow hood and growls loudly, but some scientists claim that their aggressiveness is grossly exaggerated. In most of the local encounters with live, wild king cobras, the snakes appear to be of rather placid disposition, and they usually end up being killed or subdued with hardly any histrionics. These support the view that wild king cobras generally have a mild temperament, and despite their frequent occurrence in disturbed and built-up areas, are adept at avoiding humans. Naturalist Michael Wilmer Forbes Tweedie felt that "this notion is based on the general tendency to dramatise all attributes of snakes with little regard for the truth about them. A moment's reflection shows that this must be so, for the species is not uncommon, even in populated areas, and consciously or unconsciously, people must encounter king cobras quite frequently.
=== Early life === Major Force is a product of the same U.S. Federal project which created Captain Atom during the Vietnam War. The government, in a project headed by Wade Eiling and the scientist Megala, experiments with the effects of atomic energy on an alien metal to determine its full protective abilities such as protecting a human being from a nuclear blast. After Nathaniel Adam's disappearance and the perceived failure of the Captain Atom Project, the government restarts the project with a new test subject named Clifford Zmeck and increased the amount of metal used. While in the Air Force, Zmeck is imprisoned on charges of rape and murder and sentenced to life in prison. However, he is offered a pardon in exchange for participation in the high-risk governmental experiment. Zmeck disappears into the Quantum Field, emerging one year after the return of Nathaniel Adam with abilities similar to his.
DNA damages are induced by reactive carbonyls, principally methylglyoxal and glyoxal, at a frequency similar to that of oxidative DNA damages. Such damage, referred to as DNA glycation, can cause mutation, breaks in DNA and cytotoxicity. In humans, a protein DJ-1 (also named PARK7), has a key role in the repair of glycated DNA bases.
Chase's mother stated that she last saw her daughter when visiting her in jail in October 2019, and that they had lost contact entirely after Chase failed to meet her as planned upon her release. For a decade Chase was reclusive and her family and friends could not reach her. Her former manager John Ryan began producing a documentary about his search for Chase, to be titled Finding Lilo; it was in progress by the time of Chase's death.
== External links == Observations Support Homochirality Theory. Photonics TechnologyWorld November 1998. Origins of Homochirality Archived 2010-08-21 at the Wayback Machine. Conference in Nordita Stockholm, February 2008.
Sources: en.wikipedia.org
Tapentadol, sold under the brand names Nucynta and Palexia among others, is a synthetic opioid analgesic with a dual mode of action as a highly selective full agonist of the μ-opioid receptor and as a norepinephrine reuptake inhibitor (NRI). Tapentadol is used medically for the treatment of moderate to severe pain. It is highly addictive and is a commonly abused drug. Frequently reported adverse effects include euphoria, constipation, nausea, vomiting, headaches, loss of appetite, drowsiness, dizziness, itching, dry mouth, and sweating. More severe adverse reactions can occur, including addiction and dependence, substance abuse, respiratory depression, and an elevated risk of serotonin syndrome. Concurrent use of tapendatol with serotonergic drugs can heighten the risk of excessive serotonin accumulation while concurrent use with CNS depressants — alcohol, benzodiazepines, other opioids — can heighten the risk of profound sedation, dangerously slowed breathing, and death. Analgesia occurs within 32 minutes of oral administration, and lasts for 4–6 hours. Tapentadol is taken by mouth, and is available in immediate-release and controlled-release formulations. Tapentadol's combined mechanism of action is often compared to that of tramadol. Unlike tramadol, tapentadol is not metabolised by cytochrome P450 enzymes, but rather through glucuronidation. Due to this, tapentadol has fewer interactions with other medications and fewer side effects when compared with tramadol. Like tramadol, tapentadol affects both the opioid system and the norepinephrine system to relieve pain.
Participants were randomized (1:1) to receive neoadjuvant pembrolizumab and enfortumab vedotin followed by surgery followed by adjuvant enfortumab vedotin in combination with pembrolizumab followed by pembrolizumab as a single agent or to undergo immediate surgery alone.
In 1960, the protagonist, Jack, is a passenger on a plane that crashes in the Atlantic Ocean. The only survivor, Jack makes his way to a nearby lighthouse; inside is a bathysphere that takes him to Rapture. Jack is contacted via radio by Atlas, who helps guide him through the ruined city. Atlas requests Jack's help in saving his family, who he says are in a docked bathysphere. When Jack first encounters the Little Sisters, Atlas urges him to kill them to harvest their ADAM. Dr. Brigid Tenenbaum intervenes and insists Jack should spare them, providing him with a plasmid that can remove the sea slug from their bodies and free them of their brainwashing. Jack works his way to the bathysphere, but Ryan destroys it before Jack can reach it. Infuriated, Atlas has Jack fight his way through various districts toward Ryan's lair, forcing Jack to contend with Rapture's deranged citizens along the way, such as the surgical doctor J.S. Steinman and artist and musician Sander Cohen. Jack enters Ryan's office. Ryan reveals the truth of Jack's origins: he is Ryan's illegitimate son, sold by Ryan's mistress as an embryo to Fontaine, who had Tenenbaum and Suchong rapidly age Jack into adulthood and turned into an obedient assassin, capable of accessing any of Rapture's systems locked to Ryan's genetic code and thus ensure Fontaine's victory in the war. Jack was smuggled to the surface with false memories of a normal life, waiting to be called back to Rapture when needed.
Like other AASs, oxandrolone is an agonist of the androgen receptor, similar to androgens such as testosterone and DHT. The relative binding affinity of oxandrolone for the androgen receptor is about 0.3% of that of metribolone. Activation of the androgen receptor stimulates protein synthesis, which increases muscle growth, lean body mass, and bone mineral density. Compared to testosterone and many other AASs, oxandrolone is less androgenic relative to its strength as an anabolic. Oxandrolone has as much as six times the anabolic potency of testosterone and has significantly reduced androgenic potency in comparison: oxandrolone exhibits significantly lower virilizing androgenic properties compared to testosterone, with a relative androgenic potency of only 5%. Compared to methyltestosterone, oxandrolone has about 322 to 633% of the anabolic potency and 24% of the androgenic potency. The reduced ratio of anabolic to androgenic activity of oxandrolone motivated its medical use in children and women because less androgenic effect implies less risk of virilization. The bodybuilding community also considers this fact when choosing between AASs. As of 2003 and 2011 Oxandrolone was thought to be "uniquely" far less hepatotoxic than other 17α-alkylated AASs, which was thought to be due to differences in metabolism. This turned out not to be the case in the long run, which is why it was taken off the US market in 2023.
Typically, a centrifugal clutch and sprocket are used. The centrifugal clutch expands with increasing speed, engaging a drum. On this drum sits either a fixed sprocket or an exchangeable one. The clutch has three jobs: When the engine runs idle (typically 2500–2700 rpm) the chain does not move. When the clutch is engaged and the chain stops in the wood for another reason, it protects the engine. Most importantly, it protects the operator in case of a kickback. Here, the chain brake stops the drum, and the clutch releases immediately.
Sources: en.wikipedia.org
NAD+ is an oxidized dinucleotide coenzyme that carries electrons in metabolic reactions. It is also consumed by signaling enzymes, including sirtuins and PARPs. Its reduced form is NADH.
NAD+ is the oxidized form and can accept a hydride equivalent. NADH is the reduced form and donates electrons to the electron transport chain. The two forms cycle between each other during cellular respiration.
In mammals, NAD+ is synthesized mainly through salvage pathways using nicotinamide, nicotinamide riboside, or nicotinic acid. Tryptophan can also contribute through a de novo route. The salvage pathway is often considered the primary source in many tissues.
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.