A practical reference on Karl Fischer titration: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-01-21 and is reviewed periodically as new material appears.
Nicotinamide mononucleotide, abbreviated NMN, is a naturally occurring nucleotide found in the cells of many organisms, including bacteria, plants, and mammals. Its structure consists of a nicotinamide ring attached to a ribose-phosphate group. NMN functions as an intermediate in the NAD+ salvage pathway, a recycling route that regenerates nicotinamide adenine dinucleotide. The enzyme nicotinamide phosphoribosyltransferase produces NMN from nicotinamide and phosphoribosyl pyrophosphate. A second enzyme, NMN adenylyltransferase, then converts NMN into NAD+.
Dietary sources of NMN include small amounts in certain vegetables, fruits, and other foods, although exact values vary by sample and method. Endogenous NMN concentrations are tightly regulated and often low, making measurement in blood or tissues technically demanding. After oral intake, NMN is thought to be rapidly metabolized in the intestine and liver, and intact NMN may not reach all tissues at high levels. Some rodent studies report increases in tissue NAD+ after oral NMN, while human data remain limited and sometimes rely on blood NAD+ metabolites rather than direct tissue measures.
As a commercial ingredient, nicotinamide mononucleotide is commonly supplied as a powder or capsule. Its stability depends on temperature, moisture, pH, and light exposure. Hydrolytic and thermal degradation can increase over time, so manufacturers and laboratories often store material cold and dry. Purity is typically assessed with chromatographic methods, and identity can be confirmed by mass spectrometry. Published stability data for specific finished products remain limited. More data would help define shelf life under real-world conditions.
Regulatory treatment varies by country. In the United States, NMN has been marketed as a dietary supplement, but the Food and Drug Administration has stated that it is excluded from the dietary supplement definition because it was authorized for investigation as a new drug before being marketed as a supplement. Other jurisdictions may treat it as a novel food, a supplement, or an unapproved drug ingredient. Import and sale rules can therefore differ substantially.
Quality control for NMN focuses on identity, purity, residual solvents, heavy metals, and microbial limits. Because the molecule can absorb water, moisture content and packaging are relevant to shelf life. Suppliers may provide certificates of analysis, but independent verification is often needed for research or commercial use. The long-term stability of different crystal forms, salt forms, and formulations is not fully characterized in the public literature. Some degradation products and their effects on product performance remain open questions.
| Property | Value | Notes |
|---|---|---|
| Chemical name | Nicotinamide mononucleotide | Nucleotide intermediate in NAD+ salvage pathway |
| Common abbreviation | NMN | Also written as β-NMN |
| Molecular formula | C11H15N2O8P | Uncharged parent form |
| Molar mass | 334.22 g/mol | Calculated from formula |
| CAS Registry Number | 1094-61-7 | For β-nicotinamide mononucleotide |
Nicotinamide mononucleotide, abbreviated NMN, is a naturally occurring nucleotide. Its structure combines a nicotinamide base with a ribose sugar and a phosphate group. Within cells, NMN sits on the biosynthetic route that recycles nicotinamide back into nicotinamide adenine dinucleotide, or NAD+. Because NAD+ participates in redox reactions and signaling, enzymes that produce and consume it influence many metabolic processes. The compound is therefore best described as an intermediate rather than a final signaling molecule.
In the canonical salvage pathway, nicotinamide phosphoribosyltransferase, known as NAMPT, transfers a phosphoribosyl group to nicotinamide and releases NMN. A second enzyme, NMN adenylyltransferase, then attaches an adenylyl group to NMN to form NAD+. Alternative routes exist, including a pathway that uses nicotinamide riboside and its phosphorylated forms. The relative contribution of extracellular NMN to intracellular NAD+ pools remains an area of active investigation, and the roles of specific transporters and enzymes are not completely defined.
Common laboratory methods for NMN include high-performance liquid chromatography with ultraviolet detection, liquid chromatography coupled to mass spectrometry, and nuclear magnetic resonance spectroscopy. Because the nicotinamide ring absorbs ultraviolet light, HPLC-UV at wavelengths near 260 nm can be used for purity assessment. LC-MS and LC-MS/MS provide greater sensitivity and are often applied to biological samples. Identification typically relies on matching retention time, mass-to-charge ratio, and fragmentation pattern to a reference standard.
NMN is generally handled as a hygroscopic and light-sensitive solid in laboratory settings. Recommended storage is typically at -20°C or below, often under desiccation and protected from light. Aqueous solutions are less stable than the solid and may degrade through hydrolysis or other pathways, so fresh preparation is common for analytical work. Repeated freeze-thaw cycles can reduce sample integrity. Stability depends on pH, temperature, buffer composition, and the presence of metal ions, so specific shelf-life values should be determined experimentally rather than assumed.
Natural sources of NMN include mammals, plants, and microorganisms, where it functions as an intermediate in NAD+ salvage and biosynthesis pathways. In mammals, the enzyme nicotinamide phosphoribosyltransferase produces NMN from nicotinamide and phosphoribosyl pyrophosphate. NMN is then converted to NAD+ by nicotinamide mononucleotide adenylyltransferase. Some foods contain measurable NMN, but reported amounts vary widely by species, tissue, and analytical method. The extent to which dietary NMN contributes to cellular NAD+ pools remains an open research question.
Chemically, NMN is described by the molecular formula C11H15N2O8P and a molecular mass near 334.22 g/mol. The beta anomer has a CAS Registry Number of 1094-61-7. It is typically supplied as a white to off-white powder for laboratory use. The molecule carries a phosphate group and a positively charged nicotinamide ring, giving it polar and water-soluble character. These properties influence how it is detected, purified, and stored in research and analytical laboratories.
Quality control for NMN typically checks identity, assay purity, residual solvents, heavy metals, and microbial limits, depending on the intended use and market. A certificate of analysis may report appearance, solubility, water content, and storage recommendations. Independent verification can compare chromatographic retention time and mass spectrum against a certified reference standard. Regulatory expectations differ between research chemicals, dietary ingredients, and pharmaceutical products. Impurity profiles and stability data are often requested for product approval, and open questions remain about how best to standardize NMN measurements across laboratories.
NMN is a polar, water-soluble nucleotide. In solid form it is usually a white to off-white powder. The compound is sensitive to heat, light, moisture, and extremes of pH, and aqueous solutions tend to degrade faster than dry material. Recommended storage for research samples is typically -20 °C or below in a sealed, desiccated container protected from light. Repeated freeze-thaw cycles should be avoided, and these handling practices help maintain identity and purity during laboratory use.
Analytical identification of NMN commonly uses high-performance liquid chromatography with ultraviolet detection, liquid chromatography-mass spectrometry, and nuclear magnetic resonance spectroscopy; HPLC can estimate purity by peak area, while mass spectrometry confirms molecular mass and fragmentation. NMR provides structural confirmation. Because NMN is charged, ion-pairing reagents or hydrophilic interaction liquid chromatography columns can improve retention and peak shape. In biological samples, LC-MS/MS with stable isotope internal standards is often used to quantify NMN and related NAD+ metabolites. Method validation is important because matrix effects and rapid enzymatic interconversion can complicate measurements.
=== EC 2.6.1: Transaminases === EC 2.6.1.1: aspartate transaminase EC 2.6.1.2: alanine transaminase EC 2.6.1.3: cysteine transaminase EC 2.6.1.4: glycine transaminase EC 2.6.1.5: tyrosine transaminase EC 2.6.1.6: leucine transaminase EC 2.6.1.7: kynurenine—oxoglutarate transaminase EC 2.6.1.8: deleted EC 2.6.1.9: histidinol-phosphate transaminase EC 2.6.1.10: deleted, included with EC 2.6.1.21, D-amino-acid transaminase EC 2.6.1.11: acetylornithine transaminase EC 2.6.1.12: alanine—oxo-acid transaminase EC 2.6.1.13: ornithine aminotransferase EC 2.6.1.14: asparagine—oxo-acid transaminase EC 2.6.1.15: glutamine—pyruvate transaminase EC 2.6.1.16: glutamine—fructose-6-phosphate transaminase (isomerizing) EC 2.6.1.17: succinyldiaminopimelate transaminase EC 2.6.1.18: β-alanine—pyruvate transaminase EC 2.6.1.19: 4-aminobutyrate transaminase EC 2.6.1.20: deleted EC 2.6.1.21: D-amino-acid transaminase EC 2.6.1.22: (S)-3-amino-2-methylpropionate transaminase EC 2.6.1.23: 4-hydroxyglutamate transaminase EC 2.6.1.24: diiodotyrosine transaminase EC 2.6.1.25: deleted, Now included with EC 2.6.1.24 diiodotyrosine transaminase EC 2.6.1.26: thyroid-hormone transaminase EC 2.6.1.27: tryptophan transaminase EC 2.6.1.28: tryptophan—phenylpyruvate transaminase EC 2.6.1.29: diamine transaminase EC 2.6.1.30: pyridoxamine—pyruvate transaminase EC 2.6.1.31: pyridoxamine—oxaloacetate transaminase EC 2.6.1.32: valine—3-methyl-2-oxovalerate transaminase EC 2.6.1.33: dTDP-4-amino-4,6-dideoxy-D-glucose transaminase EC 2.6.1.34: UDP-N-acetylbacillosamine transaminase EC 2.6.1.35: glycine—oxaloacetate transaminase EC 2.6.1.36: L-lysine 6-transaminase EC 2.6.1.37: (2-aminoethyl)phosphonate—pyruvate transaminase EC 2.6.1.38: histidine transaminase EC 2.6.1.39: 2-aminoadipate transaminase EC 2.6.1.40: (R)-3-amino-2-methylpropionate—pyruvate transaminase EC 2.6.1.41: D-methionine—pyruvate transaminase EC 2.6.1.42: branched-chain-amino-acid transaminase EC 2.6.1.43: aminolevulinate transaminase EC 2.6.1.44: alanine—glyoxylate transaminase EC 2.6.1.45: serine—glyoxylate transaminase EC 2.6.1.46: diaminobutyrate—pyruvate transaminase EC 2.6.1.47: alanine—oxomalonate transaminase EC 2.6.1.48: 5-aminovalerate transaminase EC 2.6.1.49: dihydroxyphenylalanine transaminase EC 2.6.1.50: glutamine—scyllo-inositol transaminase EC 2.6.1.51: serine—pyruvate transaminase EC 2.6.1.52: phosphoserine transaminase EC 2.6.1.53: Now EC 1.4.1.13, glutamate synthase (NADPH) EC 2.6.1.54: pyridoxamine-phosphate transaminase EC 2.6.1.55: taurine—2-oxoglutarate transaminase EC 2.6.1.56: 1D-1-guanidino-3-amino-1,3-dideoxy-scyllo-inositol transaminase EC 2.6.1.57: aromatic-amino-acid transaminase EC 2.6.1.58: phenylalanine(histidine) transaminase EC 2.6.1.59: dTDP-4-amino-4,6-dideoxygalactose transaminase EC 2.6.1.60: aromatic-amino-acid—glyoxylate transaminase EC 2.6.1.61: identical to EC 2.6.1.40, (R)-3-amino-2-methylpropionate—pyruvate transaminase EC 2.6.1.62: adenosylmethionine—8-amino-7-oxononanoate transaminase EC 2.6.1.63: kynurenine—glyoxylate transaminase EC 2.6.1.64: glutamine—phenylpyruvate transaminase EC 2.6.1.65: N6-acetyl-β-lysine transaminase EC 2.6.1.66: valine—pyruvate transaminase EC 2.6.1.67: 2-aminohexanoate transaminase EC 2.6.1.68: Now classified as EC 2.6.1.13, ornithine aminotransferase and EC 2.6.1.36, L-lysine 6-transaminase EC 2.6.1.69: identical to EC 2.6.1.11, ((acetylornithine transaminase))|identical to EC 2.6.1.11, acetylornithine transaminase EC 2.6.1.70: aspartate—phenylpyruvate transaminase EC 2.6.1.71: lysine—pyruvate 6-transaminase EC 2.6.1.72: D-4-hydroxyphenylglycine transaminase EC 2.6.1.73: methionine—glyoxylate transaminase EC 2.6.1.74: cephalosporin-C transaminase EC 2.6.1.75: cysteine-conjugate transaminase EC 2.6.1.76: diaminobutyrate—2-oxoglutarate transaminase EC 2.6.1.77: taurine—pyruvate aminotransferase EC 2.6.1.78: aspartate—prephenate aminotransferase EC 2.6.1.79: glutamate—prephenate aminotransferase EC 2.6.1.80: nicotianamine aminotransferase EC 2.6.1.81: succinylornithine transaminase EC 2.6.1.82: putrescine aminotransferase EC 2.6.1.83: LL-diaminopimelate aminotransferase EC 2.6.1.84: arginine—pyruvate transaminase EC 2.6.1.85: aminodeoxychorismate synthase EC 2.6.1.86: 2-amino-4-deoxychorismate synthase EC 2.6.1.87: UDP-4-amino-4-deoxy-L-arabinose aminotransferase EC 2.6.1.88: methionine transaminase EC 2.6.1.89: dTDP-3-amino-3,6-dideoxy-α-D-glucopyranose transaminase EC 2.6.1.90: dTDP-3-amino-3,6-dideoxy-α-D-galactopyranose transaminase EC 2.6.1.91: Identical to EC 2.6.1.34, UDP-N-acetylbacillosamine transaminase EC 2.6.1.92: UDP-4-amino-4,6-dideoxy-N-acetyl-β-L-altrosamine transaminase EC 2.6.1.93: neamine transaminase EC 2.6.1.94: 2′-deamino-2′-hydroxyneamine transaminase EC 2.6.1.95: neomycin C transaminase EC 2.6.1.96: 4-aminobutyrate—pyruvate transaminase EC 2.6.1.97: archaeosine synthase EC 2.6.1.98: UDP-2-acetamido-2-deoxy-ribo-hexuluronate aminotransferase EC 2.6.1.99: L-tryptophan—pyruvate aminotransferase EC 2.6.1.100: L-glutamine:2-deoxy-scyllo-inosose aminotransferase EC 2.6.1.101: L-glutamine:3-amino-2,3-dideoxy-scyllo-inosose aminotransferase EC 2.6.1.102: GDP-perosamine synthase EC 2.6.1.103: (S)-3,5-dihydroxyphenylglycine transaminase EC 2.6.1.104: 3-dehydro-glucose-6-phosphate—glutamate transaminase EC 2.6.1.105: lysine—8-amino-7-oxononanoate transaminase EC 2.6.1.106: dTDP-3-amino-3,4,6-trideoxy-α-D-glucose transaminase EC 2.6.1.107: β-methylphenylalanine transaminase EC 2.6.1.108: (5-formylfuran-3-yl)methyl phosphate transaminase EC 2.6.1.109: 8-amino-3,8-dideoxy-α-D-manno-octulosonate transaminase EC 2.6.1.110: dTDP-4-dehydro-2,3,6-trideoxy-D-glucose 4-aminotransferase EC 2.6.1.111: 3-aminobutanoyl-CoA transaminase EC 2.6.1.112: (S)-ureidoglycine—glyoxylate transaminase EC 2.6.1.113: putrescine—pyruvate transaminase EC 2.6.1.114: 8-demethyl-8-aminoriboflavin-5′-phosphate synthase EC 2.6.1.115: 5-hydroxydodecatetraenal 1-aminotransferase EC 2.6.1.116: 6-aminohexanoate aminotransferase EC 2.6.1.117: L-glutamine—4-(methylsulfanyl)-2-oxobutanoate aminotransferase EC 2.6.1.118: [amino-group carrier protein]-γ-(L-lysyl)-L-glutamate aminotransferase EC 2.6.1.119: vanillin aminotransferase
==== Deficit in fear memories ==== Irvine and colleagues in 2006 showed that preventing autophosphorylation of CaMKII cause mice to have impaired initial learning of fear conditioning. However, after repeated trials, the impaired mice exhibited similar fear memory formation as the control mice. CaMKII may play a role in rapid fear memory, but does not completely prevent fear memory in the long run. In 2004, Rodrigues and colleagues found that fear conditioning increased phosphorylated CaMKII in lateral amygdala synapses and dendritic spines, indicating that fear conditioning could be responsible for regulating and activating the kinase. They also discovered a drug, KN-62, that inhibited CaMKII and prevented acquisition of fear conditioning and LTP.
In an organic light-emitting diode (OLED), the electroluminescent material composing the emissive layer of the diode is an organic compound. The organic material is electrically conductive due to the delocalization of pi electrons caused by conjugation over all or part of the molecule, and the material therefore functions as an organic semiconductor. The organic materials can be small organic molecules in a crystalline phase, or polymers. The potential advantages of OLEDs include thin, low-cost displays with a low driving voltage, wide viewing angle, and high contrast and color gamut. Polymer LEDs have the added benefit of printable and flexible displays. OLEDs have been used to make visual displays for portable electronic devices such as cellphones, digital cameras, lighting and televisions.
Sources: en.wikipedia.org
On 24 February 2022, Russia launched a full-scale invasion of Ukraine, occupying large parts of the country and unilaterally declaring the annexation of southeastern Ukraine in September that year. Soon after, journalist H. D. S. Greenway cited the Russian invasion of Ukraine and 4 February joint statement between Russia and China (under Putin and Xi Jinping) as one of the signs that Cold War II had officially begun. Jaro Bilocerkowycz, Associate Professor of Political Science at the University of Dayton, wrote that the invasion of Ukraine could be the start of a "new Cold War", placing Ukraine "at the center of a geopolitical struggle reminiscent of the Cold War days when Germany and its capital city Berlin were split in two". In March 2022, Harvard historian Fredrik Logevall asserted that the conflict over Ukraine was "fundamentally different from the Cold War" because it did not have the "massive arms race and a general absence of diplomacy, and a deep ideological schism". Yale historian Arne Westad agreed and said that Putin's statements about Ukraine resembled late 19th- and early 20th-century colonial and imperial ideas, rather than those of the Cold War. In June 2022, journalist Gideon Rachman asserted the Russian invasion of Ukraine as the start of a second Cold War. In response to US plans to deploy long-range missiles in Germany, including SM-6 and Tomahawk cruise missiles and developmental hypersonic weapons, Putin stated in July 2024 that the situation was reminiscent of the Cold War.
In order to successfully complete a fermentation with minimum to no negative attributes being added to the wine, yeast needs to have the full assortment of its nutritional needs met. These include not only an available energy source (carbon in the form of sugars such as glucose) and yeast assimilable nitrogen (ammonia and amino acids or YAN) but also minerals (such as magnesium) and vitamins (such as thiamin and riboflavin) that serve as important growth and survival factors. Among the other nutritional needs of wine yeast:
Unmanned aerial vehicle (UAV, drone) – A drone is an aircraft without an onboard pilot, flown by remote control by a pilot in another location, usually in a piloting station on the ground. They are used by the military for reconnaissance and ground attack, and more recently by the civilian world for news reporting and aerial photography. The pilot uses aircraft controls like a joystick or steering wheel, which create control signals which are transmitted to the drone by radio to control the flight surfaces and engine. A telemetry system transmits back a video image from a camera in the drone to allow the pilot to see where the aircraft is going, and data from a GPS receiver giving the real-time position of the aircraft. UAVs have sophisticated onboard automatic pilot systems that maintain stable flight and only require manual control to change directions.
Sources: en.wikipedia.org
In contrast, Slavic settlements in southern Ukraine started to appear relatively early during Cuman rule, with the earliest, such as Oleshia, dating back to the 11th century. Early "Proto-Cossack" groups are generally reported to have come into existence within what is now Ukraine prior to the 13th century as the influence of Cumans grew weaker, although some have ascribed their origins to as early as the mid-8th century. Some historians suggest that the Cossack people were descended from East Slavs, Turks, Tatars, Circassians and others who settled or passed through the vast regions. There are archeological indications, according to Turkologists, that Cossacks are descendants of the native Cumans of Ukraine, who had lived there long before the Mongol invasion. Other theories expand upon that assertion to suggest that the first Cossacks were of Turkic origin. For example, according to Serhii Plokhy, the first Cossacks were of Turkic rather than Slavic stock. Christoph Baumer states that Cossack predecessors from the thirteenth century onward were mainly of Turkic stock, but from the sixteenth century the Cossacks were increasingly joined by Slavs such as Russians and Poles, Baltic Lithuanians and people from today's Ukraine, thus becoming a Slav-Tatar ethnic hybrid. The theory is also reflected in the Constitution of Pylyp Orlyk of 1710 and the Hrabianka Chronicle, which claims Khazar origins for the Cossacks. The Khazar origin myth became popular during the rule of Ivan Mazepa, a reaction against the Polish myth of Sarmatism.
4-maleylacetoacetate is converted to 4-fumarylacetoacetate, this compound can be broken down into fumarate and acetoacetate by the enzyme fumarylacetoacetate hydrolase. The conversion of 4-maleylacetoacetate to fumarylacetoacetate is a step in the catabolism of phenylalanine and tyrosine, amino acids acquired through dietary protein consumption. When 4-maleylacetoacetate isomerase is unable to function properly, the 4-maleylacetoacetate may be converted instead to succinylacetoacetate and further broken down into succinate and acetoacetate by fumarylacetoacetate hydrolase.
Activation energies consistent with proline isomerization, which typically has an activation of about 20 kcal/mol. Two-state folding kinetics indicative of both fast-folding and slow-folding populations in the unfolded or denatured state. "Double-jump" assays in which proline-containing proteins are unfolded and refolded, and the population of non-native proline conformations are studied as a function of the extent of folding. Acceleration of the in vitro folding rate by the addition of a prolyl isomerase. Acceleration of the in vitro folding rate in mutant protein variants with one or more proline residues replaced by another amino acid. Not every proline peptide bond is critical to the structure or function of a protein, and not every such bond has a significant influence on folding kinetics, especially trans bonds. Furthermore, some prolyl isomerases have a degree of sequence specificity and therefore may not catalyze the isomerization of prolines in certain sequence contexts.
Sources: en.wikipedia.org
NMN is nicotinamide mononucleotide, a nucleotide intermediate in the NAD+ salvage pathway. Cells use it to help regenerate NAD+, a coenzyme involved in energy metabolism and cellular signaling. It is present naturally in many organisms and is also produced synthetically for research and consumer products.
NMN is the immediate precursor to NAD+ in the salvage pathway. The enzyme NMN adenylyltransferase adds an adenylate group to NMN to form NAD+. Because NAD+ levels decline with age in some tissues, researchers study whether raising NMN availability can influence NAD+ metabolism.
No. Human evidence is limited, and no regulatory agency has approved NMN for treating or preventing aging. Some trials measure NAD+ metabolites or metabolic markers, but their results do not establish a clinical benefit. Larger, longer studies with standardized endpoints are needed.
Laboratory samples are often kept cool, dry, and protected from light, with frozen storage used for longer periods. Finished products should follow label instructions and avoid excessive heat or moisture.