The short version of redox coenzyme fits in a sentence. The long version — which is the one that helps — is below.
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Nicotinamide adenine dinucleotide, abbreviated NAD+, is a dinucleotide built from adenine, nicotinamide, two ribose sugars, and two phosphate groups. The oxidized form carries a positive charge on the nicotinamide ring, while the reduced form, NADH, is neutral. This pair acts as a reversible electron carrier in cells. NAD+ is present in bacteria, plants, animals, and fungi. Its structure allows it to accept and donate electrons without being consumed in the reactions it supports.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molar mass | 663.43 g/mol | For the free acid form; salts have higher mass. |
| Appearance | White to off-white powder | Often hygroscopic; may clump on exposure to air. |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar organic solvents. |
| Typical storage | -20 °C, desiccated | Protect from light and moisture; avoid repeated freeze-thaw. |
| Common synonyms | beta-NAD, DPN | DPN stands for diphosphopyridine nucleotide, an older name. |
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.
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.
==== Cyclodextrin-type CSP ==== Cyclodextrins (CDs) are cyclic oligosaccharides of six, seven, or eight glucose units designated as α, β, and γ cyclodextrins respectively. Depicted in the diagram below. Daniel Armstrong is considered the pioneer of micelle and cyclodextrin-based separations. Cyclodextrins are covalently attached to silica by Armstrong process and provide stable CSPs. The primary hydroxyl groups are used to anchor the CD molecules to the modified silica surface. CDs are chiral because of innate chirality of the building blocks, glucose units. In cyclodextrin the glucose units are α-(1,4)- connected. The shape of CD looks like a shortened cone (see the sketch). The inner surface of the cone forms moderately hydrophobic pocket. The width of the CD-cavity is identified with the quantity of glucose units present. In cyclodextrins, secondary hydroxyl groups (OH-2 and - 3) line the upper rim of the cavity, and an essential 6-hydroxyl group is positioned at the lower rim. The hydroxyl group offer chiral binding points, which appear to be fundamental for enantioselectivity. Apolar glyosidic oxygen makes the pit hydrophobic and guarantees inclusion complexing of the hydrophobic moiety of analytes. Interactions between the polar area of an analyte and secondary hydroxyl groups at the mouth of the pit, joined with the hydrophobic connections inside the pit, give a unique two-point fit and lead to enantioselectivity.
Brachytherapy is used to place a sealed radioactive source inside or near the body to treat cancer, such as prostate cancer. Afterloading brachytherapy is often combined with teletherapy, which is external radiation delivered from a greater distance than brachytherapy. It is not classified as a nuclear medicine procedure, although like nuclear medicine, it uses the radiation emitted by radionuclides. After initial interest in brachytherapy in the early 20th century, its use declined in the mid-20th century because of the radiation exposure to physicians from manual handling of the radiation sources. It was not until the development of remote-controlled afterloading systems and the use of new radiation sources in the 1950s and 1960s that the risk of unnecessary radiation exposure to physicians and patients was reduced. In the afterloading procedure, an empty, tubular applicator is inserted into the target volume (e.g., the uterus) before the actual therapy and, after checking the position, loaded with a radioactive preparation. The preparation is located at the tip of a steel wire that is advanced and retracted step by step under computer control. After the pre-calculated time, the source is withdrawn into a safe and the applicator is removed. The procedure is used for breast cancer, bronchial carcinoma or oral floor carcinoma, among others. Beta emitters such as 90Sr or 106Ru or 192Ir are used.
Adrenocorticotropic hormone (ACTH; also adrenocorticotropin, corticotropin) is a polypeptide tropic hormone produced by and secreted by the anterior pituitary gland. It is also used as a medication and diagnostic agent. ACTH is an important component of the hypothalamic-pituitary-adrenal axis and is often produced in response to biological stress (along with its precursor corticotropin-releasing hormone from the hypothalamus). Its principal effects are increased production and release of cortisol and androgens by the zona fasciculata and zona reticularis, respectively. ACTH is also related to the circadian rhythm in many organisms. Deficiency of ACTH is an indicator of secondary adrenal insufficiency (suppressed production of ACTH due to an impairment of the pituitary gland or hypothalamus, cf. hypopituitarism) or tertiary adrenal insufficiency (disease of the hypothalamus, with a decrease in the release of corticotropin releasing hormone (CRH)). Conversely, chronically elevated ACTH levels occur in primary adrenal insufficiency (e.g. Addison's disease) when adrenal gland production of cortisol is chronically deficient. In Cushing's disease, a pituitary tumor leads to excessive production of ACTH, which stimulates the adrenal cortex to produce high levels of cortisol.
Sources: en.wikipedia.org
It is now known that the underlying physiological correlation for the increase in EPSP size is a postsynaptic upregulation of AMPARs at the membrane, which is accomplished through the interactions of AMPARs with many cellular proteins. The simplest explanation for LTP is as follows (see the long-term potentiation article for a much more detailed account). Glutamate binds to postsynaptic AMPARs and another glutamate receptor, the NMDA receptor (NMDAR). Ligand binding causes the AMPARs to open, and Na+ flows into the postsynaptic cell, resulting in a depolarization. NMDARs, on the other hand, do not open directly because their pores are occluded at resting membrane potential by Mg2+ ions. NMDARs can open only when a depolarization from the AMPAR activation leads to repulsion of the Mg2+ cation out into the extracellular space, allowing the pore to pass current. Unlike AMPARs, however, NMDARs are permeable to both Na+ and Ca2+. The Ca2+ that enters the cell triggers the upregulation of AMPARs to the membrane, which results in a long-lasting increase in EPSP size underlying LTP. The calcium entry also phosphorylates CaMKII, which phosphorylates AMPARs, increasing their single-channel conductance.
==== Vaal Civic Association ==== The organisation which spearheaded the 3 September march was the VCA, a residents' organisation partly modelled on the successful Soweto Civic Association. Launched on 9 October 1983, VCA was an affiliate of the UDF, and two senior officials in the UDF's Transvaal branch – Curtis Nkondo and Elliot Shabangu – were guest speakers at its launch in October 1983. Its inaugural chairman was Lord McCamel, a local priest with a parish in Evaton, and his deputy was Esau Ralitsela.
In men and women, the sole requirement for being considered a dwarf is having an adult height of 147 cm (4 ft 10 in) or less, and it is almost always sub-classified with respect to the underlying condition that is the cause of the short stature. Dwarfism is usually caused by a genetic variant; achondroplasia is caused by a mutation on chromosome 4. If dwarfism is caused by a medical disorder, the person is referred to by the underlying diagnosed disorder. Disorders causing dwarfism are often classified by proportionality. Disproportionate dwarfism describes disorders that cause unusual proportions of the body parts, while proportionate dwarfism results in a generally uniform stunting of the body. Disorders that cause dwarfism may be classified according to one of hundreds of names, which are usually permutations of the following roots:
wstd: weight of internal standard wspl: weight of sample n[H]std: the integrated area of the peak selected for comparison in the standard, corrected for the number of protons in that functional group n[H]spl: the integrated area of the peak selected for comparison in the sample, corrected for the number of protons in that functional group MWstd: molecular weight of standard MWspl: molecular weight of sample P: purity of internal standard
Sources: en.wikipedia.org
=== Filming === By May 2025, the second season of The Librarians: The Next Chapter had begun filming. The series is filmed on-location in Belgrade, Serbia, with the Military Museum entrance of the Belgrade Fortress serving as the exterior of "Belgrade Castle" where the fictional library is housed, and interiors shot in a Serbian studio.
Results for bedsores were conflicting and research on mixed wounds was of poor quality, but promising. There is no evidence of increased significant complications. The review concluded "There is now sufficient evidence to show that NPWT is safe, and will accelerate healing, to justify its use in the treatment of diabetes-associated chronic leg wounds. There is also evidence, though of poor quality, to suggest that healing of other wounds may also be accelerated."
=== Indian retail reforms on hold === According to Bloomberg, on 3 December 2011, the Chief Minister of the Indian state of West Bengal, Mamata Banerjee, who is against the policy and whose Trinamool Congress brings 19 votes to the ruling Congress party-led coalition, claimed that India's government may put the FDI retail reforms on hold until it reaches consensus within the ruling coalition. Reuters reports that this risked a possible dilution of the policy rather than a change of heart., Several newspapers claimed on 6 December 2011 that India parliament is expected to shelve retail reforms while the ruling Congress party seeks consensus from the opposition and the Congress party's own coalition partners. Suspension of retail reforms on 7 December 2011 would be, the reports claimed, an embarrassing defeat for the Indian government, suggesting it is weak and ineffective in implementing its ideas. Anand Sharma, India's Commerce and Industry Minister, after a meeting of all political parties on 7 December 2011 said, "The decision to allow foreign direct investment in retail is suspended till consensus is reached with all stakeholders." In February 2014, Vasundhara Raje led newly elected Rajasthan Government reversed the earlier Government's decision of allowing FDI in retail in the state. It reasoned that the sources of domestic retail are primarily local whereas international retail affects domestic manufacturing activity and hence reduces employment opportunities.
==== Emigration, immigration, and demographic shifts ==== Creoles and other ethnic groups are emigrating mostly to the United States, but also to the United Kingdom and other developed nations for better opportunities. Based on the latest US Census, the number of Belizeans in the United States is approximately 160,000 (including 70,000 legal residents and naturalized citizens), consisting mainly of Creoles and Garinagu. Because of conflicts in neighbouring Central American nations, refugees from El Salvador, Guatemala, and Honduras have fled to Belize in significant numbers from the 1980s onward, and have significantly added to Belize's Hispanic population. This has significantly changed the country's ethnic makeup. In the 2020 US Census Data, Belizeans made the top 5, ranking at number 4, of largest "Some Other Race Alone" or "Some Other Race Alone or in Any Combination" group. The number of Belizeans in the "Some Other Race Alone" was 11,311 people, and the number of Belizeans in the "Some Other Race Alone or in any Combination" was 48,618 people. However, the US State Department estimates upwards 100,000 Belizeans are in the US, making it the largest Belizean diaspora outside of Belize. $2.62 billion US dollars were given in aid to Belize from the United States between 2020 and 2023, to help combat an increase in trafficking, including drug and human, narcotic smuggling, and the spread of organized gang violence. The aid was dedicated to reinforcing Belize's police enforcement system and tighter border regulations.
== Genome == The genome of T. pallidum was first sequenced in 1998 and revealed a small 1.14 Mbp genome, one of the smallest bacterial genomes. The GC-content is 52.8%. The DNA sequences of T. pallidum species are more than 99.7% identical, and PCR-based assays are effective at differentiating these species. About 92.9% of DNA was determined to be open reading frames, 55% of which had predicted biological functions, while 17% matched hypothetical proteins of unknown function in other organisms and the remainder (28%) did not have significant similarity to other known sequences. The small size of the T. pallidum genome indicates that the species has limited metabolic capabilities, and thus mostly relies on its host for many molecules typically provided by biosynthetic pathways. For instance, it is missing genes encoding key enzymes in oxidative phosphorylation and the tricarboxylic acid cycle. Thus, T. pallidum is no longer able to synthesize fatty acids, nucleic acids, and amino acids, instead relying on its mammalian hosts for these materials. T.pallidum's low levels of diversity within its DNA sequence, forces the pathogen to utilize horizontal gene transfer for genetic diversity, although the specific mechanism is not well understood. It may possibly be a clonal species that still employs recombination. The strains T. pallidum pertenue (TPE) and T.pallidum endemicum (TEN) also experience gene transfer via different subspecies but are notably geographically isolated.
Sources: en.wikipedia.org
It indicates the oxidized form, which has a positive charge on the nicotinamide nitrogen. The reduced partner NADH lacks that charge and carries added electrons. The plus sign is part of the standard abbreviation, not a separate ion.
No. It also serves as a substrate for signaling and DNA-repair enzymes such as sirtuins and PARPs. Those reactions consume NAD+ and connect its availability to cellular regulation. Energy transfer remains its most abundant known role.
NAD+ is the oxidized electron acceptor, while NADH is the reduced electron carrier. They form a reversible redox pair and differ by a hydride ion. Cells maintain different ratios of the two depending on conditions and compartment.
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.